Browsing by Subject "Clinical Pharmacology"

Now showing 1 - 20 of 51
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    A mixed method study of the factors influencing the validity of medical and medication histories obtained from potential healthy adult clinical trial participants
    (2019) Ltayef, Hanan; Allen, Elizabeth; Annemie, Stewart
    Background: The medical histories of patients are data picked up by a doctor by making inquiries of the patient and of other individuals who know the individual and can give a reasonable response. In clinical trials, obtaining an accurate medical and treatment history is also an important factor in establishing whether or not a person is an eligible participant, and thereafter supports the assessment of any change in health during the trial, for example, the assessment of adverse events (AEs). Study objectives: To understand discrepancies between the medical histories from online self-reports, electronic medical records, and in-depth interviews of those applying to be part of an adult volunteer database for clinical trials; explore ways of engaging with potential volunteers, such that self-reported medical histories are as comprehensive as possible; explore the feasibility of accessing electronic records for those responding to advertisements. Methodology: This study was designed as mixed methods, with sequential explanatory design collecting quantitative and qualitative data and nested in an existing adult volunteer database. people from the Cape Town community were invited to join the database, in response to an advertisement and through a link to the database website; particularly those who were potentially eligible for a typical healthy volunteer trial, and who reported different information to that obtained from the electronic records. Results: 38 people responded to the online questionnaire, the majority being female. According to the online self-report questionnaire, ten people (10/38; 26.3%) had chronic medical conditions; mostly HIV (7/10; 70%). We accessed the Western Cape electronic medical records for only 8/38 (21%). Comparing the online questionnaire with the medical records, it was found that 25% of respondents had no difference in information. 10/38 people (26.3%) agreed to participate and were available for an in-depth interview. The main findings were: 1) a very low response rate to the advertisement, 2) people in this community are willing to consider taking part in clinical research, but have different understandings of what that means, 3) there were discrepancies between online self-reported health and medication data and what was found in a pilot database of electronic public health records and during a face-to-face interview, 4) the reason for these differences, as perceived by participants, included forgetting some information, feeling it was not relevant or important to report because of the attributes of the online questionnaire and 5) these participants had no concerns about us accessing their electronic medical records. Conclusion: Our study provides some evidence for optimal places to advertise for an adult volunteer database, and the appropriate wording and format of both the advertisements and the online questionnaire. More efforts are needed to educate the general public on understand the meaning of clinical trials. Electronic medical records may be accessed to help understand potential participants’ eligibility for trials, but the feasibility of accessing such data timeously may need further negotiation.
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    A pharmacokinetic and antimalarial efficacy evaluation of pyridodibemequines and their metabolites
    (2021) Redhi, Devasha; Wiesner, Lubbe; Egan, Timothy John
    The recurring challenge of the emergence of drug resistance necessitates the continual development of improved antimalarial treatments, which can target parasite strains that display reduced susceptibility towards current therapy. Consequently, a novel series of dual functioning pyridodibemequine (PDBQ) compounds were designed with the intention of reversing resistance in chloroquine-resistant (CQR) strains of Plasmodium falciparum. These hybrid molecules integrate a 4-amino-7-chloroquinoline antiplasmodial core with a modified dibenzylmethylamine side chain, which interacts with the CQR mutant P. falciparum chloroquine resistance transporter (PfCRT) to hinder the efflux of chloroquine (CQ) from its site of action, thereby reversing CQ resistance. The parent compounds of the PDBQ series, which differ in the ortho-, meta-, and para-orientation of the dibenzylmethylamine side chain, displayed favourable in vitro potency against chloroquine-sensitive (CQS) and CQR strains of P. falciparum; however, they were shown to be metabolically labile. Structure elucidation demonstrated that all formed PDBQ metabolites retained the 4-amino-7-chloroquinoline pharmacophore of the parent. Thus, the major metabolites, M1 and M2, generally conserved the in vitro antimalarial activity and selectivity of the parent compounds. Mechanistic studies revealed that the antiplasmodial activity of the PDBQ parent compounds and major metabolites primarily results from the inhibition of haemozoin formation, culminating in a toxic accumulation of ferriprotoporphyrin IX. The parents and major metabolites exhibited minimal toxicity against a mammalian cell line, and the metabolites are proposed to display reduced systemic toxicity, and human ether-a-go-go-related gene liability compared to the parent compounds. Furthermore, the major metabolites generally exhibited similar or improved in vitro solubility, permeability, lipophilicity, and metabolic stability compared to the parent compounds. Therefore, given their favourable in vitro characteristics, the major active metabolites of each parent PDBQ compound were further evaluated in this project to determine their potential as early preclinical antimalarial lead candidates. The proof of concept study presented herein investigated the in vivo pharmacokinetics (PK) of the PDBQ series of parents and major metabolites in a healthy murine model to allow the rational selection of candidates to be evaluated for their in vivo antimalarial efficacy and PK in a P. falciparum-infected murine model. For the PK studies in healthy and malaria-infected mice, analyte detection from whole blood was achieved using high-performance liquid chromatography coupled to tandem mass spectrometry. The bioanalytical methods were developed and partially validated based on a fit-for-purpose approach, which ensured that the generated PK concentration data was reliable and accurate. Lastly, given the significance of combination therapy in delaying the onset of drug resistance, fixed-dose ratio isobologram analyses were performed to probe the potential of the lead candidates to be used synergistically with an antimalarial partner drug possessing a distinct mechanism of action to haemozoin inhibition. Additionally, the ability of the lead candidates to reverse CQ resistance was evaluated in a CQR strain of P. falciparum. A comparative PK study was performed in a healthy murine model to determine whether the parent PDBQ compound should be used as a strategy to deliver the active metabolites or whether the active major metabolite should be directly administered. This was achieved by oral administration of the parent PDBQ compound and subsequent quantification of the parent compound and formation of the major metabolites. In addition, each pre-synthesised major metabolite was orally administered, at the equivalent parent dose, to characterise the PK profile of the individual active metabolite. These PK studies revealed that the overall oral exposure of the antimalarial pharmacophore was markedly greater after direct administration of the preformed metabolite compared to the cumulative oral exposure of the parent and formed metabolites after administration of the parent PDBQ compound. Furthermore, the metabolites attained higher maximal concentrations and maintained circulating concentrations which favourably exceeded their respective in vitro half-maximal inhibitory concentration at 24 h post-oral administration compared to the parent compounds at the equivalent oral dose. These findings substantiated the direct administration of the preformed PDBQ major metabolite over the parent compound. From the series of PDBQ metabolite derivatives, compounds 43M1 and 47M1 displayed the highest maximal concentrations of 8 ± 1 and 9.4 ± 0.5 μM, respectively and the greatest oral exposures of 62 ± 3 and 93 ± 9 µM.h, respectively, after single 20 mg/kg oral administrations of either 43M1 or 47M1. Given their encouraging PK profiles, 43M1 and 47M1 were selected to progress to the subsequent phase of the study which evaluated their in vivo antimalarial efficacy and pharmacokinetic/pharmacodynamic (PK/PD) relationship in a P. falciparum-infected humanised murine model. 43M1 and 47M1 were efficacious against asexual intraerythrocytic P. falciparum infection in humanised mice, where both compounds displayed a 98% reduction in parasitaemia after 4 consecutive daily oral administrations of 20 mg/kg of either 43M1 or 47M1 compared to the untreated control. The PK/PD analysis revealed dose-dependent reductions in parasitaemia; and the doses required to produce 90% of the maximal parasiticidal response (ED90) were 12 and 7.7 mg/kg for 43M1 and 47M1, respectively. Additionally, the oral exposures required to achieve the effect at the ED90 were 6.2 and 18.6 µM.h for 43M1 and 47M1, respectively. 43M1 or 47M1 demonstrated overall in vitro antimalarial synergy with dihydroartemisinin or atovaquone and additivity with methylene blue in CQS and CQR strains of P. falciparum. 43M1 or 47M1 with mefloquine or lumefantrine displayed in vitro antimalarial synergy in a CQS strain of P. falciparum; however, in a CQR strain, antagonism and additivity were displayed with mefloquine and lumefantrine, respectively. Additionally, 43M1 and 47M1 were unable to potentiate the in vitro antiplasmodial activity of CQ in a CQR strain of P. falciparum which suggested that, unlike the parent PDBQ compound, the metabolite did not possess the ability to reverse CQ resistance. The promising in vivo antimalarial efficacy of 43M1 and 47M1 against P. falciparum and their prospective in vitro antimalarial synergy with dihydroartemisinin and atovaquone underlines the potential of 43M1 and 47M1 for further development as preclinical antimalarial candidates.
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    The antiplasmodial, toxicity and pharmacokinetic properties of synthetic derivatives of the natural product Curcumin
    (2008) Okalebo, Faith Apolot; Smith, Peter J; Chibale, Kelly; Guantai, Anastasia N
    Includes bibliographical references.
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    Antiretroviral therapy adherence and effectiveness in a private sector disease management programme in Southern Africa
    (2008) Nachega, Jean B; Maartens, Gary
    Includes abstract. Includes bibliographical references.
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    The clinical role of therapeutic drug monitoring of antiretrovirals : a Cochrane systematic review
    (2008) Kredo, Tamara; Cohen, Karen
    The objective of this study is to evaluate whether ARV TDM reduces mortality and morbidity of adult patients on cART.
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    Clinical, pharmacokinetic, and genetic determinants of change in serum creatinine among Southern Africans on dolutegravir based antiretroviral therapy
    (2023) Mpofu, Rephaim; Sinxadi, Phumla; Maartens Gary
    Introduction: Dolutegravir increases serum creatinine by inhibiting renal secretion of creatinine, potentially resulting in inappropriate regimen switches. We investigated determinants of early changes in serum creatinine in a Southern African cohort starting dolutegravir-based antiretroviral therapy. Methods: We conducted a secondary analysis of data from participants in a randomised controlled trial of dolutegravir with tenofovir disoproxil fumarate (TDF) or tenofovir alafenamide fumarate (TAF) plus emtricitabine (ADVANCE, NCT03122262). We assessed clinical, pharmacokinetic, and genetic factors associated with the change in serum creatinine from baseline to week 4 using linear regression adjusting for age, sex, baseline serum creatinine, HIV-1 RNA viral load, CD4 T-cell count, total body weight, and co-trimoxazole use. Results: We included 689 participants, of whom 470 had pharmacokinetic data and 315 had genetic data. Mean change in serum creatinine was 11.3 µmol.L-1. Dolutegravir area under the 24-hour concentration-time curve (change in creatinine regression coefficient [β] = 2.78 [95% confidence interval 0.54, 5.01]) and male sex (β = 5.20 [2.92, 7.48]) were associated with an increased change in serum creatinine at week 4, while higher baseline serum creatinine (β = -0.22 [-0.31, -0.12]), use of TAF (β = -2.30 [-4.06, -0.53]) and Uridine glucuronosyltransferase 1A1 (UGT1A1) polymorphism rs929596 (β = -2.33 [-4.49, -0.17]; not significant after adjustment for multiple comparisons) were associated with a decreased change in serum creatinine. Conclusion: We identified clinical and pharmacokinetic determinants of change in serum creatinine in participants starting a dolutegravir-based regimen. UGT1A1 polymorphisms may play a role, but further research on genetic determinants is needed.
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    Comparison of three levels of ascertainment of antenatal medication use at Gugulethu Midwife Obstetric Unit
    (2022) van Der Hoven, Jani; Kalk, Emma; Allen, Elizabeth
    Background The use of medicines and/or remedies among pregnant women is common. Pregnant women are generally excluded from clinical trials due to ethical reasons. There are therefore minimal data available about the safety of most drugs during pregnancy by the time they come to the market, and post-marketing evaluation of medicine use during pregnancy is required. In South-Africa, with mass treatment campaigns for Tuberculosis (TB) and Human Immunodeficiency Virus (HIV), the introduction of new therapeutic agents and frequent self-medication, it is important for reliable methods to determine medicine exposures, including the frequency and timing of use, to support such evaluations. Databases about medication exposures are promising resources for pharmaco-epidemiological investigations, however the optimal method of ascertainment of medicine use during pregnancy is uncertain. Different data sources could also be better for different types of medication. To improve the quality of data, a combination of data sources may be ideal but time-consuming and expensive. By looking at and comparing three data sources: 1) self-report, 2) clinician records and 3) electronic dispensing systems, we aimed to identify the optimal method of ascertainment of antenatal medicine use for multiple medication types. Methods The aim of this investigation was to provide a more comprehensive reflection of the drug exposures during pregnancy and to make recommendations to strengthen routine clinical data capturing to improve maternity case reporting. The data of 988 pregnant women seeking antenatal care at Gugulethu Midwife Obstetric Unit (GMOU) in Cape Town between 2016 and 2018 were used. The three data sources consisted of self-reports gathered by an interviewer administered questionnaire at up to three antenatal visits to the GMOU; clinical records as recorded in the Pregnancy Exposure Registry (PER); and linked electronic dispensing data obtained from the Provincial Health Data Centre (PHDC) of the Western Cape Department of Health. Medication exposure data were coded using the Anatomical Therapeutic Chemical (ATC) Classification system, an internationally acknowledged system to classify medicine maintained by the WHO. ATC codes were assigned to active ingredients, depending on the therapeutic indication. The three data sources were then assessed in terms of missing or overlapping information and evaluated on the level of agreement between sources using Spearman's rank coefficient and Cohen's Kappa. Results According to the Spearman rank test, the PER and PHDC datasets as a whole showed the highest correlation both at 1st and 5th ATC level. The overlaps between the datasets were poor and the Kappa agreement between the sources was low for most therapeutic classes, except for HIV treatments. An “almost perfect” Kappa agreement existed between anti-diabetic medication (ATC A10) reported in the self-report and PHDC datasets. Traditional, herbal, complementary and home remedies were only reported in the self-report dataset. Conclusion We found an overall poor agreement between data sources, with one alone not able to effectively capture all data. The datasets should thus be used in conjunction to ensure accurate and reliable record of exposure. Self-report was the best data source for traditional, home, herbal and complementary medicine exposures while the PER provided a better and more complete reflection of influenza vaccines and vitamins. The best method of ascertaining antenatal medicine exposure therefore depends on the type of medicine being investigated, and choice of data source depends on the objectives of the investigation. This study suggests that PER, PHDC and self-report should ideally be used together since each is critical to ensure accurate, reliable and effective exposure data, although this will have resource and cost implications.
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    Determination of biomarkers for toxicity and antiretroviral adherence in hair in South African patients
    (2018) Johnston, Jenna; Wiesner, Lubbe; Smith, Peter
    Background: Substance abuse is one of the many factors associated with poor levels of antiretroviral adherence and is also prevalent among HIV-infected individuals. Ethyl glucuronide, a minor metabolite of alcohol, is a stable biomarker in hair that can be used to detect and monitor alcohol consumption over long time periods. Drugs of abuse are also detected in hair. Hair provides a longer window of drug detection compared to blood and urine. Recently, hair has also been studied as an alternative matrix for adherence monitoring and concentrations of antiretrovirals in hair have been shown to be closely correlated with virologic outcomes. This study investigated the impact of substance abuse on adherence among HIV-infected patients attending an antiretroviral therapy clinic in Cape Town by measuring drug concentrations in hair. Efavirenz levels in hair were also measured to investigate the usefulness of using hair analysis as a method of adherence monitoring within the South African context. Method: This study describes the development and validation of three liquid chromatography tandem mass spectrometry methods of hair analysis. The first method developed was for the quantification of ethyl glucuronide in 20 mg samples of hair. This method was validated over the calibration range 7.5 - 480 pg/mg. Secondly, a qualitative method was developed to screen hair samples for amphetamine, methamphetamine, cocaine, benzoylecgonine, cocaethylene and methaqualone. The final method developed was for the quantification of efavirenz in 0.2 mg samples of hair. This method was validated over the calibration range 0.625 - 40 ng/mg. The validated methods were applied to 257 samples of hair collected from 135 HIV-infected patients during visits to the clinic at weeks 16, 32 and 48. The results generated from the analysis of the hair samples were analysed in the context of additional adherence measurements collected for a related randomized controlled study. Results: Analysis of the hair samples for ethyl glucuronide demonstrated that 27% of the samples analysed contained levels above 30 pg/mg which is the cutoff value suggested by the Society of Hair Testing to identify heavy drinkers. The results also show limitations to using the CAGE alcohol abuse screening tool which had a poor sensitivity of only 28.8%. Eight (5.9%) out of the 135 participants were identified to be chronic drug users, and of these five (62.5%) were identified to be heavy drinkers as well. The most commonly abused drug identified in the screen was methaqualone. The median efavirenz levels at weeks 16, 32 and 48 were 5.52 ng/mg (IQR: 3.60 - 9.77), 5.75 ng/mg (IQR: 3.21 - 8.18) and 4.89 ng/mg (IQR: 3.10 - 7.94) respectively. Participants with the poor CYP2B6 metaboliser genotype had significantly higher median efavirenz hair concentrations compared to participants with intermediate and extensive genotypes (P < 0.0001). Efavirenz levels in hair and plasma samples were strongly correlated throughout the study (Spearman correlation coefficients: 0.672 - 0.741, all P values < 0.0001). Substance abuse had no impact on adherence measured by an electronic adherence monitoring device. No significant correlation was observed between adherence and levels of efavirenz in hair. Conclusions: Methods of hair analysis were developed and successfully applied to hair samples in the context of better understanding the impact of substance abuse on adherence. The results from the analysis of the hair samples provided insight into the prevalence of substance abuse among HIV-infected patients. The strong correlation observed between levels of efavirenz in hair and plasma suggest that, in this subset of HIV-infected patients, a single plasma concentration was as good an adherence measure as a hair concentration. The hair analysis methods developed and validated in this study are novel in South Africa and demonstrate the potential of this matrix to be used in various contexts within the country.
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    Determination of Rifapentine and 25-O-desacetyl Rifapentine from 100 µl human breastmilk by LC-MS/MS using protein precipitation and solid phase extraction
    (2019) Mkhize, Buyisile; Wiesner, Lubbe; Kellermann, Tracy; Norman, Jennifer
    There is currently no information available on the transfer of the second-line anti-TB drug, rifapentine and its metabolite, into breastmilk. The subsequent implications to the breastfed infant, as well as consequences of long-term exposure to potentially sub-therapeutic drug levels with regards to the development of drug resistant bacteria is therefore not known. A liquid chromatography method with detection by mass spectrometry (LC-MS/MS) is described for the quantification of rifapentine and its metabolite, 25-O-desacetyl rifapentine in human breastmilk, using rifampicin-d3 as an internal standard. An AB Sciex 4000 mass spectrometer at unit resolution in the multiple reaction monitoring (MRM) mode was used to monitor the transition of the protonated precursor ions m/z 877.5, m/z 835.4 and m/z 827.4 to the product ions m/z 151.1, m/z 453.2 and m/z 151.200 for rifapentine, 25-Odesacetyl rifapentine and rifampicin-d3, respectively. Ions were produced using Electro spray ionisation (ESI) in the positive ionisation mode. An Agilent Poroshell 120 EC-C18 (4.6 x 50 mm, 2.7 μm) column was used for chromatographic separation using an isocratic method of acetonitrile containing 0.1% formic acid and water containing 10% methanol and 0.1% formic acid (55:45, v/v), at a flow rate of 450 µl per minute. The retention times for rifapentine, 25- O-desacetyl rifapentine and rifampicin-d3 were ≈2.67, ≈1.88 and ≈1.96 minutes, respectively. The method was developed and validated according to FDA guidelines. The extraction method consisted of a combination of protein precipitation and C18 solid phase extraction. Rifapentine and 25-O-desacetyl rifapentine showed no significant carry over on the Agilent autosampler. The method was reproducible when analysed with human breastmilk from six different sources from Western Cape Maternity Breastmilk Bank. Rifapentine mean extraction yield was 84.2% (%CV = 1.7) and that of 25-O-desacetyl rifapentine was 71.1% (%CV = 10.8). Rifapentine had a mean process efficiency of 80.4% (%CV = 4.7) and that of 25-O-desacetyl rifapentine was 95.7% (%CV = 5.7). Intra- and inter day validations over 3 days were performed. The calibration curves fit a quadratic regression with 1/x weighting over a concentration range of 2 - 2000 ng/ml for both rifapentine and 25-Odesacetyl rifapentine based on the analyte/internal standard peak area ratios, the accuracy ranged from 92.9% to 105.5% for both rifapentine and 25-O-desacetyl rifapentine standards. The Quality Controls accuracy ranged from 97.4% to 106.0% for both rifapentine and 25-Odesacetyl rifapentine. Stock solutions were shown to be stable for 69 days at -80°C. v Rifapentine and 25-O-desacetyl rifapentine were stable in human breastmilk for up to 72 hours at approximately -80°C and -20°C, on benchtop for ≈4.5 hours on ice and after three freeze-thaw cycles. Rifapentine and 25-O-desacetyl rifapentine were shown to be stable on the autosampler over a period of approximately 48 hours after which the entire batch could be reinjected. Autosampler stability revealed a decrease in peak area ratios, indicating that a partial batch cannot be reinjected after 48 hours in case of instrument failure. This method will be utilized in the analysis of patient samples from a clinical study in South Africa in breastfeeding women with tuberculosis.
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    Determination of total, unbound, and intracellular concentrations of the antiretroviral drugs Efavirenz, Lopinavir, and Ritonavir
    (2022) Kriegler Foster, Katie; Wiesner, Lubbe; Kellermann, Tracy
    Efavirenz, lopinavir, and ritonavir are antiretroviral drugs used for the treatment of HIV in South Africa. Plasma concentrations of these drugs are routinely monitored to ensure efficacy, minimise adverse effects, and adjust dosing. However, variability exists in patient treatment response and tolerability, which cannot always be explained by the therapeutic drug monitoring results. This may be due to variability in the amount of drug reaching the target site within the HIV-infected cells. Therefore, intracellular drug concentrations could provide a more accurate depiction of drug exposure. An alternative to intracellular drug concentrations could be the quantitation of drug not bound to plasma proteins as this is the portion able to diffuse into tissues and cells to exert a therapeutic effect. A method is described for the quantification of intracellular efavirenz, lopinavir, and ritonavir from one million human peripheral blood mononuclear cells. In addition, the quantification of unbound efavirenz, lopinavir, and ritonavir from human plasma using ultracentrifugation is demonstrated, including a novel surrogate matrix. The two methods were validated according to the United States Food and Drug Administration and European Medicines Agency guidelines and proven to be accurate, precise, and reproducible. Both methods were submitted to the United States National Institute of Allergy and Infectious Diseases' Clinical Pharmacology Quality Assurance group for review and have been approved for use on clinical samples. A proof-of-concept correlation study of intracellular, unbound, and total drug concentrations is described using blood samples from six HIV-positive patients. A further patient unresponsive to lopinavir treatment, despite total plasma concentrations within the normal therapeutic range, was also evaluated. Paired plasma and cell samples indicated that the drug reached the target site within the cells, eliminating a possible cause of treatment failure. These findings show the utility and validity of these methods in a clinical setting to provide an overall view of treatment response and support their novel application in individualised patient care in South Africa.
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    The determination of β-endosulfan and endosulfan sulfate in human serum with dialkylphosphate metabolites as urinary markers using LC-MS/MS electrospray ionization
    (2017) Bergh, Werner; Wiesner, Lubbe; Van der Merwe, Marthinus Johannes
    Two separate bioanalytical methods were developed, validated and applied to determine agricultural exposure to organochlorine and organophosphorus pesticides using different biological matrices as reference sources. The method that was validated for the quantification of the organochlorine compounds was used to simultaneously determine β-endosulfan [6, 7, 8, 9, 10, 10- hexacloro-1, 5, 5a, 6, 9, 9a- hexahydro- 6, 9-methano-2, 4, 3-benzodioxathiepin-3- oxide] and one of its main metabolites, endosulfan sulfate, in human serum. In a second bioanalytical method, urinary dialkylphosphate metabolites have been assessed as markers to estimate the exposure to organophosphorus pesticides, focusing on three of the six organophosphorus urinary metabolites, namely dimethyl phosphate, dimethyl thiophosphate and diethyl phosphate. For both the bioanalytical methods, liquid-liquid extraction was used for sample preparation and high performance liquid chromatography with tandem mass spectrometry as detection method due to its high sensitivity and selectivity. Chromatographic separation for both bioanalytical methods was achieved by performing reverse phase chromatography on C18 analytical columns. Isocratic elution with a mobile phase composed of acetonitrile, methanol and water was employed for the analysis of the organochlorine compounds while the organophosphorus compounds were eluted using gradient elution with a mobile phase consisting of acetonitrile and 20 mM ammonium acetate. A triple quadrupole mass spectrometer equipped with an electrospray ionization source operating in the negative ionization mode was used for mass detection of all the analytes, employing multiple reaction monitoring as scan mode. Calibration standards and quality control samples for both analyses were prepared in the biological matrix in which the samples for each determination were collected, i.e. serum for the determination of the organochlorine compounds and stripped urine for the organophosphorus compounds. Deuterated internal standards were used in the bioanalytical method for the determination of the organophosphorus compounds whereas the organochlorine compounds were determined without the use of an internal standard due to unavailability of suitable internal standards. The calibration ranges for the determination of β-endosulfan and endosulfan sulfate were 0.8 ng/ml to 200 ng/ml and 0.117 ng/ml to 30 ng/ml, respectively, and 1.0 ng/ml to 30 ng/ml for the dialkylphosphate metabolites of the organophosphorus compounds. These sensitive and robust quantitation methods were successfully applied to quantify 219 serum and 187 urine samples that were collected from agricultural workers with the purpose to determine whether they were exposed to any of the investigated organochlorine or organophosphorus compounds. No traces of β-endosulfan and endosulfan sulfate were found in any of the serum samples that were analyzed, however, significant amounts of the three organophosphorus compounds dimethyl phosphate, dimethyl thiophosphate and diethyl phosphate were present in the urine samples.
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    Development and validation of liquid chromatography mass spectrometry (L/C/MS/MS) assay for the determination of plasma 4betahydroxycholestrol and cholesterol in HIV infected children in Africa
    (2015) Ngwalero, Precious; Wiesner, Lubbe; McIlleron, Helen
    4β-hydroxycholesterol (4β-OHC) is a metabolite of cholesterol formed by Cytochrome (CYP) 3A4/5/7 enzymes. It has recently been proposed as an endogenous biomarker forCYP3A4/5/7 activity. This may be useful in prediction of drug-drug interactions and other metabolic processes affected by regulators of CYP3A activity. The aim of this study was to develop and validate an LC/MS/MS assay for the determination of 4β-OHC in human plasma and use 4β-OHC as a biomarker of CYP3A4/5/7 metabolism in HIV-infected children with and without treatment in Africa. Determination of 4β-OHC from plasma was performed by saponification and derivatisation reaction processes followed by high performance liquid chromatography with MS/MS detection on an AB Sciex Qtrap 5500 mass spectrometer. Since 4β-OHC is an endogenous metabolite in human plasma, a stable isotope labelled (SIL) analogue, 4β-OHC-D7, was used as a surrogate analyte for the preparation of calibration standards and quality controls. A second SIL analogue, 4β-OHC-D4 was used as the internal standard. The transitions of the protonated derivatised products were monitored atm/z 613, 620 and 617 to the product ions m/z 490, 497 and 494 for 4β-OHC, 4β-OHC-D7and 4β-OHC-D4 respectively. The calibration curve fitted a quadratic (weighted by1/concentration2) regression over the range 2-500 ng/ml. Validation accuracy and precision statistics summary for three consecutive runs were between 98.9% and 103%, and 3.5%and 12% respectively of all quality controls. The assay's recovery, selectivity and analyte stability were established. The validated assay was successfully applied on clinical samples, where 4β-OHC was used as a biomarker to investigate the levels of CYP3A induction in HIV-infected children with and without treatment containing non-nucleoside reverse transcriptase inhibitors (NNRI).It was found that plasma 4β-OHC concentrations at baseline were significantly lower in children belonging to the naïve group compared to nevirapine (NVP) and efavirenz (EFV)groups. When NVP and EFV groups were compared at non-baseline treatment weeks, the median 4β-OHC concentrations were significantly higher in EFV group than the NVP group. Regarding the effect of time on treatment, a significant increase in 4β-OHC concentrations was observed from baseline to each of the non-baseline weeks in naïve group. Conversely, in the NVP group, there was a significant decrease in 4β-OHC concentrations from baseline to each of the non-baseline weeks. Time did not show any significant effect on 4β-OHC concentrations in EFV group. Furthermore, at baseline, age, sex and weight did not affect 4β-OHC concentrations in all the three groups. This study has provided a method that would be utilised to determine plasma 4β-OHC concentrations using relatively small volumes - typical of samples taken from children. The results of this study suggest that children on antiretroviral therapy (ART) are at risk of effects of CYP3A induction, as indicated by the increase of 4β-OHC concentrations in the NVP and EFV groups. Additionally, prolonged use of the ART may activate some nuclear receptors that regulate CYP3A enzyme activity thereby negatively affecting, for example, the regulation of lipid and glucose metabolism. The developed method may therefore be useful in predicting drug-drug interactions in the context of multiple therapy and may also be used in predicting other metabolic processes affected by regulators of CYP3A activity. Further prospective studies with larger sample sizes are required to confirm and build on the evidence shown in this study.
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    The development of practical psychopharmacological guidelines for the South African context
    (2001) Saunders, Jane Noreen; Robins, A
    Includes bibliographical references.
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    The development, initial implementation and support of a primary health care training programme in rational drug use
    (1998) Orrell, Catherine Jane; Folb, Peter I; Woods, David R
    The Rational Drug Use Training Project is a district-oriented programme designed to improve rational drug use among primary health care prescribers in the South African public sector. This thesis describes the development of the project and details the initial implementation study in 3 facilities in Region B of KwaZulu-Natal. This was a small before-after study, with no control. There were three components: 1. A series of easily collectable drug use indicators, adapted from those developed by WHO/INRUD. These allow primary health care staff to monitor their prescribing patterns in a district or facility. Ninety sets of prescribing indicators were collected as a baseline at 3 facilities in KwaZulu-Natal in December 1996, by the district trainers and the Rational Drug Use Training Project staff. The process was repeated in March 1997, after the training intervention, by the district trainers alone. 2. The intervention was a 2-day training workshop in rational drug use. This is problem-based and trained on-site in primary health facilities. Training was done by 8 district trainers from Region B who were taught to present the workshop by the Rational Drug Use Training Project staff. The workshop covers principles of prescribing, use of standard treatment guidelines, principles of clinic stock management and principles of good dispensing. Staff are encouraged to develop their self-learning skills through questioning, and seeking answers to clinical and drug related queries. 3. A set of resources, including texts, treatment guidelines and information centres, to provide quality, safe and unbiased drug information, are made accessible to staff at primary care level. These are available by post, telephone or e-mail. The Primary Care Medicines Resource Centre at the University of Durban-Westville was developed as a result of this study. Significant improvements in prescribing habits were noticed after the study. There was an increase in the percentage of drugs prescribed by their generic names (p=0.000); an increase in the number of medications adequately labelled (p=0.0132); a decrease in the cost of prescriptions (p=0.0134); and a decrease in the number of prescriptions that did not follow standard treatment guidelines at all for that diagnosis (p=0.0109). The Mann-Whitney U- test was used for statistical analysis. There were no significant changes in the average number of drugs per prescription; the percentage of drugs from the Essential Drugs List; and the number of prescriptions that completely followed standard treatment guidelines. Qualitative feedback was favourable too. This was a difficult study to undertake. The staff and funding organisation, Health Systems Trust, fell outside of the provincial health structure and met resistance at that level. Regional politics shaped the programme's design. District trainers needed for the cascade approach were not available. District staff remained entrenched in a traditional health hierarchy and found it difficult to function as a team. The will of district prescribing staff to learn was low. Rational drug use training is only one of a number of essential elements of in-service training urgently needed by these staff. Despite these problems, quantitative and qualitative success was shown. The Training Manual, developed in support of the training, has been in demand. The Primary Care Medicines Resource Centre is growing. Primary care prescribers have been motivated to monitor their own practices and manage their own clinic stock. The project is a successful example of multi-disciplinary and institutional collaboration. The Rational Drug Use Training Project has expanded to eight other health districts in 1997. A list of criteria, such as the need for a district trainer, have been set. These must be met by the district before training will commence. The project is a resource for Initiative for Sub-District Support, a joint district development programme of Health System Trust and the Department of Health. Most expansion in 1998 will be through this initiative. The difficulties encountered and achievements made during this small study will be used to support, and hopefully strengthen, the development of the primary health care oriented district health system, so urgently needed by the South African population.
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    Efavirenz pharmacogenetics and metabolic toxicity in black South Africans
    (2022) Makgai, Lesiba Meshack; Sinxadi, Phumla Z; Maartens, Gary
    Background: Efavirenz is associated with hepatotoxicity, dyslipidaemia and dysglycaemia. We aimed to determine if CYP2B6 composite metaboliser genotypes influence lipids, glucose and ALT concentrations. Methods: Data and DNA from South African antiretroviral therapy (ART)-naïve participants initiating efavirenz with emtricitabine plus tenofovir disoproxil fumarate (TDF) were used to characterise associations between CYP2B6 metaboliser genotypes and the percentage difference in metabolic parameters from baseline to week 48 using univariate and multivariate linear regression models. Results: A total of 171 participants were successfully genotyped. Median baseline age was 32 years, CD4 count was 292 cells/mm3 and log10 viral load was 4.42 copies/ml. Univariate analyses showed significant associations between CYP2B6 slow metaboliser genotype and total cholesterol (β = 13.78, p = 0.003), LDL cholesterol (β = 15.89, p = 0.008) and HDL cholesterol (β = 24.78, p = 0.002). These associations remained significant in multivariate analyses adjusting for age, sex, weight, baseline CD4 cell count and viral load [total cholesterol (β = 14.93, p< 0.001), LDL cholesterol (β = 15.57, p = 0.014), and HDL cholesterol (β = 24.22, p< 0.001)]. No associations were found between CYP2B6 metaboliser genotype and triglycerides, glucose or ALT. Conclusion: Among Black South African participants on efavirenz-based ART, CYP2B6 slow metaboliser genotype was associated with high cholesterol concentrations. In an African population with high prevalence of CYP2B6 slow metabolisers, close monitoring of lipids is needed.
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    Effect of dihydroartemisin-piperaquine for malaria intermittent preventive treatment on dolutegravir exposure in pregnant women living with HIV
    (2023) Banda, Clifford; Barnes, Karen; Maartens Gary
    Background: In sub-Saharan Africa, the disease burden of malaria and HIV infections overlap. In settings with moderate-to-high malaria transmission intensity, pregnant women living with HIV (PWLHIV) require both antiretroviral therapy and malaria intermittent preventive treatment (IPTp). Dihydroartemisinin-piperaquine has been identified as a promising alternative to sulfadoxine-pyrimethamine for malaria prevention in pregnancy. However, another antimalarial drug, artesunate-amodiaquine, similar to dihydroartemisininpiperaquine, was previously shown to reduce dolutegravir exposure in non-pregnant adults. Objective: To investigate the effect of dihydroartemisinin-piperaquine for IPTp on dolutegravir plasma exposure in pregnant women on dolutegravir-based antiretroviral therapy. Methods: We conducted an open-label, non-randomised, fixed sequence, pharmacokinetic study in PWLHIV in Malawi. Dolutegravir concentrations were measured over a 24-hour period, before and after the recommended three-day treatment dose of dihydroartemisininpiperaquine in 12 pregnant women in their 2nd or 3rd trimester. Non-compartmental analysis was performed, and geometric mean ratios (GMRs) and 90% confidence intervals (CIs) were generated to compare dolutegravir pharmacokinetic parameters between the two treatment periods. Results: Co-administration of dihydroartemisinin-piperaquine and dolutegravir increased dolutegravir's overall exposure (AUC0-24hr) and maximum concentration (Cmax) by 30% (GMR,1.30; 90% CI, 1.11-1.52) and 31% (GMR, 1.31; 90% CI,1.13-1.51), respectively. Furthermore, dolutegravir's trough (C24) concentration increased by 42% (GMR,1.42; 90% CI,1.09-1.85). The combined treatments were well tolerated with no serious adverse events observed. Conclusion: Dihydroartemisinin-piperaquine may be administered as IPTp with dolutegravir-based antiretroviral therapy in pregnant women as the modest increase in dolutegravir exposure, similar to pharmacokinetic parameter values published previously, assures its efficacy without any clinically significant adverse events observed in this small study
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    Effect of obesity on dolutegravir exposure in Black Southern African adults living with HIV
    (2022) Mondleki, Enkosi; Sinxadi, Phumla Zuleika; Maartens, Gary
    Background: Dolutegravir, a component of the preferred first-line antiretroviral therapy (ART) regimen has been associated with increased weight gain, which is markedly higher when combined with tenofovir alafenamide (TAF), the newer tenofovir prodrug instead of tenofovir disoproxil fumarate (TDF). South Africa has a high prevalence of obesity, especially among women. Understanding dolutegravir exposure in the patients with obesity is important for dose optimisation. Aims: We compared the pharmacokinetic parameters of dolutegravir in Southern African adults living with HIV with and without obesity. Methods: Blood samples were collected at various time points over a 24 hour-period for dolutegravir assays. Non-compartmental analysis was conducted and geometric mean ratios (GMRs), with 90% confidence intervals (CIs), were generated to compare dolutegravir pharmacokinetic parameters between the groups. Regression analyses to assess predictors of dolutegravir exposure were done. Results: 40 participants were enrolled, 26 were women and 10 had obesity. Dolutegravir area under the concentration-time curve to 24-hours (AUC0-24hr) and the maximum concentrations (Cmax) were marginally lower in participants with obesity: GMR 0.91 (90% CI, 0.71-1.16) and GMR 0.86 (90% CI, 0.68-1.07), respectively. In a multivariate linear regression analysis adjusting for age, sex, body mass index (BMI), creatinine clearance and randomisation arm (TAF or TDF), a unit increase in BMI was associated with 1.2% lower dolutegravir AUC0-24h, (P = 0.035). Conclusion: Dolutegravir exposure was marginally lower in participants with obesity, but this is not clinically significant. Our findings suggest that there is no need to dose adjust dolutegravir in people with obesity.
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    Effect of rifampicin-based antitubercular therapy on nevirapine plasma concentrations in South African adults with HIV-associated tuberculosis
    (2013) Cohen, Karen; Maartens, Gary; McIlleron, Helen
    Sub-Saharan Africa is overwhelmed by dual epidemics of human immunodeficiency virus (HIV) and tuberculosis (TB) infection. Non-nucleoside reverse-transcriptase inhibitor (NNRTI)-based antiretroviral therapy (ART) is recommended for first-line treatment in adult HIV treatment programmes in resource-limited settings [1]. Many South African HIV-infected patients initiate ART while on TB treatment, 38 percent in one local study [2]. In addition, although ART reduces the incidence of TB, incidence in patients on ART is higher than in the HIV uninfected population [3], therefore incident TB on ART requiring concomitant treatment is very common. Efavirenz is regarded as the NNRTI of choice for TB co-infected patients [1] as outcomes are superior compared to those achieved with nevirapine-based ART [4] and concomitant TB treatment does not significantly reduce efavirenz concentrations [5]. However nevirapine is cheaper than efavirenz and is used extensively used in lower income countries with limited access to efavirenz [1]. Data characterising the extent to which concomitant rifampicin-based TB treatment decreases nevirapine plasma concentration therefore remain important.
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    Liver Injury in HIV-positive Patients on Antituberculosis and/or Antiretroviral Therapy – Assessing Causality
    (2022) Gunter, Hannah May; Cohen, Karen
    Background We compared performance of the Roussel Uclaf Causality Assessment Method (RUCAM) with multidisciplinary expert panel review in identifying a drug-induced liver injury (DILI) due to antituberculosis therapy (ATT) and/or antiretroviral therapy (ART). Methods Cases were drawn from a prospective registry of hospitalised adults with suspected DILI due to ATT and/or ART in Cape Town, South Africa. Participants had to fulfil American Thoracic Society criteria for ATT interruption (alanine transaminase [ALT]≥5 times upper limit of normal [ULN]/ALT≥3 times [ULN] and symptomatic). Causality assessment by expert panel review served as reference standard. The panel ranked potentially implicated drugs as certain, probable, possible, or unlikely causes guided by World Health Organization Uppsala Monitoring Centre criteria. The RUCAM was performed for each potentially implicated drug. We calculated sensitivity and specificity of the RUCAM in identifying a probable/certain drug cause for liver injury. Results We included 48 participants. All were HIV-positive. Twenty-seven were on concomitant ART and ATT, with a median of 6 potentially hepatotoxic drugs per case. Sensitivity and specificity of the RUCAM in identifying a probable/certain drug cause of liver injury compared with expert panel review was 11% and 85% respectively. Implicated drugs (times ranked probable/certain by panel) were isoniazid (18/0), pyrazinamide (17/0), rifampicin (15/1), efavirenz (6/4), lopinavir/ritonavir (1/0). Conclusions HIV-positive patients with liver injury received multiple potentially implicated drugs, which may increase liver injury risk and complicates causality assessment. Compared with expert panel review, the RUCAM had low sensitivity in detecting probable or certain drug causes of liver injury.