A systematic review of the symptomatic treatment of the cough in whooping cough

Abstract

Background: There are between 20 - 40 million cases of whooping cough annually world-wide, 90% of which occur in developing countries, resulting in an estimated 200 - 300 O00 fatalities each year. Much of the morbidity is due to the paroxysmal cough. Corticosteroids, salbutamol (a β₂- adrenergic stimulant), and pertussis-specific immunoglobulin have been proposed as standard treatment for the cough. Antihistamines have also been administered. No systematic review of the effectiveness of any of these interventions or others has been performed. Objective: in this systematic review we aim to assess the effectiveness of interventions used to reduce the severity of the coughing paroxysms in whooping cough in children and adults. Selection criteria: Randomised and quasi randomised controlled trials of any intervention that reduced the severity of the coughing paroxysms in whooping cough; excluding antibiotics and vaccines. Study selection: All interventions aimed at reducing the severity of the coughing paroxysms in children or adults with whooping cough with any of the following outcome measures met inclusion criteria for the review; i) frequency of paroxysms of coughing (primary outcome), ii) frequency of vomiting, iii) frequency of whoop, iv) frequency of cyanotic spells, v) development of serious complications, vi) mortality from any cause, vii) side effects due to medication, viii) admission to hospital, and ix) duration of hospital stay. Search strategy: We searched the Cochrane Controlled Trials register, Acute Respiratory infectious Disease Group Specialised Trials register, MEDLINE, LILACS, scanned reference lists of identified trials, contacted authors of identified trials and the relevant pharmaceutical companies. Data collection and analysis: Studies were selected, quality assessed and data extracted by two reviewers independently. Results: Nine studies satisfied the inclusion criteria but four had insufficient data for further meta-analysis of our pre-specified outcomes. Studies were old and poorly reported. The largest study had a total sample size of 49 and the smallest study nine. All studies were performed in industrialised settings. Eligible studies assessed diphenhyramine, pertussis immunoglobulin, dexamethasone and salbutamol. No statistically significant benefit was found for any of the interventions. Diphenhydramine was associated with a mean increase of 1.90 coughing spells per 24 hours [95%Cl - 4.66; 8.46] and pertussis immunoglobulin a mean decrease in hospital stay of 0.70 days [95% Cl -3.79; 2.39]. and a mean reduction of 3.10 whoops per 24 hours [95% CI - 6.22; 0.02]. Dexamethasone resulted in a mean decrease in hospital stay of 3.45 days [95% Cl - 15.34; 8.44] and salbutamol in a weighted mean decrease in coughing paroxysms of 0.95 per 24 hours [95% Cl - 6.21; 4.31]. Reviewers' conclusion: Although assessments have been performed on a whole range of interventions, including diphenhyramine, pertussis immunoglobulin, dexamethasone and salbutamol, insufficient evidence exists to draw conclusions about the effects of any of them.