Symptomatic treatment of the cough in whooping cough.

BACKGROUND: The worldwide incidence of whooping cough (pertussis) has been estimated at 48.5 million cases and nearly 295,000 deaths per year. In low-income countries, the case-fatality rate among infants may be as high as 4%. Much of the morbidity of whooping cough in children and adults is due to the effects of the paroxysmal cough. Cough treatments proposed include corticosteroids, beta 2-adrenergic agonists, pertussis-specific immunoglobulin, antihistamines and possibly leukotriene receptor antagonists (LTRAs).

OBJECTIVES: To assess the effectiveness and safety of interventions to reduce the severity of paroxysmal cough in whooping cough in children and adults.

SEARCH METHODS: We updated searches of the Cochrane Central Register of Controlled Trials (CENTRAL Issue 2, 2012), which contains the Cochrane Acute Respiratory Infections Group's Specialised Register, the Database of Abstracts of Reviews of Effects (DARE Issue 2, 2012) accessed from The Cochrane Library, MEDLINE (1950 to January 2012), EMBASE (1980 to January 2012), AMED (1985 to January 2012), CINAHL (1980 to January 2012) and LILACS (January 2012). We searched Current Controlled Trials to identify trials in progress.

SELECTION CRITERIA: We selected randomised controlled trials (RCTs) and quasi-RCTs of any intervention (excluding antibiotics and vaccines) to suppress the cough in whooping cough.

DATA COLLECTION AND ANALYSIS: Two review authors (SB, MT) independently selected trials, extracted data and assessed the quality of each trial for this review in 2009. Two review authors (SB, KW) independently reviewed additional studies identified by the updated search in 2012. The primary outcome was frequency of paroxysms of coughing. Secondary outcomes were frequency of vomiting, frequency of whoop, frequency of cyanosis (turning blue), development of serious complications, mortality from any cause, side effects due to medication, admission to hospital and duration of hospital stay. 

MAIN RESULTS: Ten trials were included of varying sample sizes (N = 9 to 135) from high-income countries. Study quality was generally poor. Included studies did not show a statistically significant benefit for any of the interventions. Only six trials including a total of 196 participants reported data in sufficient detail for analysis. Diphenhydramine did not change coughing episodes; the mean difference (MD) of coughing spells per 24 hours was 1.9; 95% confidence interval (CI) - 4.7 to 8.5. One study on pertussis immunoglobulin reported a possible mean reduction of -3.1 whoops per 24 hours (95% CI -6.2 to 0.02) but no change in hospital stay (MD -0.7 days; 95% CI -3.8 to 2.4). Dexamethasone did not show a clear decrease in length of hospital stay (MD -3.5 days; 95% CI -15.3 to 8.4) and salbutamol showed no change in coughing paroxysms per 24 hours (MD -0.2; 95% CI -4.1 to 3.7). Only one trial comparing pertussis immunoglobulin versus placebo reported data on adverse events: 4.3% in the treatment group (rash) versus 5.3% in the placebo group (loose stools, pain and swelling at injection site).

AUTHORS' CONCLUSIONS: There is insufficient evidence to draw conclusions about the effectiveness of interventions for the cough in whooping cough.