Over-the-Counter Antitussives for Acute Cough

A Cochrane review [Abstract] 1 included 29 studies (19 in adults, 10 in children) with a total of 4 835 people (3 799 adults and 1 036 children). Twenty-one studies reported adverse effects. There was a wide range across studies, with higher numbers of adverse effects in participants taking preparations containing antihistamines and dextromethorphan.

Results of studies in adults:

• Six studies compared antitussives with placebo and had variable results. Three studies compared the expectorant, guaifenesin with placebo, one indicated significant benefit whereas the other two did not. One study found that a mucolytic reduced cough frequency and symptom scores. Two studies examined antihistamine-decongestant combinations and found conflicting results. Four studies compared other combinations of drugs with placebo and indicated some benefit in reducing cough symptoms. Three studies found antihistamines were no more effective than placebo in relieving cough symptoms.

Results of studies in children:

• Antitussives (3 studies), antihistamines (3 studies), antihistamine decongestants (2 studies) and antitussive/bronchodilator combinations (1 study) were no more effective than placebo. No studies using expectorants met our inclusion criteria. The results of one study favoured active treatment with mucolytics over placebo. One study tested two paediatric cough syrups and both preparations showed a 'satisfactory response' in 46% and 56% of children compared to 21% of children in the placebo group. One study indicated that three types of honey were more effective than placebo over a three-day period.

Another Cochrane review [Abstract] 1 focusing on OTC cough medications as an adjunct to antibiotics in children and adults with pneumonia included 4 studies with a total of 224 subjects (exclusively children in one study, adolescents or adults in 3 studies). Only 2 studies comparing mucolytics with placebo had extractable pneumonia-specific data. They demonstrated no significant difference for the primary outcome of 'not cured or not improved' for mucolytics. A secondary outcome of 'not cured' was reduced (OR 0.36, 95% CI 0.16 to 0.77; NNT 5, 95% CI 3 to 16 for children and OR 0.32, 95% CI 0.13 to 0.75; NNT 5, 95% CI 3 to 19 for adults). In a post hoc analysis combining data for children and adults, again there was no difference in the primary outcome of 'not cured or not improved' (OR 0.85, 95% CI 0.40 to 1.80) although mucolytics reduced the secondary outcome 'not cured' (OR 0.33, 95% CI 0.19 to 0.60; NNT 4, 95% CI 3 to 8).

Comment: The quality of evidence is downgraded by limitations in study quality (inadequate or unclear randomization method and allocation concealment), by inconsistency (variability in results across studies, heterogeneity in interventions and outcomes), by indirectness (differences in studied patients), and by imprecise results (limited study size for each comparison).

References

• Smith SM, Schroeder K, Fahey T. Over-the-counter (OTC) medications for acute cough in children and adults in community settings. Cochrane Database Syst Rev 2014;(11):CD001831. [PubMed].
• Chang CC, Cheng AC, Chang AB. Over-the-counter (OTC) medications to reduce cough as an adjunct to antibiotics for acute pneumonia in children and adults. Cochrane Database Syst Rev 2014;(3):CD006088. [PubMed].