By John Griffiths
LONDON (Reuters Health) – There is little evidence that over-the-counter (OTC) cough medicines are effective, British researchers said on Friday.
Drs. Knut Schroeder and Tom Fahey, from the University of Bristol, reviewed 15 clinical trials, involving 2166 patients, that compared OTC cough medicines with placebo.
In nine of the trials, treatment with OTC medicine "was no better than placebo," the Bristol researchers note. "Even when trials had significant results, the effect sizes were small and of doubtful clinical relevance." Their findings appear in the February 9th issue of the British Medical Journal.
British doctors are encouraged to recommend OTC medicines for acute coughs, and the UK's telephone-based health advice service, NHS Direct, also recommends simple cough medicines for dry coughs, the researchers note. "The advice given by NHS Direct to use over-the-counter cough medicines should be re-evaluated until more evidence becomes available on their effectiveness," Dr. Fahey told Reuters Health.
"To get results we can really trust, proper trials of over-the-counter cough medicines should be carried out independently," he said. "Previous studies have been poorly designed, and several of the studies have been supported by pharmaceutical companies. In other cases sources of funding were not made clear so there could have been conflicts of interest."
NHS Direct's National Clinical Advisor Jill Stringer said the service uses advice validated by experts and based on best available evidence. "This advice is under rigorous constant review to ensure it reflects current best practice," she said.
A spokeswoman for Boots the Chemist said all their OTC medicines are licensed by the Medicines Control Agency and comply with standards of safety, quality, and efficacy. "We know that our customers find our cough and cold remedies effective in soothing many of the symptoms such as high temperature and inability to sleep, and they aid the recovery process," she said.
Ultimately, it is up to patients to decide whether to take a cough medicine, Dr. Fahey concluded. "There is little evidence that they do any harm, but they may also not have any benefits. In fact, they probably act as a placebo."