Anaesthetists call for cough medicine restrictions

By Madeleine Morris

Anaesthetists are calling for more than 50 over-the-counter cough medicines to be restricted because of fears a commonly used cough-suppressant is causing a severe allergic reaction in a small number of people during surgery.

During the past three years in Australia, six people have died after having a severe allergic reaction to muscle relaxants routinely used in general anaesthetics.

Many more people suffered anaphylaxis but survived thanks to the quick response of medical teams.

Australian and New Zealand Anaesthetic Allergy Group chairman Michael Rose said the group believed pholcodine, the active ingredient in a number of cough syrups and lozenges, was a factor in people developing the anaphylactic reaction.

“We would like to see pholcodine made prescription only,” Dr Rose said.

He said research suggested a small number of people who use pholcodine form an antibody which can react with some muscle relaxants used in anaesthetics, potentially putting them at great risk when undergoing surgery.

The main evidence of a potential link between pholcodine and severe allergy to muscle relaxants comes from Scandinavia.

A decade ago Norway had 10 times as many instances of anaphylaxis during surgery as neighbouring Sweden.

The populations were very similar except in one area – Norway had high pholcodine use and in Sweden it was banned.

“In 2007 the drug company that was manufacturing pholcodine in Norway voluntarily removed it from the market,” Dr Rose said.

“And since that time the rate of allergic reactions to muscle relaxants has fallen and the rate of antibodies in the population has also fallen.”

Based on that research France, one of the few countries in the world with high pholcodine use other than Australia, made it prescription only.

Dr Rose admitted the evidence of a link between pholcodine and anaphylaxis was not conclusive, but said due to the rarity of the allergy, proving without doubt a link was not practically possible, as millions of people would need to be tested.

“I don’t think we should sit around and wait for conclusive evidence … If we sit around and wait for that time, many people may have reactions needlessly,” he said.

He said the group would gather its own data on anaphylaxis during surgery with the aim of going back to the TGA next year to again make the case for restricting pholcodine.

Links between cough medicine and reactions ‘inconsistent’

But Australia’s drugs regulator, the Therapeutic Goods Administration, rejected the anaesthetic allergy group’s call to restrict pholcodine, after performing its own analysis.

“The data … does not seem to support any association,” a TGA spokeswoman said.

The TGA points to the European Medicines Agency’s (EMA) recent analysis of pholcodine, including the Norway-Sweden case, which found potential links to be “inconsistent” and “circumstantial”.

The group said it would continue to monitor the safety of pholcodine.

The Australian Self-Medication Industry (ASMI), the peak body for over-the-counter drug manufacturers, also emphasised the review’s decision that based on current evidence, pholcodine was safe.

“The EMA review concluded that … benefits outweighed the risks, and that it was worthwhile keeping the product on the market,” ASMI’s director of regulatory and scientific affairs Steve Scarff said.

However, there is not a lot of current evidence into pholcodine’s efficacy.

It was first approved in the 1950s when testing standards were less rigorous, while in the past 30 years there was only one small study into its effectiveness, which did not include a placebo control group.

A large-scale review into pholcodine and a range of other cough suppressants conducted last year by the respected Cochrane Group found “no good evidence” for or against their use in suppressing acute cough.

Specialist pain physician at Barwon Health in Geelong and a commentator on TGA affairs Michael Vagg said the over-the-counter cold medicines were big business.

“So the case for us to continue to use pholcodine is not compelling in any way in a medical sense, but it’s compelling in a commercial sense because there are 50-odd products on the shelf every day that use pholcodine and it’s about a half-a-billion dollar a year business, the cold and flu industry,” Dr Vagg said.

“I think it’s a poor decision by the TGA,” he said.