Off-label drug use reaches 11%

Doctors often prescribe a drug for conditions other than what it was originally meant to treat, a Quebec study finds.

Prescription drugs are given off label for purposes or groups of patients that regulatory agencies like Health Canada haven’t officially approved, such as prescribing medication for anxiety to someone with insomnia.

The researchers worry that off-label prescribing can lead to adverse events. A classic example was the appetite suppressor fen-phen, which could cause serious cardiac valve damage when prescribed off label for weight loss.

"The prevalence of off-label use was 11 per cent," Dr. Tewodros Eguale of McGill University and his co-authors concluded in Monday's online issue of the Archives of Internal Medicine. "Of off-label prescriptions, 79 per cent lacked strong scientific evidence."

To come to that conclusion, the researchers checked into off-label drug use by analyzing electronic health records for 113 primary care physicians treating 50,823 patients in Quebec cities between 2005 and 2009.

To use the electronic records, doctors had to say why they were prescribing a medication, which allowed the researchers to link prescribed drugs to conditions and the characteristics of the patients.

The types of drugs that were prescribed off-label most often included:

• Central nervous system drugs such as neurogenic pain medications like gabapentin, the antidepressant amitripyline and anti-epilepsy medication topiramate.
• Anti-infective agents that kill germs or stop their spread. 
• Ear-nose-throat-medications.

The highest proportion of off-label prescriptions were for central nervous system drugs. 

The researchers pointed to a doctor's lack of knowledge about drugs and the scarcity of approved or effective drugs as possible reasons driving off-label prescribing.

Women received more off-label prescriptions than men because they were more likely to be treated for problems where the practice is common, such as anxiety, nocturnal leg pain and insomnia.

Doctors try 'what seems reasonable'

Older drugs were also prescribed off label more. Since those medications were on the market for longer, there were more opportunities for doctors to discover new uses, the study's authors said.

Also, when a drug goes off-patent, the manufacturer is unlikely to apply to regulators for a new purpose.

It's important to consider the strength of evidence to judge if inappropriate prescribing is occurring, said Dr. Patrick O'Malley of the Uniformed Services University of the Health Sciences in Bethesda, Md. in a journal editorial published with the study.

"The reality is that when faced with difficult symptom syndromes that are unresponsive to available treatments, clinicians resort to trying what seems reasonable in order to alleviate suffering," O'Malley said.

He called for better tracking of medications by diagnosis and appropriateness, instead of making decisions based on clinical trial results or guidelines.

The study was funded by the Canadian Institutes of Health Research.