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Archive for August 26th, 2009

Off-Label Use of Prescription Drugs

A recent survey of 599 primary care physicians and 600 psychiatrists found that:

The adjusted response rate was 47%, respondents were similar to non-respondents, and physicians commonly prescribed the drugs examined. The average respondent accurately identified the FDA-approval status of just over half of the drug-indication pairs queried (mean 55%; median 57%). Accuracy increased modestly (mean 60%, median 63%) when limited to drugs the respondent reported having prescribed during the previous 12 months. There was a strong association between physicians’ belief that an indication was FDA-approved and greater evidence supporting efficacy for that use (Spearman’s 0.74, p < 0.001). However, 41% of physicians believed at least one drug-indication pair with uncertain or no supporting evidence (e.g., quetiapine [Seroquel®] for dementia with agitation) was FDA approved.

These results are interesting, but deserve to be dissected a bit further. Taken at face value they indicate that physicians need better education regarding the FDA indications and (more importantly) the evidence-base for commonly prescribed drugs. This is an uncontroversial recommendation, and I personally strongly advocate more thorough physician continuing medical education.

Of course, at SBM we have to also dissect the weaknesses of any study we examine. This was a voluntary survey with a 47% response rate, which opens the door for significant responder bias. The survey does not broadly represent different specialties and therefore its relevance beyond primary care and psychiatry is uncertain. The details of the study may also have greatly influenced the outcome.

For example, one of the drug-indication pairs was gabapentin for diabetic peripheral neuropathy. Gabapentin is not specifically indicated for diabetic neuropathy, but it is indicated for post-herpetic neuralgia. Both conditions are forms of neuropathic pain, and it is highly scientifically plausible for a treatment of one condition to also be effective for the other. In fact, there is strong evidence that gabapentin is effective for diabetic neuropathy, and it is commonly prescribed for this condition (in fact insurance companies often require that it is first line treatment as it is now available generically and is therefore less expensive than newer drugs that are indicated specifically for diabetic neuropathy). In other words, this was one of the easiest mistakes to make.

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Posted in: Pharmaceuticals

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