Blog | Monday, June 11, 2012

QD: News Every Day--One in ten prescriptions are off-label, despite lack of evidence

More than 10% of prescriptions are for off-label indications, and 80% of those uses have little evidence supporting them, a Canadian study found.

The highest proportion of off-label prescribing occurred with central nervous system drugs (26.3%), anti-infective agents (17.1%), and ear-nose-throat medications (15.2%), according to a report in the Archives of Internal Medicine.

Among central nervous system drugs, the highest proportions of off-label use were for anticonvulsants (66.6%), antipsychotics (43.8%), and antidepressants (33.4%). The lowest off-label prescribing was for formulary-restricted drugs (2.9%) and blood and coagulation drugs (1.7%).

More specifically, nocturnal leg pain and benign positional vertigo were treated 100% of the time off-label. Neurogenic pain was treated off-label 99.5% of the time, often with gabapentin, amitriptyline and topiramate.

Other off-label prescribing rates included included fibromyalgia (67.0%), arrhythmia (60.2%), generalized anxiety disorder (46.5%) and insomnia (43.6%).

Drugs with the highest off-label use included quinine sulfate (99.5% of prescriptions) followed by gabapentin (99.2%), clonazepam (96.2%), amitriptyline hydrochloride (93.7%), trazodone hydrochloride (92.6%), and betahistine dihydrochloride (91.5%). Researchers noted that among the top 15 drugs most frequently used off-label, eight did not meet study criteria for having strong scientific evidence.

Scientific support for an off-label use was lowest for antineoplastic (0%) and ear-nose-throat (1.6%) drug classes and highest for cardiovascular (58.8%) and dermatologic (65.9%) drug classes.

Specifically, the lowest prevalence of off-label use was for diabetic drugs (0%-2%), lipid-lowering agents (0%-0.5%), and migraine medications (0%).

Physicians who ranked themselves as evidence-based, as assessed by the Evidence-Practicality-Conformity questionnaire, were less likely to prescribe off-label. A 5-point increase in the physicians' score decreased off-label prescribing by 7% (AOR, 0.93; 95% CI, 0.88 to 0.99).

Researchers drew their conclusions after applying data from Quebec, Canada, where documentation of treatment indication is mandatory. 113 primary care physicians wrote more than a quarter-million prescriptions for more than 50,000 patients from 2005 through 2009. Each drug indication was classified as on-label or off-label according to the Health Canada drug database.