The number of Americans taking the narcolepsy and shift work sleep disorder drug modafinil has increased almost 10-fold over the past decade, according to a new study.
What's more, the majority of those prescriptions were written for so-called off-label conditions, such as depression and multiple sclerosis, researchers found.
"I think modafinil is still a good medication in appropriate clinical circumstances, but… with modafinil as with many other medications, there's certainly a lot more off-label prescriptions, and patients and physicians have to be appropriately cautious in those circumstances," study author Dr. David Claman told Reuters Health.
Claman and colleagues from the University of California, San Francisco, used a nationally-representative sample of outpatient appointments to track modafinil prescriptions and related diagnoses between 2002 and 2009. During that time, the number of patients receiving the drug, marketed as Provigil and costing up to a few hundred dollars per month, increased from about 58,000 to 556,000.
Prescriptions rose the fastest - 15 times over - among patients who did not have one of the conditions for which modafinil is approved by the U.S. Food and Drug Administration (FDA). That type of prescribing is known as off-label.
Overall, 89 percent of all people who received modafinil during the study period were prescribed the drug off-label. Psychiatrists and neurologists were especially likely to prescribe the medication, according to findings published Monday in JAMA Internal Medicine.
Modafinil can cause side effects including headache, dizziness, drowsiness and stomach problems. It has also been tied to serious allergic reactions, such as in the liver.
Claman said that with any medicine, doctors have to weigh the drug's benefits with its potential harms.
"The nice thing about on-label use is at least it's a little better defined, what is the therapeutic benefit and what are the risks of side effects," he said.
With a less-studied, off-label condition, that's harder to figure out.
"Hopefully there's still a potential therapeutic benefit, but you're always trying to balance those things out, and that's the biggest issue with off-label medications."
The marketer of Provigil, Cephalon, agreed to a settlement in 2008 over charges claiming it promoted modafinil for off-label purposes.
Although doctors may prescribe medicines off-label, companies cannot market them outside of FDA-approved indications. Since the lawsuit, Cephalon has been acquired by the drug company Teva.
A representative from Teva said Provigil and a similar drug, armodafinil (marketed as Nuvigil) are indicated for adults with excessive sleepiness linked to shift work disorder, sleep apnea or narcolepsy.
"We do not recommend use of modafinil or armodafinil outside of the approved, FDA indications for these medicines," the representative told Reuters Health in an email.