Blog | Tuesday, February 7, 2012

QD: News Every Day--Doctors stick with a few favorite drugs, but still willing to vary

Most doctors stick with a few favorite prescriptions, but are willing to vary their habits to meet their patients' conditions and comply with the formularies of patients' insurers, researchers found.

While a single drug accounts for 40% to 70% percent of most doctors' new prescriptions in a drug class, comorbidities and the multitude of health insurers have prompted physicians to adopt broader prescribing habits.

The study examined the 10 most widely used classes of therapeutic drugs in the U.S. from 2005 to 2007, based on medical and pharmaceutical claims from 29 large U.S. employers. Starting in 2005, all pharmacy claims identified prescribers by a masked Drug Enforcement Administration number, allowing researchers to track prescriptions from the same physician to different patients in different insurance plans. Results appeared in The American Journal of Managed Care.

When examining brand versus generic drugs, the authors noted that nearly half of the physicians prescribing angiotensin-converting enzyme (ACE) inhibitors and nonsteroidal anti-inflammatory drugs prescribed only generics. Also, 90% of physicians prescribing opiates did so, while less than 1% of physicians prescribed only generic statins or proton pump inhibitors.

In drug classes where there are more generics, naturally more generics were prescribed. In the five drug classes where the generic share is closest to one-half (38%-61%), between 80% and 89% of physicians prescribed both brand and generic medications as initial prescriptions, the authors wrote.

Only a small percentage of physicians prescribed a single drug in a class, ranging from less than 1% for selective serotonin reuptake inhibitors to 15% for ACE inhibitors. In eight of the 10 classes, the median physician prescribed three or four different drugs. "This reflected broad prescribing patterns given that the median number of initial prescriptions per physician in our sample ranged from six to eight in the 10 classes," the authors wrote.

For selective serotonin reuptake inhibitors, 45% of physicians prescribed five or more different drugs in the class. Among those who prescribed as many as eight to 12 different drugs to start, 72% prescribed five or more different drugs and less than 2% prescribed only one or two drugs.

Researchers also reported that physicians prescribing one or two drugs were more likely to prescribe the leading drug in a class, "which in most cases was the most heavily promoted drug." Among physicians prescribing just one statin, 80% prescribed the market leader and most heavily promoted drug.

Proton pump inhibitors had only one generic drug during the study. Prescribers with narrow prescribing patterns in this class were split between high prescribers of the brand drug and high prescribers of the generic. "Perhaps due to the degree of similarity between these 2 products (esomeprazole, the top brand, and generic omeprazole), physicians generally prescribed one drug or the other."

In contrast, the leading brand and generic antihistamines have different active ingredients and most physicians prescribed both, the authors noted. Physicians with broader prescribing patterns leaned toward generic and/or less common brands.

There is a widespread perception that physicians prescribe a narrow range of drugs within a therapeutic class because of prior experience with the drug, and because of pharmaceutical marketing and drug detailing, the authors said.

"Despite these perceptions, we find surprisingly broad prescribing across 10 prominent classes," the authors concluded. "Physicians whose patients were covered by a wider array of health plans and formularies tended to have broader prescribing habits, as did physicians who treated patients with varying comorbidities. This suggests that attempts to match specific drugs to a patient's health condition and formulary design were important factors in deviating from their favorite drug. While physicians whose prescribing habits were narrow were more likely to prescribe highly advertised drugs, few doctors prescribed these drugs exclusively."