Between 1999-2012, overall prescription drug use increased among U.S. adults, with this increase seen for the majority of but not all drug classes, according to a study in the November 3 issue of JAMA.

Use of prescription drugs represents a major expenditure in the United States, and research suggests that use of prescription drugs is increasing. Yet much of the information about prescription use is derived from pharmacy databases or expenditure data, neither of which directly captures use at the population level. It is important to document patterns of prescription drug use to inform both clinical practice and research, according to background information in the article.

Elizabeth D. Kantor, Ph.D., M.P.H., formerly of the Harvard T.H. Chan School of Public Health, Boston, and colleagues evaluated trends in prescription drug use using nationally representative data from the National Health and Nutrition Examination Survey (NHANES). Participants included 37,959 U.S. adults, age 20 years and older. Seven NHANES cycles were included (1999-2000 to 2011-2012), and the sample size per cycle ranged from 4,861 to 6,212. Within each NHANES cycle, use of prescription drugs in the prior 30 days was assessed overall and by drug class.

The researchers found that the prevalence of prescription drug use increased from 51 percent in 1999-2000 to 59 percent in 2011-2012, while the prevalence of polypharmacy (use of five or more prescription drugs) increased from 8 percent to 15 percent. Use of medications for hypertension increased (20 percent-27 percent), as did medications to treat hyperlipidemia, a trend largely driven by statins (7 percent-17 percent). Use of antidepressants also increased (7 percent-13 percent). Among the 18 drug classes used by more than 2.5 percent of the population at any point over the study period, the prevalence of use increased in 11 drug classes.

Prescription drug use increased significantly among persons 40 to 64 years of age and also among those 65 years and older, but not among adults 20 to 39 years old.

The most commonly used individual drug in 2011-2012 was simvastatin (7.9 percent), increasing from 2.0 percent in 1999-2000. The remaining top 10 drugs included lisinopril, levothyroxine, metoprolol, metformin, hydrochlorothiazide, omeprazole, amlodipine, atorvastatin, and albuterol; all of the top 10 most commonly used drugs increased over the study period except atorvastatin.

"Eight of the 10 most commonly used drugs in 2011-2012 are used to treat components of the cardiometabolic syndrome, including hypertension, diabetes, and dyslipidemia. Another is a proton-pump inhibitor used for gastroesophageal reflux, a condition more prevalent among individuals who are overweight or obese. Thus, the increase in use of some agents may reflect the growing need for treatment of complications associated with the increase in overweight and obesity," the authors write.