Adults in the US are using more and more prescription drugs, according to a study published in JAMA.

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Use of most prescription drugs has increased in the US, reveals a new study.

Prescription drugs represent a major expenditure in the US, but there has been a lack of consolidated information at the population level, as data usually comes from pharmacy databases or expenditure records.

Elizabeth D. Kantor, PhD, formerly of the Harvard T.H. Chan School of Public Health in Boston, MA, and colleagues used nationwide data from the National Health and Nutrition Examination Survey (NHANES) to evaluate trends in prescription drug use from 1999-2012.

The team surveyed 37,959 American adults, aged 20 years and over. Seven NHANES cycles were included (1999-2000 to 2011-12); the sample size per cycle ranged from 4,861-6,212. Within each cycle, use of prescription drugs in the prior 30 days was assessed overall and by drug class.

Prescription drug use increased from 51% of the population in 1999-2000 to 59% in 2011-2012. Among the 18 drug classes used by more than 2.5% 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 aged 40-64 and those aged 65 and above, but not among people aged 20-39 years.

Polypharmacy, the use of five or more prescription drugs, rose from 8-15%, increasing significantly among all three groups, from 0.7-3.1% for those aged 20-39; from 10-15% among the 40-64s; and from 24-39% in those aged 65 plus.

Use of medications for hypertension rose from 20-27%, as did medications to treat hyperlipidemia, from 7-17%, largely driven by use of statins. The most commonly used individual drug in 2011-2012 was simvastatin, used by 7.9% of the population, up from 2% in 1999-2000. Use of antidiabetic agents increased from 4.6-8.2%.

Antidepressants and narcotic analgesics use rose in the earlier time periods but stabilized after 2005. Antidepressant use increased overall from 7-13%, and narcotic analgesics from 3.8-5.7%.

These changes may represent shifting attitudes to depression and heightened awareness of prescription opioid drug misuse or abuse. The potential for abuse may also lead to underreporting of these drugs, possibly skewing the figures in the later years.

The use of sex hormones by women dropped from 19-11%, reflecting a decline in the use of noncontraceptive hormones for menopausal therapy, from 12-4%.

Overall, prescription analgesic use remained stable at 11%, although trends differed by type. Antibiotic use was down by 1.4%.

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.

The authors write:

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 emphasize the need to update assessments of prescription drug use, as the evolution reflects the changing health needs of the population, advances in treatment, new clinical guidelines, the entrance or exit of drugs from the market, and shifts in policies regarding drug marketing and promotion.

They call for patterns of prescription drug use to be documented, to inform clinical practice and research, and to identify population subgroups at risk of underuse, misuse and polypharmacy.

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