NEW YORK (Reuters Health) - The more drugs an older patient is prescribed, the more likely the patient is to be taking an inappropriate medication, a new study shows.
Overall, 65 percent of the 196 study patients were on at least one drug that was unnecessary, a duplication of the effects of a drug they were already taking, or not recommended for older people, the researchers found.
"The steep rise in inappropriate medication use with increasing numbers of drugs provides a striking confirmation of the potential harms and need for extra vigilance" in patients prescribed multiple drugs, Dr. Michael Steinman of the San Francisco VA Medical Center and colleagues write.
Steinman and his team found that underprescribing was equally common; 64 percent of the patients were not prescribed a drug that they should have been taking.
Medication underuse and overuse were seen simultaneously in 42 percent of patients. Just 13 percent of the patients were not on an inappropriately prescribed medication or not on a drug that they should have been prescribed.
To better understand the relationship between "polypharmacy," or prescribing of multiple medications, and inappropriate prescribing, Steinman and his team evaluated VA Medical Center patients who were taking five or more drugs. All were outpatients, and their average age was about 75 years. The number of medications they took ranged from 5 to 17, with an average of about 8.
As mentioned, inappropriate drug use rose steadily with the number of different drugs a patient was prescribed. For example, those on five to six drugs averaged less than one inappropriate drug, while those taking seven to nine medications were on an average of one misprescribed drug. Patients taking 10 or more drugs averaged at least two inappropriate medications.
However, the researchers found, the frequency of underprescribing did not vary with the number of medications a patient was on. In addition, underuse was more common than overuse among patients taking fewer than eight drugs.
"Inappropriate medication use is most frequent in patients taking many medications, but underuse is also common and merits attention regardless of the total number of medications taken," the researchers conclude.
SOURCE: Journal of the American Geriatrics Society, October 2006.