Alzheimer’s patients may be combining drugs with canceling effects

People taking Alzheimer’s disease medications known as cholinesterase inhibitors are also commonly given medications that oppose their effects, according to a new study in the Journal of the American Geriatrics Society.

The interfering medications are those with anticholinergic properties—often found in drugs used to treat gastrointestinal disorders, allergies, incontinence, depression and Parkinson’s disease.

“There’s concern that if someone is taking both types of drugs—cholinesterase inhibitors and anticholinergic medications—they will antagonize each other, and neither will work,” said study leader Denise Boudreau, PhD, RPh, an associate scientific investigator at Seattle-based Group Health Research Institute.

Cholinesterase inhibitors work by inhibiting the breakdown of acetylcholine, which sends signals in the nervous system. By contrast, anticholinergics block the action of acetylcholine. Since the two types of drugs have opposite effects, it makes sense not to give both kinds of drugs to an individual person, the researchers are arguing.

Boudreau and colleagues conducted a retrospective cohort study of 5,625 people aged 50 or older who received a new prescription for cholinesterase inhibitors between 2000 and 2007. The researchers used electronic pharmacy records of Group Health Cooperative and Kaiser Permanente Colorado—nonprofit healthcare systems that together serve more than a million people. The research team found patients who also had a prescription for anticholinergics from the year before their cholinesterase prescription until the analysis ended in December 2008, or the patient left the healthcare system or died.

Among the findings:

● Of the cholinesterase inhibitor users, 37 percent were also taking at least one anticholinergic drug, and more than 11 percent took two or more. This was similar to other studies of Medicare beneficiaries, researchers said.

● For those using both medication types, dual use generally lasted three to four months, but 25 percent used both classes of drugs for more than a year.

● Anticholinergics were already being used in 23 percent of people receiving a new cholinesterase inhibitor prescription, and 77 percent continued, even after starting the cholinesterase inhibitor.

● Subjects using both medication types were not more likely to enter a nursing home or to die than those taking only cholinesterase inhibitors.

“It’s reassuring that we did not observe an association between simultaneous use of the two types of drugs and increased risk of death or nursing home placement,” Boudreau said. “But concomitant use of these drugs is, at the very least, not optimal clinical practice.”

The study was the first to use state death records and insurance claims for nursing home care to look for effects of taking both drug types, according to Group Health Research Institute.