AGS: Improper Antihistamine Use Common in Older Adults

SEATTLE, May 8 -- Only 16% of sedating antihistamine use among older patients at VA medical centers was for an appropriate indication, researchers reported here.

An "alarmingly high" 44% of the potentially inappropriate antihistamine uses were as sleep aids, noted Monica Horton, M.D., of the South Texas Veterans Healthcare System and the University of Texas Health Science Center at San Antonio, and colleagues.

Antihistamines are known to increase the risk of falls and confusion among older patients, who are "more susceptible to adverse events of drugs with anticholinergic properties," Dr. Horton said at the American Geriatrics Society meeting.

"It's over-the-counter, it's cheap, it works," she said, "But I think [these physicians] are not considering the risk of falls and confusion."

In their study, the researchers further analyzed a database established by a prior study of potentially inappropriate prescribing in veterans age 65 and older. The prior study used ICD-9 codes from the National VA inpatient, outpatient, and pharmacy databases for 1999.

Inappropriate use was defined by the so-called Zhan criteria -- the conclusions of an Agency for Healthcare Research and Quality consensus panel -- stating that allergy and urticaria should be the only indications for antihistamines in older adults.

The researchers classified each prescribed use as being "definite or probable" for insomnia, for allergy and rash, for psychiatric use, or for an unclear or unusual indication but unlikely to be for sleep.

Their findings:

• 16% of the 150,000 coded antihistamine directions for use were clearly for an appropriate indication.
• 44% of inappropriate uses were "definite or probable" for sleep indications.
• 37% of inappropriate uses were for vague indications, but unlikely to be for sleep.
• 2% of inappropriate uses were for psychiatric indications.
• 0.5% of inappropriate uses were for missing indications.

Rather than antihistamines, physicians should pursue other safer and less risky therapies for insomnia, Dr. Horton said. She advocated nonpharmacologic measures but said trazodone (Desyrel) could be an inexpensive alternative as well.

Further research is needed to determine if the potentially inappropriate antihistamine use they discovered has resulted in worse outcomes for patients, she said.

"A fall is a significant event," Dr. Horton said. "The elderly folks could lose their independence and go to a nursing home because of a fall."