Last week's column discussed a class of drugs that cause memory loss. These drugs, called anticholinergics, block the actions of an important nerve transmitter called acetylcholine, a brain chemical that is crucial to memory circuits. Acetylcholine is necessary for good memory. Anticholinergic drugs work by blocking the binding of acetylcholine to its receptor in nerve cells. Anticholinergic drugs cover a broad range of medication. They include antihistamines, tricyclic antidepressants, drugs for urinary incontinence, bronchodilators, antiemetics, antispasmodics, antiarrhythmic drugs like Digoxin, high blood pressure drugs like Procardia, analgesics like codeine, anti Parkinson drugs, corticosteroids like prednisone, skeletal muscle relaxants, ulcer drugs, diuretics like furosemide (Lasix), anti reflux drugs like ranitidine (Zantac), warfarin, psychotropic drugs, anti-anxiolytics (anti anxiety drugs), and the benzodiazepine family of depressants used to produce sedation, induce sleep, relieve anxiety and muscle spasms, and to prevent seizures.
Three recent corroborating studies
Older adults who take anticholinergic drugs - including common medications for urinary incontinence, acid reflux, Parkinson's disease, high blood pressure, and allergies - are more likely to be dependent in one or more activities of daily living and to walk more slowly than those who don't take the medicines according to a study presented at the American Geriatrics Society annual meeting in Washington, D.C. on May 3, 2008.
"These results were true even in older adults who have normal memory and thinking abilities," said Dr. Kaycee Sink, who led the study. "For older adults taking a moderately anticholinergic medication, or two or more mildly anticholinergic medications, their function was similar to that of someone three to four years older So someone who is 75 in our study and taking at least one moderately anticholinergic medication is at a similar functional level to a 78 to 79-year-old."
Common anticholinergic medicines cited in the study included the blood pressure medication nifedipine (Adalat or Procardia), the stomach antacid ranitidine (Zantac), and the incontinence medication tolterodine (Detrol).
In a separate study published in the April 2008 issue of the Journal of the American Geriatrics Society, Sink was again the lead author. This study found that older nursing home residents who took medications for dementia (cholinesterase inhibitors) and anticholinergic medications for incontinence at the same time had a 50 percent faster decline in function than those who were being treated only for dementia. "Over a year's time, the decline would represent a resident going from requiring only limited assistance in an activity to being completely dependent, or from requiring only supervision to requiring extensive assistance in an activity," said study chief Dr. Kaycee M. Sink These two drug classes "cancel each other out and should not be used in combination."
The third study
About 10 percent of the residents were taking either oxybutynin (Ditropan) or tolterodine (Detrol), the two most often prescribed drugs for urinary incontinence.
In a third study led by Dr Jack Tsao, an associate professor of neurology at Uniformed Services University in Bethesda, Md., and reported at the American Academy of Neurology 60th Annual Meeting, it was found that elderly people who took anticholinergic drugs had a 50 percent greater rate of memory decline than people in a long-term study who did not take the drugs. The study arose from experience with a patient seen by study coauthor Kenneth Heilman, MD. The woman had come in with memory complaints and hallucinations. However, Dr. Tsao said, "Her cognitive testing was essentially normal except for the memory issues, so she didn't fit the diagnosis of Alzheimer's-type dementia."
This patient had just begun treatment with tolterodine (Detrol), a drug to treat overactive bladder problems. But Dr. Heilman had seen a previous case of another woman who had memory complaints that reversed after stopping her bladder medicine. They did the same for this woman, and her memory improved. This result prompted the authors to ask the question of whether anticholinergic medicines can impair thinking in normal individuals. They concluded that initiation of medications with anticholinergic activity is associated with a more rapid decline in cognitive performance. And the more anticholinergic drugs people had in their systems, the worse their physical function, based on reports from people in the study and on independent measures of their performance. They found that medications for bladder problems and Parkinson's appeared to have the worst effect on memory. People on those drugs suffered impaired memory about three times as great as those not taking the drugs.
Next week's column will be on a happier subject: the positive effects of exercise on the prevention of Alzheimer's disease.
Mary Lou Williams, M. Ed., is a writer and lecturer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.