All medications have side effects, it’s no secret. However, some are more dangerous than others. A recent study conducted at the University of Washington reveals that one of the most common depression medications and some antihistamines are linked to an irreversible risk of dementia.
The study followed a total of 3,434 people over the age of 65 for seven years. Researchers carefully recorded the medications they took and the lifestyle they led. After that time, 797 people had developed dementia.
At this point, it was clear that some medications seemed to make a difference. However, it was curious that one-fifth of the medications these people took did not require a prescription, suggesting that even some over-the-counter medications can have very dangerous long-term side effects .
The medications that were associated with the onset of dementia were:
1. Doxepin (Sinequan) – This is a tricyclic antidepressant used to treat depression or anxiety and affects brain chemistry.
2. Chlorphenamine – This is an antihistamine that is recommended for allergy symptoms or when you have the flu or a cold, to treat symptoms such as sneezing, runny nose, itchy eyes, nose and throat, rhinitis and rhinorrhea.
3. Diphenhydramine (Denadryl) – This is another antihistamine that, despite being one of the oldest, is also one of the most prescribed and is even the drug of choice for treating allergies. It also has a sedative and hypnotic effect, so it is sometimes used to help people sleep.
4. Oxybutynin (Ditropan) – This is an anticholinergic agent used to reduce muscle spasms in the bladder and urinary tract. It is indicated for overactive bladder or for people who feel the need to urinate frequently.
By analysing the doses taken by the people who participated in the study, the researchers concluded that daily use of these drugs for three years can irreversibly increase the risk of suffering from dementia, which means that even by stopping taking them our body cannot get rid of their effect because the damage has already been done.
The risk doses would be:
– 10 mg/day of Doxepin
– 4 mg/day of Chlorphenamine or Diphenhydramine
– 5 mg/day of Oxybutynin
Why are these drugs dangerous in the long term?
The problem seems to lie in its anticholinergic effects. These drugs reduce or cancel out the effects of acetylcholine in the central and peripheral nervous system. Acetylcholine is a neurotransmitter that mediates synaptic activity, allowing one neuron to communicate with another and transmit nerve impulses.
This neurotransmitter is responsible for stimulating muscles, including those of the gastrointestinal system. It is also found in sensory neurons and the autonomic nervous system, and is involved in REM sleep.
Other research has found a link between acetylcholine and Alzheimer’s disease. In fact, brain scans of people with Alzheimer’s disease have shown a loss of approximately 90% of acetylcholine.
Waht to do?
First of all, it is important not to be alarmist. These drugs are safe as long as they are not taken frequently but only at specific stages of life. In addition, the effect they can have on a young nervous system is not the same as that which they can have on older adults.
However, this study puts its finger on the sore spot and warns us that even over-the-counter medications can have serious long-term effects.
References:
Gray, S. L. et. Al. (2015) Cumulative Use of Strong Anticholinergics and Incident Dementia a Prospective Cohort Study. JAMA Intern Med; 175(3): 401-407.
Small, D. & L. Fodero (2002) Cholinergic regulation of synaptic plasticity as a therapeutic target in Alzheimer’s disease. Journal of Alzheimer’s Disease; 4: 349-355.
