What are the potential side effects of tricyclic antidepressants?

Tricyclic antidepressants and many other medications share a group of side effects that are caused by blocking the neurochemicals called acetylcholine (ACh) and histamine (HIST) in the brain. These symptoms are commonly referred to as anticholinergic effects. Early in the history of antidepressants, anticholinergic effects were thought to play an important part in reducing depression, but nowadays they are just considered a bother. Anticholinergic effects are strongest in Elavil, Anafranil, and Sinequan, and weaker in Norpramin, Tofranil, and Pamelor.

If you have a cold or allergy, anticholinergic effects will dry up your watery nose, open your congested sinuses, reduce your cough, and keep your eyes from being red and watery. They will probably reduce your seasickness symptoms as well. However, if you do not have a cold, allergy, or seasickness, you may not appreciate the dry mouth, dry eyes, decreased perspiration, weight gain, and increased tendency toward constipation that are caused by the antidepressants with the strongest anticholinergic effects. At high doses of Elavil or Anafranil, you might even have temporarily blurred vision or difficulty urinating. Elders may have an increased risk for falls and clouded thinking, especially if their antidepressant dose is too high.

Strongly anticholinergic antidepressants produce a sedative effect, which can make you feel relaxed or drowsy, depending on your viewpoint. Anticholinergic antidepressants make it easier to go to sleep at night, but depending on the antidepressant and the dose, you may feel drowsy during the day.

At high doses, strongly anticholinergic antidepressants produce a feeling of distance from current activities, sometimes likened to seeing the world through a thick pane of glass. If your conscious mind is currently filled with pain and misery, this distance can be a great relief. If negative thoughts are bombarding your mind and you cannot stop them, tricyclics can slow them down and keep your thoughts from going too far in painful or dangerous directions. However, if you are trying to write a book or do your taxes, this feeling of mild detachment is a nuisance. Many allergy and cold products such as Benadryl (diphenhydramine) produce similar effects.

Anticholinergic effects may increase your appetite. If you have not been able to eat anything and you have lost so much weight that you are gaunt, tricyclics can make it easier to get back to normal eating patterns. Otherwise, you may tend to gain weight, and you will have to watch what you eat.

Fortunately, these anticholinergic effects diminish over time. In the meantime, keeping a fresh water bottle handy protects you from dry mouth, and psyllium supplements (like Metamucil) will help prevent constipation while lowering your cholesterol levels. Drinking a little coffee, tea, or a soft drink can help counteract any daytime sleepiness you may encounter.

Tricyclic antidepressants have a few other side effects that you should be aware of. Norepinephrine brain cells contain a special class of switches called norepinephrine alpha-1 receptors. When norepinephrine antidepressants turn on these switches, you may be more likely to become dizzy or fall if you stand or sit up quickly. This effect is called postural hypotension, and it affects some individuals more than others. Until you find out whether you are vulnerable, you should be careful not to rise suddenly from a lying, sitting, bent over, or kneeling position when you are starting a classic antidepres-sant. Before you stand up, grab a solid object for support, and count to ten as you rise slowly. If you find yourself suffering from postural hypotension, know that the effect usually declines over a few days to weeks. Until then, drink plenty of fluids and consume extra salt to help keep your blood pressure from dropping when you rise.

Tricyclic antidepressants may also worsen heart disease, if you have any heart problems. Ask your psychiatrist and primary care doctor about the cardiac effects of tricyclic antidepressants.