side effects
Anticholinergic Side Effects
Anticholinergic side effects are reviewed separately since they may be a consequence of both antipsychotic medications and the medications that are used to treat some of the side effects associated with those drugs. While those “side effect medications” may reduce or eliminate other side effects of antipsychotic drugs, they, in turn, have their own side effects.
While the term “anticholinergic side effects” may be intimidating, it is not that difficult to understand. Remember, side effects are simply any effects of a drug other than those that we refer to as the drug’s therapeutic effects. Side effects may be annoying, harmful, neutral; or they may even be beneficial.
Anticholinergic side effects are the direct result of our "meddling" with the levels of the neurotransmitter acetylcholine or blocking its receptors. When drugs do this, the result is the production of unintended side effects.
The neurotransmitter acetylcholine acts on two classes of receptors that are quite different; nicotinic and muscarinic receptors. Nicotinic receptors are found in skeletal muscles, in nerve ganglia (collections of nerve cell bodies), and in the CNS (central nervous system). For this purpose, we are not concerned with these receptors. Muscarinic receptors are present throughout the CNS (the brain) and the peripheral (outside the brain) nervous tissue.
Acetylcholine is the primary neurotransmitter for the parasympathetic, somatic, and preganglionic sympathetic nerves; and for nerves in some parts of the CNS. In other words, it has some activity inside and outside of the brain. Side effects related to this neurotransmitter can occur in the brain and in the body.
Acetycholine dilates (expands) blood vessels; decreases heart rate; constricts bronchioles (the small airways in the lungs); increases the production of mucous in the respiratory tract; produces contractions or cramping of the intestines; stimulates the production of saliva, sweat and tears; and constricts the pupil of the eye.
Agonists are simply drugs that mimic acetylcholine because they have a similar structure. Enzyme inhibitors interfere with the breakdown of acetylcholine and so its actions persist. Ultimately, they have the same net effect as agonists. Antagonists block acetylcholine receptors. For this reason they are termed “anticholinergic”. It is this class of drugs that we are concerned with here.
Anticholinergic side effects are generally only an annoying nuisance, but they may be more problematic. They are simply the opposite effects of acetylcholine and include:
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dry mouth -
dry eyes
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blurred vision
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may produce or exacerbate glaucoma
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increased heart rate
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dry warm skin and/or flushing
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difficulty emptying our bladder
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constipation
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headaches
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confusion
Dry mouth may increase the chance of developing cavities, or in extreme cases, may produce ulcers.
Dry eyes may be a problem for people who wear contact lenses.
Blurred vision is related to the slowing of the movement of the lens of the eye forward or backward to focus.
Patients with “narrow angle glaucoma” should consult their eye doctor before they begin any medications that have anticholinergic side effects, as these drugs may worsen this condition.
An increased heart rate is a common symptom of many drugs with anticholinergic side effects. It is generally benign unless patients experience a very rapid heart rate or are experiencing an irregular heart beat. Some patients are not aware of some increase, while other are quite cognizant and find it uncomfortable.
The inability to perspire may be important under warm conditions.
Drugs with anticholinergic side effects relax the bladder (they interfere with the contractions that serve to empty the bladder). They also delay the urge to empty the bladder. Urinary retention (the inability to fully empty the bladder) is usually the result of medications that have effects on histamine resulting in a tightening of the circular muscle (valve) at the outlet of the bladder. This may increase our risk for developing bladder infections.
Constipation can usually be alleviated with stool softeners or mild laxatives.
Headaches rarely occur as a result of anticholinergic side effects.
These side effects may include confusion. This should always be considered when patients with schizophrenia appear to be more disorganized or have worsening memory problems. Anticholinergic side effects in the brain also appears to be related to impaired learning (http://www.apa.org/journals/releases/bne1181223.pdf).
Anticholinergic Syndrome
Anticholinergic Syndrome consists of toxic psychosis, agitation, confusion, mydriasis (dilated pupils), urinary retention, ileus (a lack a movement of materials through the bowel), hot flushed dry skin, and tachycardia (rapid pulse).
Severe anticholinergic side effects may lead to seizures, coma and death.
The following series of similes are used by medical students to remember anticholinergic side effects: Dry as a bone, blind as a bat, red as a beet, hot as an oven, and mad as a hatter.
(Sources: The author’s knowledge base, unless otherwise noted.)
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