Atropine and medications like it are known as anticholinergics. They block muscarinic receptors, which are a subtype of receptors for acetylcholine. They are widely distributed throughout the autonomic nervous system, which is the part of the nervous system that works automatically, not under conscious control. These receptors are present both in the nerve ganglions, where they affect transmissions between two nerve cells, and in organs throughout the body. Symptoms therefore affect many different systems in the body.
Effects on the Brain
Anticholinergics can cause delirium, a state that includes confusion and hallucinations, typically visual ones. According to "Kaplan and Sadock's Comprehensive Textbook of Psychiatry," delirium is a common occurrence among elderly patients who are hospitalized for any reason. People who have dementia are at a greater risk for delirium. Atropine-like medications also tend to cause memory loss, more often in elderly patients. In younger patients, for whom these medications may be used to treat side effects of certain psychiatric drugs, they can induce euphoria, and are sometimes abused as a street drug for this reason.
Eyes and Mouth
Atropine can cause widened pupils, which lead to blurry vision. When given atropine drops for an eye exam, the patient needs to wait till the effect subsides before he can drive.
Dry mouth is a common symptom. It can be very uncomfortable for patients who are taking anticholinergics on a long-term basis, and they often need to sip liquid constantly to relieve the dryness. Certain conditions cause an excess of salivation, and in these cases the anticholinergic affect is beneficial.
Other Symptoms
Anticholinergics can cause a rapid heart rate. According to "Harrison's Principles of Internal Medicine," sometimes they induce a disturbance in the heart rhythm. Decreased sweating and dilation of blood vessels lead to dry, red skin, and put the patient at risk of heat stroke. Difficulty urinating and urinary retention may occur, particularly in men with prostatic hypertrophy. This side effect can be put to good use if anticholinergics are used to treat bed wetting. Nausea and constipation may occur.
References
- "Kaplan and Sadock's Comprehensive Textbook of Psychiatry"; Virginia Sadock and Pedro Ruiz (editors); 2009
- "Harrison's Principles of Internal Medicine"; Anthony Fauci et al.; 2008
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