An antimuscarinic is a compound that competes for places on muscarinic acetylcholine receptors, blocking the actions of neurotransmitters that would normally use these receptors. Some block all receptors, while others may be more selective. These compounds can be found in nature, and some used by the medical profession are derived from natural sources while others are synthetic in origin. Synthetic antimuscarinics tend to be more selective, as they can be tailored for specific uses. Doctors use these compounds in the treatment of a wide variety of conditions.
Two common examples are scopolamine and atropine. Depending on the dosage and the antimuscarinic involved, patients can experience a variety of effects. These compounds tend to depress the central nervous system and can lower breathing and heart rate, cause fatigue, and reduce gastrointestinal motility. One use for these compounds is in eye examinations, as they dilate the pupil. They are also used in preparation for general anesthesia, the treatment of some disorders involving the bladder, and management of Parkinson's disease, as they can alleviate tremors.
These drugs are not safe for use in all patients. Patients with a history of gastric ulcers, heart problems, and glaucoma can be at risk from some antimuscarinic compounds. If a doctor feels they are necessary, he will have to weigh the risks and benefits and prescribe with care. It may be possible to use a selective synthetic to accomplish a desired goal, or a low dosage to treat a patient without putting her in danger.
An overdose of antimuscarinic drugs can cause severe illness. The central nervous system depression can progress to the point of coma, as the patient may not be able to breathe independently and the heart rate could become highly irregular. Patients on medications with an antimuscarinic action must follow the directions carefully, taking only the prescribed dose at set intervals. Patients who miss doses should not double up their next doses, and in the event of vomiting after taking the medication, the patient should call the doctor to find out what to do.
Hospitals have stores of antimuscarinic drugs available to treat patients in a variety of situations. Doctors and nurses calculate dosages carefully and may have a protocol they need to follow when administering medication to make sure patients receive the right dose and to minimize the chances of doubling up doses or giving medication to a patient who could be endangered by it.