Medicines called antiemetics are sometimes needed to ward off nausea and vomiting from anesthesia, chemotherapy, motion sickness or something else. Doctors choose from several categories, including drugs that work primarily through the chemical messengers serotonin, dopamine, acetylcholine and histamine. Each family of drugs has its own set of potential benefits and side effects such that drug use may be tailored to a particular kind of nausea and vomiting.
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Serotonin Receptor Blockers, Like Ondansetron
Some examples are ondansetron (Zofran), granisetron (Granisol), palonosetron (Aloxi) and dolasetron (Anzemet). Drugs in this family work to suppress signals from one of the special areas of the brain responsible for causing nausea and vomiting. These drugs are effective even for severe types of nausea such as that triggered by some types of cancer chemotherapy. Common side effects include headaches, drowsiness, dizziness and constipation. When used with other drugs that promote serotonin in the body, there is a potential risk of something called serotonin syndrome from too much serotonin. Drugs in this family may be used in pregnancy if clearly needed.
Dopamine Receptor Blockers, Like Metoclopramide
The dopamine receptor blocker family is a large, diverse group of drugs. They include metoclopramide (Reglan), droperidol (Inapsine) and prochlorperazine (Procomp). These drugs work both by facilitating stomach movements and emptying -- such as in people with diabetes whose stomachs are slow to empty -- and by reducing nausea and vomiting signals from the nervous system. They are also used for vomiting caused by chemotherapy and anesthesia, but this group has more side effects and potential interactions than the serotonin receptor blockers. Adverse reactions include movement problems, such as slowing down of body movements or tremors, or behavioral changes such as drowsiness, restlessness or agitation.
Cholinergic Receptor Blockers, Like Scopolamine
Scopolamine (Transderm Scop) is the major drug in this class that is used for nausea and vomiting, especially in the prevention of motion sickness. Scopolamine is available as a skin patch that is best applied 12 hours before the anticipated need, but it may be effective when applied up to 2 to 3 hours before travel, and a single patch can last for up to 3 days. Common side effects from this patch are dry mouth, drowsiness and blurred vision.
Histamine Receptor Blockers, Like Promethazine
Some examples of drugs in this family are promethazine (Phenergan), diphenhydramine (Benadryl), dimenhydrinate (Dramamine) and meclizine (Dramamine Non Drowsy). Although these drugs are commonly used for allergies, they are also effective for nausea and vomiting, especially after surgery or due to motion sickness. They work similarly to cholinergic receptor blockers by reducing the intensity of nausea signals to the brain. Side effects for this group of medications include sleepiness, confusion, dry mouth and -- infrequently -- blurry vision.
Other Drugs and Drug Combinations
Some other drugs are dronabinol (Marinol) and aprepitant (Emend). Dronabinol increases appetite and controls nausea, but its side effects include mood changes, behavior changes, racing of the heart and withdrawal syndromes. Aprepitant is a new drug that blocks neurokinin receptors. It is usually combined with a serotonin receptor blocker and steroids like dexamethasone for severe vomiting that occurs with certain cancer chemotherapies and after surgeries and general anesthesia. After surgery, the serotonin receptor blockers, either alone or in combination with a histamine or cholinergic receptor blocker, are useful to control nausea and vomiting. Occasionally, sedatives like lorazepam are also used for nausea and vomiting.