What are these types of medicines, and what do they consist of?
Medications called antiemetics are sometimes needed to prevent nausea and vomiting from anesthesia, chemotherapy, dizziness, or similar symptoms.
Doctors choose from various categories, including drugs that work, primarily through serotonin, dopamine, and histamine.
Each family of drugs has its own set of potential benefits and side effects such that drug use can be adapted to a particular type of nausea and vomiting.
Nausea and vomiting occur for many reasons. The most common causes are:
- Self-limited illnesses (virus or food poisoning) last from a few hours to days.
- The toxins
- Certain medications
People should consult a doctor if nausea and vomiting are persistent or are accompanied by other severe symptoms such as abdominal pain, fever, yellowing of the skin (jaundice), or bleeding.
People with severe or ongoing vomiting who have other serious medical problems, are elderly or are very young, but usually pregnant or breastfeeding, should also seek medical attention.
Dizziness can occur in many places, including travel by car, air, or boat. This may be the best indication for over-the-counter medications for nausea and vomiting associated with driving in a vehicle.
Other inner ear problems, which are related to motion sickness, can create a feeling of nausea.
Serotonin receptor blockers, such as Ondansetron.
Some examples are Ondansetron, granisetron (Granisol), palonosetron (Aloxi), and dolasetron (Anzemet). The drugs in this family of medications work to suppress signals from one of the particular areas of the brain responsible for causing nausea and vomiting.
These drugs are effective even for severe 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 serotonin exacerbation.
Drugs in this family can be used in pregnancy if necessary.
Dopamine receptor blockers, such as metoclopramide
The family of dopamine receptor blockers is a large and diverse group of drugs. They include metoclopramide (Reglan), droperidol (Inapsine), and prochlorperazine (Procomp).
These drugs work by facilitating the movements of the stomach and emptying – as in people with diabetes whose belly is slow to open – and by reducing the signs of nausea and vomiting in 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 serotonin receptor blockers.
Adverse reactions include:
Movement problems include decreased body movements, tremors, or behavioral changes such as drowsiness, restlessness, or agitation.
Blockers of the cholinergic receptor, like Escopolamine.
Escopolamine (Transderm Scop) is the primary drug of this class used for nausea and vomiting, especially in preventing motion sickness.
Escopolamine is available as a skin patch that is best applied 12 hours before the anticipated need but can be effective when applied up to 2 to 3 hours before travel, and a single patch can last up to 3 days.
The common side effects of this patch are:
Dry mouth, drowsiness, and blurred vision.
Blockers of histamine receptors, such as Promethazine.
Some examples of drugs in this family are Promethazine (Phenergan), Benadryl, Dramamine, and Meclizine. Although these medications are commonly used for allergies, they are also effective for nausea and vomiting, especially after surgery or dizziness.
They work similarly to cholinergic receptor blockers by reducing the intensity of nausea signals in the brain.
Side effects of this group of medications include:
Drowsiness, confusion, dry mouth, and – rarely – blurred vision.
Other drugs and drug combinations.
Some other medications are dronabinol (Marinol) and aprepitant (Emend). Dronabinol increases appetite and controls nausea, but its side effects include mood swings, behavioral changes, restless heart, and withdrawal syndromes.
Aprepitant is a new drug that blocks neurokinin receptors. It is usually combined with a serotonin receptor blocker and steroids such as dexamethasone for severe vomiting with certain cancer chemotherapies and after surgeries and general anesthesia.
After surgery, serotonin receptor blockers, alone or combined with histamine or cholinergic receptor blocker, help control nausea and vomiting. Occasionally, sedatives such as lorazepam are also used for nausea and vomiting.
In general terms, antiemetics can be divided into two groups:
- drugs that are effective in the fight against dizziness
- drugs that are powerful against nausea and vomiting due to other causes.
The exact way these drugs work is not known, although they can act by pressing the chemoreceptor activation zone, which is located in the brain’s hypothalamus and controls vomiting.
Anticholinergic drugs and antihistamines are effective against motion sickness. Although many are available, none is entirely free of side effects (e.g., dry mouth and blurred vision with anticholinergics, drowsiness with antihistamines).
The most effective drugs in this group are the anticholinergic drug Scopolamine and the antihistamine Promethazine.
Nausea and vomiting other than those associated with motion sickness are present in many diseases, for example, radiation sickness, postoperative vomiting, and liver disease.
In these cases, the most effective antiemetics are phenothiazines (also used in psychiatric medicine) and metoclopramide.
Serotonin antagonists, such as Ondansetron, effectively prevent nausea and vomiting associated with cancer chemotherapy.