Nausea and vomiting are common features of migraine. Approximately 80 percent of migraine attacks are accompanied by nausea, and an estimated 30 percent are accompanied by vomiting. Antiemetics are drugs that treat nausea and vomiting. They are sometimes combined with analgesics, ergotamines, or triptans (although triptans have their own nausea-relieving properties). Adding an antiemetic to migraine therapy — either within a combination drug or as a separate medication — can help you keep oral medications down and ease stomach discomfort.
Antiemetics are available in oral, injectable, suppository, and intravenous formulations. Oral formulations are most useful when they are taken early in a migraine episode, as vomiting later in an attack can prevent proper absorption. Suppositories and injections are helpful if medicine is not staying down. Intravenous formulations of prochlorperazine (Compazine) or chlorpromazine (Thorazine) may be administered in a doctor's office, urgent care, or emergency department setting.
Prescription antiemetics include ondansetron (Zofran), promethazine (Phenergan), and metoclopramide (Reglan). Metoclopramide also stimulates the gastrointestinal system, providing the added benefit of improving the absorption of other analgesics. This results in faster pain relief when the drug is taken in conjunction with an analgesic.
Drugs with antiemetic properties fall into several different pharmaceutical categories, so their side effects can vary. Some antiemetics, including promethazine, include antihistamines that can cause dizziness, drowsiness, and dry mouth. Prochloraperazine and chlorpromazine are both antipsychotic drugs that can cause these same side effects, along with constipation, chills, blurred vision, and nasal congestion.
One particular side effect of the antipsychotic drugs used as antiemetics, called acute dystonia, is uncommon but striking when it occurs. This consists of a sustained set of movements affecting the eyes or the head and neck or the limbs that can last for hours. It is a benign phenomenon, but can be quite distressing. Fortunately it is quickly relieved by anticholinergic medications such as diphenhydramine (Benadryl).
Metoclopramide increases gastrointestinal motility, so it may cause diarrhea in some people. In rare cases, long-term use of metoclopramide can cause tardive dyskinesia — involuntary tremors or muscle spasms that persist even after the drug is no longer used.
The newest class of migraine drugs under development is known as oral calcitonin-gene-related peptide (CGRP) receptor antagonists. These drugs work by blocking the CGRP neurotransmitter, a pain-related brain chemical that is elevated during a migraine attack. Trials have shown that these drugs are similar in efficacy to triptans and may have fewer side effects.