Trimethobenzamide (Oral)

As an antihistamine, trimethobenzamide works by decreasing activity in the region of the brain that triggers nausea and vomiting.


Trimethobenzamide helps relieve the nausea and vomiting that some patients experience after surgery. It's also used to treat nausea, vomiting and diarrhea caused by gastroenteritis, a viral stomach infection. By treating vomiting and diarrhea quickly, a serious loss of fluids (dehydration) by the patient is prevented.

Trimethobenzamide belongs to the class of drugs knows as antihistamines. It works by decreasing activity in the region of the brain that triggers nausea and vomiting. This medication should only be prescribed to prevent or relieve nausea and vomiting, and is not recommended for children due to the high risk of severe side effects.

Conditions treated

  • Postoperative nausea and vomiting
  • Gastroenteritis-associated nausea

Type of medicine

  • Antihistamine

Trimethobenzamide Side Effects

Headache, diarrhea, dizziness, drowsiness and blurred vision are some the common side effects that may occur. These symptoms are not uncommon and may disappear as your body adjusts to the medication. The patient should immediately notify their doctor or pharmacist if any of these side effects persist or get worse.

The patient should keep in mind that their doctor prescribes this medication once they have assessed whether the benefits outweigh the risks that come with side effects. Many people who use trimethobenzamide do not experience serious side effects.

If any of the following serious side effects occur, patients are advised to tell their healthcare professional right away:

  • Mood changes, e.g. depression
  • Confusion and restlessness
  • Yellowing of the eyes and skin
  • Muscle spasms
  • Dark urine
  • Shaking (tremor)
  • Unusual uncontrolled movements (arms, legs, face, tongue, mouth)

Medical help should be sought immediately for very severe side effects, such as seizure. A very strong allergic reaction to this medication is rare. However, the patient should get emergency medical any of the following symptoms of an allergic reaction occur: rash, swelling and itching of the face, throat and tongue, trouble breathing, extreme dizziness.

Some patients may also experience other side effects not listed here. Patients are advised to contact their doctor immediately if they experience any other side effects.


Trimethobenzamide should only be used for treating or preventing nausea and vomiting. The patient should take his or her medication exactly as their doctor prescribed. It's also important to read the prescription label carefully and follow all the directions given. Patients should not change the dosage by taking either smaller or larger quantities, or by using the medicine beyond the duration they were prescribed.

Unless directed by the physician, this medication should not be used for relieving nausea and vomiting in children. When giving this medicine to a child, one must be careful not to exceed the recommended dose. This is because the side effects of this drug may manifest more severely in children.

The amount of medication the patient needs to take depends on the strength of the medicine. Additionaly the number of doses to take each day, the intervals allowed between doses, and the duration of treatment with this medication all depend on the medical condition they are using the medicine for.

Trimethobenzamide is available in capsule form to take by mouth. It is usually taken 3 ' 4 times a day. Patients should be sure to take the medication at about the same times every day. For capsules (oral dosage), the typical dosage for adults is 300 milligrams (mg) three or four times a day as prescribed. For children, give as directed by the physician.

Missed dose:

If the patient missed a dose, they must take it as soon they remember. They should however go back to the regular schedule if it's almost time for the next scheduled dose. Patients are strongly advised against double dosing (possibly in an attempt to make up for a missed dose).


It's very important that emergency medical attention is sought as soon as an overdose is suspected. The patient should call his or her nearest poison control center immediately. The national poison hotline for US residents is. 1-800-222-1222. Those in Canada can call their local poison center directly.

Major Drug Interactions

Although some medications should not be used together, there may be cases where they are prescribed together even if an interaction is expected. In such cases, the doctor may advise certain precautions or alter the dosage. When taking trimethobenzamide, it's vital that the patient informs their doctor whether they are also using any of the drugs highlighted below. The interactions given here have been chosen based on how significantly the drug is likely to interact with trimethobenzamide. The list may not be all inclusive.

Using trimethobenzamide with any of these medicines is not recommended, except under special circumstances as determined by the physician. The patient is strongly advised to talk to their healthcare provider about all of his or her medical conditions, allergies, as well as all the medicines they use.

  • Metoclopramide
  • Bromopride

Other interactions:

Around the time of taking certain medications, it may be necessary to avoid consumption of certain foods, beverages or substances, as unpleasant interactions may occur. Alcohol and tobacco in particular may cause interactions. The patient should tell his or her pharmacist/doctor if they are taking other drugs that induce drowsiness, such as opioid pain relievers (e.g. codeine, hydrocodone), marijuana, alcohol, and drugs for relieving anxiety.

Having other medical problems may affect usage of this medicine. Patients should inform their healthcare professional if they suffer from any other medical conditions, particularly:

  • Electrolyte imbalance (high/low levels of minerals in the blood)
  • Dehydration
  • Intestinal infection' a severe infection may aggravate the side effects
  • High fever
  • Kidney disease'should be used with caution, as slow removal of this medicine may increase its effects


Before taking trimethobenzamide, the patient should let his or her doctor know if they are allergic to trimethobenzamide or any other drugs. They should also tell the pharmacist or doctor what other non-prescription and prescription drugs they plan to use or are using. They should as well mention the herbal products and nutritional supplements they are taking or are planning to take. The patient should in particular not fail to mention any of the following: antihistamines, antidepressants, anxiety medications, sleeping pills, sedatives, barbiturates, tranquilizers, and other drugs for relieving nausea and vomiting.

Additionally, it's very important that the patient notifies their doctor if they have Reye's Syndrome. This is a condition that affects the liver and brain, and can occur after suffering a viral illness, high fever, inflammation of the brain, or among those who have previously had liver disease.

This medication is not recommended for use in children. However, the healthcare professional may determine the benefits of treatment with this medication outweigh the risks. If a child has been prescribed trimethobenzamide capsules, it's important to discuss with the doctor about the benefits and risks of taking the medicine. Before trimethobenzamide is given to a child, the pharmacist or doctor should be informed f the child has any of these symptoms: drowsiness, vomiting, confusion, seizures, aggression, lethargy, yellowing of skin and eyes, flu-like symptoms, dehydration, and diarrhea.

Patients should avoid driving or working on tasks that require alertness, until they observe how trimethobenzamide affects them.

As alcohol can make trimethobenzamide side effects worse, patients who take alcoholic beverages should ask their doctor about the safe use of alcohol while taking this medication.

The patient should also inform her doctor if she is pregnant or (planning to get pregnant soon). The doctor will then consider the risks versus the benefits of using the medicine while pregnant and advice the patient accordingly.

As for nursing mothers, it is not yet known if this medication is passed through breast milk. Weighing the potential benefits against the risks is necessary before taking trimethobenzamide while breastfeeding.


Trimethobenzamide capsules should be stored at room temperature. The medicine package should not be kept in the bathroom, but a dry place that is safe out of the reach of children and pets. Patients should consult their pharmacist on how to dispose of unused drugs once the healthcare professional determines that use of the medication is no longer necessary.


Trimethobenzamide capsules are used to treat the vomiting and nausea that sometimes occur after surgery or from gastroenteritis (a virus infection in the stomach). While this medication can be effective at relieving and preventing these symptoms, it can be potentially harmful to patients who fail to tell their doctor about other medications they are using, or other health conditions they suffer from. Those with Reye's Syndrome or a history of liver disease in particular should be sure to notify their doctor.

This medication use trimethobenzamide is not recommended in children, except when the physician determines that the potential benefits outweigh the risks. And even when a child is prescribed the medication, special care in dosing as well as monitoring will be necessary to ensure it is not causing any harm to the child. Pregnant or nursing mothers should use trimethobenzamide with caution as no safety data on the drug is available yet.

Last Reviewed:
December 25, 2017
Last Updated:
April 05, 2018
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