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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Other
Trimethobenzamide is an antiemetic agent used to treat postoperative nausea and vomiting and symptoms associated with gastroenteritis. It works by inhibiting the chemoreceptor trigger zone in the brain.
Name
Trimethobenzamide
Raw Name
TRIMETHOBENZAMIDE HYDROCHLORIDE
Category
Other
Salt Form
Hydrochloride
Drug Count
3
Variant Count
7
Last Verified
February 17, 2026
RxCUI
860771, 1726680, 1726682
UNII
WDQ5P1SX7Q
About Trimethobenzamide
Trimethobenzamide is an antiemetic agent used to treat postoperative nausea and vomiting and symptoms associated with gastroenteritis. It works by inhibiting the chemoreceptor trigger zone in the brain.
Detailed information about Trimethobenzamide
References used for this content
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Trimethobenzamide.
Healthcare providers typically prescribe Trimethobenzamide for the management of postoperative nausea and vomiting (PONV) and for the relief of nausea associated with acute gastroenteritis (inflammation of the stomach and intestines). Unlike some other antiemetics that have broad applications, Trimethobenzamide has a more targeted clinical niche. It is important to note that the regulatory history of this drug is complex; for instance, the FDA's Drug Efficacy Study Implementation (DESI) program previously reviewed various formulations, leading to the discontinuation of certain forms (like the suppository) in some markets due to efficacy concerns, while the oral capsules and injectable forms remain available for specific indications.
To understand how Trimethobenzamide works, one must understand the physiology of the emetic reflex (the vomiting reflex). The brain contains a specialized area known as the 'vomiting center' in the medulla oblongata. This center receives signals from various parts of the body, including the gastrointestinal tract and the chemoreceptor trigger zone (CTZ).
Trimethobenzamide acts primarily by inhibiting the chemoreceptor trigger zone (CTZ) located in the area postrema of the fourth ventricle of the brain. The CTZ is unique because it sits outside the blood-brain barrier, allowing it to detect toxins or chemical changes in the blood and cerebrospinal fluid. When the CTZ is stimulated, it sends signals to the vomiting center to initiate the physical act of emesis. Trimethobenzamide is believed to block the transmission of these emetic impulses by antagonizing specific receptors—likely dopaminergic or histaminergic, though its exact molecular targets are less clearly defined than modern agents like ondansetron. By dampening the sensitivity of the CTZ, Trimethobenzamide effectively raises the threshold for nausea and vomiting. It does not appear to significantly affect the vomiting center itself, but rather the 'alarm system' (the CTZ) that triggers it.
Understanding the pharmacokinetics (how the body processes the drug) of Trimethobenzamide is essential for optimizing its clinical use.
The FDA-approved indications for Trimethobenzamide include:
Off-label uses are less common today due to the availability of newer agents, but it has historically been used for various causes of drug-induced nausea. However, its use in pregnancy-related nausea (morning sickness) is generally avoided unless the benefit clearly outweighs the risk, as other better-studied options exist.
Trimethobenzamide is currently available in the following dosage forms:
> Important: Only your healthcare provider can determine if Trimethobenzamide is right for your specific condition. This medication should only be used under the supervision of a qualified medical professional who can monitor for efficacy and safety.
The dosage of Trimethobenzamide must be individualized based on the patient's symptoms, the severity of the nausea, and the patient's overall health status.
Trimethobenzamide is generally not recommended for use in children without explicit guidance from a pediatric specialist.
Since Trimethobenzamide is primarily excreted by the kidneys, patients with significant renal impairment (kidney disease) may require a reduced dose or increased dosing intervals. Your healthcare provider may monitor your creatinine clearance to determine the safest dose.
Because the drug is metabolized in the liver, patients with severe hepatic dysfunction (liver failure or cirrhosis) should be monitored closely. Dose adjustments may be necessary if the liver cannot process the medication efficiently.
Geriatric patients are often more sensitive to the effects of Trimethobenzamide, particularly the sedative and central nervous system effects. Doctors typically start elderly patients at the lower end of the dosing range and monitor for confusion or increased fall risk.
If you miss a dose of Trimethobenzamide, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and return to your regular schedule. Do not 'double up' or take two doses at once to make up for a missed one, as this increases the risk of side effects.
Signs of a Trimethobenzamide overdose may include extreme drowsiness, confusion, hypotension (low blood pressure), or extrapyramidal symptoms (such as muscle tremors or stiffness). In severe cases, seizures or coma could occur. If an overdose is suspected, contact a poison control center or seek emergency medical attention immediately.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop taking the medication without medical guidance, as your symptoms may return.
The most frequently reported side effect of Trimethobenzamide is drowsiness (somnolence). This effect occurs because the drug can impact the central nervous system. Patients may feel a general sense of lethargy, sleepiness, or a 'foggy' feeling. This typically begins shortly after the dose and may last for several hours. Other common effects include:
These effects are less frequent but have been documented in clinical use:
Rarely, patients may experience more unusual reactions:
> Warning: Stop taking Trimethobenzamide and call your doctor immediately or seek emergency care if you experience any of the following:
Trimethobenzamide is generally intended for short-term use. Prolonged use is not well-studied and may increase the risk of developing tolerance (where the drug becomes less effective) or more persistent movement disorders. If you find you need this medication for more than a few days, a thorough re-evaluation by your doctor is necessary to identify the underlying cause of your nausea.
There are currently no FDA black box warnings for Trimethobenzamide. However, this does not mean the drug is without risk. The potential for CNS depression and extrapyramidal symptoms remains a significant clinical concern that requires careful monitoring.
Report any unusual symptoms or persistent side effects to your healthcare provider. You may also report side effects to the FDA at 1-800-FDA-1088.
Trimethobenzamide should be used with caution, particularly in patients with pre-existing neurological or liver conditions. Because this medication causes significant drowsiness, patients must be aware of how it affects them before engaging in activities that require full mental alertness. Furthermore, the drug's ability to suppress vomiting can be dangerous if the vomiting is a symptom of a condition that requires immediate diagnosis, such as appendicitis or drug toxicity.
No FDA black box warnings for Trimethobenzamide.
For short-term use, extensive lab monitoring is usually not required. However, for patients receiving multiple doses or those with underlying health issues, the following may be monitored:
Do not drive, operate complex machinery, or participate in hazardous activities until you know how Trimethobenzamide affects you. The sedative effects can be unpredictable and may significantly increase the risk of accidents.
Alcohol should be strictly avoided while taking Trimethobenzamide. Alcohol acts as a central nervous system depressant and will dramatically increase the sedative effects of the medication, potentially leading to dangerous levels of respiratory depression or extreme lethargy.
Since Trimethobenzamide is typically used on an 'as-needed' or short-term basis, a tapering schedule is usually not necessary. However, if you have been taking it for an extended period, consult your doctor before stopping. Sudden discontinuation after long-term use could theoretically lead to a return of severe nausea.
> Important: Discuss all your medical conditions, especially any history of liver disease, kidney disease, or movement disorders, with your healthcare provider before starting Trimethobenzamide.
While there are few absolute contraindications based solely on drug-drug interactions, Trimethobenzamide should generally not be used with other drugs that cause significant Extrapyramidal Symptoms (EPS) unless absolutely necessary. Combining it with high-potency traditional antipsychotics (like haloperidol) can significantly increase the risk of severe muscle spasms and movement disorders.
Trimethobenzamide is not known to significantly interfere with most common laboratory tests (such as glucose or cholesterol panels). However, it may mask the symptoms of toxicity from other drugs (like digitalis), which could lead to misleading clinical assessments.
Most interactions with Trimethobenzamide are pharmacodynamic in nature, meaning the drugs have additive effects on the brain or nervous system. There is less evidence for significant pharmacokinetic interactions (where one drug changes the blood levels of another) compared to modern drugs, though caution with other hepatically metabolized drugs is always warranted.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. A complete list helps your pharmacist check for potentially dangerous interactions.
Trimethobenzamide must NEVER be used in the following situations:
These are conditions where the doctor must carefully weigh the benefits against the risks:
Patients who are sensitive to other benzamides or certain antihistamines should be monitored for cross-reactivity, although this is not frequently reported in clinical literature.
> Important: Your healthcare provider will evaluate your complete medical history, including any allergies or chronic conditions, before prescribing Trimethobenzamide to ensure it is the safest option for you.
Trimethobenzamide is classified by the FDA in Pregnancy Category C. This means that animal reproduction studies have shown an adverse effect on the fetus, or there are no adequate and well-controlled studies in humans. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Most healthcare providers prefer using first-line treatments for morning sickness, such as Vitamin B6 (pyridoxine) and doxylamine, before considering Trimethobenzamide.
It is not known whether Trimethobenzamide is excreted in human milk. Because many drugs are excreted in milk and because of the potential for serious adverse reactions in nursing infants (such as excessive sedation), a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
As previously emphasized, the use of Trimethobenzamide in children is highly restricted. The risk of Extrapyramidal Symptoms (EPS) and the potential association with Reye's Syndrome make it a second- or third-line choice in pediatrics. It is generally not approved for use in infants or young children for most common causes of vomiting. If used, it must be under the strict guidance of a pediatrician.
Clinical studies of Trimethobenzamide did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. However, elderly patients are known to have a higher risk of:
Doctors usually recommend the lowest effective dose for elderly patients.
In patients with moderate to severe renal impairment (Creatinine Clearance < 50 mL/min), the half-life of Trimethobenzamide may be significantly prolonged. This increases the risk of side effects. Dosage adjustments, such as reducing the frequency of administration, are often necessary. In patients on dialysis, the clearance of the drug is not well-documented, necessitating close clinical observation.
Patients with liver disease (Child-Pugh Class B or C) should be monitored for signs of increased toxicity. Since the liver is responsible for metabolizing the drug into inactive forms, a 'sluggish' liver can result in higher-than-intended concentrations of the active drug in the bloodstream.
> Important: Special populations require individualized medical assessment. Always inform your doctor if you are pregnant, planning to become pregnant, or have chronic kidney or liver issues.
Trimethobenzamide hydrochloride is an antiemetic agent whose primary site of action is the chemoreceptor trigger zone (CTZ), located in the area postrema of the medulla oblongata. Unlike some other antiemetics that work on the gastrointestinal tract (prokinetics) or the vestibular system (antihistamines for motion sickness), Trimethobenzamide specifically targets the chemical detection center of the brain. While its exact molecular binding profile is not as well-characterized as modern 5-HT3 antagonists, it is believed to interfere with the transmission of emetic impulses from the CTZ to the vomiting center. It does not appear to significantly inhibit the vomiting center directly, nor does it have significant effects on the peripheral nervous system or the gut's motility.
| Parameter | Value |
|---|---|
| Bioavailability | High (Rapidly absorbed) |
| Protein Binding | Moderate (Data varies) |
| Half-life | 7 - 9 hours |
| Tmax | 0.75 - 2 hours |
| Metabolism | Hepatic (Conjugation/Oxidation) |
| Excretion | Renal (30-50% as metabolites) |
Trimethobenzamide belongs to the class of Antiemetics. Within this broad category, it is often grouped with other central-acting agents that target the CTZ. It is distinct from phenothiazines (like prochlorperazine) because it generally lacks the significant alpha-adrenergic or strong antipsychotic properties associated with that class, although it shares the risk of extrapyramidal side effects.
Medications containing this ingredient
Common questions about Trimethobenzamide
Trimethobenzamide is primarily used to control nausea and vomiting. It is specifically indicated for the treatment of postoperative nausea and vomiting that occurs after surgery and for nausea associated with acute gastroenteritis. It works by blocking signals in a specific part of the brain called the chemoreceptor trigger zone (CTZ). While it was once available in several forms, it is now most commonly prescribed as an oral capsule or an intramuscular injection. Your doctor will determine if this medication is appropriate based on the cause of your symptoms.
The most common side effect reported by patients taking Trimethobenzamide is drowsiness or sleepiness. Many people also experience dizziness, lightheadedness, or a mild headache during the first few doses. Some patients may notice blurred vision or minor muscle cramps. Because of the risk of drowsiness, it is important to avoid driving or operating machinery until you know how the drug affects you. Most of these common side effects are temporary and will resolve once the medication is stopped.
No, you should not consume alcohol while taking Trimethobenzamide. Alcohol is a central nervous system (CNS) depressant that can significantly increase the sedative effects of the medication. Combining the two can lead to extreme drowsiness, impaired judgment, and decreased motor coordination. In severe cases, it could potentially cause dangerous levels of respiratory depression. To ensure your safety, it is best to avoid all alcoholic beverages until the medication has completely cleared your system.
Trimethobenzamide is classified as FDA Pregnancy Category C, meaning its safety in pregnant women has not been fully established. Animal studies have shown some potential for harm, but there are no adequate, well-controlled studies in humans. Because of this, healthcare providers typically only prescribe it during pregnancy if the benefits clearly outweigh the potential risks to the fetus. If you are pregnant or planning to become pregnant, you should discuss alternative treatments for nausea with your doctor. Most doctors prefer to use better-studied options for morning sickness before considering Trimethobenzamide.
When taken as an oral capsule, Trimethobenzamide typically begins to work within 10 to 40 minutes. Peak levels of the medication in the bloodstream are usually reached between 45 minutes and 2 hours after swallowing the capsule. If you receive the medication as an intramuscular injection, the onset of action may be slightly faster. The effects of a single dose generally last for about 3 to 4 hours. Because of this relatively short duration, the medication is often prescribed to be taken three or four times per day.
Yes, in most cases, Trimethobenzamide can be stopped suddenly because it is usually intended for short-term use (a few days). It is not known to cause physical dependence or a traditional withdrawal syndrome. However, if you stop taking it before the underlying cause of your nausea (such as gastroenteritis) has resolved, your symptoms may return. You should always follow the duration of treatment recommended by your healthcare provider. If you have been taking it for an unusually long period, consult your doctor before discontinuing use.
If you miss a dose, you should take it as soon as you remember. However, if it is almost time for your next scheduled dose, it is better to skip the missed dose and simply take the next one at the regular time. Do not take two doses at once to make up for the one you missed, as this increases your risk of experiencing side effects like extreme drowsiness or muscle spasms. If you are unsure what to do, contact your pharmacist or doctor for specific guidance based on your dosing schedule.
Weight gain is not a recognized or common side effect of Trimethobenzamide. Because the medication is typically used for short-term relief of acute nausea and vomiting (usually lasting only a few days), it does not have the long-term metabolic effects associated with drugs that cause weight gain, such as certain steroids or antipsychotics. If you experience unexpected weight gain while taking this medication, it is likely due to another factor or an underlying medical condition. You should discuss any significant weight changes with your healthcare provider.
Trimethobenzamide can interact with several other types of medications, particularly those that also cause drowsiness. This includes opioids, benzodiazepines, sleep aids, and certain antidepressants. It can also interact with other drugs that affect the nervous system, such as metoclopramide or antipsychotics, increasing the risk of movement disorders. It is vital to provide your doctor and pharmacist with a complete list of all prescription drugs, over-the-counter medicines, and herbal supplements you are taking. They can check for specific interactions that might make the combination unsafe.
Yes, Trimethobenzamide hydrochloride is available as a generic medication in both capsule and injectable forms. The generic version is typically more cost-effective than the brand-name version (Tigan). Generic medications are required by the FDA to have the same active ingredient, strength, dosage form, and route of administration as the brand-name drug. They must also meet the same rigorous standards for quality and purity. You can ask your pharmacist if a generic version is available and appropriate for your prescription.