Trimethobenzamide (Systemic)



INN:

Trimethobenzamide

VA CLASSIFICATION
Primary: GA609

Commonly used brand name(s): Benzacot; Stemetic; Tebamide; Tigan; Tribenzagan; Trimazide.

Note: For a listing of dosage forms and brand names by country availability, see Dosage Forms section(s).

Not commercially available in Canada.



Category:


Antiemetic—

Indications

Accepted

Nausea and vomiting (prophylaxis and treatment)—Trimethobenzamide is indicated for the control of nausea and vomiting. {01} {02} {04}


Pharmacology/Pharmacokinetics

Physicochemical characteristics:
Molecular weight—
    424.92

Mechanism of action/Effect:

Thought to inhibit the medullary chemoreceptor trigger zone. {01} {02}

Biotransformation:

Hepatic.

Elimination:
    Renal; biliary.


Precautions to Consider

Cross-sensitivity and/or related problems

The suppository dosage form contains 2% of benzocaine. Patients sensitive to benzocaine or similar local anesthetics should not use the suppository dosage form of trimethobenzamide. {01}

Pregnancy/Reproduction

Pregnancy—
Adequate and well-controlled studies in humans have not been done.

Reproduction studies in animals have not shown that trimethobenzamide causes teratogenic effects in the fetus; however, it has been shown to cause increased embryonic resorptions and stillbirths. {01} {02}

Breast-feeding

It is not known if trimethobenzamide is distributed into breast milk.

Pediatrics

Trimethobenzamide is not recommended for treatment of uncomplicated vomiting in children. Caution is required because of the suspicion that centrally acting antiemetics, when used in the presence of viral illnesses, may contribute to the development of Reye's syndrome. {01} {02} {03}


Geriatrics


No information is available on the relationship of age to the effects of trimethobenzamide in geriatric patients.

Drug interactions and/or related problems
The following drug interactions and/or related problems have been selected on the basis of their potential clinical significance (possible mechanism in parentheses where appropriate)—not necessarily inclusive (» = major clinical significance):


Note: Combinations containing any of the following medications, depending on the amount present, may also interact with this medication.

Apomorphine    (prior administration of trimethobenzamide may decrease the emetic response to apomorphine; also, concurrent use may potentiate the central nervous system [CNS] effects of either apomorphine or trimethobenzamide)


» CNS depression–producing medications (see Appendix II )    (concurrent use may potentiate the effects of either these medications or trimethobenzamide; in addition, use of trimethobenzamide as well as other antiemetic agents in patients who have recently received other medications with CNS effects, such as phenothiazines, barbiturates, or the belladonna alkaloids, has resulted in opisthotonos, convulsions, coma, and extrapyramidal symptoms {01} {02})


Ototoxic medications (see Appendix II )    (concurrent use with trimethobenzamide may mask the symptoms of ototoxicity, such as tinnitus, dizziness, and vertigo)


Medical considerations/Contraindications
The medical considerations/contraindications included have been selected on the basis of their potential clinical significance (reasons given in parentheses where appropriate)— not necessarily inclusive (» = major clinical significance).


Risk-benefit should be considered when the following medical problems exist
Dehydration or
Electrolyte imbalance or
Encephalitis or
Fever, high or
Gastroenteritis    (CNS reactions such as opisthotonos, convulsions, coma, and extrapyramidal symptoms have been reported after administration of trimethobenzamide, especially in children and in elderly or debilitated patients, or in those who have recently received other medications with CNS effects {01} {02})


Sensitivity to trimethobenzamide
Note: Antiemetic action of trimethobenzamide may impede diagnosis of such conditions as appendicitis and obscure signs of toxicity from overdosage of other medications. {01} {02}




Side/Adverse Effects
The following side/adverse effects have been selected on the basis of their potential clinical significance (possible signs and symptoms in parentheses where appropriate)—not necessarily inclusive:

Those indicating need for medical attention
Incidence rare
    
Allergic reactions{01}{02} (skin rash)
    
blood dyscrasias{01}{02} (sore throat or fever; unusual tiredness)
    
convulsions{01}{02}
    
hepatic function impairment{01}{02} (yellow eyes or skin)
    
mental depression{01}{02}
    
opisthotonos{01}{02} (body spasm with head and heels bent backward and body bowed forward)
    
Parkinson-like syndrome{01}{02} (shakiness or tremors)
    
Reye's syndrome{01}{02} (convulsions; severe or continuing vomiting)



Those indicating need for medical attention only if they continue or are bothersome
Incidence more frequent
    
Drowsiness{01}{02}{04}

Incidence less frequent
    
Blurred vision{01}{02}
    
diarrhea{01}{02}
    
dizziness{01}{02}
    
headache{01}{02}
    
muscle cramps{01}{02}





Patient Consultation
As an aid to patient consultation, refer to Advice for the Patient, Trimethobenzamide (Systemic) .

In providing consultation, consider emphasizing the following selected information (» = major clinical significance):

Before using this medication
»   Conditions affecting use, especially:
Sensitivity to trimethobenzamide or to benzocaine (for suppository form)

Pregnancy—Animal studies have shown increased fetal resorptions and stillbirths





Use in children—Trimethobenzamide is not recommended for treatment of uncomplicated vomiting, due to the possible contribution of centrally acting antiemetics to the development of Reye's syndrome

Other medications, especially CNS depression–producing medications
Other medical problems, especially dehydration, electrolyte imbalance, encephalitis, high fever, or gastroenteritis

Proper use of this medication
Not giving to children unless prescribed; giving medication only as directed

Taking medication only as directed

Proper administration of this medication (for suppository dosage form only)

» Proper dosing
Taking as soon as possible; not taking if almost time for next dose; not doubling doses

» Proper storage

Precautions while using this medication
» Avoiding use of alcohol or other CNS depression–producing medications

» Possible dizziness, lightheadedness, or drowsiness; caution when driving or doing anything else requiring alertness {01} {02}

May mask ototoxic effects of large doses of salicylates


Side/adverse effects
Signs of potential side effects, especially allergic reactions, blood dyscrasias, convulsions, hepatic function impairment, mental depression, opisthotonos, Parkinson-like syndrome, and Reye's syndrome


General Dosing Information

For parenteral dosage form only
Intravenous injection is not recommended. {01} {02}

Intramuscular administration should be made by deep injection into the upper outer quadrant of the gluteal area in order to minimize irritation at the site of injection. {01} {02}


Oral Dosage Forms

TRIMETHOBENZAMIDE HYDROCHLORIDE CAPSULES USP

Usual adult and adolescent dose
Antiemetic
Oral, 250 mg three or four times a day as needed. {01}


Usual pediatric dose
Antiemetic
Oral, 15 mg per kg of body weight a day as needed, divided into three or four doses; or for

Children weighing 15 to 45 kg: Oral, 100 to 200 mg three or four times a day, as needed. {01}


Strength(s) usually available
U.S.—


100 mg (Rx) [Tigan]


250 mg (Rx) [Tigan][Generic]

Canada—
Not commercially available.

Packaging and storage:
Store between 15 and 30 °C (59 and 86 °F), unless otherwise specified by manufacturer. Store in a well-closed container.

Auxiliary labeling:
   • May cause drowsiness.
   • Avoid alcoholic beverages.



Parenteral Dosage Forms

TRIMETHOBENZAMIDE HYDROCHLORIDE INJECTION USP

Usual adult and adolescent dose
Antiemetic
Intramuscular, 200 mg three or four times a day as needed. {01} {02}


Usual pediatric dose
Use is not recommended. {01} {02}

Strength(s) usually available
U.S.—


100 mg per mL (Rx) [Benzacot] [Stemetic] [Tigan (parabens [methyl and propyl] 0.2%—in 2-mL ampuls; phenol 0.45%—in 20-mL vials; phenol 0.45%, disodium edetate 0.2 mg—in 2-mL syringes)] [Tribenzagan][Generic]

Canada—
Not commercially available.

Packaging and storage:
Store between 15 and 30 °C (59 and 86 °F), unless otherwise specified by manufacturer. Protect from freezing.



Rectal Dosage Forms

TRIMETHOBENZAMIDE HYDROCHLORIDE SUPPOSITORIES

Usual adult and adolescent dose
Antiemetic
Rectal, 200 mg three or four times a day as needed. {01}


Usual pediatric dose
Antiemetic
Rectal, 15 mg per kg of body weight a day as needed, divided into three or four doses; or for

Children weighing less than 15 kg: Rectal, 100 mg three or four times a day as needed. {01}

Children weighing 15 to 45 kg: Rectal, 100 to 200 mg three or four times a day as needed. {01}


Note: Premature and full-term neonates—Use is not recommended. {01}


Strength(s) usually available
U.S.—


100 mg (Rx) [Tigan (2% benzocaine)][Generic]


200 mg (Rx) [Tebamide] [Tigan (2% benzocaine)] [Trimazide][Generic]

Canada—
Not commercially available.

Packaging and storage:
Store between 15 and 30 °C (59 and 86 °F), unless otherwise specified by manufacturer.

Auxiliary labeling:
   • May cause drowsiness.
   • Avoid alcoholic beverages.



Revised: 01/29/1999



References
  1. Trimethobenzamide product monograph (Beecham—US). In: PDR Physicians' desk reference. 44th ed. 1990. Oradell, NJ: Medical Economics Company, 1990. p. 666-7.
  1. Trimethobenzamide package insert (Winthrop—US), Rev 2/87, Rec 2/89.
  1. Trimethobenzamide product monograph (SmithKline Beecham—US). Rev 6/90. In: PDR Physicians' desk reference. 47th ed. 1993. Oradell, NJ: Medical Economics Company, 1993. p. 2332-3.
  1. Tigan product monograph (Roberts—US). In: PDR Physician's desk reference. 52nd ed. 1998. Montvale, NJ: Medical Economics Company, 1998. p. 2411-2.
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