Chemistry - An ethylenediamine-derivative antihistamine, tripelennamine HCl occurs as a white, crystalline powder which will slowly darken upon exposure to light. It has a melting range of 188-192°C and pKas of 3.9 and 9.0. One gram is soluble in 1 ml of water or 6 ml of alcohol.
Storage/Stability/Compatibility - Store the injection at room temperature and protect from light; avoid freezing or excessive heat. Tablets should also be stored at room temperature in tight containers.
Pharmacology - Antihistamines (H1-receptor antagonists) competitively inhibit histamine at H1 receptor sites. They do not inactivate or prevent the release of histamine, but can prevent histamine’s action on the cell. Besides their antihistaminic activity, these agents also have varying degrees of anticholinergic and CNS activity (sedation). Tripelennamine is considered to have moderate sedative activity and minimal anticholinergic activity when compared to other antihistamines.
Uses/Indications - Antihistamines are used in veterinary medicine to reduce or help prevent histamine mediated adverse effects. Tripelennamine has been used as a CNS stimulant in “Downer cows” when administered slow IV.
Pharmacokinetics - The pharmacokinetics of tripelennamine have apparently not been thoroughly studied in domestic animals or humans.
Contraindications/Precautions - Tripelennamine is not recommended to be given IV in horses (see Adverse Effects).
Adverse Effects/Warnings - CNS stimulation (hyperexcitability, nervousness, & muscle tremors) lasting up to 20 minutes, has been noted in horses after receiving tripelennamine intravenously. Other effects seen (in all species), include CNS depression, incoordination, and GI disturbances.
Tripelennamine has been mixed with pentazocine and injected by human opiate addicts and drug abusers. Be alert for clients suggesting that this drug be dispensed for their animals.
Overdosage - Overdosage of tripelennamine reportedly can cause CNS excitation, seizures and ataxia. Treat symptomatically and supportively if symptoms are severe. Phenytoin (IV) is recommended in the treatment of seizures caused by antihistamine overdose in humans; barbiturates and diazepam are generally avoided.
Drug Interactions - Increased sedation can occur if chlorpheniramine is combined with other CNS depressant drugs. Antihistamines may partially counteract the anti-coagulation effects of heparin or warfarin.
Laboratory Interactions - Antihistamines can decrease the wheal and flare response to antigen skin testing. In humans, it is suggested that antihistamines be discontinued at least 4 days prior to testing.
Doses - It is recommended to warm the solution to near body temperature before injecting; give IM injections into large muscle areas.
a) 1.1 mg/kg (2.5 ml per 100 lbs body weight) IM q6-12h prn (Package Insert; Re-Covr® - Solvay)
b) 1 mg/kg IM (Robinson 1987)
Monitoring Parameters -
1) Clinical efficacy and adverse effects
Dosage Forms/Preparations/FDA Approval Status/Withholding Times -
Tripelennamine HCl for Injection (Veterinary) 20 mg/ml in 20 ml, 100 ml, and 250 ml vials; Generic (Phoenix) (Rx) Tripelennamine HCl injection is approved for use in cattle, horses, dogs, and cats. Treated cattle must not be slaughtered for food purposes for four days following the last treatment. Milk must not be used for food for 24 hours (2 milkings) after treatment. No specific tolerance for residues have been published
Tripelennamine HCl Oral Tablets 25 mg, 50 mg; PBZ® (Geigy);Pelamine® (Major); Generic; (Rx)
Tripelennamine HCl Extended-release tablets 100 mg; PBZ-SR® (Geigy); (Rx)
Tripelennamine HCl Elixir: 37.5 mg (equivalent to 25 mg HCl) per 5 ml in 473 mls; PBZ® (Geigy) (Rx)
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