Chemistry - A phenothiazine derivative, aminopropazine fumarate occurs as a white powder with a melting point of 168°C. One gram is soluble in 11 ml of water; 200 ml of alcohol. 118 mg of the fumarate salt is equivalent to 100 mg of the base.
Storage/Stability/Compatibility - Protect from light and excessive heat.
The injectable solution is colorless to light amber in color. Should marked deviation occur from the above color, do not use.
Pharmacology - Reportedly, aminopropazine causes smooth muscle relaxation by direct action on the muscle rather than a neurotropic mechanism. It primarily reduces muscle contractions in the GI, GU, and respiratory systems. It has little CNS effect (sedation) and does not affect biliary secretion, or exhibit histaminic, sympatholytic or ganglionic blocking actions.
Uses/Indications - Aminopropazine is indicated for: “reducing excessive smooth muscle contractions, such as occur in urethral spasms associated with urolithiasis in cats and dogs, and colic spasms in horses.” (Package insert, Jenotone®—Coopers)
Pharmacokinetics - No pharmacokinetic information was located for this agent.
Contraindications/Precautions - The intravenous route is not recommended in patients with history of severe cardiac, renal or hepatic disease and the oral form of the drug should be used very cautiously in these patients.
The parenteral preparation should be given IV slowly or into a large muscle mass IM (avoid IM injections near nerves). Avoid extravascular injections and do not give subcutaneously. See Drug Interactions for more information.
Adverse Effects/Warnings - Mild tranquilization or hyperexcitability are listed as possible side effects by the manufacturer.
Overdosage - No specific information was located for this agent. It is suggested that standard overdose procedures be followed, including emptying the gut after oral ingestion if possible and treating supportively. Do not give epinephrine for hypotension (use either phenylephrine or norepinephrine if sympathomimetic pressor agents are indicated).
Drug Interactions - Aminopropazine should not be given within one month of worming with an organophosphate agent as their effects may be potentiated. Other CNS depressant agents (barbiturates, narcotics, anesthetics, etc.) may cause additive CNS depression if used with aminopropazine. Quinidine when given with phenothiazines may cause additive cardiac depression. Antidiarrheal mixtures (e.g., Kaolin/pectin, bismuth subsalicylate mixtures) and antacids may cause reduced GI absorption of oral phenothiazines. Increased blood levels of both drugs may occur if propranolol is administered with phenothiazines. Phenothiazines block alpha-adrenergic receptors, if epinephrine is then given, unopposed beta activity causing vasodilation and increased cardiac rate can occur. The manufacturer lists epinephrine as being contraindicated with aminopropazine. Phenytoin metabolism may be decreased if given concurrently with phenothiazines. Procaine activity may be enhanced by phenothiazines.
Doses - The parenteral preparation should be given slowly IV or IM into a large muscle mass.
a) 0.55 mg/kg (1 ml/100 lbs body weight) IM or IV q12h (Package insert; Jenotone® - Coopers)
Monitoring Parameters - Dependent on reason for use; monitor for efficacy.
Dosage Forms/Preparations/FDA Approval Status/Withholding Times -
Aminopropazine Fumarate for Injection 25 mg/ml, (as base) 50 ml vials; Jenotone® (Schering-Plough); (Rx)
Aminopropazine Fumarate Tablets 25 mg, bottles of 100; Jenotone® (Schering-Plough); (Rx)
Human-Approved Products: None
Aminopropazine Fumarate may also be known as proquamezine fumarate , tetrameprozine fumarate , or Myspamol® (May & Baker, U.K.).
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