Chemistry - A quaternary ammonium antimuscarinic agent, propantheline bromide occurs as bitter-tasting, odorless, white or practically white crystals, with a melting range of 156-162° (with decomposition). It is very soluble in both water and alcohol.
Storage/Stability/Compatibility - Propantheline bromide tablets should be stored at room temperature in tight containers.
Pharmacology - An antimuscarinic with similar actions as atropine, propantheline is a quaternary ammonium compound, however, and does not cross appreciably into the CNS. It, therefore, should not exhibit the same extent of CNS adverse effects that atropine possesses. For further information, refer to the atropine monograph.
Uses/Indications - In small animal medicine propantheline bromide has been used for its antispasmodic/antisecretory effects in the treatment of diarrhea. It is also employed in the treatment of hyperreflexic detrusor or urge incontinence and as oral treatment in anticholinergic responsive bradycardias. In horses, propantheline has been used intravenously to reduce colonic peristalsis and to relax the rectum to allow easier rectal examination and perform surgical procedures to the rectum.
Pharmacokinetics - Quaternary anticholinergic agents are not completely absorbed after oral administration because it is completely ionized. In humans, peak levels occur about 2 hours after oral administration. Food apparently decreases the amount of drug absorbed.
The distribution of propantheline has not been extensively studied, but like other quaternary antimuscarinics, propantheline is poorly lipid soluble and does not extensively penetrate into the CNS or eye. Propantheline is believed to be prevalently metabolized in the GI and/or liver; less than 5% of an oral dose is excreted unchanged in the urine.
Contraindications/Precautions - Use of propantheline should be considered contraindicated if the patient has a history of hypersensitivity to anticholinergic drugs, tachycardias secondary to thyrotoxicosis or cardiac insufficiency, myocardial ischemia, unstable cardiac status during acute hemorrhage, GI obstructive disease, paralytic ileus, severe ulcerative colitis, obstructive uropathy or myasthenia gravis (unless used to reverse adverse muscarinic effects secondary to therapy).
Antimuscarinic agents should be used with extreme caution in patients with known or suspected GI infections. Propantheline or other antimuscarinic agents can decrease GI motility and prolong retention of the causative agent(s) or toxin(s) resulting in prolonged symptoms. Antimuscarinic agents must also be used with extreme caution in patients with autonomic neuropathy.
Antimuscarinic agents should be used with caution in patients with hepatic disease, renal disease, hyperthyroidism, hypertension, CHF, tachyarrhythmias, prostatic hypertrophy, esophogeal reflux, and geriatric or pediatric patients.
Adverse Effects/Warnings - With the exception of fewer effects on the eye and the CNS, propantheline can be expected to have a similar adverse reaction profile as atropine (dry mouth, dry eyes, urinary hesitancy, tachycardia, constipation, etc.). High doses may lead to the development of ileus with resultant bacterial overgrowth in susceptible animals. For more information refer to the atropine monograph.
Overdosage - Because of its quaternary structure, it would be expected that minimal CNS effects would occur after an overdose of propantheline when compared to atropine. See the information listed in the atropine monograph for more information on the symptoms and signs that may be see following an overdose.
If a recent oral ingestion, emptying of gut contents and administration of activated charcoal and saline cathartics may be warranted. Treat symptoms supportively and symptomatically. Do not use phenothiazines as they may contribute to the anticholinergic effects. Fluid therapy and standard treatments for shock may be instituted.
The use of physostigmine is controversial and should probably be reserved for cases where the patient exhibits either extreme agitation and is at risk for injuring themselves or others, or for cases where supraventricular tachycardias and sinus tachycardias are severe or life-threatening. The usual dose for physostigmine (human) is 2 mg IV slowly (for average sized adult); if no response may repeat every 20 minutes until reversal of toxic antimuscarinic effects or cholinergic effects takes place. The human pediatric dose is 0.02 mg/kg slow IV (repeat q10 minutes as above) and may be a reasonable choice for treatment of small animals. Physostigmine adverse effects (bronchoconstriction, bradycardia, seizures) may be treated with small doses of IV atropine.
Drug Interactions - The following drugs may enhance the activity of propantheline and its derivatives: antihistamines, procainamide, quinidine, meperidine, benzodiazepines, phenothiazines. The following drugs may potentiate the adverse effects of propantheline and its derivatives: primidone, disopyramide, nitrates, long-term corticosteroid use (may increase intraocular pressure). Propantheline and its derivatives may enhance the actions of nitrofurantoin, thiazide diuretics, sympathomimetics. Propantheline delays the absorption, but increases the peak serum level of ranitidine. The relative bioavailability of ranitidine may be increased by 23% when propantheline is administered concomitantly with ranitidine.
Propantheline may decrease the absorption of cimetidine.
a) 0.014 mg/kg IV (Robinson 1987)
b) 30 mg IV to inhibit peristalsis for 2 hours during rectal surgery (Merkt et al. 1979)
Note: There is no commercially available injectable product available in the U.S.A.. Should a preparation be made from oral tablets, it should be freshly prepared and filtered through a 0.22 micron filter before administering. Use with caution.
Monitoring Parameters - Dependent of reason for use
1) Clinical efficacy
2) Heart rate and rhythm if indicated
3) Adverse effects
Client Information - Dry mouth may be relieved by applying small amounts of water to animal’s tongue for 10-15 minutes. Protracted vomiting and diarrhea can be serious; contact veterinarian if symptoms are not alleviated.
Dosage Forms/Preparations/FDA Approval Status/Withholding Times -
Veterinary-Approved Products: None
Propantheline Bromide Tablets 7.5 mg, 15 mg; Pro-Banthine® (Schiapparelli Searle); Generic; (Rx)
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