PHENYLPROPANOLAMINE HCL
Chemistry - A sympathomimetic amine, phenylpropanolamine HCl occurs as a white, crystallinepowder with a slightly aromatic odor, a melting range between 191° - 194°C, and a pKa of 9.4. Onegram is soluble in approximately 1.1 ml of water or 7 ml of alcohol. Phenylpropanolamine HClmay also be known as dl-Norephedrine HCl.
Pharmacologic effects of phenylpropanolamine include increased vasoconstriction, heart rate, coronary blood flow, blood pressure, mild CNS stimulation, and decreased nasal congestion andappetite. Phenylpropanolamine can also increase urethral sphincter tone and produce closure of thebladder neck; its principle veterinary indications are as a result of these effects.
Uses, Indications - Phenylpropanolamine is used chiefly for the treatment of urethral sphincterhypotonus and resulting incontinence in dogs and cats. It has also been used in an attempt to treatnasal congestion in small animals.
Phenylpropanolamine is reportedly distributed into various tissues and fluids, including the CNS.
It is unknown if it crosses the placenta or enters milk. The drug is partially metabolized to an activemetabolite, but 80-90% is excreted unchanged in the urine within 24 hours of dosing. The serumhalf-life is approximately 3-4 hours.
Contraindications/Precautions - Phenylpropanolamine should be used with caution in patientswith glaucoma, prostatic hypertrophy, hyperthyroidism, diabetes mellitus, cardiovascular disordersor hypertension. Phenylpropanolamine may cause decreased ovum implantation; uncontrolledclinical experience, however, has not demonstrated any untoward effects during pregnancy.
Overdosage - Symptoms of overdosage may consist of an exacerbation of the adverse effects listedabove or, if a very large overdose, severe cardiovascular (hypertension to rebound hypotension, bradycardias to tachycardias, and cardiovascular collapse) or CNS effects (stimulation to coma)can be seen.
If the overdose was recent, empty the stomach using the usual precautions and administer charcoaland a cathartic. Treat symptoms supportively as they occur.
Phenylpropanolamine should not be given within two weeks of a patient receiving monoamineoxidase inhibitors.
An increased chance of hypertension developing can result if phenylpropanolamine is givenconcomitantly with indomethicin (or other NSAIDs, including aspirin), reserpine, tricyclicantidepressants, or ganglionic blocking agents.
An increased risk of arrhythmias developing can occur if phenylpropanolamine is administered topatients who have received cyclopropane or a halogenated hydrocarbon anesthetic agent.
Propranolol may be administered should these occur.
Storage, Stability, Compatibility
Store phenylpropanolamine products at room temperature inlight-resistant, tight containers.Pharmacology - PHENYLPROPANOLAMINE HCL
While the exact mechanism of phenylpropanolamine's actions are undetermined, it is believed that it indirectly stimulates both alpha- and beta-adrenergic receptors by causing therelease of norepinephrine. Prolonged use or excessive dosing frequency can deplete norepinephrinefrom its storage sites, and tachyphylaxis (decreased response) may ensue. Tachyphylaxis has notbeen documented in dogs or cats, however, when used for urethral sphincter hypotonus.Pharmacologic effects of phenylpropanolamine include increased vasoconstriction, heart rate, coronary blood flow, blood pressure, mild CNS stimulation, and decreased nasal congestion andappetite. Phenylpropanolamine can also increase urethral sphincter tone and produce closure of thebladder neck; its principle veterinary indications are as a result of these effects.
Uses, Indications - Phenylpropanolamine is used chiefly for the treatment of urethral sphincterhypotonus and resulting incontinence in dogs and cats. It has also been used in an attempt to treatnasal congestion in small animals.
Pharmacokinetics - PHENYLPROPANOLAMINE HCL
No information was located on the pharmacokinetics of this agent in veterinary species. In humans, phenylpropanolamine is readily absorbed after oral administration and hasan onset of action (nasal decongestion) of about 15-30 minutes and a duration of effect ofapproximately 3 hours (regular capsules or tablets).Phenylpropanolamine is reportedly distributed into various tissues and fluids, including the CNS.
It is unknown if it crosses the placenta or enters milk. The drug is partially metabolized to an activemetabolite, but 80-90% is excreted unchanged in the urine within 24 hours of dosing. The serumhalf-life is approximately 3-4 hours.
Contraindications/Precautions - Phenylpropanolamine should be used with caution in patientswith glaucoma, prostatic hypertrophy, hyperthyroidism, diabetes mellitus, cardiovascular disordersor hypertension. Phenylpropanolamine may cause decreased ovum implantation; uncontrolledclinical experience, however, has not demonstrated any untoward effects during pregnancy.
Adverse Effects, Warnings
Most likely side effects include restlessness, irritability and hypertension. Anorexia may be a problem in some animals.Overdosage - Symptoms of overdosage may consist of an exacerbation of the adverse effects listedabove or, if a very large overdose, severe cardiovascular (hypertension to rebound hypotension, bradycardias to tachycardias, and cardiovascular collapse) or CNS effects (stimulation to coma)can be seen.
If the overdose was recent, empty the stomach using the usual precautions and administer charcoaland a cathartic. Treat symptoms supportively as they occur.
Drug Interactions
Phenylpropanolamine should not be administered with other sympathomimetic agents (e.g., ephedrine) as increased toxicity may result.Phenylpropanolamine should not be given within two weeks of a patient receiving monoamineoxidase inhibitors.
An increased chance of hypertension developing can result if phenylpropanolamine is givenconcomitantly with indomethicin (or other NSAIDs, including aspirin), reserpine, tricyclicantidepressants, or ganglionic blocking agents.
An increased risk of arrhythmias developing can occur if phenylpropanolamine is administered topatients who have received cyclopropane or a halogenated hydrocarbon anesthetic agent.
Propranolol may be administered should these occur.