|
Indications and Dosage
Oral
Hypertension in phaeochromocytoma Adult: Initially, 10 mg once daily or bid, gradually increased daily by 10 mg increments, according to patient’s response. Maintenance: 1-2 mg/kg daily in 2 divided doses.
Child: 1-2 mg/kg daily. Elderly: 10 mg daily. |
|
Contraindications
CVA, recovery period (usually 3-4 weeks) after acute MI, conditions where a decrease in blood pressure may be undesirable (e.g. coronary artery disease, stroke).
|
|
Special Precautions
Patient with heart failure, CHF, cerebrovascular diseases, cerebral or coronary atherosclerosis, respiratory infections. Renal impairment. Elderly. Children. Pregnancy and lactation.
|
|
Adverse Reactions
Significant: Postural hypotension with dizziness, compensatory tachycardia.
Eye disorders: Miosis. Gastrointestinal disorders: Gastrointestinal upset. General disorders and admininistration site conditions: Fatigue. Psychiatric disorders: Drowsiness. Reproductive system and breast disorders: Inhibition of ejaculation. Respiratory, thoracic and mediastinal disorders: Nasal congestion. |
|
Patient Counseling Information
This drug may cause dizziness and drowsiness, if affected, do not drive or operate machinery.
|
|
Monitoring Parameters
Regularly monitor blood pressure especially after each dose adjustment; pulse, orthostatics.
|
|
Overdosage
Symptoms: Profound hypotension leading to dizziness or fainting, tachycardia, collapse, vomiting, lethargy, shock. Management: Symptomatic and supportive treatment. Induce vomiting and/or gastric lavage. Treat hypotension with plasma expanders and by postural measures.
|
|
Drug Interactions
Increased hypotensive effect and tachycardia with stimulators of both α- and β-receptors (e.g. epinephrine).
|
|
Action
Description: Phenoxybenzamine covalently binds to α-receptors causing long lasting non-competitive inhibition of postganglionic synapses thus blocking the effects of epinephrine and norepinephrine at α1 and α2 receptors causing arterial and venous vasodilation and reflex tachycardia.
Onset: Within 2 hr. Duration: ≥3-4 days. Pharmacokinetics: Absorption: Incompletely and variably absorbed from the gastrointestinal tract. Bioavailability: 20-30%. Distribution: Distributed and accumulates in the adipose tissues. Metabolism: Metabolised in the liver via dealkylation into N-phenoxyisopropyl-benzylamine. Excretion: Mainly via urine and bile. Elimination half-life: Approx 24 hour. |
|
Chemical Structure
 Source: National Center for Biotechnology Information. PubChem Database. Phenoxybenzamine, CID=4768, https://pubchem.ncbi.nlm.nih.gov/compound/Phenoxybenzamine (accessed on Jan. 22, 2020) |
|
Storage
Store between 20-25°C.
Avoid contact with skin or mucous membranes by wearing gloves and protective equipment. Wash hands before and after handling. |
|
MIMS Class
|
|
ATC Classification
C04AX02 - phenoxybenzamine ; Belongs to the class of other peripheral vasodilators.
|
|
References
Anon. Phenoxybenzamine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 31/10/2017. Buckingham R (ed). Phenoxybenzamine Hydrochloride. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 18/10/2017. Joint Formulary Committee. Phenoxybenzamine Hydrochloride. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 18/10/2017. McEvoy GK, Snow EK, Miller J et al (eds). Phenoxybenzamine Hydrochloride. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 18/10/2017. Phenoxybenzamine Hydrochloride Capsule (West-Ward Pharmaceuticals Corp.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 31/10/2017.
|
Sign Out
