Phenoxybenzamine
Indications
Phenoxybenzamine is used for:
Hypertension in phaeochromocytoma
Adult Dose
Child Dose
Renal Dose
Administration
Contra Indications
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).
Precautions
Patient with heart failure, CHF, cerebrovascular diseases, cerebral or coronary atherosclerosis, respiratory infections. Renal impairment. Elderly. Children. Pregnancy and lactation. Patient Counselling 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.
Pregnancy-Lactation
Pregnancy Category: C
Lactation: Not known if excreted into breast milk, discontinue drug or do not nurse
Interactions
Increased hypotensive and cardiac accelerating effect with stimulators of both α- and β-receptors (e.g. epinephrine).
Adverse Effects
Side effects of Phenoxybenzamine :
Frequency Not Defined
Orthostatic hypotension
Tachycardia
Dizziness
Drowsiness
Fatigue
Malaise
Sedation
Dry mouth
Nausea
Vomiting
Inhibition of ejaculation
Miosis
Nasal congestion
Mechanism of Action
Phenoxybenzamine covalently binds to alpha-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.