🍽️ phenoxybenzamine hydrochloride,(prescription)

Alpha-Adrenergic Blockade: Phenoxybenzamine is a non-selective alpha-adrenergic antagonist, meaning it blocks the action of adrenaline and noradrenaline on both alpha-1 and alpha-2 adrenergic receptors. By blocking these receptors, it causes vasodilation (widening of blood vessels) and reduces the effects of sympathetic nervous system activation, leading to a decrease in blood pressure.

Treatment of Pheochromocytoma: Phenoxybenzamine is particularly effective in the management of pheochromocytoma, a rare tumor of the adrenal gland that produces excess catecholamines (epinephrine and norepinephrine). By blocking the alpha-adrenergic receptors, phenoxybenzamine helps control hypertension and reduces the risk of hypertensive crisis associated with pheochromocytoma.

Orthostatic Hypotension: One of the side effects of phenoxybenzamine is orthostatic hypotension, which is a sudden drop in blood pressure upon standing up from a lying or sitting position. This can lead to dizziness, lightheadedness, or even fainting. Patients should be advised to change positions slowly to minimize this risk.

Reflex Tachycardia: Phenoxybenzamine-induced vasodilation can trigger reflex tachycardia (rapid heart rate) as the body attempts to compensate for the decrease in blood pressure. This effect may be more pronounced in some individuals, particularly those with pre-existing cardiovascular conditions.

Nasal Congestion: Phenoxybenzamine can cause nasal congestion as a result of its alpha-blocking effects on blood vessels in the nasal mucosa. This side effect may be bothersome for some patients but is generally mild and transient.

Gastrointestinal Effects: Gastrointestinal side effects such as nausea, vomiting, and diarrhea may occur with phenoxybenzamine use. These effects are usually mild and may improve with continued use or dose adjustment.

Urinary Retention: Phenoxybenzamine may impair bladder function and lead to urinary retention, particularly in men with prostatic hypertrophy. Patients should be monitored for urinary symptoms and advised to seek medical attention if they experience difficulty urinating.

Ocular Effects: Phenoxybenzamine can cause miosis (pupil constriction) and blurred vision due to its effects on alpha-adrenergic receptors in the eye. Patients should use caution when driving or operating machinery, especially in low-light conditions.

Edema: Peripheral edema (swelling of the extremities) may occur as a result of fluid redistribution caused by phenoxybenzamine-induced vasodilation. Patients with heart failure or renal impairment may be at increased risk of developing edema.

Hypotension During Surgery: Phenoxybenzamine is sometimes used preoperatively to control blood pressure during surgical removal of pheochromocytoma. Careful monitoring of blood pressure and hemodynamic parameters is essential during surgery to prevent hypotension and maintain adequate perfusion to vital organs.

Interactions: Phenoxybenzamine may interact with other medications, particularly other antihypertensive drugs, leading to additive effects on blood pressure. Patients should inform their healthcare provider about all medications they are taking, including prescription, over-the-counter, and herbal supplements.