Prazosin (miniPress) Flashcards

Pharmacologic and Therapeutic Class

• Prazosin belongs to the adrenergic-blocking drug class.
• It is classified therapeutically as an antihypertensive agent.

Actions and Uses

• Acts as a selective alpha1-adrenergic antagonist, blocking norepinephrine at vascular smooth muscle receptors.
• Major benefit includes rapid reduction of peripheral resistance, leading to decreased blood pressure.
• Minimal impact on cardiac output and heart rate compared to other antihypertensives.
• Less reflex tachycardia observed; tolerance may develop over time.
• Commonly prescribed in combination with other drugs like beta blockers or diuretics.
• Short half-life necessitates dosage two to three times daily.

Administration Alerts

• Initiate treatment with a low first dose to prevent severe hypotension.
• Safety during pregnancy (Category C) or while breast-feeding has not been established.

Pharmacokinetics

• Onset of action: approximately 2 hours.
• Peak efficacy occurs between 2 to 4 hours post-administration.
• Effects last for less than 24 hours.

Adverse Effects

• Orthostatic hypotension is a significant risk due to alpha1 receptor blockade.
• Uncommon cases of fainting may occur about 30 minutes after the first dose; hence low initial doses are recommended at bedtime.
• Possible side effects include dizziness, drowsiness, and lightheadedness.
• Rapid blood pressure drop can trigger reflex tachycardia.
• Some patients may experience nasal congestion or ejaculation issues.

Contraindications

• Use is not recommended during pregnancy or lactation without further safety data.

Drug-Drug Interactions

• Combining prazosin with other antihypertensives and diuretics may cause dangerously low blood pressure.
• Alcohol consumption should be avoided while on this medication.

Lab Tests

• Prazosin may lead to increased urinary metabolites of vanillyl-mandelic acid (VMA) and norepinephrine, complicating pheochromocytoma screening tests.
• Can produce false-positive results in lab assessments.

Herbal/Food Interactions

• Avoid products such as saw palmetto or nettle root, as they can block alpha1 receptors resulting in additional hypotensive effects.

Treatment of Overdose

• Hypotension may be the primary outcome of overdose.
• Treatment may involve fluid expanders like normal saline or the use of vasopressors such as dopamine or dobutamine to stabilize blood pressure.

Other Drugs in this Class

• Includes medications such as acebutolol, alfuzosin, atenolol, bisoprolol, and several others with primary action on alpha1 or beta-adrenoceptors.