From the Guidelines
Prazosin belongs to the drug class of alpha-1 blockers, which work by selectively blocking alpha-1 receptors in blood vessels and the prostate, causing smooth muscle relaxation and vasodilation. This mechanism leads to decreased peripheral vascular resistance and blood pressure reduction, making prazosin primarily used to treat hypertension. It's also prescribed for benign prostatic hyperplasia (BPH) symptoms by relaxing prostate and bladder neck muscles, improving urinary flow. According to the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1, alpha-1 blockers like prazosin may be considered as second-line agents in patients with concomitant BPH.
Some key points to consider when prescribing prazosin include:
- Starting with a low dose (1 mg at bedtime) to minimize first-dose hypotension, a common side effect where blood pressure drops significantly after the initial dose, potentially causing dizziness or fainting.
- Being aware of other potential side effects, such as headache, drowsiness, and nasal congestion.
- Understanding that prazosin differs from non-selective alpha blockers by having minimal effect on alpha-2 receptors, resulting in less reflex tachycardia.
- Considering the usual dose range of 2-20 mg, taken 2 or 3 times a day, as outlined in the guideline 1.
- Recognizing that alpha-1 blockers like prazosin are associated with orthostatic hypotension, especially in older adults, as noted in the guideline 1 and 1.
Overall, prazosin is a valuable treatment option for hypertension and BPH, offering a unique mechanism of action and potential benefits for patients with specific comorbidities. However, it's essential to carefully consider the potential risks and side effects, as well as the individual patient's needs and medical history, when prescribing prazosin.
From the FDA Drug Label
Prazosin hydrochloride, USP a quinazoline derivative, is the first of a new chemical class of antihypertensives The drug class of Prazosin is antihypertensives 2.
- Main classification: Antihypertensive
- Specific class: Quinazoline derivative
From the Research
Prazosin Drug Class
- Prazosin is classified as an alpha 1-adrenoceptor antagonist 3, 4, 5.
- It is a selective alpha 1-adrenergic antagonist, which means it has little or no effect on alpha 2-adrenoceptors 3, 4.
- This selectivity is responsible for its therapeutic success in the treatment of hypertension, as it preserves the local feedback control of the release of noradrenergic transmitter by the pre-junctional alpha 2-adrenoceptors 3.
- Prazosin is also used in the treatment of congestive heart failure and has potential applications in the treatment of peripheral vasospasm due to Raynaud's phenomenon or ergotamine overdose 5.
- Alpha-1 adrenergic receptor antagonists like prazosin are used in the management of benign prostate hyperplasia (BPH) and can be combined with 5-alpha-reductase inhibitors for improved efficacy 6.
Mechanism of Action
- Prazosin works by blocking the alpha 1-adrenergic receptors in the smooth muscle of blood vessels, leading to vasodilation and a decrease in blood pressure 4, 5.
- Its selective blockade of alpha 1-receptors allows for a balanced reduction in both arteriolar and venous tone, with little change or even improvement in renal hemodynamics 4.