Minipres (Prazosin)

• Prazosin is used to manage conditions that involve excessive alpha‑1 adrenergic activity, primarily within the cardiovascular and urological systems.
• Essential hypertension: reduces systolic and diastolic blood pressure by decreasing peripheral vascular resistance.
• Benign prostatic hyperplasia: improves urinary symptoms by relaxing prostatic smooth muscle and the bladder neck.
• Hypertension (including secondary causes): may be added to combination therapy to achieve target blood pressure when monotherapy is insufficient.

• Prazosin selectively antagonizes alpha‑1 adrenergic receptors on vascular smooth muscle and in the prostate. Blocking these receptors prevents norepinephrine‑induced vasoconstriction, leading to vasodilation and lowered peripheral resistance, while also relaxing smooth muscle in the prostate and bladder neck to ease urinary outflow.

Prazosin may cause a range of adverse reactions, which are generally categorized by frequency and severity.

Common Side Effects

• Dizziness or light‑headedness
• Headache
• Fatigue
• Nasal congestion
• Nausea

Serious or Rare Side Effects

• Severe hypotension or syncope
• Priapism (prolonged erection)
• Allergic reactions such as rash, angioedema, or anaphylaxis
• Liver enzyme abnormalities

• When prescribing prazosin, clinicians should consider several precautionary measures to ensure safe use.
• Blood pressure monitoring: check baseline and periodic readings to avoid excessive hypotension.
• Initiate therapy at low dose: start with a low dose and titrate gradually to minimize orthostatic effects.
• Avoid abrupt discontinuation: taper the dose when stopping to prevent rebound hypertension.
• Caution in cardiac disease: use carefully in patients with coronary artery disease or heart failure.
• Use with caution in hepatic impairment: dose adjustment may be required in moderate to severe liver disease.
• Store at ambient temperature: keep below 25 °C in the original container, protected from moisture and light.

Prazosin can interact with other medicines, altering its efficacy or safety profile.

Major Interactions (Avoid)

• Concomitant use with other antihypertensives (e.g., ACE inhibitors, diuretics) may cause additive hypotension.
• Phosphodiesterase‑5 inhibitors (e.g., sildenafil) can precipitate severe hypotension.
• Other alpha‑1 blockers (e.g., doxazosin) increase risk of profound blood pressure drop.

Moderate Interactions (Monitor Closely)

• Diuretics: may enhance orthostatic hypotension; monitor fluid status.
• Beta‑blockers: combined effect on blood pressure may require dose adjustment.
• CYP3A4 inhibitors (e.g., erythromycin, ketoconazole): can increase prazosin plasma levels.
• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce efficacy.
• NSAIDs: may blunt antihypertensive response.