Generic Name

Terazosin

Mechanism

• Selective α1‑adrenergic blockade: Terazosin binds competitively to α1A, α1B, and α1D receptors.
• Vascular effects: Inhibition of norepinephrine binding leads to *decreased vasoconstriction*, lowering systemic vascular resistance and arterial pressure.
• Prostatic effects: Reduces tone of smooth muscle in the bladder neck and prostate, decreasing resistance to urine flow.

> Why it matters: Because of its selectivity for α1 receptors, terazosin provides efficacy while minimizing β‑adrenergic–mediated tachycardia.

Pharmacokinetics

• Absorption: Oral bioavailability ~90 %; peak concentration (Cmax) ~4–6 h post‑dose.
• Distribution: Large volume of distribution (~1 L/kg). Binds ~70 % to plasma proteins.
• Metabolism: Predominantly hepatic via CYP3A4; minor CYP1A2 involvement.
• Elimination: Primarily renal (≈55 % unchanged). Clearance ~14–18 mL/min/kg.
• Half‑life: 15–18 h; supports once‑daily dosing.
• Drug interactions: Strong CYP3A4 inhibitors (ketoconazole, ritonavir) ↑ plasma levels; CYP3A4 inducers (rifampin) ↓ levels.

Indications

• Hypertension:
• Mono‑therapy or adjunct to other antihypertensives.
• Preferred in patients with concomitant BPH.
• Benign prostatic hyperplasia (BPH):
• Symptoms of lower‑tract obstruction: weak stream, intermittent voiding, post‑micturition dribble.

Contraindications

• Contraindications:
• Severe hepatic impairment.
• Known hypersensitivity to terazosin or other α1 antagonists.
• Warnings:
• Orthostatic hypotension: First‑dose “postural drop” risk; advise standing slowly.
• Hypotension with renal or hepatic failure: Dose adjustment required.
• Atrial fibrillation / bradycardia: Monitor for heart rate changes, especially when combined with β‑blockers or β‑agonists.
• Pregnancy/Lactation: Category C; use only if benefits justify risks.

Dosing

• Take with food to reduce GI discomfort.
• Avoid alcohol and other antihypotensives until tolerance is established.

Adverse Effects

• Common:
• Dizziness / orthostatic hypotension
• Headache, fatigue
• Nasal congestion, cough
• Nausea, dyspepsia
• Serious:
• Severe hypotension or syncope
• Reflex tachycardia (if rapid BP drop)
• Angioedema (rare)
• Drug‑induced hypersensitivity (rash, eosinophilia)

Monitoring

Clinical Pearls

• Start Low, Go Slow: The “1‑step‑at‑a‑time” U‑shaped titration margin (0.4 mg → 0.8 mg → 1.6 mg → 2.0 mg) slashes orthostatic incidents.
• Morning Dosing: Scales down nocturia and helps patients maintain daytime dynamism.
• BPH‑Only Patients: Merely shrinks prostate smooth muscle; no effect on nocturnal urine volume. Pair with anticholinergics if bladder overactivity persists.
• Tip for orthostatic hypotension: Instruct patients to rise from a seated or lying position by “raising the head” first, then the legs, to mitigate reflex vasoconstriction.
• UTI‑like symptoms: A rare dilemma; differentiate between urinary retention flare‑up and infection by checking urinalysis.
• Drug interactions: Avoid concurrent use of *other α1 blockers* (e.g., doxazosin) if off‑label attempts at synergy needed; CYP3A4 inhibitors can precipitate hypersensitivity acne.
• Pregnancy caution: As terazosin is a moderate‑potency β‑blocker by cross‑reactivity, it may impede fetal blood flow — a Category C drug.

*This drug card serves as a quick reference for medical students and clinical practitioners. Always consult the latest prescribing information for comprehensive dosing and safety updates.*