Generic Name

Hytrin (terazosin)

Mechanism

Terazosin competitively blocks α₁‑adrenergic receptors on vascular smooth muscle and the prostate/urinary tract.
• ↓ Pre‑junctional norepinephrine release → vasodilation
• ↓ Post‑junctional α₁ signaling → lower peripheral vascular resistance, lower blood pressure
• ↓ Myogenic tone in the prostate → decreased bladder outlet obstruction

The drug’s selective affinity for α₁A/α₁D receptors gives its therapeutic benefit in BPH while sparing α₁B receptors in the vasculature, minimizing reflex tachycardia.

Pharmacokinetics

• Absorption: ~25 % oral bioavailability; peak plasma conc. (Cₘₐₓ) reached 4‑6 h post‑dose.
• Distribution: Volume of distribution ≈ 300 L; highly protein‑bound (~97 %).
• Metabolism: Hepatic CYP3A4/2D6 → active metabolites.
• Elimination: Primarily renal; half‑life ≈ 20‑30 h (steady‑state ≈ 35 h).
• Dose adjustment: Renal impairment—reduce frequency; hepatic impairment—monitor closely; no adjustment needed for mild‑moderate hepatic disease.

Indications

• Primary hypertension (monotherapy or combination therapy).
• Benign prostatic hyperplasia (BPH): lower urinary tract symptoms, improved urinary flow.
• Off‑label: pre‑eclampsia (rare), congestive heart failure (as adjunct).

Contraindications

• Contraindications:
• Atrial fibrillation or atrial flutter with rapid ventricular response
• Severe orthostatic hypotension
• Use in pregnancy (category C) – avoid
• Warnings:
• First‑dose syncope: Monitor orthostatic BP for 1 h after first dose.
• Drug interactions: CYP3A4 inhibitors (e.g., ketoconazole) ↑ terazosin plasma levels; CYP3A4 inducers (e.g., rifampicin) ↓ efficacy.
• Renal impairment: Accumulation may increase hypotensive risk.
• Aldosterone‑receptor blockers & NSAIDs may potentiate hypotension.

Dosing

• Take once daily in the evening for hypertension; split dosing (e.g., 0.4 mg at bedtime + 0.4 mg morning) is acceptable for BPH to improve symptom control.
• Consistency in dosing time reduces orthostatic trough effects.

Adverse Effects

• Common (≥10 %): dizziness, headache, fatigue, nasal congestion, orthostatic hypotension, nausea.
• Serious (≤1 %): severe orthostatic hypotension, syncope, myalgia, angioedema (rare), hepatotoxicity (monitor LFTs).
• Long‑term concerns: cardiovascular events if untreated; rare reports of sexual dysfunction.

Monitoring

• Blood pressure & heart rate: baseline, 1 h after first dose, then weekly until stable.
• Renal function (CrCl): baseline and quarterly.
• Liver enzymes (ALT/AST): baseline and every 6‑12 weeks if >3× ULN; discontinue if >5× ULN.
• Urinary flow (Qmax) / PVR: baseline for BPH, every 3–6 months.
• Adverse events: monitor for dizziness, syncope; adjust dose accordingly.

Clinical Pearls

• First‑dose orthostatic hypotension: The greatest drop occurs within 30–60 min after ingestion. In patients with hypertension, give the initial tablet at bedtime or instruct to stand slowly during first visit.
• Split‑dose strategy for BPH: Helps maintain plasma levels, reducing nocturia and improving daytime urinary flow.
• Drug interactions: Avoid concomitant use of α‑blockers (e.g., doxazosin) or non‑selective β‑blockers when starting terazosin; if necessary, overlap for only 3–5 days.
• Renal dosing: In CrCl 30–59 mL/min, give 0.4 mg nightly; for CrCl < 30 mL/min, consider 0.4 mg BID with close BP monitoring.
• Elderly: Higher sensitivity to orthostatic drop; start at lower end of spectrum (0.1‑0.2 mg) unless titrated by 0.4 mg.
• Pregnancy category: Terazosin is contraindicated; discuss non‑α‑blocker alternatives.
• Bioavailability and food interactions: Food does not significantly affect absorption; take with meals if GI upset.

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• Key take‑away: Hytrin offers dual benefits for hypertension and BPH through selective α₁ blockade, yet careful scheduling, titration, and monitoring are essential to mitigate orthostatic hypotension and other dose‑related adverse events.