TERAZOSIN HYDROCHLORIDE
Clinical safety rating: safe
Animal studies have demonstrated safety
Selective alpha-1 adrenergic receptor antagonist; inhibits vasoconstriction and relaxes smooth muscle in blood vessels and prostate.
| Metabolism | Extensively metabolized in the liver via hydroxylation and oxidation; CYP3A4 involved. |
| Excretion | Approximately 40% of the dose is excreted in urine (20% as unchanged drug) and 60% in feces via biliary elimination. |
| Half-life | Terminal elimination half-life is 9–12 hours in patients with normal renal function; may be prolonged in renal impairment. |
| Protein binding | 90–94% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | Approximately 0.8 L/kg, indicating extensive distribution into tissues. |
| Bioavailability | Oral bioavailability is approximately 90% under fasting conditions; food slightly delays absorption but does not significantly reduce extent. |
| Onset of Action | Oral: Peak antihypertensive effect occurs within 2–3 hours; symptomatic improvement in BPH may take 2–4 weeks. |
| Duration of Action | Antihypertensive effect persists for 24 hours with once-daily dosing; for BPH, continuous therapy is required for sustained symptom relief. |
Adults: Initial: 1 mg orally once daily at bedtime. May increase gradually to 2–5 mg once daily. Maximum: 20 mg/day.
| Dosage form | TABLET |
| Renal impairment | No adjustment required for mild to moderate impairment (GFR ≥30 mL/min). For severe impairment (GFR <30 mL/min), use with caution; data limited. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). For mild to moderate (Child-Pugh A or B), initiate at 1 mg once daily and titrate cautiously. |
| Pediatric use | Safety and efficacy not established in pediatric patients; use not recommended. |
| Geriatric use | Initiate at 1 mg once daily at bedtime; titrate slowly due to increased risk of orthostatic hypotension and falls. Consider lower maintenance doses (2–5 mg). |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other antihypertensive drugs can have additive effects Can cause marked first-dose hypotension and syncope.
| Breastfeeding | No data on excretion in human milk; M/P ratio unknown. Due to potential for adverse effects in nursing infant (hypotension), caution advised. Consider alternative agents with more safety data during breastfeeding. |
| Teratogenic Risk | Terazosin is an alpha-1 adrenergic antagonist. Limited human data; animal studies show no teratogenicity at clinically relevant doses. FDA Pregnancy Category C. Risk cannot be ruled out. In first trimester, no known association with major malformations; second and third trimester risks unknown. Use only if clearly needed. |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | BPH |
| Serious Effects |
["Hypersensitivity to terazosin or other alpha-blockers"]
| Precautions | ["Orthostatic hypotension and syncope, especially with first dose","Priapism","Intraoperative floppy iris syndrome","Dizziness and somnolence","Hepatic impairment"] |
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| Fetal Monitoring | Monitor maternal blood pressure and heart rate regularly, especially during dose titration. Assess for orthostatic hypotension in mother. Fetal monitoring not specifically required but standard prenatal care applies; ultrasound for growth if prolonged use. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment of fertility at doses up to 30 mg/kg/day. May cause priapism in males, but reversible. |