HYTRIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for HYTRIN (HYTRIN).
Selective alpha-1 adrenergic receptor antagonist; inhibits activation of postsynaptic alpha-1 receptors, resulting in relaxation of smooth muscle in the prostate and bladder neck, improving urinary flow and reducing symptoms of benign prostatic hyperplasia (BPH).
| Metabolism | Extensively metabolized in the liver via demethylation and dehydrogenation; multiple metabolites are formed, some pharmacologically active. CYP450 enzymes involved include CYP3A4 and CYP2D6. |
| Excretion | Renal: ~40% as metabolites, <1% unchanged; biliary/fecal: ~60% as metabolites; total clearance 6.4 L/h. |
| Half-life | Terminal elimination half-life: 12–13 hours (range 10–15 h); clinical context: steady state achieved in 2–3 days; dose adjustment not required in renal impairment but caution in hepatic impairment. |
| Protein binding | 90–94% bound to albumin; free fraction 6–10%. |
| Volume of Distribution | Vd: 3.9 L/kg (range 3.5–4.3 L/kg); large Vd indicates extensive tissue distribution, high affinity for vascular smooth muscle. |
| Bioavailability | Oral bioavailability: >90% (first-pass metabolism minimal); food does not affect absorption. |
| Onset of Action | Oral: 1–2 hours for first-dose effect; peak effect on blood pressure at 2–4 hours; optimal effect may require 2–4 weeks of titration. |
| Duration of Action | Antihypertensive effect: 24 hours with once-daily dosing; switch to twice-daily if needed for BPH symptoms (24-hour duration for BPH). |
Initial: 1 mg orally once daily at bedtime, increase gradually up to 20 mg/day; typical maintenance: 2-10 mg once daily. For BPH: 5-10 mg once daily. For hypertension: 1-5 mg once daily. Maximum: 20 mg/day.
| Dosage form | TABLET |
| Renal impairment | No specific GFR-based dose adjustment required; use with caution in severe renal impairment (CrCl <30 mL/min) due to potential accumulation. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). For mild to moderate (Child-Pugh A or B), initial dose 1 mg at bedtime, titrate cautiously; monitor for hypotension. |
| Pediatric use | Not approved for use in children; safety and efficacy not established. |
| Geriatric use | Initiate at 1 mg at bedtime to minimize orthostatic hypotension; titrate slowly. Elderly patients may experience increased sensitivity to hypotensive effects. Monitor blood pressure and renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for HYTRIN (HYTRIN).
| Breastfeeding | It is not known whether terazosin is excreted in human milk. The M/P ratio is unknown. Caution is advised when administered to a nursing woman; consider developmental and health benefits of breastfeeding along with mother's clinical need. |
| Teratogenic Risk | Terazosin (HYTRIN) is FDA Pregnancy Category C. No adequate and well-controlled studies in pregnant women. In animal studies, terazosin was not teratogenic in rats or rabbits at doses up to 200 mg/kg/day (rat) and 75 mg/kg/day (rabbit), but delayed fetal ossification was observed. Risk cannot be ruled out; use only if potential benefit justifies potential risk to fetus. |
■ FDA Black Box Warning
None.
| Common Effects | Dizziness Headache Drowsiness Low energy Weakness Palpitations Nausea |
| Serious Effects |
["Hypersensitivity to terazosin or any component of the formulation.","Concomitant use with phosphodiesterase-5 inhibitors (e.g., sildenafil) may increase risk of hypotension (relative contraindication; use with caution)."]
| Precautions | ["Orthostatic hypotension and syncope, especially with first dose (first-dose effect); dose titration recommended.","Priapism (rare); advise patient to seek immediate medical attention if erection persists >4 hours.","Intraoperative floppy iris syndrome (IFIS) during cataract surgery in patients on alpha-1 blockers.","Use with caution in patients with renal impairment or hepatic impairment.","May cause dizziness, drowsiness, or blurred vision; caution when driving or operating machinery."] |
| Food/Dietary |
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| Fetal Monitoring | Monitor maternal blood pressure regularly for hypotension, especially during dose titration. Assess for orthostatic hypotension. Fetal monitoring warranted in pregnant women with preeclampsia or hypertension. No specific fetal monitoring required for terazosin alone. |
| Fertility Effects | In animal studies, terazosin did not impair fertility in rats at doses up to 200 mg/kg/day. In humans, there are no data on fertility impairment. Alpha-1 blockers may cause ejaculatory dysfunction in males, but effects on female fertility are unknown. |
| No significant food interactions. Avoid grapefruit juice as it may increase drug levels. Take with or without food. Limit alcohol intake as it may enhance orthostatic effects. |
| Clinical Pearls | HYTRIN (terazosin) is an alpha-1 adrenergic blocker used for hypertension and benign prostatic hyperplasia (BPH). First-dose syncope can occur; start with 1 mg at bedtime. Titrate slowly to avoid orthostatic hypotension. Monitor blood pressure 2-3 hours after initial dose and after dose increases. May cause intraoperative floppy iris syndrome (IFIS) in cataract surgery; notify ophthalmologist. Use with caution in patients with renal impairment. Can be used alone or with other antihypertensives. |
| Patient Advice | Take the first dose at bedtime to minimize dizziness or fainting. · Avoid sudden standing or sitting up quickly to prevent orthostatic hypotension. · Report any prolonged erections lasting more than 4 hours immediately. · Avoid driving or hazardous activities until you know how the drug affects you. · Do not stop taking abruptly; consult doctor for gradual dose reduction. · Inform all healthcare providers, especially eye surgeons, that you are taking terazosin. |