CARDURA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CARDURA (CARDURA).
Selective antagonist of alpha-1 adrenergic receptors, causing relaxation of smooth muscle in blood vessels and prostate.
| Metabolism | Extensively metabolized in the liver via O-demethylation and hydroxylation; CYP3A4 is the major enzyme involved. |
| Excretion | Primarily hepatic metabolism (approx. 60-70%) with biliary excretion of metabolites; renal excretion accounts for about 30-40% of the dose, mainly as metabolites with <5% unchanged drug. |
| Half-life | Terminal elimination half-life is approximately 22 hours, allowing once-daily dosing; peak effect on blood pressure occurs at 2-6 hours post-dose. |
| Protein binding | 98-99% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | 0.5-1.0 L/kg (approximately 50-70 L in adults); indicates extensive extravascular distribution. |
| Bioavailability | Oral bioavailability is approximately 65% (range 43-81%) with minimal first-pass effect. |
| Onset of Action | Oral: 1-2 hours for antihypertensive effect (first-dose effect may occur within 1-2 hours). |
| Duration of Action | 24 hours for blood pressure control with once-daily dosing; for benign prostatic hyperplasia, symptom improvement may take 2-4 weeks. |
Initial: 1 mg orally once daily, titrated based on standing blood pressure response up to 16 mg daily as a single dose or divided twice daily. Maximum: 16 mg/day.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for GFR ≥30 mL/min. For GFR <30 mL/min, start with 0.5 mg daily and titrate cautiously due to increased sensitivity. |
| Liver impairment | Child-Pugh A: Start at 0.5 mg daily. Child-Pugh B or C: Contraindicated due to extensive hepatic metabolism. |
| Pediatric use | Safety and efficacy not established in pediatric patients; use not recommended. |
| Geriatric use | Initiate at 0.5 mg daily due to increased risk of orthostatic hypotension. Titrate slowly based on tolerability and response. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CARDURA (CARDURA).
| Breastfeeding | Excreted in human milk; M/P ratio unknown. Caution due to potential for hypotension in nursing infants. Use only if essential. |
| Teratogenic Risk | Pregnancy Category C. First trimester: No evidence of teratogenicity in animal studies; limited human data. Second/third trimesters: Potential risk of fetal hypotension and hypoxia from maternal hypotension. Avoid use in pregnancy unless benefit outweighs risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to doxazosin or other quinazolines"]
| Precautions | ["Orthostatic hypotension and syncope, especially with first dose","Use with caution in patients with hepatic impairment","Risk of priapism","Intraoperative floppy iris syndrome during cataract surgery"] |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they may increase doxazosin levels. Take with food to reduce gastrointestinal upset. No other significant food interactions. |
| Clinical Pearls |
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| Monitor maternal blood pressure and fetal heart rate during use; assess for signs of placental hypoperfusion. |
| Fertility Effects | No known adverse effects on fertility in animal studies; human data lacking. |
| CARDURA (doxazosin) is an alpha-1 blocker used for hypertension and benign prostatic hyperplasia (BPH). First-dose syncope is more common with immediate-release (IR) than extended-release (GITS). Start IR at 1 mg at bedtime and titrate slowly. GITS formulation minimizes orthostatic effects. Monitor blood pressure carefully in elderly patients. May cause intraoperative floppy iris syndrome (IFIS) during cataract surgery; do not stop therapy preoperatively. Avoid use in patients with orthostatic hypotension or micturition syncope. |
| Patient Advice | Take the first dose at bedtime to minimize dizziness. Sit or lie down if you feel lightheaded. · Avoid sudden position changes; rise slowly from sitting or lying positions. · May cause dizziness, drowsiness, or blurred vision. Do not drive until you know how CARDURA affects you. · For BPH, it may take up to 2 weeks to improve symptoms. Do not stop medication abruptly. · Inform your surgeon if you are scheduled for cataract surgery; CARDURA may affect eye surgery outcomes. · Avoid alcohol, which can worsen side effects like dizziness and low blood pressure. · For hypertension, continue regular monitoring with your healthcare provider. |