CARDURA XL
Clinical safety rating
cautionComprehensive clinical and safety monograph for CARDURA XL (CARDURA XL).
Selective alpha-1 adrenergic receptor antagonist; inhibits postsynaptic alpha-1 adrenoceptors in vascular smooth muscle and the prostate, causing vasodilation and relaxation of prostatic smooth muscle.
| Metabolism | Extensively metabolized in the liver via CYP3A4 and CYP2D6; undergoes O-demethylation and hydroxylation. |
| Excretion | Primarily hepatic metabolism via CYP3A4, with ~63% of the dose excreted in feces as metabolites and ~9% in urine as unchanged drug. Renal elimination of active drug is minimal (<1%). |
| Half-life | 15-22 hours in adults; terminal half-life is approximately 22 hours for extended-release formulation, allowing once-daily dosing. Half-life is prolonged in elderly and patients with hepatic impairment. |
| Protein binding | ~98% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 1.9-3.1 L/kg, indicating extensive distribution into tissues, including vascular smooth muscle. |
| Bioavailability | Oral extended-release: ~85% relative to immediate-release formulation, with minimal first-pass metabolism. Food does not significantly affect absorption. |
| Onset of Action | Oral extended-release: 2-4 hours for therapeutic effect on blood pressure; maximal effect may take 2-4 weeks. |
| Duration of Action | 24 hours with once-daily dosing of the extended-release formulation, providing consistent blood pressure control over the dosing interval. |
| Molecular Weight | 547.61 |
4 mg orally once daily, with breakfast. May titrate to 8 mg once daily based on response. Maximum dose: 8 mg daily.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | No dose adjustment required for renal impairment (GFR ≥30 mL/min). For GFR <30 mL/min, use with caution; no specific dose recommendation available. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). For mild to moderate impairment (Child-Pugh class A or B), start at 2 mg once daily and titrate cautiously. |
| Pediatric use | Safety and efficacy not established in pediatric patients; no recommended dosing. |
| Geriatric use | Initiate at 2 mg once daily with breakfast; titrate slowly to avoid orthostatic hypotension. Monitor blood pressure closely. |
| 1st trimester | Doxazosin is generally avoided during the first trimester due to insufficient data; animal studies have shown embryotoxicity at high doses. Use only if clearly needed. |
| 2nd trimester | Limited human data; potential for fetal hypotension and reduced placental perfusion. Use only if benefit outweighs risk. |
| 3rd trimester | Avoid in third trimester due to risk of neonatal hypotension, respiratory depression, and other adverse effects. May cause fetal bradycardia. |
Clinical note
Comprehensive clinical and safety monograph for CARDURA XL (CARDURA XL).
| Placental transfer | Doxazosin crosses the placenta in animal studies; human data are limited. Likely crosses due to low molecular weight and lipophilicity. |
| Breastfeeding | Doxazosin is excreted into breast milk in low amounts; however, safety in infants has not been established. Monitor the infant for signs of hypotension, sedation, or poor feeding. Consider alternative agents with more safety data, such as nifedipine or labetalol. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Pregnancy Category C. First trimester: No adequate studies; animal studies show increased fetal resorption and decreased fetal weight at doses 5 times the MRHD. Second and third trimesters: Potential for reduced placental perfusion due to alpha-blockade; avoid use unless benefit outweighs risk. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate for hypotension. Fetal monitoring including ultrasound for growth restriction and amniotic fluid volume if used in pregnancy. |
| Fertility Effects | Animal studies: Decreased fertility in male rats at high doses. Human data: No specific data; alpha-blockers may impair ejaculation. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to doxazosin or any component of the formulationConcomitant use with phosphodiesterase-5 inhibitors (e.g., sildenafil) due to risk of hypotensionHistory of orthostatic hypotension or syncopeSevere hepatic impairment
| Precautions | Orthostatic hypotension and syncope, especially with first dose or dose increase, Priapism (rare), Intraoperative Floppy Iris Syndrome (IFIS) during cataract surgery, Hepatic impairment: dose adjustment may be needed |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they may increase doxazosin concentrations. No other significant food interactions known. Alcohol may exacerbate hypotensive effects. |
| Clinical Pearls | CARDURA XL (doxazosin extended-release) is an alpha-1 adrenergic blocker primarily used for benign prostatic hyperplasia (BPH). Its prolonged action reduces the risk of first-dose syncope compared to immediate-release. Do not crush or chew; swallow whole. Monitor blood pressure in patients also on antihypertensives due to additive hypotensive effects. Avoid use in patients with history of orthostatic hypotension or micturition syncope. |
| Patient Advice | Take exactly as prescribed, once daily with or without food. Swallow tablet whole, do not crush or chew. · Avoid grapefruit juice as it may alter drug levels. · Possible side effects include dizziness, fatigue, and nasal congestion. Rise slowly from sitting or lying to reduce fall risk. · May cause orthostatic hypotension especially after first dose or dose increase. · If you experience lightheadedness or fainting, contact your doctor. |
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