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Alpha-1 Adrenergic Blockers
Mechanism of action |
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| Act at post-synaptic alpha-1 receptors to produce arteriole and venous vasodilation | ||||||
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alfuzosin
(Uroxatral ® )
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Oral: Adults: BPH: 10 mg once daily Dosage adjustment in renal impairment: Bioavailability and maximum serum concentrations are increased by ~50% with mild, moderate, or severe renal impairment Note: Safety has not been evaluated in patients with creatinine clearances <30 mL/minute. Dosage adjustment in hepatic impairment: Mild hepatic impairment: Use has not been studied. Moderate or severe hepatic impairment (Child-Pugh class B and C): Clearance is decreased 1 /3 to 1 /4 and serum concentration is increased three- to fourfold; use is contraindicated Administration Tablet should be swallowed whole; do not crush or chew. Administer once daily (with a meal); should be taken at the same time each day. [ Supplied: 10mg extended release tablet.] |
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doxazosin
(Cardura ® )
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Mechanism of Action Competitively inhibits postsynaptic alpha-adrenergic receptors which results in vasodilation of veins and arterioles and a decrease in total peripheral resistance and blood pressure; approximately 50% as potent on a weight by weight basis as prazosin Oral: Adults: 1 mg once daily in morning or evening; may be increased to 2 mg once daily. Thereafter titrate upwards, if needed, over several weeks, balancing therapeutic benefit with doxazosin-induced postural hypotension Hypertension: Maximum dose: 16 mg/day BPH: Goal: 4-8 mg/day; maximum dose: 8 mg/day Elderly: Initial: 0.5 mg once daily [Supplied 1 mg, 2 mg, 4 mg, 8 mg tablets] |
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prazosin (Minipress ® )
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Mechanism of Action Competitively inhibits postsynaptic alpha-adrenergic receptors which results in vasodilation of veins and arterioles and a decrease in total peripheral resistance and blood pressure Oral: Adults: Hypertension: Initial: 1 mg/dose 2-3 times/day; usual maintenance dose: 3-15 mg/day in divided doses 2-4 times/day; maximum daily dose: 20 mg Hypertensive urgency: 10-20 mg once, may repeat in 30 minutes Raynaud's (unlabeled use): 0.5-3 mg twice daily [Supplied: 1, 2, 5mg capsules] |
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tamsulosin ( Flomax ® )
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Mechanism of Action Tamsulosin is an antagonist of alpha1A adrenoreceptors in the prostate. Smooth muscle tone in the prostate is mediated by alpha1A adrenoreceptors; blocking them leads to relaxation of smooth muscle in the bladder neck and prostate causing an improvement of urine flow and decreased symptoms of BPH. Approximately 75% of the alpha1 receptors in the prostate are of the alpha1A subtype. Dosage - Oral: Adults: BPH: 0.4 mg once daily ~30 minutes after the same meal each day; dose may be increased after 2-4 weeks to 0.8 mg once daily in patients who fail to respond. If therapy is interrupted for several days, restart with 0.4 mg once daily. Dosage adjustment in renal impairment: Clcr >/= 10 mL/minute: No adjustment needed Clcr<10 mL/minute: Not studied [Supplied: 0.4 mg capsule] |
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terazosin (Hytrin ® )
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Mechanism of Action Alpha1-specific blocking agent with minimal alpha2 effects; this allows peripheral postsynaptic blockade, with the resultant decrease in arterial tone, while preserving the negative feedback loop which is mediated by the peripheral presynaptic alpha2-receptors; terazosin relaxes the smooth muscle of the bladder neck, thus reducing bladder outlet obstruction Oral: Adults: Hypertension: Initial: 1 mg at bedtime; slowly increase dose to achieve desired blood pressure, up to 20 mg/day; usual dose range (JNC 7): 1-20 mg once daily Dosage reduction may be needed when adding a diuretic or other antihypertensive agent; if drug is discontinued for greater than several days, consider beginning with initial dose and retitrate as needed; dosage may be given on a twice daily regimen if response is diminished at 24 hours and hypotensive is observed at 2-4 hours following a dose Benign prostatic hyperplasia: Initial: 1 mg at bedtime, increasing as needed; most patients require 10 mg day; if no response after 4-6 weeks of 10 mg/day, may increase to 20 mg/day [Supplied 1, 2, 5, 10 mg capsule] |
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MDX: DOXAZOSIN-TO-TERAZOSIN CONVERSION
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| According to 1 study, dosage-conversion from doxazosin to terazosin results in similar or better control of symptoms in most (83%) patients with BENIGN PROSTATIC HYPERPLASIA (BPH). In this study, patients with BPH (n=69) were switched from doxazosin to terazosin according to the following protocol: doxazosin 1 milligram (mg) to terazosin 1 mg, 2 mg to 2 mg, 4 mg to 5 mg, 8 mg to 10 mg, 12 mg to 15 mg, and 16 mg to 20 mg. There were no significant differences in International Prostate Symptom Score (IPSS), blood pressure, pulse, or adverse effects before and after the conversion (p less than 0.05). | ||||||
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