terazosin (Hytrin, Hydracin, Hytrinex, Vasocard)
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Introduction
Tradename: Hytrin.
Indications
- hypertension
- benign prostatic hypertrophy (BPH)
- adjunctive agent in the management of congestive heart failure (CHF)
- urinary calculus[6]
Dosage
- start 1 mg PO QHS, max 20 mg/day
- give 1st dose QHS (1st dose syncope)
- do NOT withdraw therapy abruptly; taper dose
Tabs: 1, 2, 5, 10 mg.
Caution:
- QHS dosing; postural hypotension & syncope may occur with the 1st dose
Pharmacokinetics
- oral bioavailability is 90%
- 90-94% bound to plasma proteins
- extensively metabolized in the liver
- excreted in feces & urine
- onset of action is within 15 minutes
- peak effects are seen in 2 hours
- duration of action 24 hours
- elimination 1/2life is 13 hours
- pharmacokinetics are not altered by uremia, CHF or aging
- maximal response for BPH is 4-6 weeks
elimination via liver
elimination via kidney
protein binding = 90-94 %
1/2life = 13 hours
Adverse effects
- common (> 10%)
- less common (1-10%)
- uncommon (< 1%)
- other
- 1st dose syncope
- fatigue
- drowsiness
- drug adverse effects of alpha-1 adrenergic receptor antagonists
- drug adverse effects of antihypertensive agents
Drug interactions
- beta blockers enhance postural hypotension reactions
- clonidine: decreased antihypertensive effect
- drug interaction(s) of phosphodiesterase-5-inhibitors with alpha-1-adrenergic receptor antagonists
- drug interaction(s) of loop diuretics with alpha-1 adrenergic receptor antagonist
- drug interaction(s) of NSAIDs & antihypertensives
Laboratory
Mechanism of action
- alpha-1 adrenergic receptor antagonist
- reduces total peripheral resistance through both arterial & venous dilation
- little or no change in heart rate or cardiac output
- increases urine flow in BPH by relaxing smooth muscle tone in the bladder neck of the prostate
- relaxes internal urethral sphincter[5]
- increases HDL cholesterol
- enhances glycolysis[7]
- may improve glucose tolerance with long-term therapy
- may lower risk of Parkinson's disease (RR=0.88)[7]
- may reduce left ventricular hypertrophy with long-term therapy
More general terms
References
- ↑ The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- ↑ Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
- ↑ 5.0 5.1 Geriatrics Review Syllabus, American Geriatrics Society, 5th edition, 2002-2004
- ↑ 6.0 6.1 Deprecated Reference
- ↑ 7.0 7.1 7.2 Simmering JE, Welsh MJ, Liu L et al Association of Glycolysis-Enhancing alpha-1 Blockers With Risk of Developing Parkinson Disease. JAMA Neurol. 2021;78(4):407-413. Feb 1. PMID: https://www.ncbi.nlm.nih.gov/pubmed/33523098 PMCID: PMC7851758 Free PMC article https://jamanetwork.com/journals/jamaneurology/fullarticle/2775976