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  Terazosin (Hytrin)
 
Author: Donna Karasic, PharmD Last modified: March 31, 2002
 

  INDICATIONS

  • Benign Prostatic Hyperplasia
  • Hypertension
  • Heart Failure (non-FDA approved use)

  DOSAGE

  • Benign Prostatic Hyperplasia: 2-10mg once a day
  • Hypertension:usual dosing range 1mg to 5mg once a day; some patients may require up to 20mg per day.

  PHARMACOKINETICS

  • Peak response for BPH is a minimum of 4 to 6 weeks
  • Peak response for hypertension 4 hours
  • Oral bioavailability is 90%
  • Terazosin is extensively metabolized by the liver
  • Renal excretion is 10% unchanged and 30% inactive metabolites
  • Renal insufficiency does not affect the pharmacokinetics
  • 55% to 60% excreted in the feces; approximately 20% is excreted as unchanged drug
  • Elimination half half is 9 to 12 hrs

  ADVERSE EFFECTS

  • Most common adverse effects include dizziness (9%),lightheadedness (3.9%), fatigue, headache (4.9%), asthenia (7.4%),somnolence (3.6%)
  • Postural hypotension and syncope (0.6-3.9%)
  • Decreased hematocrit, hemoglobin, white blood cells, total protein, and albumin
  • Lowers serum total and LDL cholesterol and triglyceride levels and increasing or not affecting HDL cholesterol (3%)
  • Impotence has been reported (1.2% to 1.6%)
  • Tachycardia, palpitations (0.9%)
  • Peripheral edema (0.9%)
  • Blurred vision (0.6%)
  • Nasal congestion, rhinitis, dyspnea and sinusitis (2.4%)

  CONTRAINDICATIONS

  • Hypersensitivity to terazosin

  DRUG INTERACTIONS

  • Beta blockers
  • Verapamil

  FORMS

  • 1mg, 2mg, 5mg and 10mg capsules

  MECHANISM OF ACTION

  • Terazosin is a selective alpha-1-adrenergic blockers
  • It has been shown to increase urinary flow rates and decrease outflow obstruction and irritation symptoms associated with BPH by preventing stimulation of alpha-1-adrenergic receptors
  • Terazosin has been shown to decrease maximum voiding detrusor pressure and prevent bladder and upper urinary tract damage
  • However, alpha-1 blockers do not reverse the underlying pathophysiology of the disorder
  • Terazosin may regulate prostate growth by inducing apoptosis in epithelial and stromal smooth muscle cells without affecting rate of cell proliferation
 
IMPORTANT POINTS/RECOMMENDATIONS
  • Due to the potential for a severe hypotensive episode upon initiation of dosing with Terazosin, it is recommended to start with 1 mg at bedtime
  • If therapy is discontinued for several days, therapy should be reinstituted using the initial 1 mg dose at bedtime
  • For BPH, it takes 4-6 weeks before having clinical response; the dose should be increased slowly to the desired response
  • Dosing adjustments may be required in patients with hepatic dysfunction
  • Dosing adjustments are not required for elderly patients
  • Carcinoma of the prostate and BPH may cause the same symptoms. Prostate cancer should be ruled out prior to treatment
  • Terazosin does not appear to significantly affect PSA levels
 
REFERENCES
  1. Hutchinson TA & Shahan DR (Eds) ;  Terazosin ;  MICROMEDEX Healthcare Series: MICROMEDEX, Greenwood Village, Colorado (Edition expires 3-2202)

Copyright © 2002 The Johns Hopkins University School of Medicine. All rights reserved.