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prazosin (Minipress, Deprazolin)
Tradename: Minipress.
Indications:
1) benign prostatic hypertrophy
2) hypertension
3) Raynaud's disease
4) severe congestive heart failure in connection with diuretics & digoxin
5) nightmares resulting from PTSD [5]; maybe not [7]
Contraindications:
- chronic PTSD in military veterans [7]
Dosage:
1) start* 1 mg PO QHS, then BID/TID
2) maximum: 20-40 mg/day
3) do NOT withdraw therapy abruptly, taper dose
4) BPH
a) 1-2 mg QD, BID, TID
b) most patients are well controlled on QHS dosing
Tabs: 1,2 5 mg.
* The 1st dose of prazosin may cause hypotension & syncope, thus it should be given before bedtime.
Pharmacokinetics:
1) oral bioavailability is 60%
2) plasma 1/2life is 2-4 hours
3) metabolized in the liver
4) excreted in the urine
Adverse effects:
1) common (> 10%)
- orthostatic hypotension*, dizziness, lightheadedness, drowsiness, headache, malaise
2) less common (1-10%)
- edema, palpitations, urinary incontinence, dry mouth, fatigue, nervousness
3) uncommon (< 1%)
- angina, dyspnea, priapism, nausea, urinary frequency, nasal congestion, nightmares, rash, sexual dysfunction, hypothermia
4) other
- reflex tachycardia
- development of tolerance
- gastrointestinal distress
- 1st dose syncope
- impotence & priapism are rare
Drug interactions:
1) beta-blockers enhance acute postural hypotensive reactions
2) verapamil increases serum prazosin levels
3) clonidine: decreases antihypertensive effect
Laboratory:
- prazosin in serum/plasma
Mechanism of action:
1) alpha-1 adrenergic receptor antagonist
2) reduces total peripheral resistence through both arterial & venous dilation
3) minimal changes in heart rate & cardiac output
4) increases urine flow in BPH by relaxing smooth muscle tone in the bladder neck of the prostate
5) increases HDL cholesterol
6) may improve glucose tolerance
7) may reduce left ventricular hypertrophy with long-term therapy
Interactions
drug interactions
drug adverse effects (more general classes)
General
alpha-1 adrenergic receptor antagonist; prostate-selective alpha blocker
piperazinyl quinazoline
Properties
MISC-INFO: elimination route LIVER
1/2life 2-4 HOURS
pregnancy-category C
safety in lactation ?
Database Correlations
PUBCHEM correlations
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
- Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed)
Lippincott-Raven, Philadelphia, 1998, pg 474
- Kaiser Permanente Northern California Regional Drug
Formulary, 1998
- Dierks MR et al,
Prozosin treatment of nightmares related to postraumatic stress
disorder.
Ann Pharmacother 2007, 41:1013
PMID: 17504838
- Drug Information & Medication Formulary, Veterans Affairs,
Central California Health Care System, 1st ed., Ravnan et al
eds, 1998
- Raskind MA et al.
Trial of prazosin for post-traumatic stress disorder in
military veterans.
N Engl J Med 2018 Feb 8; 378:507
PMID: 29414272
http://www.nejm.org/doi/10.1056/NEJMoa1507598
- Ressler KJ.
Alpha-adrenergic receptors in PTSD - Failure or time for
precision medicine?
N Engl J Med 2018 Feb 8; 378:575
PMID: 29414268
http://www.nejm.org/doi/10.1056/NEJMe1716724
Component-of
Minizide (prazosin/polythiazide)
polythiazide/prazosin