prazosin MINIPRESS
Class: Alpha 1 Antagonist/QuinazolineFDA Indications: Hypertension
Off-Label Use: PTSD, Congestive Heart Failure (in Conjunction With Cardiac Glycosides And Diuretics), Pheochromocytoma, Benign Prostatic Hyperplasia, PTSD-Related Nightmares, Raynaud Phenomenon
Prescribing
Forms: 1, 2, 5mg capsuleDose Range: 1-15 mg/day
Starting: typically started at 1 mg qhs & is gradually ↑'d to 3-15 mg as tolerated
Stopping: Avoid sudden discontinuation, as this can result in rebound hypertension; patients should be cautioned accordingly
Precautions
Serious Side Effects: Syncopal episodes (in ~1% @ doses >2mg)Side Effects: dizziness, sedation/somnolence, lightheadedness, orthostatic hypotension, headache, weakness/asthenia, palpitations, nausea
Pharmacodynamics
1° MOA: Selective α1 antagonistTarget: α1
Pharmacokinetics
t½: 2.2 (3-3.7)° TMAX: 1-3°Substrate of: BCRP, P-gp
Inhibits: ∅ ; Induces: ∅
Active Metabolites: ∅
DDIs
- - caution when co-prescribed with other medications that can lower blood pressure
Misc
- - first known selective α1-blocker; discovered in the late 1960s, approved in 1976
- - blocks α1 in arterioles & veins, lowering peripheral resistance & venous return to the heart
- - a metaanalysis and multiple clinical trials have shown that prazosin ↓'s nightmares & ↑'s sleep in patients with PTSD
- - often used adjunctively with SSRIs, though it may be considered as monotherapy
Special Populations
Category C—The limited human pregnancy experience and the animal reproduction data suggest low embryo-fetal risk.
There are no reports describing use during lactation. The manufacturer reports that small amounts are excreted into human milk which is c/w prazosin's molecular weight. The effects on a nursing infant from exposure to the drug from breast milk are unknown.
Elderly patients may be more sensitive to the hypotensive and adverse effects of prazosin.
2019 BEE℞S Recommendation: Avoid use as an antihypertensive. High risk of orthostatic hypotension and associated harms, especially in older adults; not recommended as routine treatment for hypertension; alternative agents have superior risk/benefit profile.
No dosage adjustment necessary.
No specific recommendations are available for hepatic disease. Since prazosin is extensively metabolized, it is prudent to start with the lowest initial dosage (1 mg PO qhs).
References
Package InsertDrugs In Pregnancy And Lactation 11th Ed
Foye's Principles Of Medicinal Chemistry
Clinical Pharmacokinetics Of Prazosin
DrugBank
Metabolism Of Prazosin In Rat, Dog, And Human Liver Microsomes And Cryopreserved Rat And Human Hepatocytes And Characterization Of Metabolites By Liquid Chromatography/Tandem Mass Spectrometry