Pharm 101: Prazosin
Class
Alpha-1 receptor blocker
Pharmacodynamics
- Selective alpha-1 receptor blocker in arterioles and venules
- Affinity 1000-fold greater than that for alpha-2 receptors
- Reduces BP by dilating both resistance and capacitance vessels
- Alpha-1 selectivity allows noradrenaline to exert unopposed negative feedback (mediated by presynaptic alpha-2 receptors) on its own release
Pharmacokinetics
- 50% first pass metabolism
- Extensive metabolism
- Half-life 3 hours
Clinical uses
- Chronic hypertension
- Benign prostatic hyperplasia
- Raynaud’s phenomenon (uncommon)
Adverse effects
- Postural hypotension
- Headache, lassitude
- Reduced prostate smooth muscle tone, thus alleviating prostatic urinary obstruction
- Positive serum antinuclear factor
- Increased HDL concentration
References
- Katzung BG. Basic and Clinical Pharmacology. 14e. 2018: 159-171
Pharmacology 101
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MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner