prazosin
Brand: Minipress
Beers Criteria Prototype: doxazosin
Drug Class: alpha-1 blocker
Drug Family: antihypertensive
Subclass: quinazoline alpha-1 antagonist (short-acting)
Organ Systems: cardiovascular
Mechanism of Action
Selective alpha-1 antagonist; vasodilates arteries and veins; short half-life requires multiple daily dosing.
alpha-1 adrenergic receptor
Indications
- hypertension
- BPH
- PTSD-associated nightmares (off-label)
- Raynaud's phenomenon
- pheochromocytoma perioperative management
Contraindications
- PDE-5 inhibitor use
Adverse Effects
Common
- first-dose orthostatic hypotension
- dizziness
- fatigue
Serious
- syncope (first dose)
- IFIS
Pharmacokinetics (ADME)
| Absorption | 68% oral bioavailability; reduced by food |
| Distribution | extensive tissue binding |
| Metabolism | hepatic |
| Excretion | fecal predominantly |
| Half-life | 2-3 hours |
| Onset | 30 min |
| Peak | 2-4 hours |
| Duration | 4-6 hours |
| Protein Binding | 97% |
| Vd | 0.5 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| PDE-5 inhibitors | severe hypotension | major |
Nursing Considerations
- First dose syncope risk: start at 1 mg at bedtime
- PTSD nightmares: used off-label (reduces REM sleep adrenergic activity)
- Twice to three-times daily dosing required (short half-life)
Clinical Pearls
- Original alpha-1 blocker; first-dose syncope well-established
- Off-label for PTSD nightmares: reduces noradrenergic activation in REM sleep
- Shorter half-life than doxazosin — requires TID dosing
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
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