Prazosin
Chemical
Synthetic PIPERAZINE derivative
Use
- Hypertension
- HF
- BPH
- Raynaud’s phenomenon
Presentation
Tablets
Dose
1 – 2mg TDS
Route
PO
Onset
30 mins
MoA
α1 adrenergic antagonist
↓Gq activation
↓IP3 & ↓Ca2+
VD of vascular smooth m. → arteries & veins
↓SVR
- Little reflex tachycardia because ↓DBP more
PD
CVS: ↓BP
CNS: Syncope & headaches 2° rapid ↓BP
GU: sphincter m. relaxation (tamsulosin is also α1 blocker)
PK
A
OBA 80%
D
PPB 97%
VD 0.5L/kg
M
Extensive hepatic demethylation & conjugation
Some active metabolites
E
t ½ B 3hrs
Excretion in faeces
Adverse Effects
- Syncope
- Dry mouth