Prazosin

Chemical

Synthetic PIPERAZINE derivative

Use

  1. Hypertension
  2. HF
  3. BPH
  4. 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