Acetazolamide

Chemical

A CARBONIC ANHYDRASE inhibitor

Use

  1. Metabolic alkalosis
  2. Glaucoma
  3. Altitude sickness

Presentation

PO 250mg tablets

Dose

250 – 1000mg Q4h

MoA

  • Non-competitive inhibition of CA
  • CA present in PCT (heaps), Thick Asc. LoH
  • Intercalated cells of Collecting Duct
    • ↓H+ supply in cell of tubule
    • H/Na antiporter can’t work
    • Na not reabsorbed
    • Na+, HCO3–, H2O lost in urine

PD

Renal: excretion of alkaline urine, modest diuresis

Metabolic: hyperchloraemic metabolic acidosis

Resp: ↑MV due to metabolic acidosis

CNS: ↓CSF & intraocular P by ↓rate of CSF & aqueous humour formation

PK

A

OBA 100%

D

90% PPB, high lipid solubility, crosses BBB

E

Not metabolised

K

Unchanged in urine t ½ 7hrs

Adverse Effects

  • ↓Na+, ↓K+
  • Paraesthesia
  • Fatigue
  • Drowsiness
  • Depression