Diuresis
Reversible, non-competitive inhibitor of carbonic anhydrase
PCT: ↓H+ and HCO3- prodn
↓ cytosol H+ → ↓Na+ reabs in PCT→ ↑H2O loss
↓cytosol HCO3→↑luminal HCO3→ H2O diffusion with HCO3 ,Na, K to urine
Eye: ↓Na pump, ↓AH formation

Acts in the DCT.
It is a competitive antagonist of aldosterone at the receptors in the DCT.
Decreased Na reabsorption and increased K reabsorption
= Increased Na loss and Diuresis.

Metabolic: Acidosis via ↑ excretion of bicarb (and reabsorption of Cl)
Resp: ↑MV → comp resp alk
CNS: anticonvulsant properties, ↓ CSF and IOP by ↓d formation GIT: ↓ Pancreatic and gastric
GU: mild diuresis, Na retention

Sedation and muscle weakness (due to electrolyte abnm)
Antihypertensive,
Diuresis (in 3-4 days)
Potassium retention
Anti-androgenic effect- inhbn of ovarian androgen secretion
↑renal Ca excr, ↑plasma urea
Reversible hyperchloraemic MA

IV/PO
PO BA = 100%

PO - BA 70%, extensive 1st pass metb. Onset 3-4hrs, dur upto 3 days

Lip sol: crosses BBB

70-90%

90%

Not metabolised

Hepatic: Rapidly and extensively metabolised by deacetylation and dethiolation. Active metab: canrenone and 7-alpha-spirolactone

Unchanged in urine

Urine and faeces

6-9hrs

1-2hours, metab upto 24hrs

metabolic acidosis, urinary alkalinisation, parathesias, fatigue,
hypokalaemia, N+V, abdo pain

Tox: Rashes, renal stones

↑K+(esp in renal failure). N/V and GI disturbances
Menstr irreg, Gynaecomastia
↑digoxin conc.
↓pressor response
↑effects of CVS depressants

Diuretic – Carbonic Anhydrase Inhibitor

Diuretic – Aldosterone antagonist

Glaucoma
Miniere’s disease
Altitude sickness
Adjunct in epilepsy

Oedema – CHF, cirrhosis with ascites, refractory. HTN, Nephrotic syndrome. With loop/thiazide to conserve K+, diagn of Conn's syndr

Sulfonamide

A synthetic steroid

Level 3

Level 3

250mg white tablets
500mg vials for reconstitution

25/100mg tablets

250-1000mg q6hrly
IV/PO

PO. 25-200mg/day