Acetazolamide is a carbonic anhydrase inhibitor normally used to reduce intra-ocular pressure in glaucoma. Metabolic alkalosis may be partially corrected by the use of acetazolamide. The most common cause of metabolic alkalosis on the ICU is usually the result of furosemide administration.

Uses

Metabolic alkalosis (unlicensed)

Contraindications

Hypokalaemia

Hyponatraemia

Hyperchloraemic acidosis

Severe liver failure

Renal failure

Sulphonamide hypersensitivity

Administration

• IV: 250500 mg, given over 35 min every 8 hours

Reconstitute with 5 ml WFI

Monitor: FBC, U&E and acid/base balance

How not to use acetazolamide

IM injection – painful

Not for prolonged use

Adverse effects

Metabolic acidosis

Electrolyte disturbances (hypokalaemia and hyponatraemia)

Blood disorders

Abnormal LFT

Cautions

Avoid extravasation at injection site (risk of necrosis)

Avoid prolonged use (risk of adverse effects)

Concurrent use with phenytoin (↑ serum level of phenytoin)

Organ failure

Renal: avoid (metabolic acidosis) Hepatic: avoid (abnormal LFT)

ACETYLCYSTEINE (Parvolex)

Acetylcysteine is an effective antidote to paracetamol if administered within 8 h after an overdose. Although the protective effect diminishes progressively as the overdose – treatment interval increases, acetylcysteine can still be of benefit up to 24 h after the overdose. In paracetamol overdose the hepatotoxicity is due to formation of a toxic metabolite. Hepatic reduced glutathione inactivates the toxic metabolite by conjugation, but glutathione stores are depleted with hepatotoxic doses of paracetamol. Acetylcysteine, being a sulphydryl (SH) group donor, protects the liver probably by restoring depleted hepatic reduced glutathione or by acting as an alternative substrate for the toxic metabolite.