Lithium

Question 1

How is lithium metabolised and excreted?

Answer 1

Not metabolised

Excreted essentially unchanged through the kidneys

Question 2

Which classes of medications may induce lithium toxicity?

Answer 2

NSAIDS
Angiotensin Receptor Blockers (ARBs) (‘sartans’)
Diuretics (esp. loop diuretics, e.g. frusemide)

Question 3

How is lithium absorbed, distrubuted, metabolised and excreted?

Answer 3

Absorbed entirely through the gut. Peak plasma concentrations 2-4 hours after dose, half life 18-24 hours. Initially distributes into extracellular fluid and into all water-containing tissues. Not metabolised. Excreted almost entirely through the kidneys.

Question 4

What happens in lithium induced nephrogenic diabetes insipidus?

Answer 4

The kidneys stop responding to Anti-Diuretic Hormone (ADH) and water is not concentrated -> polyuria and polydipsia