Lithium

Question 1

What is lithium and what is it used for in psychiatry?

Answer 1

Mood-stabilising drug

Prophylaxis of bipolar disorder, adjunct in refractory depression

Question 2

What is relevant about it’s therapeutic range and action in the body and leaving the body?

Answer 2

It has a very narrow therapeutic range (0.4-1.0mmol/L)

Has a long plasma half-life

Excreted primarily by kidneys

Question 3

What are the 2 theories about lithium’s mechanism of action?

Answer 3

Interferes with inositol triphosphate formation

Interferes with cAMP formation

Question 4

What are the 9 adverse effects of therapeutic lithium?

Answer 4

Nausea/vomiting, diarrhoea
Fine tremor
Nephrotoxicity (polyuria, secondary to nephrogenic diabetes insipidus)
Thyroid enlargement, may lead to hypothyroidism
ECG - T wave flattening/inversion
Weight gain
Idiopathic intracranial hypertension
Leukocytosis
Hyperparathyroidism and resulting hypercalcaemia

Question 5

How do you monitor lithium therapy?

Answer 5

Sample should be taken 12 hours post-dose
After starting lithium levels should be performed weekly and dose changed until concentrations are stable
Once established, lithium blood level should be checked every 3 months
After a CHANGE IN DOSE lithium levels should be checked a week later and weekly until levels are stable
Thyroid and renal function should be checked every 6 months