Core pharmacology

Class Group

Antipsychotic
Mood stabilizer

Legacy Cicm Level

-

Introduction

Mood stabilizer, antipsychotic

Indications Uses

1. Mania and hypomania
2. Bipolar disorder
3. Recurrent affective disorders
4. Adjunct to non-malignant chronic pain therapy

Presentation

Oral tablets containing lithium carbonate
Narrow therapeutic index. Levels should be checked within 1 week of starting and then regularly thereafter.
Therapeutic level is 0.5-1.5mmol/L

Mechanism of action

Mimics sodium ions in excitable cells to stabiles membrane potentials.

Physiological effects

CVS: Reversible ECG changes, especially TWI

CNS: Lowers seizure threshold in epileptic patients. May increase muscle tone.

GU: Polyurea and polydipsia due to ADH antagonism develops in 30% of patients

Metabolic: Hypothyroidism, hypercalcaemia, hypermagnasaemia

Adverse Effects Toxicity

1. Hypothyroidism, weight gain, pretibial oedema, tremors develop
2. Nephrogenic diabetes insipidus in 20% long term
3. Toxicity involves N/V/D, ataxia, convulsions, coma, dysrhythmias and death

Absorption

100% bioavailability

Protein binding

No protein binding.

Volume of distribution

Vd 0.5-1.3L/Kg

Excretion

95% excreted in urine unchanged. Rest in sweat.

Half-life

T1/2= 14-30 hours