If the patient has no renal impairment and acute ingestion of 25 g can rarely lead to neurotoxicity, this can be avoided with good supportive care (avoid dehydration, sodium depletion or renal impairment).

Additional assessments regarding acute ingestion:.Table: Differences between an acute ingestion and chronic toxicity:

In an acute overdose if there is a coma or seizure then other causes or toxicants need to be considered.

Coma and seizures are only present in chronic poisoning and are extremely rare.

Hypotension: Give 10 – 20 ml/kg of IV crystalloid if dehydrated and severe GI symptoms are present.

Elimination half-life is 24 hours at steady state.

Excreted in the urine and clearance is dependent on glomerular filtration and reduced in water or sodium depleted states (the kidney mistakes the lithium for sodium and therefore there is increased sodium resorption).

Lithium slowly re-distributions from the intravascular compartment to tissue compartments with a steady state volume of distribution 0.7 – 0.9 L/Kg.

In overdose peak concentration could be delayed up to 12 hours with slow-release preparations.

Completely absorbed by six hours and peak concentration at four hours with standard release preparation.

Once absorbed lithium ions substitute for sodium and potassium ions and are thought to modulate intracellular secondary messengers and potentially neurotransmitter production and release (including serotonin hence its association with serotonin toxicity). Lithium also causes a low anion gap metabolic acidosis, only two other drugs do this bromide and iodine (again an examiner’s favourite MCQ). In contrast chronic lithium toxicity has time redistribute from the gastrointestinal tract to the intravascular space and finally into the CNS resulting in neurotoxicity. Provided there is no kidney impairment neurotoxicity will not develop. Lithium is a metal and like most metals in an acute ingestion it causes nausea, vomiting, diarrhoea and abdominal pain. Lithium is commonly used to treat bipolar, for your toxicology encounter it will come in two varieties, either an acute overdose or chronic toxicity and it is important to distinguish the two (examiners love this question).

Lithium antidote