- Clinical science
Lithium is a psychiatric medication used primarily as first-line therapy for bipolar affective disorders. It is also indicated in treatment-resistant depression (TRD) and reduces the risk of suicide in depressive patients. The specific mechanism by which lithium acts to stabilize mood is still not definitively known. It is thought to be due to the inhibition of the phosphoinositide cascade causing a decrease in cyclic adenosine monophosphate (cAMP) levels. Short-term side effects of lithium are predominantly gastrointestinal, while long-term side effects involve neurological symptoms. Lithium therapy has a very narrow therapeutic index; frequent monitoring is therefore required to prevent toxicity.
|CNS and peripheral nervous system|
- Etiology: serum lithium levels > 1.5 mEq/L / 1.5–2.0 mmol/L
- Pathophysiology: : impaired concentration of urine (due to ) + uncompensated fluid losses (due to confusion or disabling comorbidities) → severe dehydration → lithium toxicity
Lithium intoxication can be explained under three categories, as follows
- Acute toxicity: : seen in patients with a low tissue level of lithium (not on regular therapy), who have acutely taken a large dose
- Acute on chronic toxicity: : seen in patients who are on chronic lithium therapy with a low tissue level, but have taken a larger dose acutely
- Chronic toxicity: : seen in patients with a high tissue level of the drug; (long term treatment) with recent high doses; , or the introduction of new therapy that exacerbates lithium effects
- System-specific description of features
- Neurological (earliest and predominant feature): dysarthria, vertigo, ataxia, nystagmus; (especially ), dysdiadochokinesia, tremor, somnolence, delirium.
- Neuromuscular: fine tremors, muscle twitches (fasciculations)
- Gastrointestinal: vomiting, diarrhea, abdominal pain
- Psychiatric: apathy, psychomotor impairment
- Others : dysrhythmias, renal failure with oliguria, myxedema coma
- Lithium intoxication can be explained under three categories, as follows
- Correct fluid and electrolyte balance
- Ventilatory support, if required
- Treat seizures and/or dysrhythmias
In severe intoxication
- IV fluid therapy: 0.9% NaCl solution (possibly in combination with forced diuresis)
- Hemodialysis; should be continued until serum lithium; concentration is < 1.0 mEq/L or for a mininum of 6 hours (if serum lithium concentration cannot be measured)
- Symptomatic therapy
Lithium has a narrow therapeutic window!
We list the most important adverse effects. The selection is not exhaustive.
- Advanced renal failure
- Severe cardiovascular disease
- Relative contraindications
We list the most important contraindications. The selection is not exhaustive.
- Monitoring serum levels of lithium is important because of its narrow therapeutic window.
- Consistent serum levels are usually expected after 5–7 days.
- Due to its slow onset of action, effects are expected 1–2 weeks after initiation of treatment.
- Optimal range of lithium serum level: 0.5–0.8 mmol/L for long-term treatment and 1.0–1.2 mmol/L for short-term treatment
How to implement lithium monitoring
- Lithium serum level: every 6–8 weeks (weekly controls when initiating lithium treatment)
- Half-time: 12–24 hours → Blood sample for serum level monitoring should be taken just before pill intake. If that is not possible, a blood sample should be taken 12 hours after pill intake!
- Suggested dosage: lithium 2–3 time daily