Lithium toxicity
Background:
Uses: Lithium often prescribed for Bipolar disorder
Has a narrow therapeutic index: therapeutic dose close to a toxic dose
Mechanism of action is still incompletely understood. Lithium increases serotonin release and receptor sensitivity as well as inhibiting release of dopamine and norepinephrine.
Elimination: Lithium is excreted exclusively by the kidneys. Any insult to kidneys can lead to impaired elimination
Causes:
For acute overdose mainly intentional overdose
For chronic Li+ toxicity with present body stores any changes changes in absorption or elimination lead to lithium levels above the narrow therapeutic window like:
volume depletion
salt restriction
advanced age with resultant decrease in GFR,
thiazide diuretics, NSAIDs, ACE inhibitors
heart failure
Workup at the ED:
Basic labs: CBC, BMP
Lithium level
Urinalysis
thyroid function panel
Co-ingestants: acetaminophen, salicylates if intentional overdose is suspected
Acute Lithium Toxicity presentation:
GI symptoms such as nausea, vomiting, and diarrhea, at times with significant volume loss.
Dry mouth
Lack of coordination
systemic and neurologic findings manifest late in acute lithium toxicity because it takes time for lithium to distribute into tissues and the CNS
Chronic Lithium Toxicity presentation:
Potent neurotoxin,altered mental status, seizures, tremor, hyper-reflexia, clonus, fasciculations, and extra-pyramidal symptoms which can persist for month regardless of serum concentration
serotonin syndrome, as well as neuroleptic malignant syndrome.
nephrogenic diabetes insipidus (creates resistance to vasopressin)
abnormal ECG findings, including QT prolongation, T-wave inversions across the precordial leads, sinoatrial dysfunction, bradycardia, complete heart block, or unmasking of a Brugada pattern.
Hypothyroidism
hyperthyroidism and thyrotoxicosis
hyperparathyroidism and hypercalcemia
Treatment and Disposicion:
Supportive care and fluids at the ED
Consult Poison control center
Renal service, for hemodialysis in severe intoxications
Psychiatric service, for patients with intentional overdose
Pt will most likely require admission for monitoring of electrolytes and renal function, hydration, medication adjustment
References:
Uptodate