Tox: Lithium

Question 1

Describe the absorption of lithium wrt GI and CNS uptake.

Answer 1

Completely absorbed in ~6hrs but CNS update and elimination are slow.
Thus, serum lithium levels do NOT correlate well with CNS effects.

Question 2

How is lithium eliminated

Answer 2

Renally. Thus, elimination depends on GFR.

Question 3

4 precursors to chronic lithium toxicity

Answer 3

1) Increase in therapeutic dose
2) Dehydration (increased renal absorption)
3) AKI/reduced GFR (renal insufficiency, use of NSAIDs, ACEi, diuretics)
4) Drug-drug interactions with SSRIs, antipsychotics

Question 4

Compare acute vs chronic lithium toxicity

Answer 4

Acute: high serum lithium levels, ++GI effects (n/v/d), minimal neuro effects, less severe.

Chronic: lower serum levels, ++CNS effects, less GI effects, more severe.

Question 5

Describe CNS symptoms seen in lithium toxicity

Answer 5

Hyperreflexia, tongue fasciculations, clonus, agitation, AMS/confusion, seizures, cerebellar findings, coma

Question 6

Describe ECG changes seen with lithium poisoning

Answer 6

T wave inversions, T wave flattening, depressed ST segments

Bradycardia, sinus node arrest.

Question 7

How is lithium poisoning diagnosed

Answer 7

Levels in acute ingestion:

• measure 4-6hrs post-ingestion, follow until peak and decline.
• peak serum level with large ingestion (esp SR) may occur >12hrs post-ingestion
• May be falsely elevated if placed in green-top tube

Chronic ingestion: may have elevated levels, otherwise clinical

Question 8

Describe lithium treatment

Answer 8

Does NOT bind AC.
WBI for acute ingestion of SR preps (though often limited by vomiting).
HYDRATION: corrects dehydration, improves renal clearance.
HD for some

Question 9

Indications for HD in lithium poisoning

Answer 9

Renal failure/anuria.
Inability to handle aggressive hydration (e.g. CHF)
Severe CNS toxicity, AMS or seizures
Level >5 mEq/L

Question 10

When should lithium levels be checked post-HD

Answer 10

immediately after then 6hrs post-HD (HD removes Li from plasma only so may get rebound increase lithium after HD as it redistributes)

Question 11

Complications of lithium use

Answer 11

Hypothyroidism (reversible).
Nephrogenic DI (reversible or permanent)
Increased risk of serotonin syndrome if used with serotonergic drugs.
SILENT: syndrome of irreversible lithium effectuated neurotoxicity (irreversible neurologic/neuropsychiatric sequelae)