S15C175 - Lithium

Question 1

Lithium pharmackinetics

Answer 1

• bear in mind that the levels in the brain and the serum can differ by 3-fold
• elimination 1/2 life is 18-60h
• excreted in urine
• serum levels do not necessarily correlate with symptoms

Question 2

Lithium side-effect

Answer 2

• tremor, polyuria, rash, fatigue, memory loss, ataxia, dysarthria, nephrogenic diabetes insipidus
• worsening tremor is a sign of toxicity
• n/v/d are common when starting tx
• hypokalemia can occur causing u waves, flattened T, ST depression, QT prolongation

Question 3

Lithium OD signs

Answer 3

• muscle fasciculations, ataxia, muscle weakness, agitation, lethargy, cognitive slowing
• GI: n/v/d, gloating, abdo pain (seen more in acute toxicity)
• renal impairment: polyuria, polydipsia
• ECG: long QT, ST dpn, TWI

Question 4

Lithium levels

Answer 4

• grade 1: 1.5-2.5 mEq/L n/v, tremor, hyperreflexia
• grade 2: 2.5-4mEq/L stupor, rigidity, HoTN
• grade 3: >4 mEq/L coma, Sz, requires HD (or 3.5mEq/L if chronic)

Question 5

Lithium OD tx

Answer 5

• CBC, chem6, extended lytes, lithium level
• Sz: benzos, barbs or general anesthesia
• no charcoal, ineffective
• 2L IV saline then 200cc/h
• sodium polystyrene sulfonate
• dialysis

-all acute ingestions get admitted, if chronic and minor can treat for 12h and d/c hom ief level