Lithium

Class Mood stabiliser
Chemistry
Monovalent cation salt; dilithium carbonate to be precise (Li2CO3)
Routes of administration

Oral only

Absorption
Oral bioavailability close to 100%
Solubility
pKa = 10.33; excellent water solubility.
Distribution
VOD ~0.6-0.7 L/k, roughly proportional to total body water. Therapeutic levels are 1.0 mmol/L, which means one has about 40-50 mmol of lithium on board when one is properly medicated
Metabolism
Not metabolised
Elimination
100% renally excreted, by mechanisms identical to those involved in handling sodium (which means any scenario where sodium is retained will also result in the increased reuptake and retention of lithium)
Time course of action
Onset of antimanic effects is 6-8 days; takes at least 24 hrs to cross the blood brain barrier. Half-life of 12-24 hrs, up to 36 hrs in the elderly
Target receptor

Multiple pharmacological targets, mostly enzyme systems that regulate the synthesis and activity of secondary messengers such as IP3

Mechanism of action

By interfering with the synthesis of secondary messengers and regulatory molecules, lithium exerts numerous effects, of which some are neuroprotective. The mechanism of action specifically responsible for the desirable mood effects is unknown

Clinical effects

Apart from improved mood regulation: - fine tremor - downbeat nystagmus - Nausea, headache - hypothyroidism - nephrogenic DI - high cholesterol - hyperparathyroidism - hypercalcemia - psoriasis and dermatitis

Literature reference

Oruch et al (2014)

CICM details of understanding Not specifically listed in the CICM syllabus
Mentioned around Deranged Physiology
Related SAQs