Clinical correlates of the lithium pump

Area of Science:

• Pharmacology
• Biochemistry
• Psychiatry

Background:

• Lithium is a common treatment for affective disorders.
• Understanding lithium's pharmacokinetics, specifically its efflux from erythrocytes, is crucial for therapeutic drug monitoring.
• The erythrocyte lithium/plasma lithium ratio is a known indicator of lithium distribution.

Purpose of the Study:

• To investigate the active efflux rate constant (ko) of lithium from erythrocytes in patients with primary affective disorder and healthy controls.
• To determine if ko is a reliable indicator of lithium toxicity and its relationship with clinical factors.

Main Methods:

• Studied the active efflux of lithium from erythrocytes.
• Expressed efflux as the rate constant ko.
• Compared ko values in patients with primary affective disorder and controls.

Main Results:

• The rate constant ko is stable within individuals over time.
• Lithium carbonate treatment inhibits ko.
• ko correlates significantly with the erythrocyte/plasma lithium ratio.
• ko is not related to age, sex, or affective disease subtype.
• Preliminary data suggest a genetic component to ko.

Conclusions:

• The erythrocyte lithium efflux rate constant (ko) is a stable, potentially useful index for assessing lithium toxicity.
• ko is influenced by lithium treatment and erythrocyte/plasma lithium levels, suggesting it reflects lithium distribution and accumulation.
• Genetic factors may play a role in regulating erythrocyte lithium efflux.