Lithuium pharmacokinetics

Lithium is absorbed rapidly and completely from the gut. The drug is distributed throughout the body water and cleared by the kidneys at a rate one fifth that of creatinine. The half-life of lithium is about 20 h. Plasma levels should be monitored, especially during the first weeks of therapy, to establish an effective and safe dosage regimen. For acute symptoms, the target therapeutic plasma concentration is 0.8–1.2 mEq/L and for maintenance 0.4–0.7 mEq/L. Plasma levels of the drug may be altered by changes in body water. Dehydration, or treatment with thiazides, (NSAIDs), ace inhibitors, and loop diuretics, may result in an increase of lithium in the blood to toxic levels. Caffeine and theophylline increase the renal clearance of lithium.