The influence of mania and depression on the pharmacokinetics of lithium. A longitudinal single-case study.

A 28-year-old woman, had, every month, a premenstrual manic-depressive cycle beginning with a hypomanic episode followed by a depression which improved with menstruation. The lithium serum level oscillated in a regular and inverse relationship to the mood changes, although the patient received a constant dosage of lithium: 16.2 mmol/l per day. The lithium level reached its highest value at the time of the greatest intensity of depression (1.10 mmol/l), and its lowest value during the time of hypomania (0.30 mmol/l), whereas it showed only small oscillations around 0.5 mmol/l when the patient's mood was normal. RBC lithium concentration and lithium excretion in the urine followed the same pattern. The daily creatinine excretion was usually within normal limits. It must be hypothesized that there are compartments or stores, to and from which lithium is transported, by mechanisms related to the biological basis of mood changes.