ATTENTION FOCUSSED ON LITHIUM ELIMINATION

Lithium urinary excretion rates correlate with magnesium and urea excretion rates 90 patients with recurrent affective disorders, who had been taking lithium for up to 9 years, were investigated as to factors influencing lithium dosage and excretion .

• Lithium urinary excretion rates correlated significantly with magnesium and urea excretion rates in both men and women, and correlated significantly with sodium and chloride excretion rates in both premenopausal and postmenopausal women .

• There were no significant correlations between the lithium/ creatinine excretion ratio and urine flow rate, or calcium/ creatinine or phosphate/ creatinine ratios.

Thus, lithium seems to be passively reabsorbed in the renal tubule, and its excretion is largely controlled by osmotic factors. Birch. N.J . eta!.: International Pharmacopsychiatry 15: 91 (No 2.1980)

The longer the duration of therapy with lithium, the longer its half-life To study the elimination half-life of lithium carbonate in 3 different body compartments, 30 patients with primary affective disorders stabilised on lithium were evaluated. Results showed that as the duration of lithium therapy increased, so did the elimination half-life. In patients on their tirst course oflithium, elimination half-lives were 1.12 days (urine), 1.28 days (plasma) and 1.22 days [red blood cells (RBCs)]. In those on lithium continuously for < 1 year, lithium elimination half-lives were 1.85 days (urine), 1.65 days (plasma) and 1.75 days (RBCs). In patients on lithium for > 1 year, elimination half-lives were 2.4 days (urine), 2.43 days (plasma), and 2.24 days (RBCs). Urine and plasma results indicate that lithium may stimulate the production of an endogenous regulator oflithium ion efflux. Goodnick. PJ . et al.: Clinical Pharmacology and Therapeutics 29: 47 (Jan 1981)

0156-2703/81 / 0321-0015 $00.50/ 0 © AOIS Press INPHARMA 21 Mar 1981 15