Indomethacin-induced lithium toxicity.

Indomethacin increases plasma lithium levels. A patient taking lithium for manic-depressive illness became delirious after indomethacin was initiated for arthritis. The probable mechanism of this interaction is the inhibition of prostaglandin synthesis by indomethacin, resulting in renal vasoconstriction and decreased renal excretion of lithium. When indomethacin is administered in addition to lithium, there is a risk of potentially fatal lithium toxicity.