The relationship between plasma lithium and the renal responsiveness to arginine vasopressin in man.

1. Arginine vasopressin (AVP) was measured in morning samples of urine from 58 patients treated with lithium for unipolar or bipolar affective disorders and from 25 healthy control subjects. 2. The AVP excretion rate was increased in the patients treated with lithium and was related to the plasma lithium concentration. The increase in AVP excretion is the result of a renal resistance to AVP so that what has been observed is an effect of lithium in vivo related to its plasma level over the therapeutic range.