Urinary excretion of interferon, albumin, and beta 2-microglobulin during interferon treatment.

Serum and urinary levels of albumin, beta 2-microglobulin, and interferon were determined in ten patients undergoing interferon therapy. The pharmacokinetics during a phase I trial of interferon administration intramuscularly is presented. Only trace amounts of interferon activity are found in the urine, even during peak serum interferon activity. Serum beta 2-microglobulin levels increased after interferon treatment, especially at the higher dosing levels. Urinary excretion of beta 2-microglobulin increased due to the relatively low affinity of the transport system. Saturation, competition, or inhibition of the absorption process for beta 2-microglobulin was not attained. Measurement of the urinary albumin/urinary beta 2-microglobulin ratio reveals no glomerular or tubular lesion, and we conclude that interferon therapy does not result in a clinically significant nephrotoxicity.