Effects of ortho-iodo-sodium benzoate (OISB) on oxygen-hemoglobin affinity and its relation to plasma concentrations in dogs.

Effects of ortho-iodo-sodium benzoate (OISB) on oxygen-hemoglobin affinity were studied in unanesthetized beagles with simultaneous measurement of its plasma concentrations. Oxygen-hemoglobin affinity changes correlated well with the plasma concentrations of the drug. Intravenous administration of 100 mg/kg of OISB increased P50 significantly from the control value of 28.6 +/- 0.8 mmHg to 29.5 +/- 0.7 mmHg and 30.0 +/- 0.5 mmHg, 5 min and 30 min after the infusion, respectively. P50 gradually decreased thereafter, and after 1 hr period, elevation was no longer significant. Administration of 200 mg/kg of OISB caused a significant increase in P50 from the control of 29.3 +/- 0.3 mmHg to 30.5 +/- 0.4 mmHg, 31.1 +/- 0.3 mmHg, 31.1 +/- 0.3 mmHg and 30.5 +/- 0.5 mmHg, at 5 min, 30 min, 1 hr and 3 hr, respectively. P50 elevation declined thereafter to control levels. Plasma concentrations of the drug reached its highest level 5 min after the administration and declined gradually thereafter. All significant elevations of P50 were accompanied by the plasma concentrations of the drug more than 200 micrograms/ml. Biological half-life of the drug was found to be about 5.5 hr.