Relation between renal and hepatic excretion of drugs. XII. Influence of dexamethasone, triiodothyronine, or phenobarbital on the elimination of sulfonamides in rats of different ages.

Relation between renal and hepatic excretion of sulfonamides depends on their physicochemical properties. So does the effect of treatment with triiodothyronine (T3), dexamethasone, or phenobarbital (PB) on elimination of sulfonamides. After repeated administration of T3, dexamethasone, or PB an intensification of biliary sulfaclomide excretion occurs whereas hepatic transport of sulfisomidine or sulfameracine is not affected. After T3 treatment, bile flow of adult rats with intact kidneys increases by 60%. This increase is connected with enhanced sodium excretion into bile. Renal excretion of the three sulfonamides investigated here seems not to be influenced by different kinds of treatment. However, if the tubular reabsorption within the kidney is diminished by forced diuresis renal sulfaclomide excretion is enhanced after treatment with T3, dexamethasone, or PB. Surprisingly, under these conditions (mannitol diuresis), sulfaclomide excretion via bile reaches only control values and stimulatory effects of all kinds of treatment are suppressed both in young and adult animals with the exception of dexamethasone in adult rats. In young rats treated with T3 or PB there is no additional compensatory increase in sulfaclomide excretion after nephrectomy whereas in adult rats sulfaclomide elimination via bile is significant diminished.