Lack of effect of non-steroid antiinflammatory drugs on lithium clearance and on delivery of tubular fluid to the loop of Henle in rats.

This paper examines a possible interaction between non-steroid antiinflammatory drugs (NSAI drugs) and renal lithium clearance in conscious, unoperated rats with diabetes insipidus (Brattleboro strain) and ordinary Wistar rats. The drugs were given with the food for 5 days before clearance determinations in the following daily doses per kg body weight: acetylsalicyclic acid 115 mg/kg, phenylbutazone 20 mg/kg, indomethacin 5 mg/kg, and penicillamine 65 mg/kg. None of the drugs affected the lithium clearance. Also urine flow, sodium clearance, potassium clearance, and prostaglandin E2 excretion remained unaffected by the treatments. The results suggest that a continued lowering of lithium clearance cannot be produced, at least not by administration of the drugs with the food. Since lithium clearance is a quantitative measure of the delivery of tubular fluid from the proximal tubules to the loop of Henle, the results also suggest that chronic administration of NSAI drugs does not influence delivery from the proximal tubules in rats. The lowering of lithium clearance observed by others after administration of the drugs by injection or by gastric tube may have been transient, lasting only for a short period after each administration.