<prompt> Most impoant cause of interstitial nepliritis is -DrugsInfectionMalignancyDehydration  <response>: Acute Interstitial nephritis is far more often encountered as an allergic reaction to drug. Drugs causing AIN - Antibiotics sulfonamides, vancomycin, erythromycin, rifampin, ethambutol, acyclovir NSAIDS Diuretics rarely thiazides, loop diuretics, triamterene Anticonvulsantsphenytoin,valproate,carbamazapine,phenobarbitol PPIS Ref:Harrison 20 th edition pg no 2157 