- Pharmacokinetic studies: For the first 40 patients enrolled into the study, venous blood will be obtained for determination of the serum concentration of the study drugs at either of the following time intervals from administration of the study drug- 3, 12, 24 or 48 hours. An indwelling catheter with two way stop cock will be introduced to avoid repeated venipuncture which will be taken off 3 hours after administration of the study drug; all subsequent blood samplings will be done by individual venipunctures. This will require only 1.0 ml of venous blood, and serum will be separated and stored at -70EC until assayed. For determination of stool concentration of the study drugs, aliquots of stool (About 5.0 ml each) will be obtained from stool collected over each 6 hour period during the first two days of the study, and like serum, will be stored and analyzed.