reaches the large intestine, by bacteria as well. Some of the newer penicillin preparations such as penicillin V are fairly resistant to an acid environment The absorption of penicillin following oral administration is greatly influenced by the presence of food in the stomach and the rate of gastric emptying more predicta ble results are obtained if the drug is taken on an empty stomach Blood levels obtained following administration of 100.000 units of penicillin G sodium by various routes are shown in Fig53-1. It is clear that very transient high levels reaching 2 to 4 units/ml can be obtained by either the intravenous or intramuscular route. The same dose given orally produces a blood level of only about 0.4 units/ml, but demonstrable activity remains for a longer time. The rapid decline of penicillin blood levels results from rapid renal clearance of the antibiotic. It has been well established that penicillin is actively secreted by the renal tubules, apparently by the same mechanism as p-aminohippurate or iodopyracet Diodrast). Drugs have been developed that can block this tubular secretor mechanism. One of these is probenecid(Benemid), which is quite effective. It is of little use in penicillin therapy,reaches the large intestine, by bacteria as well. Some of the newer penicillin preparations such as penicillin V are fairly resistant to an acid environment. The absorption of penicillin following oral administration is greatly influenced by the presence of food in the stomach and the rate of gastric emptying. More predictable results are obtained if the drug is taken on an empty stomach. Blood levels obtained following administration of 100,000 units of penicillin G sodium by various routes are shown in Fig.53-1. It is clear that very transient high levels reaching 2 to 4 units/ml can be obtained by either the intravenous or intramuscular route. The same dose given orally produces a blood level of only about 0.4 units/ml, but demonstrable activity remains for a longer time. The rapid decline of penicillin blood levels results from rapid renal clearance of the antibiotic. It has been well established that penicillin is actively secreted by the renal tubules, apparently by the same mechanism as p-aminohippurate or iodopyracet (Diodrast). Drugs have been developed that can block this tubular secretory mechanism. One of these is probenecid (Benemid), which is quite effective. It is of little use in penicillin therapy