For 2 days after, 200 000 to 250 000 U by mouth 4 times per day. 1960 (8) Step I: prophylaxis 2 days before surgery with procaine penicillin 600 000 U IM on each day Step II: day of surgery: procaine penicillin 600 000 U IM supplemented by crystalline penicillin 600 000 U IM 1 hour before surgical procedure Step III: for 2 days after surgery: procaine penicillin 600 000 U IM each day 1965 (9) Day of procedure: procaine penicillin 600 000 U, supplemented by crystalline penicillin 600 000 U IM 1 to 2 hours before the procedure For 2 days after procedure: procaine penicillin 600 000 U IM each day 1972 (10) Procaine penicillin G 600 000 U mixed with crystalline penicillin G 200 000 U IM 1 hour before procedure and once daily for the 2 days after the procedure 1977 (11) Aqueous crystalline penicillin G (1 000 000 U IM) mixed with procaine penicillin G (600 000 U IM) 30 minutes to 1 hour before procedure and then penicillin V 500 mg orally every 6 hours for 8 doses. 1984 (12) Penicillin V 2 g orally 1 hour before, then 1 g 6 hours after initial dose 1990 (13) Amoxicillin 3 g orally 1 hour before procedure, then 1.5 g 6 hours after initial dose 1997 (1) Amoxicillin 2 g orally 1 hour before procedure IM indicates intramuscularly. *These regimens were for adults and represented the initial regimen listed in each version of the recommendations. In some versions, 1 regimen was included. of patients and providers, would be reasonable and prudent, and would represent the conclusions of published studies and the collective wisdom of many experts on IE and relevant national and international societies. 