The oral use of penicillin phenoxymethyl in a rheumatic fever prophylaxis program was investigated. The frequency of recurrences of rheumatic fever were low overall (1.6/100 patient years). Among children who complied with the program, as determined by assay of urine for penicillin activity, no recurrences were noted. Approximately three fifths of the children receiving penicillin carried penicillin resistant α-hemolytic streptococci in the oropharynx; resistant organisms were recovered from 22% of control children. The resistant streptococci remained sensitive to erythromycin, lincomycin, and the cephalosporin antibiotics.
Phair JP, Carleton J, Weihl C. Penicillin PhenoxymethylUse in Rheumatic Fever Prophylaxis. Am J Dis Child. 1973;126(1):48–50. doi:10.1001/archpedi.1973.02110190044008