SERUM PENICILLIN LEVEL A FTER INTRAMUSCULA R INJECTION OF 1,200,000 UNITS OF BENZATHINE PENICILLIN G IN CHILDREN WITH RHEUMATIC FEVER

The most accepted method of secondary prophylaxis in rheumatic fever (RF) has been an injection of 1,200,000 units of benzathine penicillin G (BPG) every 4 weeks, but recurrences have been reported in some patients despite such a prophylaxis program. The WHO recommended BPG injections every 3 weeks in high risk patients and situations due to some published data in favor of inadequacy of once every 4 weeks injection of BPG. Our study was designed to determine serum penicillin levels (SPL) during the 4 weeks after an intramuscular injection of 1,200,000 units of BPG, in order to find the appropriate interval between BPG injections and also to assess the effects of weight and sex on this level. We included 42 RF patients (mean±SD=14.8±11.9 years) in our study. SPL was determined by disk agar diffusion method. In this study the minimum accepted SPL to be effective against group A β-hemolytic streptococci was 0.02 µg/mL. In 46% of the patients the mean SPL decreased to <0.02 µg/mL at the end of the third week (mean ±SD=2.35 ± 1.3 weeks). The mean SPLs were significantly higher in patients who weighed <45 kg (mean±SD=38.6±4.3 kg) in comparison with those who weighed 2:45 kg (mean±SD=54.25±4.87 kg), with a p value <0.0001. There was no significant differences in mean SPL between boys and girls (p =0.145). Although in this study the mean SPL was <0.02 µg/mL in 46% of patients at the end of the third week, we could not recommend every 3 weeks injections of BPG in all patients, except in high risk patients and situations as recommended by the WHO and also in those patients who weighed 2:45 kg.