Serial serum penicillin levels following an injection of benzathine penicillin (12 lakh units) in children of rheumatic heart disease.

Abstract

In 20 children (mean age 12·0±1·7 years) of rheumatic heart disease, serum penicillin was measured by a microbiological assay on days 1, 7, 14, 18, 21, 23, 25 and 28, first following an IM injection of benzathine penicillin 12 lakh units and then after 3 months of regular monthly injections. The serum penicillin levels were 0·653±0·102 units/ml, 0·063±0·019 units/ml and 0·046±0·025 units/ml on days 1, 7 and 14 respectively. These levels were much above minimum inhibitory concentration (MIC) of penicillin (0·03±·005 units) against β-hemolytic streptococci. A precipitous fall in serum penicillin was observed after day 14. As a result of this the penicillin levels reached below MIC much before the end of the third week of injection. These results are similar to those reported by us in adults and contrast strikingly against those reported by western authors. In view of our results we recommend that for secondary prophylaxis of rheumatic fever in children of RHD injections of benzathine penicillin 12 lakh units should be given once every 3 weeks in our country.