Rheumatic fever prophylaxis in South Africa--is bicillin 1,2 million units every 4 weeks appropriate?

Rheumatic fever is a major health problem in South Africa. Although intramuscular benzathine penicillin (bicillin) 1.2 million units (MU) every 4 weeks is widely used for secondary prophylaxis, studies in other countries have shown a recurrence rate of 3-8% over 5-6 years in patients on this regimen. It has been recommended that serum penicillin concentrations should be maintained above 0.02 mg/ml to prevent such recurrences. The World Health Organisation (WHO) and the American Heart Association have recommended since 1988 that patients in high-risk areas for the development of rheumatic fever should receive benzathine penicillin 1.2 MU every 3 weeks rather than every 4. The aims of this study were, firstly, to determine the prevalence of serum penicillin concentrations below 0.02 micrograms/ml in rheumatic fever patients on benzathine penicillin 1.2 MU 4-weekly and, secondly, to study the effect of increasing the dose of 1.8 MU 4-weekly in patients with subtherapeutic concentrations. Forty-five of 51 rheumatic fever patients (88%) in this study on benzathine penicillin 1.2 MU 4-weekly had low serum penicillin concentrations (< 0.02 micrograms/ml) at the end of the 4th week after the injection. Penicillin was detected in the urine of 30 of the 45 patients (67%) with low concentrations, suggesting that such patients have tissue-bound penicillin which might be important in preventing rheumatic fever. The 15 patients (33%) with subtherapeutic serum penicillin concentrations and no detectable penicillin in the urine could be at very high risk for recurrent attacks of rheumatic fever. Fourteen of 29 patients (48%) given the higher dose of benzathine penicillin (1.8 MU 4-weekly) had subtherapeutic serum penicillin concentrations at the end of the 4th week after the injection, but in all 29 penicillin was detected in the urine. Review of our present policy of secondary prophylaxis for rheumatic fever is necessary. Concentrated preparations of benzathine penicillin (600,000 U/ml) are not available in South Africa; administration of a higher dose (1.8 MU) 4-weekly would therefore require a double injection, which could affect compliance adversely. We recommend that rheumatic fever patients in our area should receive benzathine penicillin 1.2 MU 3-weekly as recommended by the WHO until strategies for secondary prophylaxis have been evaluated further.