A child was diagnosed of having rheumatic fever. She is allergic to penicillin. Which of the following agent can be used for secondary prophylaxis in this child?

The best antibiotic for secondary prophylaxis is benzathine penicillin G (1.2 million units, or 600,000 units if 27 kg) delivered every 4 weeks. It can be given every 3 weeks, or even every 2 weeks, to persons considered to be at paicularly high risk. Oral penicillin V (250 mg) can be given twice-daily instead but is somewhat less effective than benzathine penicillin G. Penicillin allergic patients can receive erythromycin (250 mg) twice daily. Ref: Carapetis J.R. (2012). Chapter 322. Acute Rheumatic Fever. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18.