Late syphilis and recurrent secondary syphilis procaine penicillin 0.8 million U daily by intramuscular injection for 20 days benzathine penicillin 2.4 million U by intramuscular injection per week for 3 weeks Late syphilis and recurrent secondary syphilis • procaine penicillin 0.8 million U daily by intramuscular injection for 20 days • benzathine penicillin 2.4 million U by intramuscular injection per week for 3 weeks