Could late-latent syphilis be treated with a single subcutaneous infusion of long-acting penicillin?

Syphilis is an important global health threat and little has changed in its treatment since the mid-20th century. For late-latent or syphilis infection of unknown duration, the standard treatment of multiple intramuscular injections of benzathine penicillin G (BPG) are associated with significant pain and distress to clients and caregivers, negatively impacting on treatment completion. Based on pharmacokinetic modelling from a Phase I study of subcutaneous infusion of high dose BPG (SCIP), we present its feasibility, safety and tolerability for treatment of syphilis in a single infusion. SCIP leads to more sustained penicillin concentrations above the desired target with less reported pain and reduced clinic visits.