The cost-effectiveness of single-dose azithromycin for treatment of incubating syphilis

Background: Treatment of incubating syphilis with intramuscular benzathine penicillin in exposed sex partners is not always practical in the field, and exposed partners may not adhere to referrals for treatment at clinical facilities. The availability of a single-dose oral therapy could increase the number of partners treated and reduce future infections. Goal: The goal of the study was to evaluate the cost-effectiveness of directly observed oral administration of azithromycin as an alternative to referral for treatment with benzathine penicillin. Study Design: Using published probability and cost estimates, we constructed a decision-analysis model to compare the direct costs and effectiveness of field treatment with azithromycin (1-g single dose) versus referral for standard benzathine penicillin therapy. Results: At public-sector pricing ($11.50 U.S.), directly observed field treatment with azithromycin is cost-saving from both the program and healthcare system perspectives at efficacy levels as low as 75%. Azithromycin therapy is cost-saving at the wholesale price of $17.32 (sachet formulation) when efficacy is at least 90%. The more expensive tablet formulation (average wholesale price of $27.89) is not cost-saving from a program perspective, but it remains cost-saving from a healthcare system perspective if efficacy rates are at least 90%. Azithromycin therapy (1-g single dose) will result in fewer cases of early syphilis among exposed partners, provided that the drug's efficacy is at least 87%. Conclusions: Azithromycin is a cost-effective alternative treatment for incubating syphilis in settings where standard intramuscular therapy is not practical.