Diphenicillin

A new penicillin salt-N,N'-dibenzylethylenediamine dipenicillin G (Bicillin)(a)-was given, in single injections of 2,500,000 units, to 196 patients with early infectious syphilis. The seronegativity rates after three months were 65% for primary syphilis cases and 25% for secondary syphilis patients; after six months, the rates were 80% and 60%, respectively. At the end of the 21-month observation period, satisfactory results were recorded in 96.6%-100.0% of the primary syphilis patients, and in 92%-95% of those treated for secondary syphilis. The respective cumulative re-treatment rates were 3.4% and 4.1%.The results of the secondary syphilis treatment were then compared with those obtained with single-injection schedules of 2,400,000 and 4,800,000 units of procaine penicillin G in oil with 2% aluminium monostearate (PAM). The cumulative re-treatment rates 21 months after treatment were: Bicillin, 4.1%; PAM (2.4 million units), 14.2%; and PAM (4.8 million units), 5.1%. It would thus appear that a single injection of 2,500,000 units of Bicillin is as effective as one of 4,800,000 units of PAM.