Linezolid flops against benzathine penicillin G for early syphilis

In the treatment of patients with early syphilis, a 5-day course of linezolid does not appear to perform as well as the standard of care benzathine penicillin G (BPG), as shown in a study.

The study included 59 adults with serological or molecular confirmation of syphilis (either primary, secondary, or early latent). These participants were randomly assigned to receive either oral linezolid (600 mg once per day for 5 days, n=29) or intramuscular BPG (single dose of 2.4 million international units, n=30).

Researchers evaluated the participants for signs and symptoms (once per week until week 6 and at week 12, week 24, and week 48) and reagin titres of nontreponemal antibodies (week 12, week 24, and week 48).

The primary endpoint was treatment response, defined as a composite of clinical response, serological response (four-fold decline in rapid plasma reagin titre or seroreversion at any of the timepoints), and absence of relapse (presence of different molecular sequence types of T pallidum in recurrent syphilis). Clinical response was assessed at 2 weeks for primary syphilis and at 6 weeks for secondary syphilis following treatment initiation.

In the per-protocol population, treatment response after 48 weeks of follow-up was documented in 70 percent of participants in the linezolid group as opposed to 100 percent of participants in the BPG group (treatment difference, –29.6, 95 percent confidence interval [CI], –50.5 to –8.8). The difference did not meet the noninferiority criterion.

As for safety, there was no significant between-group difference in the number of drug-related adverse events (all mild or moderate), being 17 percent in both groups. None of the participants in either group had serious adverse events.

The findings suggest that linezolid should not be used to treat patients with early syphilis, according to the researchers.