LIMIT Trial: Lidocaine With Intramuscular Injection of Benzathine Penicillin G for Treponema pallidum Treatment.
Joseph Cherabie, Germysha Weatherall, Patrick Kojima et al.
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In 30 seconds
The LIMIT trial was a double-blinded, randomized, placebo-controlled study comparing 0.5 mL of 1% lidocaine with 0.5 mL saline added to intramuscular benzathine penicillin G in adults treated for syphilis at one infectious diseases clinic. Preliminary analysis of 15 participants found lower pain 10 minutes after injection with lidocaine: mean pain scores were 3 versus 6.73 with saline (P = 0.008). Eighty-seven percent reported at least a 2-point pain reduction with lidocaine relative to saline. Pain scores did not differ significantly at 24 hours.
Key findings
- At 10 minutes, mean pain scores were 3 with lidocaine and 6.73 with saline (P = 0.008).
- Eighty-seven percent of participants reported at least a 2-point pain reduction with lidocaine relative to saline at 10 minutes.
- No significant difference in pain scores between lidocaine and saline was observed at 24 hours.
Why it matters
Intramuscular benzathine penicillin G can cause substantial injection pain, which may affect treatment acceptability. This trial suggests that adding lidocaine can reduce pain shortly after injection, while the absence of a difference at 24 hours indicates that the observed benefit was not sustained at that assessment. The findings address injection comfort, not comparative antimicrobial effectiveness.
What to keep in mind
The preliminary analysis included only 15 participants from a single clinic, and follow-up pain assessments were limited to 10 minutes and 24 hours.