There is evidence to suggest that lidocaine can help reduce the pain associated with intramuscular injections of benzathine penicillin G (BPG) or Bicillin, used to treat syphilis infections. A study published in the Journal of Family Practice in 2001 compared the pain experienced during bicillin injections with and without the use of lidocaine. The study found that patients who received lidocaine injections before receiving bicillin reported significantly less pain compared to those who received bicillin injections without lidocaine. Per the International Union against Sexually Transmitted Infections (IUSTI) European Guidelines for syphilis management, lidocaine has been used as a diluent for BPG since 1998. In the United States (US), BPG often comes prepackaged and lidocaine is unable to be used as a diluent with the same ease as it is in Europe. In light of this, the investigators propose a randomized controlled trial of benzathine penicillin G with and without lidocaine to quantify any site pain reduction with lidocaine in patients being treated for syphilis.
This study is a randomized, double blinded, placebo controlled trial. During this study, patients needing BPG treatment for syphilis will be screened for any penicillin allergies and consented to their participation. Each participant will receive 2 injections of BPG, 1.2 million units each (2x1.2 million units = 2.4 million units, the standard dose for syphilis treatment), as intramuscular injections, one in each gluteal muscle, with one of the injections randomly having 0.5ml of 1% lidocaine added while the other has 0.5 ml normal saline solution. The side of each injection will be randomized by the medical assistant (MA)/nurse filling the vials and the injecting MA will be blinded, as well as the study participant, as to which vial contains lidocaine and which contains normal saline. The participants will then be asked to rate their pain from 0-10 on each site of injection at 10 minutes post injection, then again at 24 hours after injection via email electronic survey (via RedCap). The differences in pain from the two injections will be compared and analyzed to see if lidocaine reduces pain associated with BPG injections compared to the control of normal saline added to BPG.
Adults 18 years of age or above
Confirmed syphilis diagnosis (reactive RPR with confirmatory treponemal testing)
Receiving first injection in series if patient requires 3x weekly injections for syphilis treatment
Penicillin allergy (anaphylaxis)
Lidocaine allergy (anaphylaxis)
Second or third injection in series if patient requires 3x weekly injections for syphilis treatment
Pregnancy
Crossover
normal Saline
Drug0.5ml normal saline solution added to prefilled 1.2 million units Benzathine Pencillin G syringe
Lidocaine
Drug0.5ml 1% lidocaine solution added to prefilled 1.2 million units Benzathine Pencillin G syringe
Mean Pain Score (0-10) of Benzathine Penicillin G + Lidocaine Injection 10 minutes post injection
The average rating of participants' injection site pain with added lidocaine from 0 (no pain) to 10 (extreme pain) at 10 minutes post injection
Mean Pain Score (0-10) of Benzathine Penicillin G + Saline Injection 10 minutes post injection
The average rating of participants' injection site pain with added lidocaine from 0 (no pain) to 10 (extreme pain) at 10 minutes post injection
Relative difference of mean pain scores between injection types 10 minutes post injection
Comparative t-test of means of pain scores at injections sites at 10 minutes post injection
Mean Pain Score (0-10) of Benzathine Penicillin G + Lidocaine Injection 24 hours post injection
The average rating of participants' injection site pain with added lidocaine from 0 (no pain) to 10 (extreme pain) at 24 hourspost injection
Rate of Adverse reactions
To see if there are any adverse effects of adding 0.5 ml 1% lidocaine to prepackaged Benzathine Penicillin G
Rate of Use of other pain medications
To assess use of other pain medications 24 hours post injection.
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