The penicillin injections we administer to people with primary or secondary syphilis are famous because they hurt a lot. Many patients who have had to live through this experience do not accept it as an option in future infections.

The problem is that injectable penicillin, a very old antibiotic, is a very effective treatment against the syphilis bacteria.

There are studies that have tried to find out if rubbing or stretching the buttock can relieve pain. Others have changed the size of the needle to see if it helps, but the pain is so intense and lasts for so many hours that the only studies that have found an effective way to alleviate the suffering have been those where they MIXED THE ANTIBIOTIC WITH ANESTHESIA (lidocaine or mepivacaine).

If you have to get a penicillin injection because you have syphilis, tell the nurses that you can mix the powder with anaesthetic as a diluent – it doesn’t affect its effectiveness, but IT DOES KEEP YOUR POOR BUTTOCKS FROM BEING IN AGONY!

Estrada, V., Santiago, E., Cabezas, I. et al. Tolerability of IM penicillin G benzathine diluted or not with local anesthetics, or different gauge needles for syphilis treatment: a randomized clinical trial. BMC Infect Dis 19, 883 (2019).

Sukhum J, Nuttagarn J,Ya-Nin N, Poramin P, Ploypailin T, Yanisorn N, Pichaya Limpoka, M.D.* *Sexually Transmitted Disease and HIV Division, Department of Dermatology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand. Siriraj Medical Journal 2022, Vol 74, 10