Despite its long history of use in medicine, penicillin, as of 2011, still retains the ability to kill the bacterium that causes syphilis. Many other species that were originally killed by the drug developed antibiotic resistance to the point where penicillin can no longer be used to kill them. This lack of antibiotic resistance to the drug by the syphilis bug means that penicillin for syphilis can technically cure the disease, although issues like allergy can mean another antibiotic may be more suitable.
The primary treatment for syphilis globally, as of 2011, is penicillin, although some regions also use other antibiotics such as azithromycin, erythromycin or tetracycline. Almost all cases of syphilis can be cured with the administration of penicillin, although the treatment is best given in the early stages of the infection. Syphilis has three main stages; the primary stage, the secondary stage and the late stage. When an infection is allowed to progress to the late stage, irreversible damage can be caused to the organs of the body, which cannot be fixed by administration of penicillin for syphilis.
Antibiotics differ in their potential for side effects, which can vary according to the patient. Pregnant women, for example, and their babies are especially sensitive to certain drug side effects. Penicillin for syphilis, however, has proven benefits for treating infected pregnant women. Some other antibiotics that can kill the syphilis bacterium cannot cross the placental barrier properly to help treat the unborn baby.
A few cases of failure in penicillin for syphilis treatment have been noted in the medical evidence surrounding the drug's use. For the people involved, however, the failure of the normal course of penicillin to clear the infection was not due to strong resistance by the bacterium to the drug. Instead, a higher dose of the drug managed to kill off the infectious agents, without the doctor having to administer other antibiotics as a replacement. Bacterial species do tend to have an ability to become resistant to antibiotics over time, though, and with the increase in syphilis cases associated with an increase in global population, a chance of a resistant strain emerging does still exist.
Additional reasons for the replacement of penicillin for syphilis treatment are ease of administration and potential for allergic reaction. Normally, penicillin needs to be injected into the body, whereas some newer antibiotics that can cure the infection can be given as tablets. Regions of the world with poor healthcare systems could find oral medications less expensive and less risky from an infection perspective than penicillin injections. On the other hand, older medications like penicillin tend to be less expensive than newer drugs. Allergic reactions can occur in some people to penicillin, but desensitization techniques can be used so the patient does not produce allergic reactions to the drug.