TreatmentUpdate41: Vol. 4, No. 1 - March, 1993
Sean Hosein

In the earlier part of this centrury, before penicillin, "effective" treatment of syphilis usually required prolonged use of certain, often toxic, compounds. Such compounds often contained arsenic. When penicillin became available, there were claims that a single dose of benzathine penicillin (2.4 million units) could "cure" syphilis.

New Antibiotics for Other Infections

Over the past 40 years therapies for bacterial infections have progressed. New antibiotics and new tests for bacterial infections are available. As well, many controlled studies have been conducted to test the effectiveness of these new antibiotics. As a result doctors now know how to use these antibiotics to treat various infections.

Syphilis: Not Enough Research

In marked contrast with many other infections, researchers have noted that "current management [of syphilis] has changed little in the 40 years since long-acting penicillin became available." Some researchers claim there is no evidence that the microorganism that causes syphilis (T. pallidum) has developed resistance to penicillin. Changes in the management of syphilis have been slow and most have occurred in the past 5 years. Why has anti-syphilis therapy not advanced as have therapies for bacterial infections? There may be at least 2 answers:

* First, penicillin therapy appears to work when judged by the absence of symptoms/signs of syphilis. As well, researchers have noted that"...the signs of early syphilis may be subtle and even without therapy, almost always resolve spontaneously."

* Second, some doctors say that laboratory evidence of treatment failure is rare. Laboratory tests in common use do not detect T. pallidum but merely antibodies produced against this organism.

Syphilis in the AIDS Era

The appearance of AIDS has forced doctors to reconsider the usefulness of standard therapy for syphilis. It may be that because of their weakened immune system people with HIV infection are at risk for reactivated syphilis. There is some evidence that suggests long-term infection with T. pallidum may damage the immune system. Like HIV, T. pallidum may also cause immuno-suppression. Some doctors think that penicillin therapy is not very effective against syphilis. They think that the reason penicillin therapy appears to work in people without HIV infection and who have early syphilis is due to an effective immune response that works together with penicillin. Thus infection with both T. pallidum and HIV may make recovery from syphilis more difficult than in people without HIV infection.

Treating and Testing for Syphilia

T. pallidum invades the brain/spinal cord "early in the course of infection." In people without HIV infection, brain dysfunction and syphilis of the eye are not common because the immune response can limit the damage. In people with HIV infection, brain infection by T. pallidum can cause life-threatening complications. What should doctors do?

* According to some physicians, people with HIV infection should get tested for possible exposure to T. pallidum early in the course of HIV infection.

* They also suggest that those patients who have syphilis should have their CSF (cerebrospinal fluid; the fluid in which the brain and spinal cord float) analysed. For those patients whose CSF tests suggest T. pallidum infection of the brain, the doctor(s) should assume that is the case and treat patients accordingly.

What Do Doctors Do Now?

Data from a recent study suggest that at least 20% of HIV-infected people (with syphilis) either did not improve or had increased symptoms when treated with "3 weekly injections of benzathine penicillin G." Treatment with very high doses of the antibiotic ceftriaxone did not appear to be more effective than benzathine penicillin. These findings may cause confusion among some doctors when faced with a patient with HIV infection who also has reactivated syphilis. A recent editorial in the American Journal of Medicine offers some options. Until new diagnostic tests and better antibiotics appear the following courses of action are suggested:

* For patients whom doctors can trust to take their medicine as prescribed, "initial therapy with 3 weekly doses benzathine penicillin followed by [monitoring of blood test results]" is one option.

* Patients who develop high blood levels of antibodies against T. pallidum despite therapy "should be retreated" according to the editorial.

* Some doctors may choose an "aggressive" approach using the so-called "gold standard." That is, hospitalize patients for 10 to 14 days and administer 10 to 20 million units/day of penicillin G. Others may choose to use 1.2 million units/day of intramuscular procaine penicillin for 10 to 14 days. Alternatively, some doctors may use 1 to 2 grams/day of ceftriaxone daily for the same period. In patients who do not respond to initial therapy, the editorial recommends repeating treatment. There was no mention of the new antibiotics azithromycin and clarithromycin.

References:

1. Hook EW. Management of syphilis in human immunodeficiency virus infected patients. American Journal of Medicine 1992;93:477-479.

2. Fitzgerald TJ. The Th1/Th2 like switch in syphilitic infection: is it detrimental? Infection and Immunity;1992;60(9):3475- 3479.

3. Marra CM. Syphilis and human immunodeficiency virus infection. Seminars in Neurology 1992;12(1):43-50.

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Copyright © 1993 - TreatmentUpdate. Reproduced with permission. Reproduction of this article (other than one copy for personal reference) must be cleared through the Editor, The Canadian AIDS Treatment Information Exchange, 555 Richmond St. West, Suite 505, Box 1104, Toronto, ON, M5V 3B1 • Phone: 416-203-7122 • Toll Free: 1-800-263-1638 • Fax: 416-203-8284  http://www.catie.ca