Please advise regarding alternative agents for primary pcp prophylaxis for someone who is neutropenic on three times a week Bactrim, G6PD deficient, PPD positive and has a history of upper extremity osteomyelitis with purulent draining lesions, CD4 count less than 10. Also, please comment on Toxoplasmosis prophylaxis. Thank-you.

This sounds like a good test question for the infectious disease board exam!

First, the patient needs TB prophylaxis if he hasn't already had it: one year of isoniazid along with vitamin B6.

Alternatives for PCP prophylaxis depend a little on how severely neutropenic the patient is. If the absolute neutrophil count is over 500, then I would probably continue the Bactrim at the lowest possible dose (one single-strength tablet daily or one double-strength tablet three times weekly.) If the count is less than 500, then he should either take Bactrim along with G-CSF (Neupogen) or use an alternate agent for PCP prophylaxis. Alternate agents might include dapsone if the G-6PD deficiency is mild, or aerosolized pentamidine or atovaquone if it is severe.

Toxoplasmosis prophylaxis would be indicated if the patient has or has ever had a positive IgG antibody test for Toxoplasma. Appropriate forms of prophylaxis would include Bactrim or dapsone plus pyrimethamine. If neither of those agents can be given safely for the reasons mentioned above, then you're on less solid ground. Azithromycin might help, and it is indicated anyway for MAC prophylaxis. Atovaquone, an alternative form of PCP prophylaxis, may also provide some form of toxo prevention. Finally, there is some evidence that giving pyrimethamine and leucovorin can help prevent toxo in a patient who can't take Bactrim or dapsone.

I can't really comment on the osteo without knowing more about the patient and the microbiology of the lesion. I can say, however, that none of the medications I've mentioned should be relied upon to treat the osteo, which will require long-term antibiotic therapy chosen based on the most likely organisms.