Agents causing dapsone

The answers are 484-k, 483-j. (Hardman, pp 1061—1062, 1682-1683.) Sulfonamides can cause acute hemolytic anemia. In some patients it may be related to a sensitization phenomenon, and in other patients the hemolysis is due to a glucose-6-phosphate dehydrogenase deficiency. Sulfamethoxazole alone or in combination with trimethoprim is used to treat UTIs. The sulfonamide sulfasalazine is employed in the treatment of ulcerative colitis. Dapsone, a drug that is used in the treatment of leprosy, and primaquine, an antimalarial agent, can produce hemolysis, particularly in patients with a glucose-6-phosphate dehydrogenase deficiency. 

Pyrimethamine may also be combined with other antimalarials such as artemisinin derivatives, but these regimens should only be used if the malarial parasites are not resistant to the specific drugs in the regimen.13 Pyrimethamine can also be combined with a sulfonamide drug such as dapsone, sulfadiazine, or sulfamethoxazole to treat protozoal infections that cause toxoplasmosis, or fungal infections that cause Pneumocystis pneumonia.These agents are administered orally. 

The incidence of Pneumocystis carinii pneumonia (PCP) within the first year after transplantation is reported to be 3% to 5%. " Low-dose trimethoprim-sulfamethoxazole (TMP-SMX 400 mg/ 80 mg three times weekly) is effective in the prevention of PCP infections. Alternative agents include aerosolized pentamidine (300 mg every month), dapsone, and atovaquone. The duration of PCP prophylaxis is unclear. The risk of infection caused by P. carinii is likely to decrease as immunosuppression is reduced therefore, prophylaxis in patients requiring treatment for acute rejection may be appropriate. 

Zidovudine is rapidly absorbed from the G1 tract with peak serum concentrations occurring within 30 to 90 minutes. It binds to plasma proteins to the extent of 35 to 40%. Zidovudine is rapidly metabolized in the liver to the inactive 3 -azido-3 -deoxy-5 -0-beta-D-glucopyranuronosylthymi-dine (GAZT), which has an apparent elimination half-life of 1 hour. Zidovudine undergoes glomerular filtration and active tubular secretion. Coadministration of zidovudine with agents such as dapsone, pentamidine, amphotericin B, flucytosine, vincristine, vinblastine, adriamycin, and interferon with potential to cause nephrotoxicity or cytotoxicity to hematopoietic elements, enhance its risk of adverse effects. Probenecid will inhibit the renal excretion of zidovudine. 

B. Other Agents Alternative drugs for leprosy include rifampin (see above) and clofaziinhie. Clofazimine is given in cases of dapsone resistance or intolerance. The drug causes gastrointestinal irritation and marked skin discoloration. 

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