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Dapsone (Dapsone) - Drug Interactions, Contraindications, Overdosage, etc

 
 



DRUG INTERACTIONS



Rifampin lowers Dapsone levels 7 to 10-fold by accelerating plasma clearance; in leprosy this reduction has not required a change in dosage. Folic acid antagonists such as pyrimethamine may increase the likelihood of hematologic reactions.

A modest interaction has been reported for patients receiving 100 mg Dapsone daily in combination with trimethoprim 5 mg/kg q6h. On Day 7, the serum Dapsone levels averaged 2.1 ± 1.0 μg/mL in comparison to 1.5 ± 0.5 μg/mL for Dapsone alone. On Day 7, trimethoprim levels averaged 18.4 ± 5.2 μg/mL in comparison to 12.4 ± 4.5 μg/mL for patients not receiving Dapsone. Thus, there is a mutual interaction between Dapsone and trimethoprim in which each raises the level of the other about 1.5 times.

A crossover study1 designed to assess the potential of a drug interaction between Dapsone, 100 mg/day and trimethoprim, 200 mg every 12 hours, in eight asymptomatic HIV positive volunteers (average CD4 count 524 cells/mm3) demonstrated that there was not a significant drug intreraction between Dapsone and trimethoprim. However, an earlier report2 also by Lee et al, in 78 HIV infected patients with acute Pneumocystis carinii pneumonia, receiving Dapsone, 100 mg/day and higher trimethoprim dose, 20 mg/kg/day, demonstrated that the serum levels of Dapsone were increased by 40% and trimethoprim levels were increased by 48% when the drugs were administered concurrently.

Carcinogenesis, mutagenesis: Dapsone has been found carcinogenic (sarcomagenic) for male rats and female mice causing mesenchymal tumors in the spleen and peritoneum, and thyroid carcinoma in female rats. Dapsone is not mutagenic with or without microsomal activation in S. typhimurium tester strains 1535, 1537, 1538, 98, or 100.


OVERDOSAGE


Nausea, vomiting, hyperexcitability can appear a few minutes up to 24 hours after ingestion of an overdosage. Methemoglobin induced depression, convulsions or severe cyanosis requires prompt treatment. In normal and methemoglobin reductase deficient patients, methylene blue, 1-2 mg/kg of body weight, given slowly intravenously, is the treatment of choice. The effect is complete in 30 minutes, but may have to be repeated if methemoglobin reaccumulates. For non-emergencies, if treatment is needed, methylene blue may be given orally in doses of 3-5 mg/kg every 4-6 hours. Methylene blue reduction depends on G6PD and should not be given to fully expressed G6PD deficient patients.

CONTRAINDICATIONS



Hypersensitivity to Dapsone and/or its derivatives.

REFERENCES



  1. Lee, B., et al., Zidovudine, Trimethoprim, and Dapsone Pharmacokinetic Interactions in Patients with HIV Infection. Antimicrobial Agents and Chemotherapy, May 1996; 1231-1236.
  2. Lee, B., et al., Dapsone, Trimethoprim, and Sulfamethoxazole Plasma Levels During Treatment of Pneumocystis Carinii Pneumonia in Patients with AIDS, Annals of Internal Medicine, 1989; 110:606-611.

Store at 20°- 25° C (68°- 77°F). [see USP Controlled Room Temperature]. Protect from light.

Rx only. Keep this and all medication out of the reach of children.

JACOBUS PHARMACEUTICAL CO., INC.
P.O. Box 5290
Princeton, NJ 08540

Revised August 2009




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