Dapsone

Pharmacogenomic Information in the Context of the FDA-Approved Drug Label*

Although the Dapsone drug label does not specifically mention genetic testing, the FDA state precaution should be taken prior to initiating treatment with dapsone for G6PD deficient individuals, a condition caused by variants in the g6pd gene that can be determined by enzymatic or genetic tests (see the G6PD VIP).

Excerpts from the dapsone tablet drug label:

"Hemolysis and Heinz body formation may be exaggerated in individuals with a glucose-6-phosphate dehydrogenase (G6PD) deficiency, or methemoglobin reductase deficiency, or hemoglobin M. This reaction is frequently dose-related. Dapsone should be given with caution to these patients or if the patient is exposed to other agents or conditions such as infection or diabetic ketosis capable of producing hemolysis. Drugs or chemicals which have produced significant hemolysis in G6PD or methemoglobin reductase deficient patients include Dapsone, sulfanilamide, nitrite, aniline, phenylhydrazine, napthalene, niridazole, nitro-furantoin and 8-amino-antimalarials such as primaquine. Toxic hepatitis and cholestatic jaundice have been reported early in therapy. Hyperbilirubinemia may occur more often in G6PD deficient patients. When feasible, baseline and subsequent monitoring of liver function is recommended; if abnormal, Dapsone should be discontinued until the source of the abnormality is established."

"Dose-related hemolysis is the most common adverse effect and is seen in patients with or without G6PD deficiency. Almost all patients demonstrate the inter-related changes of a loss of 1-2g of hemoglobin, an increase in the reticulocytes (2-12%), a shortened red cell life span and a rise in methemoglobin. G6PD deficient patients have greater responses."

Excerpts from the dapsone gel (ACZONE

) drug label:

"Some subjects with G6PD deficiency using ACZONE

Gel developed laboratory changes suggestive of mild hemolysis. (5.1)(8.6)"

"Oral dapsone treatment has produced dose-related hemolysis and hemolytic anemia. Individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency are more prone to hemolysis with the use of certain drugs. G6PD deficiency is most prevalent in populations of African, South Asian, Middle Eastern and Mediterranean ancestry. There was no evidence of clinically relevant hemolysis or anemia in patients treated with ACZONE

Gel, 5%, including patients who were G6PD deficient. Some subjects with G6PD deficiency using ACZONE

Gel developed laboratory changes suggestive of mild hemolysis. If signs and symptoms suggestive of hemolytic anemia occur, ACZONE

Gel, 5% should be discontinued. ACZONE

Gel, 5% should not be used in patients who are taking oral dapsone or antimalarial medications because of the potential for hemolytic reactions. Combination of ACZONE

Gel, 5%, with trimethoprim/sulfamethoxazole (TMP/SMX) may increase the likelihood of hemolysis in patients with G6PD deficiency."

SUMMARY
The FDA label recommends caution be taken when giving dapsone to G6PD deficient individuals, due to an increased risk of hemolytic adverse reactions, in particular in combination with other drugs which may increase the likelihood of hemolytic adverse reactions.

For the complete drug label text with sections containing pharmacogenetic information highlighted, see the Dapsone tablet drug label PDF and Dapsone gel drug label PDF.