Dapsone

Author: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand,1997.


What is dapsone?

Dapsone is a sulphone antibiotic available for many years to treat leprosy. In New Zealand, 100 mg and 25 mg tablets are available.

Dapsone is used to treat various skin conditions including:

Dapsone treatment requires careful laboratory monitoring.

Contraindications to dapsone

Dapsone should not be taken by anyone that is allergic to dapsone. Some patients with sensitivity to other sulphone antibiotics can tolerate dapsone. 

The dose of dapsone may need to be lower than normal in people with significant heart or lung disease. This is due to the drug's effect on oxygen carrying capacity of  blood cells.

Dapsone should be avoided during pregnancy and breast feeding.

Side effects of dapsone

Minor, relatively infrequent side effects

  • Gastrointestinal upset including nausea or vomiting.
  • Headache.
  • Blue discolouration of lips and fingertips.

Side effects of greater importance

  • Anaemia (low haemoglobin or blood count) is common in patients receiving dapsone; it is usually mild. It is possibly less likely if you are taking antioxidants such as ascorbic acid (vitamin C) or cimetidine tablets. Possible symptoms of anaemia include tiredness and shortness of breath. More severe anaemia is likely if you have a rare condition known as glucose-6-phosphate dehydrogenase (G6PD) deficiency.
  • Allergy may cause a widespread skin rash. It is rarely associated with potentially fatal severe drug hypersensitivity syndrome, in which there is prolonged rash, fever, swollen lymph glands and internal organ failure (liver, lungs, heart, kidneys).
  • Uncommonly, weakness of the foot and hand muscles can occur, particularly with long term dapsone therapy with doses greater than 100 mg per day. Once per week it is advisable to test your ability to walk on your "tip-toes" and to test your hand grip strength.
  • It has been reported to cause renal papillary necrosis (kidney disease).
  • Rarely, psychosis (hallucinations or delusions) has been reported.

Rare, but potentially serious side effects

  • A significant decrease in the white blood count typically presents with fever, sore throat, skin infections, or other local signs of infection. Commonly a widespread red skin rash is also present.
  • Rarely, an illness resembling glandular fever develops, causing severe fatigue, fever, sore throat, rash and prominent lymph glands.
  • Tell your doctor promptly if these symptoms occur.

Usually, a blood test is performed as a base-line before starting dapsone. It is then checked after about a week on therapy, and then about once a month, depending on the dose and state of the blood count.

Follow instructions precisely regarding the timing of these tests.

Dapsone gel

Dapsone gel 7.5% once daily (trade name Aczone®) is available in the US and Australia for topical treatment of acne. It is usually well tolerated, but rarely causes the skin at the site of application to become dry and red. There is a low risk of haemolysis and the other side effects of oral treatment described above.

New Zealand approved datasheets are the official source of information for these prescription medicines, including approved uses and risk information. Check the individual New Zealand datasheet on the Medsafe website.

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