What is dapsone?
Dapsone is a tablet taken for several and varied dermatological conditions. The dose varies between 50 and 200 mg a day taken all at once. The duration of treatment will depend on the progress made and can vary from months to several years.
Regular monitoring by your doctor is essential when commencing this medication because of the potential serious side effects. Dapsone can be taken with or without food but has to be taken at the same time every day.
How does dapsone work?
Dapsone works on the inflammatory cells, particularly the neutrophils (a type of white blood cell) and reduces inflammation of the skin.
What is dapsone used for?
Most commonly dapsone is prescribed by dermatologists to treat dermatitis herpetiformis.
It may also be prescribed for:
- Linear IgA disease (bullous dermatosis of childhood)
- Systemic lupus erythematosus
- Erythema elevatum diutinum
- Autoimmune bullous diseases
- Pyoderma gangrenosum
- Sweet’s syndrome (acute febrile neutrophilic dermatosis)
- Behcet’s syndrome.
Precautions when taking dapsone
- Do not take dapsone if you have had allergic reactions to sulphur-based drugs including sulfapyridine, sulphonamide or sulfones.
- Please let your doctor know if you have any pre-existing lung, heart or blood disorders.
- Let your doctor know if you or any other family member has a glucose-6-phosphate dehydrogenase deficiency.
- Do not give your medication to anyone else.
- Dapsone has not been proven to be safe in pregnancy. However there have been several instances of dapsone use in pregnant women without any adverse effects.
- Do not breastfeed when takingdapsone.
- Do not take the following medications with dapsone – trimethoprim, probenicid, pyrimethamine, rifamipicin, sulphonamides and hydroxychloroquine – unless this has been specifically discussed with your doctor.
What monitoring is required?
Initially several baseline blood tests will be performed to make sure there are no underlying problems. These include a full blood count to check for liver and kidney function and glucose-6-phosphate dehydrogenase enzyme levels. If the results of these tests are all satisfactory, then regular blood tests (initially weekly, then fortnightly and decreasing to every 3 to 4 months when stable) will be needed to ensure you are coping well with the medication.
What to expect when taking dapsone and potential side effects
- The most common side effects are stomach ache, nausea and loss of appetite.
- Haemolytic anaemia: Dapsone affects red blood cells and can cause them to break down. In most cases this is only noticeable in blood tests but it may occasionally lead to increased tiredness and fatigue.
- Methaemoglobinaemia: As dapsone affects the red blood cells in our body, it can reduce their capacity to carry oxygen. It may make you feel breathless (especially if you already have lung or heart problems) and the reduced oxygen can make your tongue look bluish. Let your doctor know if you are experiencing any of these side effects.
- There are two very serious side effects that you need to be aware of:
- Agranulocytosis: This is caused by a sudden drop in the infection fighting cells and usually occurs 3 to12 weeks after starting the treatment. This could result in serious infections. If you develop any fevers or flu-like symptoms while taking dapsone, let your doctor know. Stopping the medication can reverse this and should be done as soon as possible.
- Hypersensitivity syndrome: This is a combination of signs and symptoms including fever, rash and liver abnormalities. It occurs 3 to 6 weeks after starting the treatment.
Notify your doctor immediately if you develop these signs. Some deaths have been reported from agranulocytosis and hypersensitivity syndrome.
- Nerve damage: The most common form of nerve damage is weakness in the leg muscles. Sensation can sometimes be affected. In rare cases eye and mental state changes have been reported.
Please notify your doctor if you develop any unusual signs or symptoms while taking dapsone. Being aware of the potential side effects is vital so that you know what reactions you may expect and when you need to seek medical advice. Please read the product information sheet that comes with dapsone and discuss any questions with your doctor.
This information has been written by Dr Kavita Enjeti