Trip Answers

Question answered:21/11/09

Medscape, an American clinical website, has a section on dapsone monitoring [1], this reports:

“Before starting therapy, a complete blood count, reticulocyte count, glucose-6-phosphate dehydrogenase level, liver function studies, urinanalysis and renal function tests should be performed. During therapy, complete blood count, reticulocyte count, platelet count and leukocyte count with differential should be obtained weekly for the first month, then twice per month during the next two months and every three months thereafter. Liver and renal function should be tested every three months. Methemoglobin levels should be obtained in patients who become symptomatic for methemoglobinemia.”

The BNF reports [2]:

“Blood disorders On long-term treatment, patients and their carers should be told how to recognise signs of blood disorders and advised to seek immediate medical attention if symptoms such as fever, sore throat, rash, mouth ulcers, purpura, bruising or bleeding develop”

The British Association of Dermatologists have a patient information leaflet on dapsone [3] and this reports:

“How will I be monitored for the side effects of dapsone treatment?

You will need blood tests to make sure that your blood and liver are working normally before starting dapsone. These tests will take place frequently after starting it, and thereafter every three months while you remain on the dapsone. An urgent blood count needs to be taken in between if you develop any of the symptoms or side effects mentioned above.”

Finally, GP Notebook discuss monitoring [4], reporting:

“dapsone, in doses of 25-100 mg/day, will control the itching but it is essential to monitor blood count since haemolysis is a frequent side effect

some degree of haemolysis is inevitable. However those patients with increased risk of glucose-6-dehydrogenase deficiency should be screened before commencing therapy because they can develop acute haemolysis

methaemoglobulinaemia may also develop and may precipitate angina in susceptible patients

monitoring whilst on treatment with dapsone (1)
 - pre-treatment FBC and reticulocyte count - these to repeated weekly for the first four weeks then monthly for 3 months; after initial 3 months then check every 3-6 months
 - other pre-treatment bloods - U+Es, LFTs, g - LFTs and U+Es monitored monthly for first 3 months and then every 3-6 months”

References

1) http://www.medscape.com/viewarticle/440403_7
2) http://bnf.org/bnf/bnf/58/3926.htm?q=%22dapsone%22
3) http://www.bad.org.uk/site/806/default.aspx
4) http://www.gpnotebook.co.uk/simplepage.cfm?ID=-200933356
 

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