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I have read this article with interest following my recent research in this area in one oncology centre in the UK.
Due to multiple outbreaks of Pneumocystis pneumonia amongst oncology patients, PCP prophylaxis was given to all patients deemed to be at substantial risk of such infection. This included those on long term steroids and any chemotherapy regime likely to cause lymphopenia. As discussed in your article, the antibiotic dapsone was given second line if patients were intolerant of first line co-trimoxazole prophylaxis.
Over a two-year period, forty-seven patients on chemotherapy were prescribed dapsone. Thirteen of these patients had an arterial or venous blood gas within this period during episodes of acute hospital care. Methemoglobin levels can be measured on blood gases and therefore these results were reviewed retrospectively. Eleven of the thirteen (85%) had raised levels of methemoglobin (range 2% to 29.3%). Seven of the nine patients on chemotherapy for advanced lung cancer had a blood gas during the two-year period; all seven had raised levels of methemoglobin.
As such we now recommend considering alternative second line PCP prophylaxis such as the antiprotozoal agent atovaquone, which has proven efficacy in treating PCP infections (1). Those prescribing dapsone for patients on chemotherapy may wish to monitor methemoglobin levels.
Competing Interests: None declared.References
- 1. KIRCHNER, J., 2022. Atovaquone and Dapsone for PCP Prophylaxis. [online] Aafp.org. Available at: <https://www.aafp.org/pubs/afp/issues/1999/0415/p2334.html> [Accessed 9 September 2022]