Study objectives Oral high dose busulfan (1,4-butanediol dimethanesulfonate) is frequently used in conditioning regimens prior to haematopoietic stem cell transplantation. As tablets with high dose busulfan are not commercially available, it is common practice to extemporaneously prepare capsules in hospital pharmacies. However, proper content uniformity assays are lacking.

Methods An HPLC–mass spectrometry (MS) method that was previously validated for quantification of plasma levels of busulfan was adapted for determination of the content uniformity of capsules comprising 50 mg of busulfan for high dose regimens.

Results Intraday and interday variability and imprecision were less than 2.2%.

Conclusions The data indicate high specificity and sensitivity of this novel assay.