Comparison of the fed and fasting states on the absorption of melphalan in multiple myeloma.

Melphalan absorption was studied over three consecutive days in five patients with multiple myeloma. On 1 day melphalan (approximately 7 mg/m2 = 10-12 mg) was administered IV, on 1 day PO fasting, and on 1 day PO after a standard breakfast. The order was different for each patient to minimise trends that might affect absorption. Melphalan concentrations were determined by high-pressure liquid chromatography and fitted to biexponential equations by computer. The parameters of these equations were in broad agreement with previously published data, and melphalan absorption varied between patients. Considerable differences were observed in the melphalan concentration curves between the 'PO fed' and 'PO fasting' days: on the PO fed days the delay before absorption started was longer (1.1 +/- 0.5 h as against 0.3 +/- 0.1 h); peak plasma levels were one-third the value (65 +/- 15 ng/ml; 195 +/- 80 ng/ml) and occurred at twice the time after administration (2.8 +/- 0.8 h; 1.3 +/- 0.3 h); and areas under the curve were smaller 10.8 +/- 4.7 min X micrograms/ml; 23.8 +/- 13.8 min X micrograms/ml). There was a significant difference between the fraction of the dose of melphalan absorbed on the PO fed day (0.49 +/- 0.20) and on the PO fasting day (0.93 +/- 0.22), with P less than 0.005. This work suggests that melphalan should be taken first thing in the morning to obtain greatest absorption.