Effect of a low-protein diet on doxorubicin pharmacokinetics in the rabbit.

Malnutrition involving protein deficiency, which commonly occurs in cancer patients receiving anthracycline treatment, is considered to be a risk factor for the development of cardiotoxicity. Protein deficiency has been shown to impair the metabolism of drugs such as theophylline and acetaminophen. If protein deficiency also impairs anthracycline metabolism, it could explain at least in part the enhanced anthracycline toxicity associated with malnutrition. We tested this idea by determining the effect of a low-protein, isocaloric diet on doxorubicin pharmacokinetics in rabbits. The animals were randomized into two groups for 8-12 weeks. Rabbits in group 1 received a low-protein (5%), isocaloric diet, whereas those in group 2 received a normal-protein (15%) diet. Both groups (group 1, n = 15; group 2, n = 14) were given 5 mg/kg doxorubicin by i.v. bolus. After doxorubicin injection, blood samples were obtained over the next 52 h for the measurement of doxorubicin and doxorubicinol plasma concentrations by high-performance liquid chromatography (HPLC) with fluorometric detection. The low-protein diet significantly decreased doxorubicin clearance (48 +/- 3 vs 59 +/- 4 ml min-1 kg-1; P less than 0.05), prolonged the terminal elimination half-life (28 +/- 2 vs 22 +/- 2 h; P less than 0.05), and increased the area under the plasma concentration/time curve extrapolated to infinity (1722 +/- 122 vs 1405 +/- 71 ng h ml-1; P less than 0.05) as compared with the values determined for rabbits fed the standard rabbit chow (15% protein). The volume of distribution for doxorubicin was not altered by the low-protein diet. In addition, in rabbits fed the the low-protein diet, the terminal elimination half-life of the alcohol metabolite, doxorubicinol was prolonged (52 +/- 5 vs 40 +/- 2 h; P less than 0.05). Thus, a low-protein diet causes a reduction in the ability of rabbits to eliminate doxorubicin and possibly its alcohol metabolite doxorubicinol. If a similar alteration in anthracycline pharmacokinetics occurs in malnourished cancer patients, this phenomenon may contribute to their increased risk of developing cardiotoxicity associated with anthracycline therapy.