An oral glutamine dosage of 7.5 g for 3 weeks, administered for preventing mucositis/stomatitis of breast cancer patients receiving anthracycline-based chemotherapy, did not cause any side effects but reduced the incidence of significant oral mucositis. In another study, patients with advanced or metastatic cancer receiving fluorouracil/leucovorin in chemotherapy were supplemented with glutamine at 30 g/d for 15 days for preventing mucositis/stomatitis. In this study, a reduction of mucositis/stomatis was also observed without any side effects attributable to glutamine supplementation. Similarly, 30 g oral glutamine given daily to colorectal cancer patients receiving oxaliplatin reduced the incidence and severity of peripheral neuropathy and also did not cause any side effects. In a mixed patient group (cancer or intestinal failure) on home total parenteral nutrition due to colon resection or inflammatory enteropathy, the parenteral infusion of glutamine at a dose of 0.285 g/kg body weight (equivalent to 20 g/70 kg body weight) for 4 weeks resulted in the elevation of liver enzymes in 3 patients. Those abnormities subsided after discontinuation of the glutamine-total parenteral nutrition administration. Interestingly, during the course of the study, plasma levels of glutamine did not increase.
Therefore, it seems questionable whether the increase in liver enzymes was due to glutamine or to the concomitant overload of fat application or glucose supply. Both factors increase liver enzymes under certain conditions. Interestingly, the three patients received a rather high level of total energy (2888, 2574, and 2314 kcal5, respectively), which, rather than the glutamine supplementation, may have triggered the deterioration of hepatic metabolism.