In a dose escalation study of 32 patients with
refractory solid tumors, d-limonene was given orally at
0.5-12 g/m2/day (1-24 g/day, considering an average
area per person is 1.9 m2). Patients initially received dlimonene
for 21 days. The maximum tolerated oral dose
was 8 g/m2/day (15 g/day). Nausea, vomiting, and diarrhea
were the only side effects observed and were dose
dependent. One breast cancer patient was on the dose
of 8 g/m2/day (15 g/day) for 11 months. The authors
concluded that d-limonene had low toxicity after single
and repeated dosing for up to one year