Analgesic Effects of Sokeikakketsuto on Chemotherapy-Induced Mechanical Allodynia and Cold Hyperalgesia in Rats

The anticancer agents including oxaliplatin, paclitaxel, and bortezomib cause severe peripheral neuropathy. The Kampo medicine Sokeikakketsuto (SOKT) has been widely used to treat several types of pain. In this study, the analgesic effects of SOKT on oxaliplatin-, paclitaxel-, and bortezomib-induced peripheral neuropathy were investigated in rat models. Rats were treated with oxaliplatin (4 mg/kg, intraperitoneally (i.p.), twice a week for four weeks), paclitaxel (4 mg/kg, i.p., twice a week for two weeks), or bortezomib (0.2 mg/kg, i.p., twice a week for two weeks). SOKT (0.3 or 1.0 g/kg) or duloxetine hydrochloride (30 mg/kg, as a positive control) was administered orally after neuropathy developed. Mechanical allodynia and cold hyperalgesia were assessed using the von Frey test and the acetone test, respectively. These tests were performed immediately before and 30, 60, 90, and 120 min after the administration of the drugs. Repeated treatment of oxaliplatin induced mechanical allodynia and cold hyperalgesia. A single administration of SOKT (1 g/kg, per os (p.o.)), as well as duloxetine, temporarily reversed both the mechanical allodynia and the cold hyperalgesia. Repeated administration of paclitaxel and bortezomib also induced the mechanical allodynia. SOKT and duloxetine reversed the mechanical allodynia caused by bortezomib, but not by paclitaxel. SOKT might have the potential to become a new drug to relieve the symptom of oxaliplatin- or bortezomib-induced peripheral neuropathy.