Effect of expression of P-glycoprotein in tumor tissue on analgesic efficacy of morphine and buprenorphine in advanced cancer patients with pain

Abstract

Objective To evaluate the effect of the expression of P-glycoprotein （P-gp） in tumor tissue on analgesic efficacy of morphine and buprenorphine in advanced cancer patients with pain. Methods One hundred and fifty advanced cancer patients with pain aged 51-64 yr weighing 54-65 kg were included in this study. The expression of P-gp was negative in the tumor tissue in 50 patients （group M1 and B1, n = 25 each） and positive in 100 patients （group M2 ,M3 ,and B2 ,B3, n =25 each）. The PCA regimen for the 6 groups were listed in the table .Pain was assessed with VAS scores （0 = no pain, 10 = worst pain） and venous blood samples were taken for determination of blood morphine/buprenorphine concentrations at 4, 12, 24 and 48 h of PCIA. Results The six groups were comparable with respect to age, body weight, M/F sex ratio, types of cancer, baseline pain level and education. The analgesic efficacy of morphine and buprenorphine was better （ VAS scores were significantly lower）in P-gp expression negative patients （group M1 and B1 ） than in P-gp expression positive patients （group M2 and B2 ）. Higher doses of morphine and buprenorphine provided better analgesic efficacy in P-gp expression positive patients in group M3 and B3 than in group M2 and B2. Plasma morphine and buprenorphine concentrations were comparable between group M1 , B1 and M2, B2 and were significantly higher in group M3 and B3 at each time point. Conclusion Positive P-gp expression in the tumor tissue can decrease the analgesic efficacy of morphine and buprenorphine in advanced cancer patients with pain. Key words: Glycoproteins; Morphine; Buprenorphine; Neoplasms; Analgesia