Fumiaki Kitazawa

Transport mechanism of anthracycline derivatives in human leukemia cell lines: uptake and efflux of pirarubicin in HL60 and pirarubicin-resistant HL60 cells

Abstract We studied the transport mechanism of pirarubicin (THP) in HL60 and its THP-resistant (HL60/THP) cells, which showed no expression of mdr1 mRNA on Northern blot analysis. Under physiological conditions, the uptake of THP by both types of cell was time- and temperature-dependent. The amount of drug transport in the resistant cells was significantly less than that in the parent cells within 3 min of incubation. THP uptake was significantly higher in the presence than in the absence of 4 mM 2,4-dinitrophenol (DNP) in glucose-free Hanks’ balanced salt solution in both HL60 and HL60/THP cells and the increases were approximately equal. In the presence of DNP, the uptake of THP by both types of cell was concentration-dependent, and there were no significant differences in the apparent kinetic constants (Michaelis constant (Km), maximum velocity (Vmax) and Vmax/Km) for THP uptake between HL60 and HL60/THP cells. Additionally, THP transport was competitively inhibited by its analogue doxorubicin. The efflux of THP from HL60/THP cells was significantly greater than that from HL60 cells, and the release from both types of cell was completely inhibited by decreasing the incubation temperature to 0°C and by treatment with DNP in glucose-free medium. In contrast, the P-glycoprotein inhibitors verapamil and cyclosporin A did not inhibit THP efflux. However, genistein, which is a specific inhibitor of multidrug resistance-associated protein (MRP), increased the THP remaining in the resistant cells, and the value was approximately equal to that of the control group in the sensitive cells. These results suggest that THP is taken up into HL60 and HL60/THP cells via a common carrier by facilitated diffusion, and then pumped out in an energy-dependent manner. Furthermore, the accelerated efflux of THP by a specific mechanism, probably involving MRP, other than the expression of P-glycoprotein, resulted in decreased drug accumulation in the resistant cells, and was responsible, at least in part, for the development of resistance in HL60/THP cells.

Combination of lenalidomide and low-dose dexamethasone therapy promotes the anticoagulant activity of warfarin in patients with immunoglobulin light-chain amyloidosis

The present study aimed to evaluate the drug interactions between warfarin and combination chemotherapy with lenalidomide and low-dose dexamethasone in immunoglobulin light-chain (AL) amyloidosis patients with unstable international normalized ratios (INR). The changes to INR values over time in 3 AL amyloidosis patients treated with warfarin and a combination of lenalidomide and low-dose dexamethasone between March 2011 and February 2015 were analyzed retrospectively. The mean INR value was 1.52 prior to the combination chemotherapy, and the value increased 1.7-fold during treatment. The median time to reach maximum values was 17 days. Horns drug Interaction Probability Scale indicated a possible interaction between lenalidomide and warfarin. These patients exhibited no marked alterations in hepatic function or serum albumin concentrations prior to and following combination chemotherapy and no additional administration of CYP2C9 inhibitors or vitamin K supplements was conducted. In addition, no patient experienced chemotherapy-induced nausea or appetite loss. These findings suggest that the total clearance or protein binding of warfarin remained unchanged. Therefore, the combination of warfarin and lenalidomide may cause a pharmacodynamic interaction, more likely by inhibiting the production of interleukin-6. In conclusion, clinically important interactions between warfarin and lenalidomide and low-dose dexamethasone therapy were observed in AL amyloidosis patients, where INR values signi ficantly increased. Therefore, close and regular monitoring of patients during the course of treatment is important, and the dose of warfarin should be reduced if required.

Pharmacokinetic Interaction Between Tacrolimus and Fentanyl in Patients Receiving Allogeneic Hematopoietic Stem Cell Transplantation

BACKGROUND Tacrolimus and fentanyl are well-known cytochrome P450 (CYP) 3A4 substrates with a narrow therapeutic range. However, the pharmacokinetic interaction between tacrolimus and fentanyl is unclear. The aim of this study was to determine whether drug interaction exists between tacrolimus and fentanyl. MATERIAL AND METHODS A retrospective study was performed in 6 patients who had received allogeneic hematopoietic stem cell transplantation between April 2010 and March 2015. The patients received continuous intravenous infusion of fentanyl with concomitant use of tacrolimus, and the blood concentrations of tacrolimus were evaluated using fluorescence polarization immunoassay. RESULTS The clearance (CL) of tacrolimus decreased significantly from 1.28 to 0.68 mL/min/kg with concomitant use of fentanyl. The CL changed with time and dose of fentanyl administration. In addition, the CL of tacrolimus was reverted by stopping fentanyl infusion. Horns drug interaction probability scale indicated a probable category or possible category, suggesting a drug interaction between tacrolimus and fentanyl. No patient showed a difference in hepatic or renal function before and after fentanyl administration. No additional administration of other CYP3A4 inhibitors was observed, suggesting that the drug interaction was mediated by CYP3A4. CONCLUSIONS The influence of fentanyl on the pharmacokinetics of tacrolimus was demonstrated to be of clinical importance. It is proposed that the dose of tacrolimus be reduced by 40% when used in combination with fentanyl.