Diltiazem disposition and metabolism in recipients of renal transplants

Calcium channel blockers for preventing acute tubular necrosis in kidney transplant recipients

BACKGROUND

The incidence of delayed graft function in cadaveric grafts has increased over the last few years due in part to the large demand for cadaveric kidneys necessitating the use of kidneys from marginal donors. Calcium channel blockers have the potential to reduce the incidence of post-transplant acute tubular necrosis (ATN) if given in the peri-operative period. However, there is controversy surrounding their use in this situation with no consensus as to their efficacy.

OBJECTIVES

To evaluate the benefits and harms of using calcium channel blockers in the peri-transplant period in patients at risk of ATN following cadaveric kidney transplantation.

SEARCH STRATEGY

We searched the Cochrane Renal Group's specialised register, the Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library) MEDLINE (from 1966) and EMBASE (from 1980). The Trials Search Coordinator was contacted to develop the search strategy. Date of last search: January 2007

SELECTION CRITERIA

Randomised controlled trials comparing calcium channel blockers given in the peri-transplant period with controls were included. Quasi-randomised trials were excluded.

DATA COLLECTION AND ANALYSIS

Data was extracted and quality assessed independently by two reviewers, with differences resolved by discussion. Dichotomous outcomes are reported as relative risk (RR) and measurements on continuous scales are reported as mean differences (WMD) with 95% confidence intervals (CI).

MAIN RESULTS

Thirteen trials (724 participants) were suitable for inclusion. Treatment with calcium channel blockers in the peri-transplant period was associated with a significant decrease in the incidence of post-transplant ATN (RR 0.62, 95% CI 0.46 to 0.85) and delayed graft function (RR 0.55, 95% CI 0.42 to 0.73). There was no difference between control and treatment groups in graft loss, mortality, requirement for haemodialysis. There was insufficient information to comment on adverse events.

AUTHORS' CONCLUSIONS

These results suggest that calcium channel blockers given in the peri-operative period may reduce the incidence of ATN post-transplantation. The result should be treated with caution due to the heterogeneity of the trials which made comparison of studies and pooling of data difficult.

Calcium channel blockers for preventing acute tubular necrosis in kidney transplant recipients

BACKGROUND

The incidence of delayed graft function in cadaveric grafts has increased over the last few years due in part to the large demand for cadaveric kidneys necessitating the use of kidneys from marginal donors. Calcium channel blockers have the potential to reduce the incidence of post-transplant acute tubular necrosis (ATN) if given in the peri-operative period. However, there is controversy surrounding their use in this situation with no consensus as to their efficacy.

OBJECTIVES

To evaluate the benefits and harms of using calcium channel blockers in the peri-transplant period in patients at risk of ATN following cadaveric kidney transplantation.

SEARCH STRATEGY

We searched the Cochrane Renal Group's specialised register, the Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library) MEDLINE (from 1966) and EMBASE (from 1980). The Trials Search Coordinator was contacted to develop the search strategy. Date of last database and register search: January 2005

SELECTION CRITERIA

Randomised controlled trials comparing calcium channel blockers given in the peri-transplant period with controls were included. Quasi-randomised trials were excluded.

DATA COLLECTION AND ANALYSIS

Data was extracted and quality assessed independently by two reviewers, with differences resolved by discussion. Dichotomous outcomes are reported as relative risk (RR) and measurements on continuous scales are reported as weighted mean differences (WMD) with 95% confidence intervals (CI).

MAIN RESULTS

Ten trials were suitable for inclusion. Treatment with calcium channel blockers in the peri-transplant period was associated with a significant decrease in the incidence of post transplant ATN (RR 0.57, 95%CI 0.40 to 0.82) and delayed graft function (RR 0.51, 95% CI 0.36 to 0.72). There was no difference between control and treatment groups in graft loss, mortality, requirement for haemodialysis. There was insufficient information to comment on adverse events.

AUTHORS' CONCLUSIONS

These results suggest that calcium channel blockers given in the peri-operative period may reduce the incidence of ATN post-transplantation. The result should be treated with caution due to the heterogeneity of the trials which made comparison of studies and pooling of data difficult.

Diltiazem use in tacrolimus-treated renal transplant recipients

BACKGROUND

Calcium channel blockers are widely used in the treatment of post-transplant hypertension but have the potential for drug interaction with calcineurin inhibitors. Renal allograft outcomes when diltiazem is used with cyclosporine have been reported, but similar data with tacrolimus are not available.

METHODS

We performed a retrospective analysis of all our renal transplant recipients from March 1997 to March 2002 who were given tacrolimus, mycophenolate mofetil and prednisone. Patients were divided into two groups based on whether diltiazem was started in the first postoperative week. Outcome measures included renal function up to 2 years post-transplant, blood pressure (BP) control, tacrolimus exposure, and costs related to tacrolimus monitoring.

RESULTS

Sixty-four patients constituted the diltiazem group and 32 the control group. Their baseline characteristics were similar. The mean average daily dose of diltiazem used was 213.95 mg/day. There was no difference in renal function, graft survival, or patient survival over 2 years. BP control was similar although the diltiazem group required more medication. Diltiazem was discontinued in four patients due to side-effects. There was no difference in tacrolimus-related side-effects between the two groups. There was also no difference in tacrolimus exposure, cost related to tacrolimus monitoring, or combined costs when the expense of diltiazem was added.

CONCLUSION

Diltiazem use is acceptably safe and efficacious in renal transplant recipients treated with tacrolimus-based immunosuppressive therapy. It can be considered as a first-line antihypertensive in these patients and is cost neutral for tacrolimus use.

Pharmacokinetic interaction between tacrolimus and diltiazem: dose-response relationship in kidney and liver transplant recipients

OBJECTIVE

To study the dose-response relationship of the pharmacokinetic interaction between diltiazem and tacrolimus in kidney and liver transplant recipients.

DESIGN

Nonrandomised seven-period stepwise pharmacokinetic study.

PATIENTS

Stable kidney (n = 2) and liver (n = 2) transplant recipients maintained on oral tacrolimus twice daily but not taking diltiazem.

METHODS

Patients were treated with seven incremental dosages of diltiazem (0 to 180 mg/day) at > or = 2-weekly intervals. At the end of each interval, 13 blood samples were taken over a 24-hour period to allow determination of morning (AUC(12)), evening (AUC(12-24)) and 24-hour (AUC(24)) areas under the concentration-time curve for tacrolimus, as well as AUC(24) for diltiazem and three of its metabolites.

RESULTS

There was considerable interpatient variability in tacrolimus-sparing effect. In the two kidney transplant recipients, an increase in tacrolimus AUC(24) occurred following the 20 mg/day dosage of diltiazem (26 and 67%). The maximum increase in tacrolimus AUC(24) occurred at the maximum diltiazem dosage used (180 mg/day), when the increase was 48 and 177%. In the two liver transplant recipients, an increase in tacrolimus AUC(24) did not occur until a higher diltiazem dosage (60 to 120 mg/day) was given. The increase at the maximum diltiazem dosages used (120 mg/day in one and 180 mg/day in the other) was also lower (18 and 22%) than that exhibited by the kidney transplant recipients. The increase in tacrolimus AUC(12) was similar to the increase in AUC(12-24) when diltiazem was given in the morning only (dosages < or = 60 mg/day). Hence, diltiazem affects blood tacrolimus concentrations for longer than would be predicted from the half-life of diltiazem in plasma.

CONCLUSIONS

The mean tacrolimus-sparing effect of diltiazem was similar in magnitude to the cyclosporin-sparing effect previously reported. Whether the lesser tacrolimus-sparing effect with diltiazem seen in the liver transplant recipients was due to functional differences in the transplanted liver is not known, but it was not due to lower plasma diltiazem concentrations. Diltiazem makes a logical tacrolimus-sparing agent because of the potential financial savings and therapeutic benefits. Because of interpatient variability, the sparing effect should be demonstrated in each patient and not merely assumed.