Tacrolimus therapy for refractory acute renal allograft rejection: a 4-year experience with an aggressive approach

Tacrolimus: a further update of its pharmacology and therapeutic use in the management of organ transplantation

Tacrolimus (FK-506) is an immunosuppressant agent that acts by a variety of different mechanisms which include inhibition of calcineurin. It is used as a therapeutic alternative to cyclosporin, and therefore represents a cornerstone of immunosuppressive therapy in organ transplant recipients. Tacrolimus is now well established for primary immunosuppression in liver and kidney transplantation, and experience with its use in other types of solid organ transplantation, including heart, lung, pancreas and intestinal, as well as its use for the prevention of graft-versus-host disease in allogeneic bone marrow transplantation (BMT), is rapidly accumulating. Large randomised nonblind multicentre studies conducted in the US and Europe in both liver and kidney transplantation showed similar patient and graft survival rates between treatment groups (although rates were numerically higher with tacrolimus- versus cyclosporin-based immunosuppression in adults with liver transplants), and a consistent statistically significant advantage for tacrolimus with respect to acute rejection rate. Chronic rejection rates were also significantly lower with tacrolimus in a large randomised liver transplantation trial, and a trend towards a lower rate of chronic rejection was noted with tacrolimus in a large multicentre renal transplantation study. In general, a similar trend in overall efficacy has been demonstrated in a number of additional clinical trials comparing tacrolimus- with cyclosporin-based immunosuppression in various types of transplantation. One notable exception is in BMT, where a large randomised trial showed significantly better 2-year patient survival with cyclosporin over tacrolimus, which was primarily attributed to patients with advanced haematological malignancies at the time of (matched sibling donor) BMT. These survival results in BMT require further elucidation. Tacrolimus has also demonstrated efficacy in various types of transplantation as rescue therapy in patients who experience persistent acute rejection (or significant adverse effect's) with cyclosporin-based therapy, whereas cyclosporin has not demonstrated a similar capacity to reverse refractory acute rejection. A corticosteroid-sparing effect has been demonstrated in several studies with tacrolimus, which may be a particularly useful consideration in children receiving transplants. The differences in the tolerability profiles of tacrolimus and cyclosporin may well be an influential factor in selecting the optimal treatment for patients undergoing organ transplantation. Although both drugs have a similar degree of nephrotoxicity, cyclosporin has a higher incidence of significant hypertension, hypercholesterolaemia, hirsutism and gingival hyperplasia, while tacrolimus has a higher incidence of diabetes mellitus, some types of neurotoxicity (e.g. tremor, paraesthesia), diarrhoea and alopecia.

CONCLUSION

Tacrolimus is an important therapeutic option for the optimal individualisation of immunosuppressive therapy in transplant recipients.

Time course of response to pulse methylprednisolone therapy in renal transplant recipients with acute allograft rejection

All rejection episodes that occurred from 1990 to 1995 treated by the University of Colorado renal transplant service were evaluated through a review of patient charts. Seventy-one episodes of rejection were treated initially with pulse steroids consisting of pulse methylprednisolone, 500 mg/d for 3 days, with sufficient follow-up to determine whether the patient would respond to this treatment. There was no difference between responders and nonresponders to methylprednisolone treatment with respect to serum creatinine level at time of diagnosis, age of allograft, nadir serum creatinine level, or presence of oliguria. The time course of change in serum creatinine levels (in milligrams per deciliter) in responders and nonresponders was similar until day 5, at which time significant differences could be seen (P < 0.01). In the 34 patients treated with OKT3 (muromonab-CD3), statistically significant differences between responders and nonresponders were only seen at day 14, but the small number of nonresponders (n = 4) makes this analysis inconclusive. Based on these data, it appears one cannot truly evaluate whether a patient will respond to three daily pulses of methylprednisolone until at least 3 days have passed since completion of therapy.