MICOPHENOLAT MOFETIL VERSUS AZATHIOPRINE : EFFECTS ON RENAL GRAFT FUNCTION IN EARLY POSTTRANSPLANT PERIOD

All conventional immunosuppressive tree drugs-protocols are based on Cyclosporine; consisting of low doses of Cyclosporine (CsA), Azathioprine (AZA) or Mycophenolate Mofetil (MMF) and Prednisolone. AZA has been used in clinical transplantation for more than  years and was the fi rst immunosuppressive agent to achieve widespread use in organ transplantation. MMF was introduced in clinical practice in  after several clinical trials proved that it was more effi cient than AZA for prevention of acute rejection episodes. Our aim was to evaluate infl uence of AZA and MMF on renal graft function in early post-transplant stage. Study recruited  patients who underwent kidney transplantation in University Clinical Centre Tuzla. All patients received CsA and corticosteroid-based immunosuppression, as a part of triple immunosuppressive regiment,  patients received AZA and  MMF. In order to assess renal graft function, following parameters were evaluated: glomerular fi ltration rate GFR (ml/min) creatinine clearance (CrCl) (ml/min),  h urine output (ml/day), and from the serum potassium, sodium, urea and creatinine (mmol/dm). Signifi cantly higher average values of  hour urine output were recorded during fi rst seven postoperative days in patients receiving MMF compared to those treated with AZA. Serum creatinine values showed statistically signifi cant decrease, starting with the second postoperative day, in MMF vs. AZA group (,±, vs. ,±,; p<,). GFR was signifi cantly higher in MMF compared to the AZA group of patients. On the fi rst post-transplant day CrCl was higher in AZA group (,± vs. ,±,; p=,), next six days situation is reversed CrCl is signifi cantly higher in the MMF group (,± vs. , ±,  p=,). MMF vs. AZA therapy was associated with protective eff ect against worsening of renal function in fi rst seven post-transplant days.


Introduction
Th e fi rst attempts at immunosuppression used total-body irradiation, AZA was introduced in the early s, and was soon routinely accompanied by Prednisolone.Th e polyclonal antibody preparations antithymocyte globulin and antilymphocyte globulin became available in the mid-s.Th e situation was transformed in the early s with the introduction of CsA ().Th e initiation of CsA in kidney transplantation produced statistically signifi cant amelioration in graft survival rates to greater than  at  year ().CsA has greatly improved morbidity and mortality in transplantation patients; however its use is often accompanied by renal related unwanted side eff ects such as tubular atrophy, interstitial fi brosis, and focal hyalinosis of small renal arteries and arterioles (, ).Calcineurin-inhibitor therapy, a key component of triple immunosuppressive regiments for patients undergoing transplantation, has also been implicated as a principal cause of post-transplant renal dysfunction (, ).
Cyclosporine reduces renal blood fl ow by causing vasoconstriction of aff erent arterioles and in the longer term by a variety of mechanisms including intimal thickening in blood vessels, hypertension and hyperlipidemia, and also leads to interstitial fibrosis in the kidney ().All conventional immunosuppressive tree drugs-protocols are based on CsA; consisting of low doses of CsA, AZA or MMF and Prednisolone ().Azathioprine has been used in clinical transplantation for more than  years and was the fi rst immunosuppressive agent to achieve widespread use in organ transplantation ().Developers of AZA, Gertrude Elion and George Hitchings, were acknowledged by a share of the  Nobel Prize ().Azathioprine is a pro-drug that releases -mercaptopurine which is afterwards converted into active component -thioinosine-'-monophosphate.Active component of AZA interferes with production of deoxyribonucleic acid (DNA) by incorporation into cellular DNA, where it inhibits purine nucleotide creation and interferes with synthesis and metabolism of ribonucleic acid (RNA) (, ).When cyclosporine was introduced, AZA became second-line drug, and was used as an adjunctive agent in most circumstances.With the introduction of MMF, its use has been discontinued in many programs ().Mycophenolate Mofetil was introduced in clinical practice in  after several clinical trials proved that it was more effi cient than AZA for prevention of acute rejection episodes (,).Mycophenolate Mofetil is an inactive prodrug that is converted to its active compound mycophenolic acid (MPA) by intestinal, liver and plasma esterase's ().Mycophenolic acid is potent, non-competitive, reversible inhibitor of inosine--monophosphate dehydrogenase, an enzyme necessary for lymphocyte mitosis ().Mycophenolic acid is relatively specifi c inhibitor of lymphocyte proliferation; whose inhibitory doses do not aff ect other proliferatory tissues, selectivity of MMF is its most important feature.Mycophenolate Mofetil inhibits proliferation of T and B lymphocytes, antibody production and generation of cytotoxic T cells.Mycophenolate Mofetil was found to be a more eff ective agent than AZA by virtue of its capacity to reduce the incidence of acute rejection episodes when used with cyclosporine (and later with tacrolimus) and corticosteroids ().Various clinical studies comparing MMF to AZA have demonstrated superiority of MMF in prevention of acute rejection episodes (, ).Our aim was to evaluate infl uence of MMF and AZA on renal graft function in early post-transplant period.

Patients and Methods
This is an observational cohort study; it recruited  patients who underwent kidney transplantation in University Clinical Centre Tuzla.Of the patients studied   were men and   women, whose age at transplantation was , ± , years.All patients received CsA and corticosteroid-based immunosuppression, as a part of triple immunosuppressive regiment,  patients received AZA and  MMF.All patients were assessed as ASA IV (American Society of Anaesthesiologists) physical status.Balanced anaesthesia was used in all transplant patients.Postoperatively all patients were placed in Intensive Care Unit (ICU); length of ICU stay depended on function of transplanted kidney and general condition of the patients.Continuous monitoring of central venous pressure (CVP), arterial pressure and oxygen saturation of blood, were applied.Central venous route was insured trough sublacvian vein and was used for intravenous fluids administration and CVP measuring.Fluid resuscitation depended on CVP values.In order to assess renal graft function, following parameters were evaluated: GFR (ml/min) CrCl (ml/min),  h urine output, and from the serum potassium, sodium, urea and creatinine (mmol/dm).During fi rst seven post transplant days all parameters were assessed daily.CVP was measured every four hours; in our research were used average daily values.Glomerular fi ltration rate was calculated using following formula: GFR=  × Cr -, ×Age-,  × Bun-, ×, (female) ().Creatinine clearance was calculated by using formula proposed by Cockcroft and Gault, which is formula widely used to detect onset of renal insufficiency.

Statistical analysis
Th e statistical analysis was performed using Student ttest, p-value of , or less was considered statistically signifi cant.

Results
Th

Discussion
Over the last  years allograft and renal transplant recipient survival have considerably ameliorated, this is a result of many factors, especially improvement in effi ciency and lessening in toxicity of immunosuppressive drugs.Th is study was undertaken in order to evaluate infl uence of two diff erent immunosuppressive agents on renal graft function in first seven post-transplant days.Renal function has long been recognized as a critical determinant of the probability of graft survival, and its critical role as a predictor of survival has been confi rmed in the United Network for Organ Sharing (UNOS) database ().Risk of acute kidney rejection is greatest in early post-transplant period; therefore during this period close monitoring is warranted.Assessment of renal graft function in our study, (during fi rst seven postoperative days) was based on daily monitoring of GFR, serum creatinine levels, CrCl and  hour urine output, in both AZA and MMF group.Th e glomerular fi ltration rate is traditionally considered the best overall index of renal function in health and disease.Serum creatinine and calculated CrCl have been proposed as outcome measures in renal transplantation as well as in primary renal diseases ().Forty of  recipients were given AZA and to  MMF as a part of triple immunosuppressive treatment.Th e patients who received MMF had signifi cantly higher values of  hour urine output during observed period, compared to patients treated with AZA.Creatinine clearance was also signifi cantly higher in MMF group (,± vs. ,±,; p=,), with the exception of the first post-transplant day (,± vs. ,±,; p=,).Sita et al. found that more stable CrCl, i.e., a lower rate of loss of CrCl, was associated with the use of MMF versus AZA, during six month post-transplant period ().In the study conducted by Gourishankar and colleagues, a more stable creatinine clearance was associated with use of MMF versus AZA ().In our research statistically signifi cant decrease in average values of serum creatinine values was also observed in MMF group, after the fi rst post-transplant day.We also found signifi cantly higher values of GFR in the MMF group.Gill and colleagues conducted a retrospective analysis of , fi rst kidney only transplant recipients, with allograft survival of at least  years.Patients were classifi ed according to the type of maintenance Calcineurin (conventional cyclosporine, cyclosporine microemulsion, tacrolimus) and purine metabolism inhibitor (AZA, MMF) they received after transplantation.Th e objective of the study was to determine the effect of immunosuppressive agents on the rate of kidney allograft function loss by monitoring changes in GFR.
Patients receiving MMF demonstrated slower decline in GFR than those patients receiving AZA ().Mycophenolate Mofetil is a non-nephrotoxic immunosuppressant specifi c for T and B-cells.Compared with AZA, superior safety and effi cacy of MMF has been demonstrated in hearth, kidney and liver transplant recipients (, , ).Th e use of MMF with lower cyclosporine dosages has been reported to improve renal function while maintaining adequate immunosuppression ().Azathioprine has been used in clinical transplantation for over  years but MMF is a more powerful immunosuppressant associated with better short-termand probably better long-term-outcomes (, ).

Conclusion
Our research analyzed infl uence of two diff erent immunosuppressive treatments on renal allograft function in fi rst seven postoperative days.Detection of renal graft deterioration in early post-transplant stage can be an important predictor of chronic rejection which is the most important cause of graft loss in long-term studies.According to our results, MMF vs. AZA therapy was associated with protective eff ect against worsening of renal function in fi rst seven post-transplant days.
e study was conducted in University Clinical Centre Tuzla.It included  patients mean age , ±,  years,  were males and  females.Mean donor age was , ±,  years,  donors were younger then  years and  were older.All transplant patients received CsA and steroids postoperatively; besides CsA  patients were treated with MMF, and the rest of them with AZA.Statistical analysis shoved significantly higher average values of  hour urine output in a group of patients receiving MMF compared to the patients being treated with AZA (Figure ).Average values of serum creatinine did not differ signifi cantly on the fi rst post-transplant day (,±, vs.