Drug safety issues in pregnancy following transplantation and immunosuppression: effects and outcomes

Human pregnancy safety for agents used to treat rheumatoid arthritis: adequacy of available information and strategies for developing post-marketing data

For female patients with rheumatoid arthritis, the availability of a host of new disease modifying antirheumatic drugs has raised important questions about fetal safety if a woman becomes pregnant while she is being treated. In addition, there is limited safety information regarding many of the older medications commonly used to treat rheumatoid arthritis in women of reproductive age. Current summary pregnancy risk information for selected medications used to treat rheumatoid arthritis is reviewed in the context of the pregnancy label category. In addition, the strengths and weaknesses of post-marketing strategies for developing new pregnancy safety information are described.

Effects of maternally administered drugs on the fetal and neonatal kidney

The number of pregnant women and women of childbearing age who are receiving drugs is increasing. A variety of drugs are prescribed for either complications of pregnancy or maternal diseases that existed prior to the pregnancy. Such drugs cross the placental barrier, enter the fetal circulation and potentially alter fetal development, particularly the development of the kidneys. Increased incidences of intrauterine growth retardation and adverse renal effects have been reported. The fetus and the newborn infant may thus experience renal failure, varying from transient oligohydramnios to severe neonatal renal insufficiency leading to death. Such adverse effects may particularly occur when fetuses are exposed to NSAIDs, ACE inhibitors and specific angiotensin II receptor type 1 antagonists. In addition to functional adverse effects, in utero exposure to drugs may affect renal structure itself and produce renal congenital abnormalities, including cystic dysplasia, tubular dysgenesis, ischaemic damage and a reduced nephron number. Experimental studies raise the question of potential long-term adverse effects, including renal dysfunction and arterial hypertension in adulthood. Although neonatal data for many drugs are reassuring, such findings stress the importance of long-term follow-up of infants exposed in utero to certain drugs that have been administered to the mother.

Current issues in pediatric transplantation

Pediatric solid organ transplantation is so successful that >80% of children will survive to become teenagers and adults. Therefore, it is essential that these children maintain a good quality life, free of significant long-term side effects. While intensive immunosuppressive regimens (containing CsA, tacrolimus, MMF, and steroids) effectively reduce acute or chronic rejection, they can produce long-term side effects including viral infection, renal dysfunction, hypertension, and stunting. The development of effective methods of diagnosis, prevention, and treatment of CMV means that this is no longer a significant cause of mortality, but morbidity remains high. In contrast, infection rates of EBV remain high in EBV-negative pre-transplant patients. However, pre-emptive reduction of immunosuppression or treatment with rituximab or adoptive T-cell therapy is effective in preventing/treating post-transplant lymphoproliferative disease. Recent protocols have concentrated on reducing CsA immunosuppression, to prevent unacceptable cosmetic effects, and to reduce the hypertension, hyperlipidemia, and nephrotoxicity. Both CsA and tacrolimus cause a 30% reduction in renal function, with 4-5% of patients developing severe chronic renal failure. The use of IL-2 inhibitors for induction therapy with low-dose calcineurin inhibitors, in combination with renal-sparing drugs such as MMF or sirolimus for maintenance immunosuppression, should prevent significant renal dysfunction in the future. The concept of steroid-free immunosuppression with IL-2 inhibitors, tacrolimus, and MMF is an attractive option, which may reduce stunting and renal dysfunction. However, these regimens may be associated with the increased development of de-novo autoimmune hepatitis in 2-3% of children. The most important challenge to long-term survival in transplanted children is the management of non-adherence and other adolescent issues, particularly when transferring to adult units, as this is the time when many successful transplant survivors lose their grafts.

Myasthenia gravis: management issues during pregnancy

Myasthenia gravis (MG) often affects women in the second and third decades of life, overlapping with the childbearing years. The course of the disease is unpredictable during pregnancy; however, worsening of symptoms occurs more likely during the first trimester and postpartum. MG can be well managed during pregnancy with relatively safe and effective therapies. Anticholinesterase drugs are the mainstay of treatment, when MG symptoms are not satisfactorily controlled, corticosteroids, azathioprine and in some cases cyclosporin A can be used. Until information is available regarding safety, mycophenolate mofetil should be discontinued before pregnancy. Pregnancy should be avoided in women treated with methotrexate because of the risk of causing typical malformations. Plasmapheresis and intravenous immunoglobulins have been successfully used in the treatment of MG crisis during pregnancy. Caesarean section is recommended only for obstetric reasons; forceps delivery and vacuum extraction are sometimes required. Epidural anesthesia is advised to reduce physical and emotional stress. MG during pregnancy can lead to serious life-threatening conditions, including respiratory insufficiency; therefore, intensive checkups by a gynaecologist and a neurologist are necessary. Women with myasthenia gravis should not be discouraged from conceiving; however, they should discuss their plan for pregnancy with their neurologist and their gynaecologist.

Antirheumatic Drugs in Pregnancy and Lactation

OBJECTIVE

To review the toxicity issues of commonly used antirheumatic drugs in pregnancy and lactation.

METHODS

A review of the medical literature using Medline database via Ovid was performed to identify the toxicities of antirheumatic drugs in pregnancy and lactation.

RESULTS

Many rheumatologic diseases in women often first present during the childbearing years. In most cases, antirheumatic therapy is required for their disease control. Glucocorticoids may be used during pregnancy; however, first-trimester use should be avoided if possible and breastfeeding should occur 4 hours after the last dosing. Nonsteroidal antiinflammatory drugs (NSAIDs) and cyclooxygenase-2 (COX-2) inhibitors should be discontinued 6 to 8 weeks before delivery. NSAIDs are compatible with lactation, although there is potential risk of jaundice and kernicterus. There is insufficient data on COX-2 inhibitors and lactation. Hydroxychloroquine and sulfasalazine may be continued throughout pregnancy and lactation. Methotrexate and leflunomide are contraindicated during pregnancy and lactation. Cyclophosphamide and mycophenolate mofetil should be avoided during pregnancy and lactation. Azathioprine and cyclosporine A could be used with caution during pregnancy if felt there is a need to suppress disease activity. They are not compatible with breastfeeding. There are insufficient data regarding tumor necrosis factor-antagonists, anakinra, and rituximab in relation to pregnancy and lactation. Male patients should be made aware of the effects methotrexate, leflunomide, sulfasalazine, and cyclophosphamide may have on their fertility.

CONCLUSIONS

Health care providers should discuss the risks and benefits of antirheumatic therapy during conception, pregnancy, and lactation with their patients. Better maternal and fetal outcomes can be expected if the pregnancy is planned, the rheumatic disease is stable, and if appropriate medication adjustments can be made ahead of time.

Myasthenia gravis and pregnancy

Treatment considerations for women who have MG and are of childbearing age are complicated. When possible, before pregnancy, establishing a plan for therapy is ideal, recognizing the potential concerns for the patient and the fetus. Decisions about treatment during pregnancy must balance the potential complications for the fetus, the patient, and even the integrity of the pregnancy. Most women who have MG are able to complete pregnancy successfully and deliver a healthy baby; however, there always is some risk that NMG may occur. Pregnant patients who have MG are served best at centers capable of providing coordinated expert care from neurologic, obstetric, and pediatric providers.

Medical management of the pregnant patient with inflammatory bowel disease

Gastroenterologists are not infrequently faced with questions regarding pregnancy when advising or treating their patients with inflammatory bowel disease (IBD). To advise patients effectively, the following factors must be considered: (1) the inheritance patterns of IBD for accurate counseling and family planning; (2) the effects of active IBD versus medications or surgery on fertility; (3) the effects of pregnancy on the course of IBD; (4) the effects and potential risks of active IBD versus those of diagnostic tests, medical treatments, and surgical treatments on the developing fetus; (5) approach to delivery; and (6) the risks of breast-feeding while receiving treatment for IBD.

The risk of congenital abnormalities in children fathered by men treated with azathioprine or mercaptopurine before conception

BACKGROUND

Immunosuppressive therapy with azathioprine and mercaptopurine is commonly used in patients with various chronic diseases. The few existing data on the reproductive safety of these drugs after paternal use before conception are inconclusive.

AIM

To examine the risk of congenital abnormalities in children fathered by men exposed to azathioprine or mercaptopurine before conception.

METHODS

This was a Danish population-based cohort study, based on data from the Prescription Database, the Medical Birth Registry and the Hospital Discharge Registry of North Jutland County, Denmark. Fifty-four exposed pregnancies, in which the father filed a prescription for azathioprine or mercaptopurine (between 1 January 1991 and 31 December 2001) before conception, were included. The controls comprised 57 195 pregnancies with no paternal azathioprine or mercaptopurine use.

RESULTS

Four children with congenital abnormalities (underlying paternal diseases: glomerulonephritis and severe skin disease) were found in 54 exposed pregnancies (7.4%), compared with 2334 (4.1%) in controls. The adjusted odds ratio for congenital abnormalities in children fathered by men treated with azathioprine or mercaptopurine was 1.8 (95% confidence interval, 0.7-5.0).

CONCLUSIONS

Our data may indicate that paternal use of azathioprine or mercaptopurine before conception is associated with an increased risk of congenital abnormalities. However, more data are needed to determine whether the association is causal.

Experience with cyclosporine

The introduction of cyclosporine (CyA) was a landmark in transplantation, and in the two decades that have followed, enormous experience has been acquired in its use. This has led to both an understanding of its mechanism, pharmacokinetics and toxicity, and the continued evolution of its clinical application. Many of the initial complexities related to the hydrophobic nature of the molecule, and its variable absorption were addressed by the introduction of the microemulsion formulation Neoral. Despite this, the therapeutic window for CyA remains narrow, and therapeutic drug monitoring, recognized early after its introduction, is essential. However, this too has been redefined with single-point, 2-hour, postdose monitoring being demonstrated to correlate better with dose and outcome than the traditional 12-hour trough level. Implementation of such techniques may impact on efficacy and the long-term effects of nephrotoxicity. The need to gain experience with new facets of CyA is likely to continue. In particular, the use of reduced doses to minimize nephrotoxicity during long-term management has produced favorable early results. Furthermore, in the near future the availability of generic CyA formulations will increase. It cannot be assumed that these will be bioequivalent to the current preparations, and modifications of therapy, outside of current experience, may be required. However, if 20 years of CyA usage has taught us anything, it is that different formulations may have very different biological behavior, and at least this situation can be approached with a caution gained from long experience.

Gynecologic issues of the adolescent female solid organ transplant recipient

Advances in the field of transplant medicine are providing adolescent recipients with continual improvements in health and quality of life. With expanding opportunities for normal social and sexual relationships, adolescents require careful attention to their gynecologic and reproductive health (Box 1). Medical considerations vary depending on the type of organ transplanted, underlying and comorbid conditions, and current medication use. Most adolescent girls achieve menarche, however, and irregular cycles should be evaluated and managed with the same considerations applied to healthy young women. The management of menstrual disorders frequently uses hormonal contraceptive methods. Many transplant recipients also are sexually active and require a contraceptive method to prevent a mistimed pregnancy. With careful attention to organ function, other medical problems, and concurrently prescribed medications, many transplant recipients can use safely the currently available methods of hormonal contraception.

Strategies for optimizing immunosuppression in adolescent transplant recipients: a focus on liver transplantation

Adolescence is a difficult time for transplant recipients; they must learn to take responsibility for their own behavior and medication, and to balance their developing sexuality in a body that has been transformed by the adverse effects of immunosuppression. More than 80% of children survive transplantation to adolescence and adulthood, thus long-term outcome and tailoring of immunosuppression is of great importance. To date, the most experience with long-term immunosuppression regimens is cyclosporine, which is well tolerated and effective. Long-term adverse effects include hypertension, nephrotoxicity, and post-transplant lymphoproliferative disease (PTLD). The recent development of tacrolimus has improved the cosmetic adverse effects related to cyclosporine, but has similar rates of hypertension and nephrotoxicity, and possibly a higher rate of PTLD. There has been a recent, welcome development in renal sparing drugs, such as mycophenolate mofetil, which has no cosmetic adverse effects, does not require drug level monitoring and is thus particularly attractive to teenagers. Recent surveys demonstrate recovery of renal function with mycophenolate mofetil, if started prior to irreversible renal dysfunction. There are currently little published data on the use of sirolimus (rapamycin) in the pediatric population, but preliminary studies suggest that the future use of interleukin-2 receptor antibodies may be beneficial for immediate post-transplant induction of immunosuppression. It is important when planning immunosuppression for adolescents to consider the effects of drug therapy on both males and females in order to maintain fertility and to ensure safety in pregnancy. Noncompliance is a problem in this age group, but adequate practical measures and support should reduce noncompliance, and allow good, long-term graft function.

Immunosuppression in pregnancy: choices for infant and maternal health

Successful pregnancy outcomes are possible after all types of solid organ transplantation and thousands of successful pregnancies in such women have been reported. As immunosuppressive medications are required to maintain adequate graft and maternal survival, major concerns are the effect of these agents on the fetus and the effect of pregnancy on the well being of mother and graft, against a background of continuing advances and modifications in immunosuppressive therapy. Women should avoid unnecessary medications during pregnancy but clinicians worry most about teratogens; agents (environmental, pharmaceuticals or other chemicals) that cause abnormal development, whether this be an overt structural birth defect or more subtle derangements of embryonic or fetal development. A concern is that any agent or combination of agents and maternal condition(s) may be teratogenic, a risk that is increased in the transplant population. The goal of immunosuppression is to ensure graft and patient survival by preventing acute rejection. Combinations of agents allow for synergistic effects while minimising drug toxicities. No specific combination has been deemed optimal and the effects of more recently available combinations require further study. Although there are known theoretical risks to mother and fetus, successful pregnancies are now the rule in transplant recipients. This is without an apparent increase in the type or incidence of malformations in the newborns, and usually with no evidence of graft dysfunction and/or irreversible deterioration either related to prepregnancy graft problems or unpredictable gestational factors. For immunosuppression, what is best for the mother and her survival should ensure the best outcome for the fetus and, although no specific malformation pattern has been reported to date, there are some interesting trends worthy of continued analyses. A balance of good maternal and graft outcome with the lowest risk of fetal toxicity must be the goal of management.

Transition of care between paediatric and adult gastroenterology. Liver transplantation

With the increasing success of liver transplantation in children, a growing number of children are reaching an age when it is no longer appropriate for them to be followed by paediatricians. Clinicians looking after these liver allograft recipients need to be aware of the additional problems and needs in this group of young patients. While life after transplantation is usually near normal, a proportion of adolescents suffer from physical and psychological stresses that may result in social and behavioural problems. Non-compliance can have a major adverse impact on graft function. Immunosuppression needs to be adjusted to maintain good graft function, but also to keep to a minimum the adverse effects including renal failure and malignancy. The adverse cosmetic effects of some immunosuppressive drugs can be particularly troublesome at this stage in life. Overall, adolescent liver allograft recipients can have an excellent quality of life. Health care professionals need to be aware of the additional problems that this group of patients may have and they will need to adapt the follow-up in response to these issues.

Azathioprine, mercaptopurine and birth outcome: a population-based cohort study

BACKGROUND

Data on the safety of azathioprine and mercaptopurine during pregnancy are very sparse.

AIM

To examine the risk of adverse birth outcomes in women who took up prescriptions for azathioprine or mercaptopurine during pregnancy.

METHODS

This is a Danish cohort study based on data from a population-based prescription registry, the Danish Birth Registry and the Hospital Discharge Registry. To examine the risk of congenital malformations, we included nine pregnancies exposed 30 days before conception or during the first trimester. To examine perinatal mortality, pre-term birth and low birth weight, we included 10 pregnancies exposed during the entire pregnancy. Eleven different exposed women were included in the study. Outcomes were compared with those of 19 418 pregnancies in which no drugs were prescribed to the mothers.

RESULTS

Fifty-five per cent of the exposed women had inflammatory bowel disease and 45% other diseases. Adjusted odds ratios for congenital malformations, perinatal mortality, pre-term birth and low birth weight were 6.7 (95% confidence interval, 1.4-32.4), 20.0 (2.5-161.4), 6.6 (1.7-25.9) and 3.8 (0.4-33.3), respectively.

CONCLUSIONS

Our results suggest that there is an increased risk of congenital malformations, perinatal mortality and pre-term birth in children born to women treated with azathioprine or mercaptopurine during pregnancy. More data are needed to determine whether the associations are causal or occur through confounding.

Pregnancy outcomes in female renal recipients: a comparison of systemic lupus erythematosus with other diagnoses

This study compares pregnancy outcomes in systemic lupus erythematosus (SLE) patients post renal transplant with recipients with other primary diagnoses, utilizing data from the National Transplantation Pregnancy Registry, Philadelphia, PA. Recipients were referred from transplant centers nationwide. A retrospective analysis was performed using data from questionnaires, hospital records and telephone interviews. Outcomes of pregnancies post renal transplant secondary to lupus nephritis (SLE: n = 38; 60 pregnancies) were compared with the pregnancy outcomes of renal recipients with other diagnoses (non-SLE: n = 247; 374 pregnancies). Drug-treated hypertension during pregnancy was less common in the SLE group than in the non-SLE group (45.0% vs. 62.5%, p = 0.015). There were fewer cesarean sections in the SLE group (30.2 vs. 53.2%, p = 0.008). There was no primary or gestational diabetes in the SLE group. There were no other statistical differences in maternal conditions or pregnancy outcomes between the SLE and non-SLE groups, or in the incidence of post pregnancy graft loss. Female recipients transplanted for renal failure secondary to lupus nephritis can successfully maintain pregnancy. Outcomes are comparable to renal recipients with other diagnoses. Newborns in both groups were often premature and had low birthweight. Overall childhood health was reported to be good; there were no apparent predominant structural malformations among the children.

Optimal immunosuppression in teenagers

Adolescence is a difficult time for transplant recipients, who need to cope with the challenges of becoming independent from their parents, as well as taking responsibility for their own behavior and medication. They need to balance their developing sexuality with a body image which may be affected by the side-effects of immunosuppression. It is now anticipated that more than 80% of children will survive their transplant to become teenagers and adults, and it is therefore important to ensure that immunosuppressive medication is acceptable, convenient for drug level monitoring and free of significant long-term side-effects.

The influence of ciclosporine A on the vasoactive effects of serotonin in in vitro perfused human umbilical arteries

BACKGROUND

Pregnancy is feasible in organ-transplanted women, but little is known about possible effects of ciclosporine A on the circulation in the fetus and placenta.

AIM

To investigate the influence of ciclosporine A (CsA) on the vasoactive effects of serotonin in human umbilical arteries.

STUDY DESIGN AND SUBJECTS

In vitro perfusion was performed in umbilical cord segments from seven organ-transplanted patients on CsA based immunosuppression and in 17 cords from uncomplicated pregnancies. Serotonin was administered in stepwise increasing concentrations from 10(-10) to 10(-5) M. In preparations from normal pregnancies, serotonin 10(-7) M, was administered before and 30 min after the start of a continuous CsA infusion (1.0 mg/l). The influence of CsA 0.1 or 1.0 mg/l on the basal, unstimulated perfusion pressure was investigated in separate experiments.

OUTCOME MEASURES

Changes in perfusion pressure due to constrictory or dilatatory responses.

RESULTS

In all preparations from the organ-transplanted patients, serotonin induced a constrictory response that was non-significantly lower than that observed in the control group. The frequency of a dilatatory response preceding the vasoconstriction was 3/7 and 12/17 (non-significant) in the CsA-treated and control groups, respectively. In the experiments with CsA administration, a non-significant increase in the constrictory serotonin response was observed as compared to the control experiments. CsA did not alter the basal, unstimulated perfusion pressure.

CONCLUSION

CsA did not have any significant influence on the vasoactive effect of serotonin in human umbilical arteries perfused in vitro.

Drugs in pregnancy. Renal disease

The management of pregnant women with renal impairment presents a major challenge to obstetricians, nephrologists, and ultimately paediatricians. As renal failure progresses there is an increase in both maternal and fetal complications. Often these women have intercurrent medical conditions and, prior to conception, are receiving a broad range of prescribed medications. A successful obstetric outcome relies upon careful pre-pregnancy counselling and planning, obsessive monitoring during pregnancy, and close liaison between different specialist teams. Experience is mounting in the management of pregnant transplant recipients, but the introduction of newer immunosuppressive agents which have great promise in prolonging graft survival present new problems for those recipients of a kidney transplant who are planning to conceive. We review drug prescription for pregnant patients with renal impairment, end-stage renal failure, or a kidney transplant.

Drugs in pregnancy. Rheumatological disorders

Rheumatic diseases occur frequently in women of childbearing years, necessitating drug treatment during a concurrent pregnancy in order to control maternal disease activity and to ensure a successful pregnancy outcome. Inflammatory rheumatic diseases with mainly musculoskeletal involvement may cause acute episodes of arthritis. Autoimmune, systemic diseases may flare with manifestations of haematological, dermatological or renal disease or give rise to thromboembolism during pregnancy. Treatment with non-steroidal anti-inflammatory drugs, corticosteroids, anticoagulants, immunosuppressive or even cytotoxic drugs may be required to acquire disease control. Unfortunately, controlled studies on the use of antirheumatic drugs during gestation exist only for a few drugs. This chapter presents data on the use of antirheumatic drugs during pregnancy, addressing the risk of teratogenicity, possible long-term effects on the infant exposed to drugs antenatally, and maternal side-effects which interfere with pregnancy. Recommendations for pre-pregnancy counselling and necessary adjustment of drug treatment before and during pregnancy are given.

Pregnancy in transplant recipients

A growing number of transplant recipients are women of reproductive age or children who will reach reproductive age. Thus, menstrual function and pregnancy increasingly are important issues because fertility is restored to women who were previously unable to conceive. To date, successful pregnancies have been reported in female recipients of kidney, liver, heart, pancreas-liver, bone marrow, and lung transplants. Women often become pregnant while being maintained on numerous medications, including immunosuppressive agents, and their care providers must be able to counsel and care for them. Information to date suggests that immunosuppressive medications are safe for use during pregnancy and are important in preventing maternal and fetal complications secondary to graft rejection. Although no formal guidelines have been established due to limited clinical experience, there are a few criteria that are commonly agreed on to improve the probability of a successful pregnancy outcome and the maintenance of graft function in transplant patients. Successful management of the pregnant transplant patient requires a cooperative effort between the obstetrician and transplant team.

Review of the course and outcome of 100 pregnancies in 84 women treated with tacrolimus

BACKGROUND

The increasing use of tacrolimus as a primary immunosuppressant is paralleled by a growing number of pregnancies occurring in mothers receiving tacrolimus systemically.

METHODS

In this retrospective analysis during 1992-1998; data sources were case reports from clinical studies, spontaneous reports from health care professionals, routine surveys by transplant registries, and the published literature.

RESULTS

One hundred pregnancies in 84 mothers were recorded. Mean maternal age was 28 years. All except one mother (autoimmune disease) were solid organ transplant recipients (66% liver and 27% kid- ci ney). Mean time from transplantation to conception was 26 months. The mean daily dose of tacrolimus (range 11.7-12.8 mg/day) and the mean tacrolimus whole blood level (range 8.5-11.5 ng/ml) remained fairly constant from preconception through the third trimester. The most frequent maternal complications were graft rejection followed by preeclampsia, renal impairment, and infection. All cases of rejection were successfully treated with corticosteroids and did not result in graft loss. Of 100 pregnancies, 71 progressed to delivery (68 live births, 2 neonatal deaths, and 1 stillbirth), 24 were terminated (12 spontaneous and 12 induced), 2 pregnancies were ongoing, and 3 were lost to follow-up. Mean gestation period was 35 weeks with 59% deliveries being premature (<37 weeks). The birth weight (mean 2573 g) was appropriate for gestational age in 90% of cases. Most common complications in the neonate were hypoxia, hyperkalemia, and renal dysfunction. These were transient in nature. Four neonates presented with malformations, without any consistent pattern of affected organs.

CONCLUSION

Pregnancy in tacrolimus-treated transplant recipients resulted in a favourable outcome. Complications of the mother and neonate were similar to those previously described with other immunosuppressants.

Review of select transplant subpopulations at high risk of failure from standard immunosuppressive therapy

Despite improvements in short-term graft and patient survival rates for solid organ transplants, certain subgroups of transplant recipients experience poorer clinical outcome compared to the general population. Groups including pediatrics, African-Americans, diabetics, cystic fibrosis patients, and pregnant women require special considerations when designing immunosuppressive regimens that optimize transplant outcomes. Problems specific to pediatric transplant recipients include altered pharmacokinetics of immunosuppressive drugs, such as cyclosporine (CsA) and tacrolimus (poor absorption, increased metabolism, rapid clearance), the need to restore growth post-transplantation, and a high incidence of drug-related adverse effects. African-Americans have decreased drug absorption and bioavailability, high immunologic responsiveness, and a high incidence of post-transplant diabetes mellitus. Diabetics and cystic fibrosis patients exhibit poor absorption of immunosuppressive agents, which may lead to underimmunosuppression and subsequent graft rejection. Pregnant women undergo physiologic changes that can alter the pharmacokinetics of immunosuppressives, thus requiring careful clinical management to minimize the risks of either under- or overimmunosuppression to mother and child. To achieve an optimal post-transplant outcome in these high-risk patients, the problems specific to each group must be addressed, and immunosuppressive therapy individualized accordingly. Drug formulation greatly impacts upon pharmacokinetics and the resultant level of immunosuppression. Thus, a formulation with improved absorption (e.g., CsA for microemulsion), higher bioavailability, and less pharmacokinetic variability may facilitate patient management and lead to more favorable outcomes, especially in groups demonstrating low and variable bioavailability. Other strategies aimed at improving transplant outcome include the use of higher immunosuppressive doses, different combinations of immunosuppressive agents, more frequent monitoring, and management of concurrent disease states.

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.