The use of other drugs to allow a lower dosage of cyclosporin to be used. Therapeutic and pharmacoeconomic considerations

Personalized Medicine: New Perspectives for the Diagnosis and the Treatment of Renal Diseases

The prevalence of renal diseases is rising and reaching 5-15% of the adult population. Renal damage is associated with disturbances of body homeostasis and the loss of equilibrium between exogenous and endogenous elements including drugs and metabolites. Studies indicate that renal diseases are influenced not only by environmental but also by genetic factors. In some cases the disease is caused by mutation in a single gene and at that time severity depends on the presence of one or two mutated alleles. In other cases, renal disease is associated with the presence of alteration within a gene or genes, but environmental factors are also necessary for the development of disease. Therefore, it seems that the analysis of genetic aspects should be a natural component of clinical and experimental studies. The goal of personalized medicine is to determine the right drug, for the right patient, at the right time. Whole-genome examinations may help to change the approach to the disease and the patient resulting in the creation of "personalized medicine" with new diagnostic and treatment strategies designed on the basis of genetic background of each individual. The identification of high-risk patients in pharmacogenomics analyses will help to avoid many unwarranted side effects while optimizing treatment efficacy for individual patients. Personalized therapies for kidney diseases are still at the preliminary stage mainly due to high costs of such analyses and the complex nature of human genome. This review will focus on several areas of interest: renal disease pathogenesis, diagnosis, treatment, rate of progression and the prediction of prognosis.

Diltiazem co treatment with cyclosporine for induction of disease remission in sight-threatening non-infectious intraocular inflammation

PURPOSE

To investigate the effects of diltiazem co-treatment with microemulsified cyclosporine-A (CsA) on dosage, blood concentrations of CsA, as well as therapeutic and side effects in patients with sight-threatening non-infectious intraocular inflammation.

METHODS

A prospective, randomized, placebo-controlled, open-label trial of 39 patients with sight-threatening non-infectious intraocular inflammation. The change in visual acuity (LogMAR), the grade of inflammatory activity, therapeutic concentration of CsA in the blood and systemic and renal toxicity were determined after comparing two groups, one treated with CsA and diltiazem (treatment group), and the other without diltiazem (control group).

RESULTS

Compared with the control group, the concentration of CsA in the blood of the treatment group significantly increased (P < 0.05) requiring a reduction in dosage of CsA (P < 0.05).

CONCLUSION

In patients with severe intraocular inflammation treated with CsA and diltiazem, blood concentrations of CsA increased as the dosage decreased. This efficient combination therapy reduced patient's economic burden, at the same time decreasing systemic and renal toxicity which in turn may promote the use of CsA for longer periods.

Liver injury associated with ketoconazole: review of the published evidence

The azole antifungal agent ketoconazole has been available since 1981 for the treatment of fungal infections. In 2013, the American Food and Drug Administration and the European Medicines Agency issued warnings or prohibitions against the clinical use of oral ketoconazole due to the risk of liver injury which may lead to liver transplantation or death. From the available published evidence it is difficult to determine the actual incidence or prevalence of liver injury during clinical use of ketoconazole as an antifungal. Hepatic injury, when it occurs, is generally evident as asymptomatic and reversible abnormalities of liver function tests. However, serious liver injury has been reported. Alternatives to ketoconazole (such as itraconazole, fluconazole, voriconazole, and terbinafine) are available, but improved safety with respect to liver injury risk is not clearly established. We are not aware of published reports of significant ketoconazole-associated liver injury in volunteer study participants when ketoconazole has been used as a CYP3A inhibitor in the context of clinical research on drug metabolism. Possible alternatives to ketoconazole as prototype CYP3A inhibitors include ritonavir and potentially itraconazole, but not clarithromycin.

Cyclosporine/ketoconazole reduces treatment costs for nephrotic syndrome

Cyclosporine A (CyA) is an effective agent for the treatment of glucocorticoid-dependent idiopathic nephrotic syndrome (GCDNS), but costs are prohibitive in resource-poor societies. The objectives of this study were to evaluate the efficacy and safety of reducing the dose of CyA by co-administering ketoconazole. A prospective study targeting children 2-18 years of age with GCDNS in remission with CyA monotherapy was conducted. CyA dose was reduced by 50% and ketoconazole was added at 25% of the recommended therapeutic dose, and the drug levels and therapeutic and adverse effects (AE) were monitored. Continued combined therapy after completion of the 4-week trial period was offered. Ten patients (median age 9.5 years, range 3.0-16.0 years) were enrolled in the study. At week 4, the CyA dose was 2.2 ± 0.7 mg/kg/day compared with 5.6 ± 0.9 mg/kg/day at enrolment (P < 0.0001). No AE were noted. All patients continued ketoconazole treatment for at least 3 months. CyA drug cost savings were 61%, and approximately 60% with ketoconazole cost included. The combination of an expensive immunosuppressive drug with a cheap metabolic inhibitor reduced the treatment costs by> 50% without increased adverse events or drug monitoring needs. This intervention demonstrates how access of patients with limited resources to needed drugs can be improved by interference with physiological drug elimination.

Pharmacogenomics: a new paradigm to personalize treatments in nephrology patients

Although notable progress has been made in the therapeutic management of patients with chronic kidney disease in both conservative and renal replacement treatments (dialysis and transplantation), the occurrence of medication-related problems (lack of efficacy, adverse drug reactions) still represents a key clinical issue. Recent evidence suggests that adverse drug reactions are major causes of death and hospital admission in Europe and the United States. The reasons for these conditions are represented by environmental/non-genetic and genetic factors responsible for the great inter-patient variability in drugs metabolism, disposition and therapeutic targets. Over the years several genetic settings have been linked, using pharmacogenetic approaches, to the effects and toxicity of many agents used in clinical nephrology. However, these strategies, analysing single gene or candidate pathways, do not represent the gold standard, being the overall pharmacological effects of medications and not typically monogenic traits. Therefore, to identify multi-genetic influence on drug response, researchers and clinicians from different fields of medicine and pharmacology have started to perform pharmacogenomic studies employing innovative whole genomic high-throughput technologies. However, to date, only few pharmacogenomics reports have been published in nephrology underlying the need to enhance the number of projects and to increase the research budget for this important research field. In the future we would expect that, applying the knowledge about an individual's inherited response to drugs, nephrologists will be able to prescribe medications based on each person's genetic make-up, to monitor carefully the efficacy/toxicity of a given drug and to modify the dosage or number of medications to obtain predefined clinical outcomes.

Severe Human Traumatic Brain Injury, but Not Cyclosporin A Treatment, Depresses Activated T Lymphocytes Early after Injury

Severe traumatic brain injury (TBI) leads to an immunocompromised state responsible for an increased morbidity and mortality. Our understanding of the mechanisms responsible for this brain damage is incomplete. Damage maybe mediated by a complex cascade of neuroinflammation, and cytokine activation. In addition, translocation and accumulation of T cells in the brain parenchyma could take place and be related to detrimental effects. Our aims in this prospective randomized pilot study, were to detect the early effect of severe TBI upon cell-mediated immunity, to verify if early immunologic impairment correlates with neurologic outcome, and finally, to test the effect of early administration of iv infusion of cyclosporin A upon cell-mediated immunologic function. Forty-nine patients with severe TBI were studied. Thirty-six of these patients received a 24-h intravenous infusion of Cyclosporin A, or two 24-h infusions of the drug. 10 patients were in the placebo group. Three patients, not enrolled in the cyclosporin trial, were studied only for the relationship between cellular immunity, neurological outcome, and infection rate. T cell counts and microbiological cultures were performed in all patients. Sixty-five percent of patients demonstrated reduced T lymphocyte counts on admission. Furthermore, reduction of T cell numbers was related with significantly worse neurologic outcome and an increase in pulmonary infection. There was no significant difference between the placebo and CsA treated patients for the studied immunological parameters, or for incidence of infection. We also observed sequestration/diapedesis of T cells into the brain parenchyma, around contusions, after human TBI and we speculate that this could be responsible for further brain damage.

Impact of the cyclosporine-ketoconazole interaction in children with steroid-dependent idiopathic nephrotic syndrome

BACKGROUND

Children with steroid-dependent nephrotic syndrome experience serious side effects from steroid therapy. Cyclosporine A (CsA), which is an effective agent in the treatment of steroid-dependent nephrotic syndrome, is expensive and, consequently, often unaffordable in developing countries. Many studies have documented the benefit of ketoconazole administration in transplant adults treated with CsA. We have conducted a retrospective study with the objective of addressing cost-savings, safety, and the efficacy of the co-administration of ketoconazole and CsA to children with steroid-dependent nephrotic syndrome.

METHODS

This study included 102 nephrotic patients who were steroid-dependent and who received cyclosporine therapy. The commonest pathologic lesions were focal segmental glomerulosclerosis (64 patients) and minimal change disease (36 patients). Among the patients participating in the study, 78 received daily ketoconazole therapy (ketoconazole group) in the form of a 50-mg dose accompanied by an initial one-third decrease in the CsA dose, while 24 received CsA alone (non- ketoconazole group). All of the patients were children (below 18 years), and the male-to-female ratio was 3:1. The mean duration of treatment was 22.9 months. The characteristics of both groups were comparable.

RESULTS

Co-administration of ketoconazole significantly reduced mean doses of CsA by 48% with a net cost savings of 38%. It also resulted in a significant improvement in the CsA response and a more successful steroid withdrawal as well as a decrease in the frequency of renal impairment. Liver function tests remained normal in both groups up to and including the final follow-up (mean of 33.6 months).

CONCLUSIONS

The co-administration of ketoconazole to CsA in children with idiopathic steroid-dependent nephrotic syndrome safely results in a significant reduction in CsA cost, which causes great concern in developing countries. It may also improve CsA response.

Effects of berberine on the blood concentration of cyclosporin A in renal transplanted recipients: clinical and pharmacokinetic study

OBJECTIVE

To study the effects of berberine (BBR) on the blood concentration and pharmacokinetics of cyclosporin A (CsA) in renal-transplant recipients.

METHODS

In a randomized and controlled clinical trial, 52 renal-transplant recipients were treated with CsA and 0.2 g BBR three times daily for 3 months, while another 52 subjects received CsA without BBR co-administration. Blood trough concentration of CsA and biochemistry indexes for hepatic and renal functions were determined. For the pharmacokinetic study, six renal-transplant recipients were included with a 3-mg/kg dosage of CsA twice daily before and after oral co-administration of 0.2 g BBR three times daily for 12 days.

RESULTS

The trough blood concentrations and the ratios of concentration/dose of CsA in the BBR-treated group increased by 88.9% and 98.4%, respectively, compared with those at baseline (P < 0.05). As for the BBR-free group, they rose by 64.5% and 69.4%, respectively, relative to those at baseline (P < 0.01). Nevertheless, the final blood concentrations and the ratios of concentration/dose of CsA in BBR-treated patients were still 29.3% and 27.8%, respectively, higher than those in BBR-free patients (P < 0.05). No significant effects on liver or renal functions were observed under coadministration of BBR. After co-administration of BBR in six patients for 12 days, the mean AUC of CsA was increased by 34.5% (P < 0.05). The mean time taken to reach the peak blood concentration (t(max)) and the mean half-life (t(1/2)) of CsA were increased by 1.7 h and 2.7 h, respectively (P < 0.05). The average percentage increases in the steady-state drug concentration (Css) and minimum blood concentration (Cmin) were 34.5% and 88.3%, respectively (P < 0.05). In addition, the average percentage decrease in CL/F was 40.4% (P < 0.05) and the peak-to-through fluctuation index was significantly reduced (P < 0.01).

CONCLUSION

The BBR can markedly elevate the blood concentration of CsA in renal-transplant recipients in both clinical and pharmacokinetic studies. This combination may allow a reduction of the CsA dosage. The mechanism for this interaction is most likely explained by inhibition of CYP3A4 by BBR in the liver and/or small intestine.

The effect of HMG-CoA reductase inhibitors on chronic allograft rejection

Hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors have pleiotropic actions that affect many systems other than lowering blood cholesterol concentrations. Hypercholesterolaemia is an adverse effect of immunosuppressive drug therapy and hence it is a common finding after organ transplantation. HMG-CoA reductase inhibitors lower cholesterol concentrations in transplant recipients but they also offer additional benefits. Since they impair the production of mevalonate, they reduce the concentrations of downstream products including farnesyl and geranyl phosphate. These isoprenoid moieties are required for protein prenylation and HMG-CoA reductase inhibitors impair this function in some cells. This action affects the immune system, especially in patients taking cyclosporin, and has been proposed as the mechanism whereby these drugs increase the half-life of transplanted organs. Other mechanisms have also been proposed including an increase in the free fraction of cyclosporin and a reduction in the time that low density lipoprotein (LDL) spends in blood. The latter effect reduces the extent of oxidation of LDL and hence reduces the damage caused by oxidised LDL. Chronic rejection is poorly understood but appears to involve both immune and non-immune processes. HMG-CoA reductase inhibitors affect both processes. At present, the evidence of benefit from statin prescription is confined to heart and kidney transplant recipients but it is likely that recipients of other organ transplants would also benefit. Drug interactions between cyclosporin and HMG-CoA reductase inhibitors are a limiting factor to their use. Pravastatin appears to be the best HMG-CoA reductase inhibitor for organ transplant recipients because of its lesser potential to interact with cyclosporin and hence cause myositis, which may thus allow higher doses to be used. Other, non-immunosuppressive drugs (including diltiazem and ketoconazole) have been shown to reduce transplant organ damage by unknown mechanisms and are widely prescribed in some transplant centres. More specific inhibitors of protein prenylation may afford useful immunosuppression, thereby prolonging transplant organ half-lives and also reducing the risk of cancer.

Calcium channel blocker class heterogeneity: select aspects of pharmacokinetics and pharmacodynamics

Calcium channel blockers (CCBs) comprise a heterogeneous group of compounds with unique structures and pharmacologic characteristics. These agents are employed in the treatment of hypertension, coronary ischemia, and/or supraventricular arrhythmias. CCBs are both substrates for, and in the instance of verapamil and diltiazem inhibitors of, cytochrome P450 3A4. In the case of verapamil and diltiazem, this inhibitory effect increases the likelihood of drug-drug interactions with other compounds similarly metabolized by cytochrome P450 3A4. Much of the debate with reference to a cardiovascular risk for CCBs has been quieted with the advent of sustained-release delivery systems that offer a more gradual rate of drug delivery. The most common side effects with CCBs are vasodilatory in nature and include peripheral edema, flushing, and headache. Despite the potential for side effects with CCBs, their potent blood pressure-lowering effect makes them a prerequisite for blood pressure control in many patients.

Co-administration of cyclosporine and ketoconazole in children with minimal change nephrotic syndrome

BACKGROUND/AIMS

The use of cyclosporine A (CsA) in the treatment of idiopathic nephrotic syndrome was firstly reported in 1986. On the other hand, many studies have documented the benefit of ketoconazole (keto) administration in renal and cardiac transplant adults treated with CsA, but this co-administration has not been reported in children with minimal change disease (MCD). Thus, deliberate use of keto to reduce the need for cyclosporine is not new, but it is particularly relevant because of the high cost of cyclosporine.

METHODS

This study included 46 children with MCD who were steroid resistant or dependent and received CsA. Among them, 31 received daily keto therapy (keto group) in a dose of 50 mg with concomitant decrease of the CsA dose by one third while 15 patients received CsA alone (non-keto group).

RESULTS

The mean (+/-SD) duration of CsA treatment was 25.7 +/- 13.7 months. The characteristics of both groups were comparable. Co-administration of keto significantly improved the response to CsA therapy (from 60 to 94%) and decreased the frequency of renal impairment (from 27 to 3%). Hepatic function remained within the normal range in both groups. Co-administration of keto significantly reduced mean doses of CsA with overall net cost savings of about 34%.

CONCLUSION

From this study, we may conclude that co-administration of low dose ketoconazole to cyclosporine in children with idiopathic MCD is safe. This combination significantly reduces CsA cost and, moreover, keto may improve the response to cyclosporine and may have a favorable effect on the kidney function.

Immunosuppressant Drug Monitoring: Is the Laboratory Meeting Clinical Expectations?

OBJECTIVE:

To review the literature relating to immunosuppressant drug measurement as performed in therapeutic drug monitoring laboratories associated with transplantation centers and consider whether the assay methods widely used for patient dosage management achieve acceptable quality criteria in the context of other sources of variability with these drugs.

DATA SOURCES:

Articles used were accessed primarily through MEDLINE, as well as references cited in related publications. Searches were restricted to organ transplantation in humans.

STUDY SELECTION AND DATA EXTRACTION:

Emphasis was placed on the literature relating to the quality of immunosuppressant drug assays, their limitations, and evidence of clinical benefit in dosage individualization.

DATA SYNTHESIS:

There is a dilemma evident between the quality of the analytical services offered by some diagnostic immunoassay manufacturers and the ability of a significant number of clinical laboratories globally to select only appropriate assay methods.

CONCLUSIONS:

In many cases, clinical laboratories fail to meet the reasonable clinical expectations required for interpretation of immunosuppressant drug assay results as an adjunct to optimal dosage individualization and patient care.

Co-administration of cyclosporine and ketoconazole in idiopathic childhood nephrosis

The concomitant use of cyclosporine (CsA) and ketoconazole (keto) in children with nephrotic syndrome (NS) has never been reported in the literature. This retrospective cohort study was conducted to investigate cost saving, safety, and efficacy of co-administration of keto and CsA in children with NS. The study included 186 nephrotic children receiving CsA therapy. Most were steroid dependent or resistant, and the most common pathology was focal segmental glomerulosclerosis (62%). Among our patients, 137 received daily keto therapy (keto group) 50 mg/day in addition to CsA, while 49 received CsA alone (non-keto group). The characteristics of both groups were comparable and the mean (+/-SD) duration of treatment was 22.9 +/- 8.1 months. Co-administration of keto significantly reduced the mean dose of CsA with an overall net cost saving of 37%. It also resulted in a significant improvement of CsA response, more successful steroid withdrawal, and decreased the frequency of renal impairment. Keto was generally well tolerated and safe. We conclude that co-administration of low-dose keto with CsA in children with idiopathic NS is safe, significantly reduces the cost of CsA therapy, and may improve the patient outcome.

Concomitant administration of cyclosporine and ketoconazole in idiopathic nephrotic syndrome

BACKGROUND

The deliberate use of ketoconazole to reduce the need for cyclosporine (CsA) is not new, but it is particularly relevant because of the high cost of CsA. Many studies have documented this benefit in renal and cardiac transplants, but this co-administration has not been reported in patients with nephrotic syndrome.

METHODS

This retrospective study included 207 nephrotic patients who were steroid resistant, dependent or frequent relapsers and received CsA therapy. Among these patients 153 received daily ketoconazole therapy in a dose of 50 mg with concomitant decrease of one-third of the CsA dose while 54 patients received CsA alone. The majority of our cases were children (179 were below 18 years) and male to female ratio was 1.7:1.

RESULTS

The great majority of the study population received the drugs for 1-2 years. Patients who received CsA and ketoconazole were comparable with those who received CsA alone regarding age, sex, duration of renal disease, renal pathology, severity of nephrotic syndrome, renal function, hepatic function and steroid response. Co-administration of ketoconazole significantly reduced mean doses of CsA by 37% after 1 month and 47% at 1 year with overall net cost savings of 37%. Hepatic functions remained within the normal range in both groups. Additionally, co-administration of ketoconazole significantly improved the response to CsA therapy, successful steroid withdrawal and decreased the frequency of renal impairment.

CONCLUSIONS

Co-administration of keto with CsA in idiopathic nephrotic patients significantly reduces CsA costs and may improve its response.

Ketoconazole alters cyclosporine pharmacokinetic profile and may predispose to acute rejection

Ketoconazole (KET) is frequently used as a cyclosporine (CyA)-sparing agent. Adequate exposure to CyA is critical to avoid acute rejection (AR) or chronic rejection (CR). We compared the pharmacokinetic profiles of nine stable renal transplant patients on CyA before and after conversion to KET (200 mg/d of KET simultaneous with CyA). The CyA doses were adjusted to achieve similar drug exposures. The mean dose reduction of CyA while on KET was 83% from 3.2 +/- 0.9 to 0.6 +/- 0.2 (P <.000). Addition of KET produced a significant decrease in the absorption parameters of CyA and an increased elimination half-life. Coefficient of variation (CV) of AUC was significantly increased. Serum creatinine (SCr) at 3 months after switch remained the same. One patient experienced a grade I AR episode (11%). There were no adverse effects related to KET. Although addition of KET to CyA can significantly decrease the CyA dose, the observed pharmacokinetic changes involved decreased absorption and increased CV, which may respectively relate to AR and CR. The 11% AR rate observed is of concern. We do not recommend switching patients to KET as this may imply an increased risk of late AR or CR.

Diltiazem co-treatment in renal transplant patients receiving microemulsion cyclosporin

BACKGROUND

Usage of cyclosporin (the Hong Kong Hospital Authority's single largest item of drug expenditure) continues to increase, mainly due to increasing numbers of renal allograft patients taking it as long-term antirejection therapy. Diltiazem, an antihypertensive agent, interferes with the first pass extraction of oral cyclosporin, thus serving to conserve its dosage.

AIMS

In renal transplant patients, to assess whether diltiazem co-treatment could achieve worthwhile dosage conservation of Neoral (a relatively new microemulsified cyclosporin formulation), safely.

METHODS

A randomized, placebo-controlled, double-blind clinical trial was undertaken at three local hospitals. Renal transplant recipients receiving Neoral as prophylactic immunosuppression were randomized to two treatment arms. Active treatment consisted of diltiazem tablets 30 or 60 mg twice daily for patients weighing < 60 or >or= 60 kg, respectively. One hundred and ten eligible patients gave their informed consent, and were followed up for at least six months. The mean difference in the dollar cost in the sixth month was the primary outcome. Secondary/ancillary outcomes included changes in cyclosporin dosage and blood level, and untoward clinical events including rejection. Outcomes were evaluated by intention to treat analyses.

RESULTS

During weeks 23-26 (sixth month) post randomization, diltiazem co-treatment yielded an estimated average cost saving per patient on drugs of 15%[the 95% confidence interval (CI) of the difference being HK dollars 609 +/- 517 or pound 50 +/- 42], with no apparent excess of untoward or adverse events, complications, hospitalization, outpatient visits, or inferior quality of life.

CONCLUSIONS

This diltiazem co-treatment regime applied to the nearly 1800 surviving renal allograft patients followed up in Hospital Authority hospitals could have saved approximately HK dollars 14.3 million ( pound 1.17 million) annually, without adverse sequelae.

Effect of cyclophosphamide on serum cyclosporine levels at the conditioning of hematopoietic stem cell transplantation

We retrospectively analyzed the factors that affect serum cyclosporine (CsA) concentrations up to day 14 after allogeneic hematopoietic stem cell transplantation (HSCT). In all, 103 transplant recipients who received MTX and CsA for acute GVHD prophylaxis were analyzed. No significant relationships between serum CsA concentrations and gender, age, serum creatinine levels, AST/ALT levels, or antibiotic/fluconazole administration were found by comparing median CsA concentrations or by using longitudinal or regression multivariate analyses. However, the mean of the median serum CsA concentration in patients (n=54) receiving the regimen containing cyclophosphamide (CY) (149.7 ng/ml; 95% confidence interval (CI): 132.1-167.4) was significantly (P<0.0001) lower than that in patients (n=49) receiving the non-CY regimen (217.3 ng/ml; 95% CI: 198.9-235.6). Longitudinal analysis and regression multivariate analysis showed that only administration of CY had a significant effect on the serum CsA concentration. Our results suggest that administration of CY during conditioning can reduce the effects on serum CsA concentrations during the 2 weeks following HSCT. The mechanism of this effect is not clear, but it may be due to the autoinduction of CY.

Interaction with indinavir to enhance systemic exposure of an investigational HIV protease inhibitor in rats, dogs and monkeys

1. The use of a beneficial interaction between indinavir and compound A, a potent investigational HIV protease inhibitor to enhance systemic exposure of compound A, was investigated. 2. When administrated alone, compound A underwent extensive hepatic first-pass metabolism in rats and monkeys, resulting in low oral bioavailability. 3. In vitro studies with liver microsomes revealed that compound A metabolism was mediated exclusively by CYP3A enzymes in rats, dogs and monkeys. Indinavir, which also was metabolized predominantly by CYP3A enzymes, extensively inhibited compound A metabolism in microsomes, whereas compound A showed weak inhibitory potency on indinavir metabolism. 4. Consistent with in vitro observations, co-administration of the two compounds resulted in a 17-fold increase in oral AUC of compound A in rats owing to the inhibition of metabolism of compound A by indinavir, whereas compound A did not affect indinavir metabolism as indicated by the unchanged indinavir AUC. Similarly, the systemic exposure of compound A in dogs and monkeys was increased substantially following oral co-administration with indinavir by 7- and > 50-fold, respectively. 5. Enhancement in compound A systemic exposure by indinavir in humans, as predicted based on the in vivo animal and in vitro human liver microsomal data, was confirmed in subsequent clinical studies.

Interaction between ketoconazole and almotriptan in healthy volunteers

The interaction between almotriptan, a 5-HT1B/1D agonist, and the potent CYP3A4 inhibitor ketoconazole was examined in 16 healthy volunteers. Subjects received (A) 12.5 mg almotriptan orally on Day 2 of a 3-day regimen of 400 mg ketoconazole once daily and (B) 12.5 mg almotriptan in a crossover design. Plasma and urine concentrations of almotriptan were measured by HPLC. Treatment effects on almotriptan pharmacokinetics were assessed by analysis of variance. Ketoconazole coadministration increased mean almotriptan AUC and Cmax from 312 to 490 ng h/mL and 52.6 to 84.5 ng/mL, respectively. Mean oral clearance was decreased from 40.7 to 26.2 L/h by ketoconazole, with an accompanying increase in the fraction of almotriptan excreted unchanged in the urine (40.6% to 53.3%) and a decrease in renal clearance (16.4 to 13.8 L/h). These effects were statistically significant. The effects of ketoconazole on almotriptan clearance were consistent with inhibition of the CYP3A4-mediated metabolism and a slight effect on the active tubular secretion of almotriptan.

Cyclosporin monitoring in Australasia: 2002 update of consensus guidelines

Therapeutic drug monitoring of cyclosporin (CsA) has been established as part of the routine clinical treatment of patients following organ transplantation for more than 20 years, and based on contemporary knowledge, many consensus guidelines have been published to assist clinics and laboratories attain optimal strategies for patient care. This article addresses the newer directions in CsA monitoring, with particular reference to the Australasian situation that has evolved since the 1993 Australasian guideline. These changes have included the introduction of alternative assay methodologies, changed CsA formulation from Sandimmun to Neoral throughout Australasia, and alternatives to trough concentration (C0) monitoring, especially 2-hour concentration (C2) monitoring and associated validated dilution protocols to accurately quantitate the higher whole blood CsA concentrations. The revision was prepared following a recent survey of all Australasian CsA-monitoring laboratories where discordant practices were evident.

Mechanisms of clinically relevant drug interactions associated with tacrolimus

The clinical management of tacrolimus, a macrolide used as immunosuppressant after transplantation, is complicated by its narrow therapeutic index in combination with inter- and intraindividually variable pharmacokinetics. As a substrate of cytochrome P450 (CYP) 3A enzymes and P-glycoprotein, tacrolimus interacts with several other drugs used in transplantation medicine, which also are known CYP3A and/or P-glycoprotein inhibitors and/or inducers. In clinical studies, CYP3A/P-glycoprotein inhibitors and inducers primarily affect oral bioavailability of tacrolimus rather than its clearance, indicating a key role of intestinal P-glycoprotein and CYP3A. There is an almost complete overlap between the reported clinical drug interactions of tacrolimus and those of cyclosporin. However, in comparison with cyclosporin, only few controlled drug interaction studies have been carried out, but tacrolimus drug interactions have been extensively studied in vitro. These results are inconsistent and are of poor predictive value for clinical drug interactions because of false negative results. P-glycoprotein regulates distribution of tacrolimus through the blood-brain barrier into the brain as well as distribution into lymphocytes. Interaction of other drugs with P-glycoprotein may change tacrolimus tissue distribution and modify its toxicity and immunosuppressive activity. There is evidence that ethnic and gender differences exist for tacrolimus drug interactions. Therapeutic drug monitoring to guide dosage adjustments of tacrolimus is an efficient tool to manage drug interactions. In the near future, progress can be expected from studies evaluating potential pharmacokinetic interactions caused by herbal preparations and food components, the exact biochemical mechanism underlying tacrolimus toxicity, and the potential of inhibition of CYP3A and P-glycoprotein to improve oral bioavailability and to decrease intraindividual variability of tacrolimus pharmacokinetics.

Comparison of trough, 2-hour, and limited AUC blood sampling for monitoring cyclosporin (Neoral) at day 7 post-renal transplantation and incidence of rejection in the first month

The use of alternative strategies to the traditional pre-dose/trough (C0) blood sampling for cyclosporine (CsA) therapeutic drug monitoring has the potential to revolutionize analytical practices which have, in many centers, been established for some 20 years. While the C0 sample has previously been recommended, current attitudes are increasingly proposing alternatives for assessing CsA exposure, including various limited sampling strategies of the AUC (lssAUC) in the early postdose period, or alternative single-point nontrough samples, such as a 2-hour postdose sample (C2). The present study has reviewed a series of consecutive renal transplant recipients over 18 months where CsA was the primary immunosuppressant. The lssAUC performed at around day 7 posttransplantation included drawing blood at 0, 2, and 4 hours postdose, giving AUC(0-4). The aim of this study was to review the occurrence of acute biopsy-proven rejection in the first month and consider which of (simultaneously measured) C0, C2 or AUC(0-4) was a better early indicator of this adverse outcome. The result was best described by comparing the data from rejectors (n = 13) and nonrejectors (n = 42) for these 3 indices of CsA exposure (i.e., C0, C2 or AUC(0-4)). There was no evidence that C0 predicted the likelihood of such adverse clinical outcomes. In contrast, rejectors tended to have lower mean C2 CsA concentrations, and the incidence of rejection was 0.0 when C2 exceeded 1200 microg/L (n = 10). While the data are limited in the higher C2 CsA concentration range, it is nevertheless consistent with more recent recommendations suggesting that the CsA at C2 should target 1700 microg/L in this first month posttransplantation. As 64% of the patients were also receiving a CsA-sparing agent (diltiazem [DTZ]), the relationships were also investigated to determine whether any affect of concomitant DTZ therapy could be demonstrated. However, in this small sample, no significant affect of DTZ was seen.

Cyclosporin and ketoconazole interaction for treatment of perianal fistulas in the dog

OBJECTIVE

To assess the use of concurrent ketoconazole and low dose cyclosporin administration in a group of dogs with clinical evidence of perianal fistulas, and to determine if this combination could be used to manage perianal fistulas effectively.

DESIGN

Prospective clinical trial

PROCEDURE

Sixteen dogs with clinical evidence of perianal fistulas were given ketoconazole (10 mg/kg once daily) and cyclosporin (1 mg/kg twice daily initially) for 16 weeks. Blood cyclosporin assays were performed regularly and cyclosporin doses were altered to achieve a stable blood level above 200 ng/mL. Regular examinations assessed the dogs' general health, changes in clinical behaviour, fistula size and number. A complete blood count and serum biochemical analysis was performed in all dogs before and after the treatment period, and after 8 weeks of treatment in 12 dogs. Dogs were assessed for recurrence of lesions at 1, 3 and 12 months after the trial.

RESULTS

All dogs showed marked improvement in lesions and behaviour within 14 days of the medication. Fourteen dogs completed the trial. Two dogs were excluded due to concurrent disease. Thirteen dogs (93%) showed complete resolution of fistulas during the treatment period. Seven dogs (50%) had no recurrence after 12 months. Recurrence was seen in three dogs (21%) at 8, 10 and 12 months after treatment, and in three dogs (21%) within 1 month of treatment. The medication was well tolerated. Side effects included transient anorexia, vomiting and lethargy in some dogs, increased shedding of hair and gingival hyperplasia. Ketoconazole administration allowed a dramatic reduction in cyclosporin dose (over 90% in 12 dogs and 80% in the other two) compared to previously reported cases treated with cyclosporin alone.

CONCLUSION

The use of combined ketoconazole and cyclosporin provided an effective treatment for perianal fistulas. Outcomes were similar to those seen with cyclosporin alone, but allowed a significant reduction in cyclosporin dose and, therefore, cost. The use of immunosuppressive therapy in the treatment of perianal fistulas was effective and avoided many of the problems associated with surgical treament.

Medical Management Considerations for Patients With Lung Transplantation

Lung transplantation has become an accepted modality for the treatment of end-stage lung disease. Adult and pediatric patients with a variety of lung diseases, including cystic fibrosis, chronic obstructive pulmonary disease, and idiopathic pulmonary fibrosis are candidates for lung transplantation. Lung transplantation can extend survival and improve quality of life for these patients. With the introduction of new immunosuppressive agents and enhanced surgical and medical care, both short- and long-term morbidity and mortality in these populations, although not as good as other transplant types, are improving. After lung transplantation, recipients continue to face a number of obstacles including post-operative complications, complex drug regimens, drug-induced toxicities, infection, and rejection. An understanding of the management and monitoring issues after lung transplantation is the focus of this review.

Cytokines and cell surface receptors as target end points of immunosuppression with cyclosporine A

Targets of cyclosporine (CsA) were identified from an array of stimulated lymphocyte responses (sLR) comprising 34 stimulation conditions in whole blood from 3 normal human volunteers (NHV) containing clinically relevant CsA concentrations (0-1200 ng/ml) in vitro. In whole blood from 5 additional NHV, selected targets (intracellular interleukin-2 [IL-2], tumor-necrosis factor-alpha [TNF-alpha], and interferon-gamma [IFN-gamma]) were measured in phorbol myristate acetate (PMA)-ionomycin-stimulated T lymphocytes. Effect:concentration relationships were analyzed with E(max) pharmacodynamic (PD) equations and expressed as the concentration associated with one-half maximal inhibitory effect (EC(50)). CsA demonstrated a rich matrix of inhibitory effects on T cells (CD3(+)), B cells (CD19(+)), dendritic cells (DC) (CD11c(+)), and basophils (CD123(+)) but not on monocytes (CD14(+)) (n = 3). PD analyses suggested that the EC(50) of CsA (1) for IL-2 in CD3(+) cells in NHV (n = 8) was similar to the EC(50) demonstrated by us previously in CD4(+) cells from transplanted patients (n = 13) (EC(50) = 260 ng/ml vs. 249 ng/ml), (2) for each cytokine was different under identical stimulation conditions (TNF-alpha, 324 ng/ml; IFN-gamma, 504 ng/ml), and (3) was relatively constant for a given cytokine under different stimulation conditions (e.g., PMA-ionomycin or the staphylococcal enterotoxin B [SEB] superantigen). In conclusion, inhibition of cytokine targets by CsA is concentration dependent. Further, a given CsA concentration may produce similar inhibitory effects across different stimulation conditions. Measurement of cytokine target expression may, therefore, allow effect-controlled administration of CsA during clinical transplantation.

Effects of the antifungal agents on oxidative drug metabolism: clinical relevance

This article reviews the metabolic pharmacokinetic drug-drug interactions with the systemic antifungal agents: the azoles ketoconazole, miconazole, itraconazole and fluconazole, the allylamine terbinafine and the sulfonamide sulfamethoxazole. The majority of these interactions are metabolic and are caused by inhibition of cytochrome P450 (CYP)-mediated hepatic and/or small intestinal metabolism of coadministered drugs. Human liver microsomal studies in vitro, clinical case reports and controlled pharmacokinetic interaction studies in patients or healthy volunteers are reviewed. A brief overview of the CYP system and the contrasting effects of the antifungal agents on the different human drug-metabolising CYP isoforms is followed by discussion of the role of P-glycoprotein in presystemic extraction and the modulation of its function by the antifungal agents. Methods used for in vitro drug interaction studies and in vitro-in vivo scaling are then discussed, with specific emphasis on the azole antifungals. Ketoconazole and itraconazole are potent inhibitors of the major drug-metabolising CYP isoform in humans, CYP3A4. Coadministration of these drugs with CYP3A substrates such as cyclosporin, tacrolimus, alprazolam, triazolam, midazolam, nifedipine, felodipine, simvastatin, lovastatin, vincristine, terfenadine or astemizole can result in clinically significant drug interactions, some of which can be life-threatening. The interactions of ketoconazole with cyclosporin and tacrolimus have been applied for therapeutic purposes to allow a lower dosage and cost of the immunosuppressant and a reduced risk of fungal infections. The potency of fluconazole as a CYP3A4 inhibitor is much lower. Thus, clinical interactions of CYP3A substrates with this azole derivative are of lesser magnitude, and are generally observed only with fluconazole dosages of > or =200 mg/day. Fluconazole, miconazole and sulfamethoxazole are potent inhibitors of CYP2C9. Coadministration of phenytoin, warfarin, sulfamethoxazole and losartan with fluconazole results in clinically significant drug interactions. Fluconazole is a potent inhibitor of CYP2C19 in vitro, although the clinical significance of this has not been investigated. No clinically significant drug interactions have been predicted or documented between the azoles and drugs that are primarily metabolised by CYP1A2, 2D6 or 2E1. Terbinafine is a potent inhibitor of CYP2D6 and may cause clinically significant interactions with coadministered substrates of this isoform, such as nortriptyline, desipramine, perphenazine, metoprolol, encainide and propafenone. On the basis of the existing in vitro and in vivo data, drug interactions of terbinafine with substrates of other CYP isoforms are unlikely.

Cytochrome P450 3A: ontogeny and drug disposition

The maturation of organ systems during fetal life and childhood exerts a profound effect on drug disposition. The maturation of drug-metabolising enzymes is probably the predominant factor accounting for age-associated changes in non-renal drug clearance. The group of drug-metabolising enzymes most studied are the cytochrome P450 (CYP) superfamily. The CYP3A subfamily is the most abundant group of CYP enzymes in the liver and consists of at least 3 isoforms: CYP3A4, 3A5 and 3A7. Many drugs are mainly metabolised by the CYP3A subfamily. Therefore, maturational changes in CYP3A ontogeny may impact on the clinical pharmacokinetics of these drugs. CYP3A4 is the most abundantly expressed CYP and accounts for approximately 30 to 40% of the total CYPcontent in human adult liver and small intestine. CYP3A5 is 83% homologous to CYP3A4, is expressed at a much lower level than CYP3A4 in the liver, but is the main CYP3A isoform in the kidney. CYP3A7 is the major CYP isoform detected in human embryonic, fetal and newborn liver, but is also detected in adult liver, although at a much lower level than CYP3A4. Substrate specificity for the individual isoforms has not been fully elucidated. Because of large interindividual differences in CYP3A4 and 3A5 expression and activity, genetic polymorphisms have been suggested. However, although some gene mutations have been identified, the impact of these mutations on the pharmacokinetics of CYP3A substrates has to be established. Ontogeny of CYP3A activity has been studied in vitro and in vivo. CYP3A7 activity is high during embryonic and fetal life and decreases rapidly during the first week of life. Conversely, CYP3A4 is very low before birth but increases rapidly thereafter, reaching 50% of adult levels between 6 and 12 months of age. During infancy, CYP3A4 activity appears to be slightly higher than that of adults. Large interindividual variations in CYP3A5 expression and activity were observed during all stages of development, but no apparent developmental pattern of CYP3A5 activity has been identified to date. Profound changes occur in the activity of CYP3A isoforms during all stages of development. These changes have, in many instances, proven to be of clinical significance when treatment involves drugs that are substrates, inhibitors or inducers of CYP3A. Investigators and clinicians should consider the impact of ontogeny on CYP3A in both pharmacokinetic study design and data interpretation, as well as when prescribing drugs to children.

Inhibition and induction of cytochrome P450 and the clinical implications

The cytochrome P450s (CYPs) constitute a superfamily of isoforms that play an important role in the oxidative metabolism of drugs. Each CYP isoform possesses a characteristic broad spectrum of catalytic activities of substrates. Whenever 2 or more drugs are administered concurrently, the possibility of drug interactions exists. The ability of a single CYP to metabolise multiple substrates is responsible for a large number of documented drug interactions associated with CYP inhibition. In addition, drug interactions can also occur as a result of the induction of several human CYPs following long term drug treatment. The mechanisms of CYP inhibition can be divided into 3 categories: (a) reversible inhibition; (b) quasi-irreversible inhibition; and (c) irreversible inhibition. In mechanistic terms, reversible interactions arise as a result of competition at the CYP active site and probably involve only the first step of the CYP catalytic cycle. On the other hand, drugs that act during and subsequent to the oxygen transfer step are generally irreversible or quasi-irreversible inhibitors. Irreversible and quasi-irreversible inhibition require at least one cycle of the CYP catalytic process. Because human liver samples and recombinant human CYPs are now readily available, in vitro systems have been used as screening tools to predict the potential for in vivo drug interaction. Although it is easy to determine in vitro metabolic drug interactions, the proper interpretation and extrapolation of in vitro interaction data to in vivo situations require a good understanding of pharmacokinetic principles. From the viewpoint of drug therapy, to avoid potential drug-drug interactions, it is desirable to develop a new drug candidate that is not a potent CYP inhibitor or inducer and the metabolism of which is not readily inhibited by other drugs. In reality, drug interaction by mutual inhibition between drugs is almost inevitable, because CYP-mediated metabolism represents a major route of elimination of many drugs, which can compete for the same CYP enzyme. The clinical significance of a metabolic drug interaction depends on the magnitude of the change in the concentration of active species (parent drug and/or active metabolites) at the site of pharmacological action and the therapeutic index of the drug. The smaller the difference between toxic and effective concentration, the greater the likelihood that a drug interaction will have serious clinical consequences. Thus, careful evaluation of potential drug interactions of a new drug candidate during the early stage of drug development is essential.

Drug delivery systems for cyclosporine: achievements and complications

The review deals with the preparation, properties, and analysis of different kinds of cyclosporine delivery systems, such as solid formulations, liposomes, emulsions and microemulsions and targeted cyclosporine formulations. The review points out a key role of delivery systems in increasing the therapeutic effectiveness of cyclosporine. Comparative studies of the prior marketed formulation, Sandimmune, with a new microemulsion formulation, Neoral, are discussed including some data on clinical development of Neoral.

Effect of metabolic inhibitors on cyclosporine pharmacokinetics using a population approach

Drugs known to inhibit the metabolism of cyclosporine are administered concomitantly to those who undergo cardiothoracic transplantation. The aim of this study was to examine in quantitative terms the relationship between cyclosporine oral dose rate and the trough concentration (Css(trough)) at steady state in patients who undergo cardiothoracic transplantation and are administered cyclosporine alone or in combination with drugs known to inhibit its metabolism. Dose and whole blood cyclosporine Css(trough) observations measured using the enzyme-multiplied immunoassay technique (EMIT) (396 observations) or the TDx assay (435 observations) were collected as part of routine blood concentration monitoring from 182 patients who underwent cardiothoracic transplantation. Data were analyzed using a linear mixed-effects modeling approach to examine the effect of metabolic inhibitors on dose-rate-Css(trough) ratio. The mean (and 95% confidence interval) dose-rate-Css(trough) ratio for cyclosporine generated from concentrations measured using EMIT was 94 (82.5-105.5) Lh(-1) for patients administered cyclosporine alone, 66.7 (58.1-75.3) Lh(-1) for patients administered concomitant diltiazem, 47.9 (15.4 -80.4) Lh(-1) for patients administered concomitant itraconazole, 21.7 (14.8-28.5) Lh(-1) for patients administered concomitant ketoconazole, and 14.9 (11.8-18.1) Lh(-1) for patients concomitantly administered diltiazem and ketoconazole. For patients administered concomitant cyclosporine, ketoconazole, and diltiazem, the dosage of cyclosporine, if it is administered alone, should be 20% to achieve the same blood concentrations. This will allow safer drug concentration targeting of cyclosporine after cardiothoracic transplantation.

Clinically relevant drug-drug interactions in oncology

Although anticancer agents are one of the most toxic classes of medication prescribed today, there is relatively little information available about clinically relevant drug-drug interactions. Pharmacokinetic drug interactions have been described, including alterations in absorption, catabolism, and excretion. For example, an increased bioavailability of 6-mercaptopurine has been observed when combined with either allopurinol or methotrexate, leading to increased toxicity in some patients. Induction of etoposide or teniposide clearance by anticonvulsants has also been described, resulting in a lower systemic exposure and risk for lower anticancer activity. Alterations in elimination of methotrexate has been observed with probenecid, presumably through competition for renal secretion. There are also several examples of pharmacodynamic interactions. The combination of 5-fluorouracil plus folinic acid results in more efficient inhibition of thymidylate synthase, a finding which is now utilized routinely in the treatment of colorectal cancer. Improvements in the in vitro and early clinical testing now allow a relatively high degree of prediction of potential clinical drug interactions, prior to observations of untoward drug effects. In conclusion, drug interactions among commonly used anticancer agents have been identified. Their clinical significance can have more impact than many other classes of medications due to the narrow therapeutic index of antineoplastic agents and the potential for lethal side-effects. It is only through prospective, preclinical and early clinical evaluation that the presence of clinically significant drug interactions can be identified and the information used to provide better therapy for this significant health problem.