4-Aminopyridine in multiple sclerosis: prolonged administration.

In an earlier study, we demonstrated efficacy of single oral doses of 4-aminopyridine (4-AP) in improving motor and visual signs in multiple sclerosis (MS) patients for a mean of 4.97 hours. We attempted to determine whether efficacy could safely be prolonged using multiple daily doses over several days by administering 7.5 to 52.5 mg 4-AP to 17 temperature-sensitive MS patients in one to three daily doses at 3- to 4-hour intervals over 1 to 5 days in a double-blind study. Nine of these patients were also tested with identically appearing placebo. Thirteen of the 17 patients (76%) given 4-AP showed clinically important motor and visual improvements compared with three of nine in the placebo group. Average peak improvement scores were 0.40 for 4-AP and 0.12 for placebo. Seventy percent of the daily 4-AP improvements lasted 7 to 10 hours. The improvements for two consecutive doses of 4-AP lasted a mean of 7.07 hours (83% of the average 8.53-hour treatment-observation period) compared with 2.36 hours for placebo (26% of the average 9.06-hour treatment-observation period). No serious side effects occurred. 4-AP is a promising drug for the symptomatic treatment of MS.

Relationship of FK506 whole blood concentrations and efficacy and toxicity after liver and kidney transplantation.

FK506 (tacrolimus) is a safe and effective immunosuppressant for the prevention of organ rejection after organ transplantation. FK506 has a relatively narrow therapeutic index and the correlation of dose to blood concentration is poor as a result of moderate variability in pharmacokinetic parameters between patients. Therapeutic monitoring of whole blood FK506 drug concentrations has been used in an effort to determine whether a relationship exists between concentrations of FK506 in the blood and the development of toxicity or the risk for organ rejection. An analysis of the relationship between FK506 blood levels and the occurrence of toxicity and rejection was carried out using data from four recent clinical trials. Trough FK506 levels within a 7-day window before the onset of rejection or toxicity were analyzed using logistic regression models. In kidney transplant patients (n=92), a significant correlation between FK506 levels and the incidence of both toxicity (P=0.01) and rejection (P=0.02) was seen. In liver transplant patients from three clinical trials, FK506 levels correlated well with the incidence of toxicity (P < or = 0.01); however, there was no significant relationship between FK506 levels and the incidence of rejection. It is concluded that therapeutic monitoring of whole blood FK506 levels may be useful for minimizing the risks of both toxicity and rejection in kidney transplant patients and for minimizing the risk of toxicity in liver transplant recipients.

Effect of tacrolimus (FK506) and sirolimus (rapamycin) mono- and combination therapy in prolongation of renal allograft survival in the monkey.

BACKGROUND: Our previous studies confirmed that tacrolimus (FK506) and sirolimus [rapamycin (RAPA)], in combination, are not antagonistic but are synergistic in the prolongation of heart and small bowel grafts in the rodent. The aim of this study was to confirm further the synergistic effect of combined FK506 and RAPA in the more clinically relevant model, kidney transplantation in monkeys. METHODS: A total of 60 male Vervet monkeys were randomly assigned to 10 groups (n> or =5). Monkeys with renal allografts were treated with different doses of FK506 and/or RAPA orally for 60 days. Graft survival, body weight, clinical biochemistry determinations, oral glucose tolerance test, trough levels of the two drugs, and histopathology were investigated. RESULTS: Low doses of FK506 (1 or 4 mg/kg) combined with RAPA (0.5 mg/kg) produced synergistic effect in the prolongation of renal graft survival [combination index (CI) = 0.292, 0.565]. There were no additive or synergistic drug-associated toxicities such as hyperglycemia, nephrotoxicity, and hyperlipidemia. There also was no pharmacological antagonism. CONCLUSION: Concomitant therapy of low-dose (drug-optimal) FK506 and RAPA produced a synergistic effect in the prolongation of kidney allograft survival in Vervet monkeys without additive drug-associated toxicities.

Tacrolimus (FK506) and sirolimus (rapamycin) in combination are not antagonistic but produce extended graft survival in cardiac transplantation in the rat.

Combined use of tacrolimus (FK506) with sirolimus (rapamycin [RAPA]) was examined in a model of vascularized heart allograft in the rat. For prevention of acute rejection, three different combinations of low doses of FK506 and RAPA from day 1 up to day 14 after transplantation produced significantly longer cardiac allograft survival than each agent alone (P<0.05). Identical results were observed in a model of reversal of ongoing acute rejection, where two combinations of low doses of FK506 and RAPA from day 4 up to day 18 after surgery also demonstrated significantly longer graft survival than each immunosuppressant alone (P<0.05). All the low-dose-treated groups in these two models presented significantly longer heart graft survival than naive controls (P<0.05), confirming that both agents are potent immunosuppressants in the models chosen. These results also indicate that, in contrast with in vitro studies, the combined use of FK506 and RAPA in vivo did not produce antagonism, but rather had synergistic effect in prolonging the allograft survival as compared with each agent alone. It appears likely that the abundance of FKBP-12 available for binding in vivo prevents inhibitive competition of the two agents for their receptor.

Compromised kidney graft rejection response in Vervet monkeys after withdrawal of immunosuppressants tacrolimus and sirolimus.

BACKGROUND: In nonprimates, organ allografts are often not rejected after withdrawal of immunosuppression. In this study, we examined whether such a phenomenon also occurs in primates. METHODS: Vervet monkeys were transplanted with renal allografts and treated for 60 days with tacrolimus, or tacrolimus plus sirolimus. The drugs were totally withdrawn on day 61. The survival of the monkeys was monitored, and their response to donor- or third party-derived alloantigens was examined in vivo and in vitro. RESULTS: The majority (80-100%) of the grafts survived for at least additional 30 days with no signs of acute rejection. The compromised rejection is donor-specific, because recipient monkeys failed to reject a donor-derived skin graft, but a third-party skin graft was rejected. In vitro mixed lymphocyte reaction and interleukin-2 production in the mixed lymphocyte reaction between the recipients and their donors or between the recipients and a third party had no discernable patterns, and thus did not reflect the in vivo status of the immune system. Although the recipients could not reject the graft acutely after drug withdrawal, the kidney grafts and the donor-derived skin grafts had pathological findings of chronic rejection. CONCLUSIONS: The rejection response of the monkeys to an established graft after withdrawal of immunosuppression is compromised. The compromised rejection is specific and is not due to a permanent alteration of the immune system by the initial drug treatment. The allografts are not inert but have low levels of interaction with the recipient immune system.

Randomized trial of tacrolimus plus mycophenolate mofetil or azathioprine versus cyclosporine oral solution (modified) plus mycophenolate mofetil after cadaveric kidney transplantation: results at 2 years.

BACKGROUND: A previous report described the 1-year results of a prospective, randomized trial designed to investigate the optimal combination of immunosuppressants in kidney transplantation. Recipients of first cadaveric kidney allografts were treated with tacrolimus+mycophenolate mofetil (MMF), cyclosporine oral solution (modified) (CsA)+MMF, or tacrolimus+azathioprine (AZA). Results at 1 year revealed that optimal efficacy and safety were achieved with a regimen containing tacrolimus+MMF. The present report describes results at 2 years. METHODS: Two hundred twenty-three recipients of first cadaveric kidney allografts were randomized to receive tacrolimus+MMF, CsA+MMF, or tacrolimus+AZA. All regimens contained corticosteroids, and antibody induction was used only in patients who experienced delayed graft function. Patients were followed up for 2 years. RESULTS: The results at 2 years corroborate and extend the findings of the previous report. Patients randomized to either treatment arm containing tacrolimus experienced improved kidney function. New-onset insulin dependence remained in four, three, and four patients in the tacrolimus+MMF, CsA+MMF, and tacrolimus+AZA treatment arms, respectively. Furthermore, patients with delayed graft function/acute tubular necrosis who were treated with tacrolimus+MMF experienced a 23% increase in allograft survival compared with patients receiving CsA+MMF (P=0.06). Patients randomized to tacrolimus+MMF received significantly lower doses of MMF compared with those administered CsA+MMF. CONCLUSIONS: All three immunosuppressive regi-mens provided excellent safety and efficacy. How-ever, the best results overall were achieved with tacrolimus+MMF. The combination may provide particular benefit to kidney allograft recipients who develop delayed graft function/acute tubular necrosis. Renal function at 2 years was better in the tacrolimus treatment groups compared with the CsA group.

Randomized trial of tacrolimus (Prograf) in combination with azathioprine or mycophenolate mofetil versus cyclosporine (Neoral) with mycophenolate mofetil after cadaveric kidney transplantation.

BACKGROUND: Our clinical trial was designed to investigate the optimal combination of immunosuppressants for renal transplantation. METHODS: A randomized three-arm, parallel group, open label, prospective study was performed at 15 North American centers to compare three immunosuppressive regimens: tacrolimus + azathioprine (AZA) versus cyclosporine (Neoral) + mycophenolate mofetil (MMF) versus tacrolimus + MMF. All patients were first cadaveric kidney transplants receiving the same maintenance corticosteroid regimen. Only patients with delayed graft function (32%) received antilymphocyte induction. A total of 223 patients were randomized, transplanted, and followed for 1 year. RESULTS: There were no significant differences in baseline demography between the three treatment groups. At 1 year the results are as follows: acute rejection 17% (95% confidence interval 9%, 26%) in tacrolimus + AZA; 20% (confidence interval 11%, 29%) in cyclosporine + MMF; and 15% (confidence interval 7%, 24%) in tacrolimus + MMF. The incidence of steroid resistant rejection requiring antilymphocyte therapy was 12% in the tacrolimus + AZA group, 11% in the cyclosporine + MMF group, and 4% in the tacrolimus + MMF group. There were no significant differences in overall patient or graft survival. Tacrolimus-treated patients had a lower incidence of hyperlipidemia through 6 months posttransplant. The incidence of posttransplant diabetes mellitus requiring insulin was 14% in the tacrolimus + AZA group, 7% in the cyclosporine + MMF and 7% in the tacrolimus + MMF groups. CONCLUSIONS: All regimens yielded similar acute rejection rates and graft survival, but the tacrolimus + MMF regimen was associated with the lowest rate of steroid resistant rejection requiring antilymphocyte therapy.

Cortical blindness: a rare complication of cyclosporine therapy.

We report a bone marrow transplant patient who developed a reversible episode of cortical blindness, a rare complication of cyclosporine therapy. We review previously reported cases and the mechanisms involved in this complication.

Glucocorticoids fail to enhance the effect of FK506 and methotrexate in prevention of graft-versus-host disease after DLA-nonidentical, unrelated marrow transplantation.

Several steroid receptor-associated heat shock proteins can bind to FK506 as immunophilins. This has led to speculation that the steroid receptor and immunophilin signal transduction pathways are functionally interrelated. Indeed, in vitro work showed that FK506 treatment of intact L929 cells which were stably transfected with various reporter plasmids resulted in a potentiation of glucocorticoid hormone-induced glucocorticoid receptor-mediated gene transcription. These findings have raised the possibility of additive or synergistic immunosuppressive effects of FK506 and glucocorticoids. We tested this hypothesis in a canine model of GVHD prevention. Two groups of dogs were given 9.2 Gy total body irradiation followed by hematopoietic grafts from unrelated DLA-nonidentical donors. Among the first group of four recipients which were given FK506 and glucocorticoids, one rejected the graft, while three developed acute GVHD and died from associated complications between days 14 and 34. In the second group of nine recipients which were given FK506, glucocorticoids and methotrexate (MTX), only one dog became a long-term survivor while eight dogs died between days 21-114 with GVHD (n = 5) or FK506-associated toxicities (n = 3). Thus, addition of glucocorticoids to FK506 or FK506/MTX showed neither synergistic nor additive effects with respect to GVHD prevention in this model, and no survival advantages were seen compared to previously reported results with FK506 alone or FK506 and MTX in combination, respectively.

Tacrolimus (FK506) and methotrexate regimens to prevent graft-versus-host disease after unrelated dog leukocyte antigen (DLA) nonidentical marrow transplantation.

We previously reported an synergism between methotrexate and tacrolimus (FK506) in preventing graft-versus-host disease (GVHD) in dogs given DLA-nonidentical unrelated marrow grafts after 9.2 Gy of total body irradiation (TBI). Methotrexate was given at 0.4 mg/kg i.v. on days 1, 3, 6 and 11 and FK506 at 0.15 mg/kg/day i.m. on days 0-8 and 0.5 mg/kg/day orally on days 9-90. Half of the dogs became long-term survivors. A major toxicity was gastrointestinal, and 25% of dogs died with intussusception. The current study addresses the problem of intussusception by making changes in drug doses used. In one group of dogs, FK506 was reduced to 0.075 mg/kg i.m. on days 1-8, while methotrexate was administered per original schedule. In a second group, methotrexate was reduced to a single dose on day 7, while FK506 was either administered per the original or reduced-dose schedule. None of the 17 current dogs developed intussusception, however, all but two dogs died with GVHD (n = 12) or graft failure (n = 3). Only two dogs survived after transient GVHD. Results show that there is little room for maneuvering FK506 or methotrexate doses, and hopes of reducing gastrointestinal toxicity by dose modifications while retaining the ability to prevent GVHD were not fulfilled.

Clinical utility of monitoring tacrolimus blood concentrations in liver transplant patients.

The relationship between the dose of tacrolimus, trough tacrolimus blood concentration, and selected clinical endpoints (acute rejection, nephrotoxicity, and other toxicities) were examined in a prospective, multicenter clinical trial to validate the use of an enzyme-linked immunosorbent assay (ELISA) for monitoring whole-blood concentrations of tacrolimus in liver transplant patients. A total of 111 subjects from six transplant centers were evaluated over 12 weeks posttransplantation. In addition to trough tacrolimus blood concentrations, hematocrit, ALT, AST, GGTP, alkaline phosphatase, total bilirubin, serum creatinine, BUN, serum potassium, serum magnesium, blood glucose, and serum albumin were also measured. The relationship between trough tacrolimus blood concentrations and clinical endpoints was analyzed using both a logistic regression model and a Cox proportional hazard model. By logistic regression analysis, a statistically significant (p = 0.0465) relationship between increasing trough tacrolimus blood concentrations and decreasing risk of acute rejection was demonstrated over a 7-day time window. Nephrotoxicity and other toxicities also demonstrated statistically significant relationships with trough tacrolimus blood concentrations. The results of the Cox analysis were consistent with the logistic regression analysis. Using receiver operator characteristic curves, trough tacrolimus concentrations as measured by the ELISA method were able to differentiate the occurrence of nephrotoxicity and toxicity from nonevents. To minimize nephrotoxicity of tacrolimus, it is necessary to maintain trough blood concentrations below 15 ng/ml. This study demonstrates that the ELISA method used to measure tacrolimus blood concentrations in this study provides information of predictive value for managing the risk of nephrotoxicity, other toxicity, and rejection in liver transplant patients.

The effect of hepatic enzyme inducers on busulfan neurotoxicity and myelotoxicity.

Anticonvulsants are commonly used empirically to prevent seizures in patients receiving high-dose busulfan in preparation for bone marrow transplantation. This study evaluates the effects of two anticonvulsants with enzyme-inductive properties, phenytoin and phenobarbital, and an enzyme inducer without anticonvulsant properties, Aroclor 1254, on the myelotoxicity and acute neurotoxicity of busulfan in a murine model. To assess the neuroprotective effects of these agents, we studied the effects of a single dose of 100 mg/kg i.p. busulfan, previously shown in this model to be uniformly lethal due to neurotoxicity. A significantly greater proportion of mice survived when pretreated with phenytoin or phenobarbital as compared with Aroclor 1254 pretreatment or an untreated control group. Busulfan myelotoxicity was studied in another group of mice treated with 135-150 mg/kg given in divided doses over 6 days. The proportion of animals surviving the otherwise myeloablative effects of this regimen were significantly improved by Aroclor 1254, high-dose phenytoin, and phenobarbital pretreatment. We conclude that anticonvulsants offer protection from the acute neurotoxicity of busulfan. However, these enzyme-inducing agents may reduce the myelosuppressive effects as well. These results suggest that an inducible enzyme system such as microsomal or glutathione S-transferases plays an important role in busulfan metabolism, warranting concern over concomitant administration of agents that either induce or inhibit these enzymes.

Influence of assay methodologies and interferences on the interpretation of digoxin concentrations.

The interpretation of serum digoxin concentrations is an area where pharmacists can have substantial clinical input. Important in this interpretation is the knowledge of various factors that may interfere with the reported concentration. These include drugs, metabolites of digoxin, protein concentration, and endogenous digoxin-like substances. The patients for whom these interferences are most significant include neonates, patients with renal failure and liver disease, and pregnant women. Pharmacist knowledge of these interferences can have an important impact on the quality of patient care.

Pentamidine therapy in renal failure: case report and literature review.

The literature lacks adequate dosing guidelines for modifying pentamidine therapy in renal failure. This report describes a patient in renal failure undergoing intermittent peritoneal dialysis who is treated with pentamidine for Pneumocystis carinii pneumonia. Data on pentamidine's disposition are reviewed.

Survey of vancomycin monitoring guidelines in Illinois hospitals.

Disparity exists in published recommendations for monitoring of vancomycin serum concentrations. To evaluate the degree of disparity of practice in Illinois, directors of pathology of 202 Illinois hospitals were surveyed to assess their vancomycin monitoring practices. Of the 202 surveys mailed, 82 were returned for a response rate of 41 percent. Most hospitals have 200-500 beds (60 percent) and are nonteaching institutions (72 percent). Two thirds of the hospitals sent vancomycin to an outside laboratory for analysis. Timing of postinfusion (peak) concentrations ranged from 0 minutes following end of infusion to 360 minutes. Approximately one half of the institutions reported a peak therapeutic range of 30-40 mg/L at 30 minutes following end of infusion. A great majority of institutions were consistent in recommended trough range, with 48 of 55 reporting 5-10 mg/L. Although there is some consistency among at least half of the hospitals, there is a great deal of variability among the other half in peak monitoring guidelines.

FK506 inhibits graft-versus-host disease and bone marrow graft rejection in murine recipients of MHC disparate donor grafts by interfering with mature peripheral T cell expansion post-transplantation.

FK506 was evaluated as the sole graft-vs-host disease (GVHD) preventive agent in murine recipients of fully allogeneic donor grafts. FK506 (36 mg/kg given as a suspension on days 0 through 13, then three times per wk through day 29 post-bone marrow transplantation (BMT)) reproducibly led to 50 to 90% of FK506-treated recipients surviving a 60- to 103-day observation period. High doses of cyclosporin A did not protect mice from lethal GVHD. A kinetic study performed in mice that received FK506 demonstrated that mature donor CD3+, CD4+, and CD8+ T cells in the spleen were each reduced by > or = 64%, as compared with vehicle-treated control mice, although this effect was short lived. Thymic reconstitution studies revealed a remarkable decrease in mature CD4+ cells and cells expressing the activation Ag, CD69. In contrast, less mature CD4+8+ thymocytes were not reduced significantly and total thymocyte numbers were only marginally decreased. The fact that peripheral reconstitution of CD4+8- or CD8+4- T cells was impaired significantly at this time indicated that FK506 had a major effect on thymic maturation and/or thymic emigration. In two models specifically designed to study alloengraftment, recipients of pan-T cell-depleted (TCD) donor marrow and FK506 were noted to have accelerated hemopoietic recovery and augmented long-term multilineage peripheral blood alloengraftment, in marked contrast to controls (86 to 97% mean donor cells vs 0% in controls for all lineages). These data demonstrate that FK506 prevents GVHD and graft rejection in vivo by inhibiting mature T cell expansion post-BMT.