Role of intestinal P-glycoprotein (mdr1) in interpatient variation in the oral bioavailability of cyclosporine.

Interpatient differences in the oral clearance of cyclosporine (INN, ciclosporin) have been partially attributed to variation in the activity of a single liver enzyme termed CYP3A4. Recently it has been shown that small bowel also contains CYP3A4, as well as P-glycoprotein, a protein able to transport cyclosporine. To assess the importance of these intestinal proteins, the oral pharmacokinetics of cyclosporine were measured in 25 kidney transplant recipients who each had their liver CYP3A4 activity quantitated by the intravenous [14C-N-methyl]-erythromycin breath test and who underwent small bowel biopsy for measurement of CYP3A4 and P-glycoprotein. Forward multiple regression revealed that 56% (i.e., r2 = 0.56) and 17% of the variability in apparent oral clearance [log (dose/area under the curve)] were accounted for by variation in liver CYP3A4 activity (p < 0.0001) and intestinal P-glycoprotein concentration (p = 0.0059), respectively. For peak blood concentration, liver CYP3A4 activity accounted for 32% (p = 0.0002) and P-glycoprotein accounted for an additional 30% (p = 0.0024) of the variability. Intestinal levels of CYP3A4, which varied tenfold, did not appear to influence any cyclosporine pharmacokinetic parameter examined. We conclude that intestinal P-glycoprotein plays a significant role in the first-pass elimination of cyclosporine, presumably by being a rate-limiting step in absorption. Drug interactions with cyclosporine previously ascribed to intestinal CYP3A4 may instead be mediated by interactions with intestinal P-glycoprotein.

Prevention and management of the adverse effects associated with immunosuppressive therapy.

Advances in immunosuppressive therapy have resulted in significantly improved patient and graft survival after solid organ transplantation. However, increased use has brought attention to specific toxicities associated with the use of these agents. Corticosteroid therapy can result in a wide array of short and long term toxicities. Management of these effects has focused on alternate day and dosage reduction protocols. Myelosuppression, hepatotoxicity, alopecia and gastrointestinal adverse effects are associated with azathioprine and generally respond to a reduction in dosage or withdrawal. Cyclophosphamide myelosuppression is managed in a similar manner. Use of cyclosporin, while the mainstay of immunosuppressive therapy, is often complicated by several well documented adverse effects. Short and long term nephrotoxicity is often managed through pharmacokinetic dosing strategies as well as pharmacological intervention with calcium channel blockers, prostaglandin analogues, pentoxifylline and thromboxane antagonists. Cyclosporin-induced hypertension, hyperlipidaemia, hyperkalaemia and hyperuricaemia are generally responsive to appropriate dietary restrictions and pharmacological therapies. The adverse effects associated with polyclonal antilymphocyte agents (fever, chills, rash, arthralgias) occur in response to the administration of foreign protein substances but can be prevented by pretreatment with corticosteroids, diphenhydramine and paracetamol (acetaminophen). The administration of muromonab CD3 (OKT3) stimulates the release of cytokines resulting in potentially severe complications seen during the first 1 or 2 doses. Pretreatment with diphenhydramine, low dose corticosteroids and paracetamol as well as proper fluid management has reduced the incidence of this syndrome. However, agents such as high dose corticosteroids, indomethacin, pentoxifylline and anti-tumour necrosis factor monoclonal antibodies may further decrease the severity of cytokine-induced toxicity. Antimurine antibodies may also develop during muromonab CD3 therapy, potentially limiting the efficacy of this agent. However, continued concomitant immunosuppressive therapy has significantly reduced antibody formation. In summary, as newer agents are developed with narrow therapeutic windows, it will be critical to identify specific drug toxicity and to develop preventative and management therapeutic strategies.

Mycophenolate mofetil for obliterative bronchiolitis syndrome after lung transplantation.

BACKGROUND: The development of obliterative bronchiolitis after lung transplantation portends a poor long-term outcome because of progressive decline in allograft function. There are currently no effective means of treating this condition. METHODS: Thirteen patients in whom obliterative bronchiolitis syndrome developed after lung transplantation were treated with mycophenolate mofetil, an antimetabolite immunosuppressant, at a dose of 1.5 g orally twice daily. Patients were followed up clinically and with pulmonary function testing. RESULTS: Duration of mycophenolate mofetil therapy ranged from 1 week to 24 months (mean duration, 11.4 months). Pulmonary function test results stabilized in the majority of patients with no significant further decline in forced expiratory volume in 1 second. Two patients died of progressive obliterative bronchiolitis, 1 patient is alive with progressive disease, and 1 patient died of an acute infection. The drug was discontinued in 2 additional patients. In no patient did severe leukopenia or cytomegalovirus infection develop; 1 patient had a fungal infection, and 7 patients experienced gastrointestinal side effects. CONCLUSIONS: In the setting of obliterative bronchiolitis syndrome, mycophenolate mofetil is generally well tolerated and is associated with stabilization of pulmonary function test results. These findings suggest that the otherwise progressive process of obliterative bronchiolitis can be slowed.

Mycophenolate mofetil: effects on clinical transplantation.

Mycophenolate mofetil (MMF) is the morpholinoethylester prodrug of mycophenolic acid, an agent which inhibits the proliferation of B and T lymphocytes through the noncompetitive, reversible inhibition of inosine monophosphate dehydrogenase, itself a key enzyme in the de novo synthetic pathway of guanosine nucleotides. Currently, MMF is approved for the prevention of acute renal allograft rejection when used in combination with cyclosporin and corticosteroids. Several studies have also demonstrated that this drug is useful in the treatment of refractory rejection in renal, heart and liver transplant recipients.

Mycophenolate mofetil.

Mycophenolate mofetil is the morpholinoethylester prodrug of mycophenolic acid, an agent that inhibits the proliferation of B and T lymphocytes through noncompetitive, reversible inhibition of inosine monophosphate dehydrogenase, a key enzyme in the de novo synthetic pathway of guanine nucleotides. Currently, mycophenolate mofetil is approved for the prevention of acute renal allograft rejection when given in combination with cyclosporine and steroids. Several studies also demonstrated that the agent is effective in the treatment of refractory rejection in renal, heart, and liver transplant recipients, and may have efficacy in the treatment of chronic rejection as well.

Alloresponses in vitro and in vivo show restricted T-cell receptor V beta gene usage.

Our studies of V beta restriction in alloresponses have demonstrated that V beta restriction in H-2 + Mls-1a, class I and class II responses in MLC and in H-2 + Mls-1a disparate sponge matrix allografts, supporting the hypothesis that certain alloresponses in vitro and in vivo have more restricted V beta gene usage than previously thought.

Liquid medication dispensing and dose monitoring: the CycloTech Cyclosporine Oral Solution Dispenser.

This liquid medication dispenser offers an easy, convenient means for accurate dispensing of medication. The ability of the device to store dose size, time to next dose, remaining available doses, and doses dispensed may allow for future analysis of patient behavior and improve compliance.

Effect of grape seed extract on oxidative, color and sensory stability of a pre-cooked, frozen, re-heated beef sausage model system.

To compare grape seed extract (GSE) to common antioxidants in a pre-cooked, frozen, stored meat model system sausage was manufactured from lean beef (70%), pork fat (28%), and salt (2%). Antioxidants added for comparison with control included grapeseed extract (100, 300, and 500 ppm), ascorbic acid (AA, 100 ppm of fat) and propyl gallate (PG, 100 ppm of fat). Product was formed into rolls, frozen, sliced into patties, cooked on a flat griddle to 70 °C, overwrapped in PVC, then frozen at - 18 °C for 4 months. GSE- and PG-containing samples retained their fresh cooked beef odor and flavor longer (p < 0.05) than controls during storage. Rancid odor and flavor scores of GSE-containing samples were lower (p < 0.05) than those of controls after 4months of storage. The L* value of all samples increased (p<0.05) during storage. Thiobarbituric acid reactive substances (TBARS) of the control and AA-containing samples increased (p < 0.05); those of GSE-containing samples did not change significantly (p > 0.05) over the storage period.

Black patients with chronic hepatitis C have a lower sustained viral response rate than non-Blacks with genotype 1, but the same with genotypes 2/3, and this is not explained by more frequent dose reductions of interferon and ribavirin*.

In previous hepatitis C virus (HCV) treatment studies, Black patients not only had a lower sustained viral response (SVR) rate to interferon and ribavirin (RBV) than non-Black patients but also a higher frequency of HCV genotype 1 (GT-1) infection. The aim of this community-based study was to determine whether Black patients have a lower SVR rate independent of genotype. We prospectively enrolled 785 patients (24.8% Black, 71.5% White, 3.7% others) who received interferon alpha-2b 3 MU three times weekly + RBV 1000-1200 mg/day for 24 weeks (GT-2/3) or 48 weeks (GT-1). Black patients were more commonly infected with GT-1 (86.8%vs 64.8%, P < 0.001) and less frequently had an SVR compared with non-Black patients (8.4%vs 21.6%, P < 0.001). Within GT-1, Black patients had a lower SVR rate than non-Black patients (6.1%vs 14.1%, P = 0.004) but not within GT-2/3 (50.0%vs 36.5%, P = 0.47). Black patients had lower baseline haemoglobin levels (14.8 vs 15.3 g/dL, P < 0.001) and neutrophil counts (2900 vs 4100/mm(3), P < 0.001) and required more frequent dose reductions of RBV (29.8%vs 18.5%, P < 0.001) and interferon (4.7%vs 1.6%, P = 0.012). However, dose reductions were not associated with lower SVR rates while early treatment discontinuations were (2.9%vs 25.7%, P < 0.001). Independent predictors of SVR were GT-1 [odds ratio (OR) 0.33; 95% confidence interval (CI) 0.20-0.55; P < 0.001], Black race (OR 0.45; 95% CI 0.22-0.93; P = 0.030), and advanced fibrosis, stages 3 + 4 (OR 0.53; 95% CI 0.31-0.92; P = 0.023). In conclusion, Black patients infected with HCV GT-1 (but not GT-2/3) have a lower SVR rate than non-Black patients. This is not explained by their lower baseline haemoglobin levels and neutrophil counts that lead to higher rates of ribavirin and interferon dose reductions.

Infectious complications after OKT3 induction in liver transplantation.

The present study examines the incidence, risk factors, bacteriology, and mortality of infectious episodes and the role of antimicrobial prophylactic regimens after OKT3 induction in liver transplantation. Infections occurring in the first 6 months were evaluated according to the Centers for Disease Control criteria in 102 transplant recipients. Patients were administered OKT3 for 5 to 10 days, beginning intraoperatively, azathioprine, low-dose prednisone, and delayed introduction of cyclosporine. There were 140 major and 30 minor infections for an incidence of 1.7 infections per patient. Twenty-seven patients (26%) had no infectious episodes during the 6 months of follow-up. Bacterial and fungal infections peaked during the first month posttransplantation, whereas viral infections peaked during the second month. Infection-related mortality was 10%. One-year survival rate of patients who suffered a major infection was less than those who were infection free, but the difference was not statistically significant (79% vs. 89%; P = .61). There was a significantly higher incidence of enterococcal infections under cefotetan prophylaxis than under ampicillin-sulbactam (.375 vs. 11 infections per patient; P = .0017). There were 14 episodes of cytomegalovirus disease (14%) but no cytomegalovirus-related mortality or graft loss, and all cases responded to ganciclovir treatment. Bivariate and multivariate analyses identified only retransplantation as a risk factor for infection. In conclusion, OKT3 induction after liver transplantation is associated with a manageable incidence of bacterial, viral, or fungal infections. This is caused by, at least in part, improved anti-infective prophylaxis.

High-dose ciprofloxacin in the treatment of a renal cyst infection.

OBJECTIVE: To report a case of renal cyst infection successfully treated with ciprofloxacin. CASE SUMMARY: The clinical course of a 33-year-old woman with radiologic and symptomatic evidence of a renal cyst infection continued to worsen after 7 days of apparently adequate antibiotic therapy for Escherichia coli isolated from her urine. Antibiotic therapy with intravenous ciprofloxacin 600 mg every 12 hours was administered for 7 days and then given as oral therapy (750 mg q12h) for another 14 days. The patient's clinical condition rapidly improved on ciprofloxacin and follow-up 28 days later showed no evidence of infection. DISCUSSION: Renal cyst infections are a serious complication of polycystic kidney disease and are often refractory to standard antimicrobial therapy. Ciprofloxacin has the chemical properties and antimicrobial activity needed to treat these infections. Previously reported concentrations of ciprofloxacin in renal cyst fluid are therapeutic for the common pathogens associated with renal cyst infections. CONCLUSIONS: Ciprofloxacin appears to be a safe and effective option for treating renal cyst infections. Further controlled studies evaluating its clinical efficacy are warranted.

Evaluation of the pharmacokinetic interaction between cimetidine or famotidine and cyclosporine in healthy men.

OBJECTIVE: To investigate the potential interaction between cimetidine or famotidine and cyclosporine in healthy men. DESIGN: All subjects received oral cyclosporine at baseline, after the first week of 1 histamine2 (H2)-blocker, and a third time after a 1-week washout plus 1 week of the second H2-blocker. Blood samples were collected just before each dose of cyclosporine and for up to 36 hours afterward for pharmacokinetic analysis. SETTING: A college of pharmacy in a university teaching hospital. PARTICIPANTS: The study population consisted of 8 healthy men at least 19 years of age. MAIN OUTCOME MEASURES: Cyclosporine concentrations in whole blood were measured using a polyclonal fluorescence polarization immunoassay. Cyclosporine pharmacokinetic parameters during each of the 3 treatment periods were compared. RESULTS: The average times to maximum cyclosporine concentrations were similar between baseline (3.2 h), cimetidine (2.9 h), and famotidine (3.6 h) dosing periods. There were no significant differences in area under the curve, half-life, or maximum concentration during the 3 dosing periods. CONCLUSIONS: Neither cimetidine or famotidine produced a significant change in the pharmacokinetics of single-dose oral cyclosporine in healthy men.

Soluble interleukin-2 receptor monitoring during bacterial and viral infections in liver transplant recipients: a comparative evaluation.

We evaluated the significance of serial sIL-2R serum levels as a differential marker of immune activation during bacterial versus viral infections in liver transplant recipients. A comparative evaluation of sIL-2R levels was performed in 76 liver transplant recipients (51 pediatric and 27 adult) during bacterial versus viral infections at 7 days prior to infection diagnosis (DAY-7), the day of diagnosis (DAY 0), peak sIL-2R level and at the end of therapy (END). There were no significant elevations at any time point during bacterial infections in either adult or pediatric transplant recipients. However, adult recipients demonstrated significant elevations during viral infections when comparing DAY-7 to PEAK (3840 +/- 830 vs 7225 +/- 2814 p = 0.03), with PEAK levels significantly higher during viral versus bacterial infections in this population (7225 +/- 2814 vs 4195 +/- 1819). Pediatric recipients demonstrated similar increases in sIL-2R serum levels during viral infections from DAY-7 to PEAK (4932 +/- 887 vs 11323 +/- 2794 p = 0.0012). Significant decreases from PEAK to END were noted during viral infections in both adult and pediatric recipients (7225 +/- 2814 vs 2911 +/- 1376 p = 0.01 and 11323 +/- 2794 vs 5214 +/- 2403 p = 0.006). Pediatric recipients had higher mean sIL-2R levels than adult recipients at all time points during viral infections. In conclusion, significant elevations in mean sIL-2R serum levels were observed during viral but not bacterial infections in pediatric and adult liver transplant recipients. This suggests that serial sIL-2R monitoring is a valuable immunologic marker of viral pathogenesis and may be useful in monitoring the progression of viral infections as well as response to antiviral therapy.

Monoethylglycinexylide formation in assessing pediatric donor liver function.

Lidocaine metabolism to monoethylglycinexylide (MEGX) has been described as a novel method to assess liver function in adult transplant donors and recipients. While this assay appears to offer a number of advantages over existing liver function tests, limited work has been done to evaluate its potential in the pediatric population. This study evaluated MEGX formation in potential pediatric liver donors (n = 35) and a control group of children (n = 16). The mean MEGX formation was significantly higher in pediatric donors than in the control group (156 +/- 62 vs 106 +/- 33 ng/ml, p < 0.05). No correlation with age, total bilirubin, liver transaminases, or alkaline phosphatase could be made within each group. Significant differences in MEGX levels were noted when each group was compared to its adult counterpart. Both pediatric donors and controls had greater mean MEGX formation than has been reported for adult donors and controls (156 +/- 62 vs 127 +/- 61 ng/ml, p < 0.05 and 106 +/- 33 vs 72 +/- 36 ng/ml, p < 0.05, respectively). Drugs that alter lidocaine pharmacokinetics and their potential influence on MEGX formation were evaluated in the pediatric donor group. Donors exposed to hepatic enzyme-inducing drugs had a higher mean MEGX formation (187 +/- 60 vs 146 +/- 63 ng/ml). No significant differences were noted between donors receiving and not receiving vasopressors. In conclusion, the significant differences between pediatric and adult MEGX formation should be noted when establishing reference or normal ranges for this diagnostic test. Furthermore, concomitant drug therapy may significantly alter MEGX formation.