Genome-wide association study identifies the common variants in CYP3A4 and CYP3A5 responsible for variation in tacrolimus trough concentration in Caucasian kidney transplant recipients.

The immunosuppressant tacrolimus (TAC) is metabolized by both cytochrome P450 3A4 (CYP3A4) and CYP3A5 enzymes. It is common for European Americans (EA) to carry two CYP3A5 loss-of-function (LoF) variants that profoundly reduces TAC metabolism. Despite having two LoF alleles, there is still considerable variability in TAC troughs and identifying additional variants in genes outside of the CYP3A5 gene could provide insight into this variability. We analyzed TAC trough concentrations in 1345 adult EA recipients with two CYP3A5 LoF alleles in a genome-wide association study. Only CYP3A4*22 was identified and no additional variants were genome-wide significant. Additional high allele frequency genetic variants with strong genetic effects associated with TAC trough variability are unlikely to be associated with TAC variation in the EA population. These data suggest that low allele frequency variants, identified by DNA sequencing, should be evaluated and may identify additional variants that contribute to TAC pharmacokinetic variability.

Genotype-guided tacrolimus dosing in African-American kidney transplant recipients.

Tacrolimus is dependent on CYP3A5 enzyme for metabolism. Expression of the CYP3A5 enzyme is controlled by several alleles including CYP3A5*1, CYP3A5*3, CYP3A5*6 and CYP3A5*7. African Americans (AAs) have on average higher tacrolimus dose requirements than Caucasians; however, some have requirements similar to Caucasians. Studies in AAs have primarily evaluated the CYP3A5*3 variant; however, there are other common nonfunctional variants in AAs (CYP3A5*6 and CYP3A5*7) that do not occur in Caucasians. These variants are associated with lower dose requirements and may explain why some AAs are metabolically similar to Caucasians. We created a tacrolimus clearance model in 354 AAs using a development and validation cohort. Time after transplant, steroid and antiviral use, age and CYP3A5*1, *3, *6 and *7 alleles were significant toward clearance. This study is the first to develop an AA-specific genotype-guided tacrolimus dosing model to personalize therapy.

Genomewide Association Study of Tacrolimus Concentrations in African American Kidney Transplant Recipients Identifies Multiple CYP3A5 Alleles.

We previously reported that tacrolimus (TAC) trough blood concentrations for African American (AA) kidney allograft recipients were lower than those observed in white patients. Subtherapeutic TAC troughs may be associated with acute rejection (AR) and AR-associated allograft failure. This variation in TAC troughs is due, in part, to differences in the frequency of the cytochrome P450 CYP3A5*3 allele (rs776746, expresses nonfunctional enzyme) between white and AA recipients; however, even after accounting for this variant, variability in AA-associated troughs is significant. We conducted a genomewide association study of TAC troughs in AA kidney allograft recipients to search for additional genetic variation. We identified two additional CYP3A5 variants in AA recipients independently associated with TAC troughs: CYP3A5*6 (rs10264272) and CYP3A5*7 (rs41303343). All three variants and clinical factors account for 53.9% of the observed variance in troughs, with 19.8% of the variance coming from demographic and clinical factors including recipient age, glomerular filtration rate, anticytomegalovirus drug use, simultaneous pancreas-kidney transplant and antibody induction. There was no evidence of common genetic variants in AA recipients significantly influencing TAC troughs aside from the CYP3A gene. These results reveal that additional and possibly rare functional variants exist that account for the additional variation.

Lower calcineurin inhibitor doses in older compared to younger kidney transplant recipients yield similar troughs.

The number of older adults undergoing kidney transplantation has increased, yet little is known about calcineurin inhibitor (CNI) metabolism in this group. We studied CNI troughs and doses to determine if there were age-related differences in metabolism and dose requirements. We studied 348 young (18-34 years), 1831 middle (35-64 years) and 374 older (65-84 years) adult kidney transplant recipients enrolled in a seven-center prospective study. Troughs were obtained from each patient 2×/week in weeks 1-8 and 2×/month in months 3-6. A multivariable linear-mixed model examined the effect of age on log dose and weight normalized troughs. Older recipients had higher normalized tacrolimus troughs than middle or young age adults despite receiving doses a median of 1-2 mg/day lower. Age and CYP3A5*1 genotype had the largest effect on tacrolimus troughs. Older recipients also had higher normalized cyclosporine troughs than middle or young adults despite receiving median doses 100 mg/day lower. After normalization for dose and weight, CNI troughs were more than 50% higher in older adults than young adults. These data support age-related changes in CNI metabolism. Further studies are needed to determine optimal dosing of CNIs in the elderly.

Activated water desorption from poly(methylvinylidene cyanide).

We have investigated water desorption from the polymer poly(methylvinylidene cyanide). The angle resolved thermal desorption spectra show large deviations from the cosn theta distribution for water desorption from poly(methylvinylidene cyanide) indicative of an activated desorption process. The Arrhenius plots obtained from Polanyi-Wigner analysis of the thermal desorption data suggest that a two-state model of desorption applies, while theory suggests that lattice strain in the polymer plays a key role in the thermal desorption of water.

Evidence for an influence of local dipole excitations in thermal desorption.

Ferroelectric crystalline copolymer films of vinylidene fluoride with trifluoroethylene (70%:30%) strongly interact with the dipoles of adsorbed and absorbed water molecules. This interaction can be probed with laser-assisted thermal desorption techniques. The UV light enhancement of water desorption is strongly light polarization dependent. The electronic structure of the ferroelectric copolymer films of vinylidene fluoride with trifluoroethylene films is locally altered with incident UV radiation suggesting metastable excited states that may involve dipole reorientation.

Water absorption and desorption from the dipole ordered polymer poly(methylvinylidene cyanide).

From thermal desorption studies, we find evidence that absorbed water in the bulk of poly(methylvinylidene cyanide) is more weakly bound than is the case for copolymer films of poly(vinylidenefluoride-trifluoroethylene). Ultraviolet laser enhanced thermal desorption of absorbed water exhibits little light polarization dependence for poly(methylvinylidene cyanide) in contrast to absorbed water in copolymer films of poly(vinylidenefluoride-trifluoroethylene). The implications of these differences are discussed.

Water adsorption on and desorption from crystalline copolymers of vinylidene fluoride with trifluoroethylene.

Water adsorption and absorption on crystalline polyvinylidene fluoride with 30% trifluoroethylene, P(VDF-TrFE, 70:30), was examined by thermal desorption spectroscopy. Two distinctly different water adsorption sites are identified: one adsorbed species that resembles ice and another species that interacts more strongly with the polymer thin film. The existence of the latter species is consistent with X-ray diffraction studies of water absorbed into the bulk of copolymers of polyvinylidene fluoride with trifluoroethylene crystalline thin films. There are strong steric effects observed in the angle-resolved thermal desorption that may be a result of the large polymer thin film surface dipoles.

Cytochrome P450 isozymes 3A4 and 2B6 are involved in the in vitro human metabolism of thiotepa to TEPA.

PURPOSE: To establish the cytochrome P450 (CYP) isozymes involved in the metabolism of the alkylating agent, thiotepa, to the pharmacologically active metabolite, TEPA. METHODS: In vitro chemical inhibition studies were conducted by incubating thiotepa and pooled human hepatic microsomes in the presence of known inhibitors to CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4. Studies were also performed with cloned, expressed CYP3A4, CYP2A6, CYP2E1 and CYP2B6 microsomes, and anti-CYP2B6 monoclonal antibody. RESULTS: Known CYP3A4 inhibitors reduced TEPA production. Inhibition with CYP2E1 inhibitors was inconsistent. All other inhibitors produced little or no change in TEPA formation. Cloned, expressed CYP2B6 and CYP3A4 microsomes catalyzed TEPA formation, whereas CYP2A6 and CYP2E1 did not. Incubation of thiotepa with anti-CYP2B6 antibody and cloned, expressed CYP2B6 microsomes resulted in reductions in the formation of TEPA, but no change in TEPA formation occurred in human liver microsomes. CONCLUSIONS: Thiotepa is metabolized in human liver microsomes by CYP3A4 (major) and CYP2B6 (minor). There is a potential for CYP-mediated drug interactions with thiotepa. Pharmacokinetic variability of thiotepa may be related to expression of hepatic CYP isozymes.

Treatment and prophylaxis of cytomegalovirus disease.

The diseases caused by cytomegalovirus (CMV) may threaten the life or sight of immunocompromised individuals such as patients undergoing transplantation and those with the acquired immunodeficiency syndrome. The management of CMV disease can be difficult. The antiviral agents ganciclovir and foscarnet are effective against CMV retinitis and gastrointestinal diseases, although dose-limiting adverse effects and the need for long-term maintenance therapy may hinder their use in many patients. When used to treat CMV pneumonitis in bone marrow transplant recipients, ganciclovir alone is not as effective as when it is combined with immune globulin. Since CMV disease can be fatal, several protocols have been developed for the transplant patient population, including administration of acyclovir, ganciclovir, screened blood products, and immune globulins.

Stability of itraconazole in an extemporaneously compounded oral liquid.

The stability of itraconazole in an extemporaneously compounded oral liquid formulation was studied. A suspension was prepared from the beads contained in commercially available 100-mg itraconazole capsules and sufficient Simple Syrup, NF, to make a final volume of 60 mL. The final concentration of itraconazole in the suspension was 40 mg/mL. Three identical volumes of each suspension were prepared and stored in 2-oz capped, amber glass prescription bottles and refrigerated at 4 degrees C (range, 2-6 degrees C). Immediately after preparation and at 7, 14, 21, 28, and 35 days, samples were visually inspected and assayed in duplicate by high-performance liquid chromatography; the pH of the samples was also determined. On day 35, the mean +/- S.D. percentage of initial itraconazole concentration remaining in the three suspensions was 95.3 +/- 2.2%. The color, odor, and pH of the samples did not change appreciably over the study period. Itraconazole 40 mg/mL in an oral liquid compounded from simple syrup and beads from capsules, stored in amber glass bottles, was stable for 35 days at 4 degrees C.

Stability of tacrolimus in an extemporaneously compounded oral liquid.

The stability of tacrolimus in an extemporaneously compounded oral liquid formulation was studied. A suspension was prepared by mixing the contents of commercially available 5-mg capsules of tacrolimus with equal amounts of Ora-Plus and Simple Syrup, NF, to make a final volume of 60 mL. The final concentration of tacrolimus in the suspension was 0.5 mg/mL. Six identical suspensions were prepared, placed in three glass and three plastic amber prescription bottles, and stored at room temperature (24-26 degrees C). Immediately after preparation and at 7, 15, 30, 45, and 56 days, samples were removed and assayed in duplicate by stability-indicating high-performance liquid chromatography. At least 98% of the initial tacrolimus concentrations remained in all suspensions throughout the study period. Color, order, and pH did not change appreciably over the study period. Tacrolimus 0.5 mg/mL compounded extemporaneously in equal amounts of Ora-Plus and Simple Syrup, NF, was stable at 24-26 degrees C for at least 56 days in both glass and plastic amber prescription bottles.

High fludarabine exposure and relationship with treatment-related mortality after nonmyeloablative hematopoietic cell transplantation.

Despite its common use in nonmyeloablative preparative regimens, the pharmacokinetics of fludarabine are poorly characterized in hematopoietic cell transplantation (HCT) recipients and exposure-response relationships remain undefined. The objective of this study was to evaluate the association between plasma F-ara-A exposure, the systemically circulating moiety of fludarabine, and engraftment, acute GVHD, TRM and OS after HCT. The preparative regimen consisted of CY 50 mg/kg/day i.v. day -6; plus fludarabine 30-40 mg/m²/day i.v. on days -6 to -2 and TBI 200 cGy on day -1. F-ara-A pharmacokinetics were carried out with the first dose of fludarabine in 87 adult patients. Median (range) F-ara-A area-under-the-curve (AUC((0-∞))) was 5.0 µg h/mL (2.0-11.0), clearance 15.3 L/h (6.2-36.6), C(min) 55 ng/mL (17-166) and concentration on day(zero) 16.0 ng/mL (0.1-144.1). Despite dose reductions, patients with renal insufficiency had higher F-ara-A exposures. There was strong association between high plasma concentrations of F-ara-A and increased risk of TRM and reduced OS. Patients with an AUC((0-∞)) greater than 6.5 µg h/mL had 4.56 greater risk of TRM and significantly lower OS. These data suggest that clinical strategies are needed to optimize dosing of fludarabine to prevent overexposure and toxicity in HCT.

Atraumatic palmar midcarpal dislocation in a skeletally immature adolescent with hemiatrophy.

We report a late presentation of a palmar midcarpal dislocation in an adolescent female with open growth plates who had no history of antecedent wrist injury. Midcarpal arthrodesis improved function and eliminated progressive pain.

Isradipine therapy in hypertensive pediatric patients.

OBJECTIVE: To evaluate the dosage and effectiveness of isradipine to control acute or chronic hypertension in pediatric patients. DESIGN: Retrospective medical record review. SETTING: University teaching hospital. PARTICIPANTS: Hospitalized pediatric patients aged 1 day to 16 years with hypertension treated with isradipine between January 1994 and March 1996. MEASURES: Patient age, gender, weight, disease states, current medications, isradipine dosage and formulation, pre- and postsystolic, and pre- and postdiastolic blood pressure measurements with each dose of isradipine. RESULTS: Fifty-three patients with a mean age of 5.8 +/- 4.0 years were evaluated. A mean change in the blood pressure measurements taken before the first dose of isradipine compared with the values recorded after the last dose or at discharge for all patients was -11.8% +/- 12.5% and -17.4% +/- 19.6%, respectively, for systolic and diastolic pressure. The mean dosage of isradipine in 46 patients who received regularly scheduled doses was 0.38 +/- 0.22 mg/kg/d. Patients who demonstrated a response received a mean dosage of 0.40 +/- 0.20 mg/kg/d. The total daily dosage was administered in one dose for 1 patient, two doses for 15 patients, three doses for 27 patients, and four doses for 3 patients. CONCLUSIONS: Isradipine was an effective antihypertensive agent to reduce the systolic and/or diastolic blood pressure 10% or more compared with pretreatment measurements in 43 (81%) of 53 pediatric patients. The mean dosage was 0.38 +/- 0.22 mg/kg/d, most frequently administered in two or three equally divided doses, which is higher than the normal recommended dosage for adults.

Stability of ganciclovir sodium and amino acids in parenteral nutrient solutions.

The stability of ganciclovir sodium and amino acids in parenteral nutrient solutions was studied. Three admixtures of ganciclovir sodium plus parenteral nutrient solution were prepared, one containing ganciclovir sodium 0.83 mg/mL, 1% amino acids, and 10% dextrose injection; one containing ganciclovir sodium 1.4 mg/mL, 2.5% amino acids, and 10% dextrose injection; and one containing ganciclovir sodium 1.4 mg/mL, 5% amino acids, and 25% dextrose injection. The solutions were visually inspected for precipitates, color change, and gas formation and were tested for pH. High-performance liquid chromatography was used to measure the concentration of ganciclovir and 16 amino acids in each admixture immediately and one, two, and three hours after preparation. There was no evidence of visual incompatibility in any of the admixtures, and pH did not vary appreciably during the study. The mean ganciclovir sodium concentration remaining was greater than 100% of the initial concentration for all the admixtures at one, two, and three hours. The mean amino acid concentration remaining in the admixtures with 2.5% or 5.0% amino acids was greater than 90% of the initial concentration for each amino acid at one, two, and three hours. The mean amino acid concentration remaining in the admixture with 1% amino acids was greater than 90% of the initial level at one and two hours. Ganciclovir sodium 0.83 mg/mL was stable for at least three hours in parenteral nutrient solution with 1% amino acids, and ganciclovir sodium 1.4 mg/mL was stable for at least three hours in admixtures with 2.5% or 5% amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)