Randomized, double-blind, placebo-controlled study of XP13512/GSK1838262 in patients with RLS.

OBJECTIVE: To assess the efficacy and tolerability of the nondopaminergic agent XP13512/GSK1838262 in adults with moderate to severe primary restless legs syndrome (RLS). METHODS: Patient Improvements in Vital Outcomes following Treatment in Restless Legs Syndrome I was a 12-week, multicenter, randomized, double-blind, placebo-controlled trial of XP13512 1,200 mg or placebo taken once daily at 5:00 pm with food. Coprimary endpoints were mean change from baseline International Restless Legs Scale (IRLS) total score and proportion of investigator-rated responders (very much improved or much improved on the Clinical Global Impression-Improvement scale) at week 12 (last observation carried forward). Tolerability was assessed using adverse events, vital signs, and clinical laboratory parameters. RESULTS: A total of 222 patients were randomized (XP13512 = 114, placebo = 108) and 192 patients (XP13512 = 100, placebo = 92) completed the study. At week 12, the mean change from baseline IRLS total score was greater with XP13512 (-13.2) compared with placebo (-8.8). Analysis of covariance, adjusted for baseline score and pooled site, demonstrated a mean treatment difference of -4.0 (95% confidence interval [CI], -6.2 to -1.9; p = 0.0003). More patients treated with XP13512 (76.1%) were responders compared with placebo (38.9%; adjusted OR 5.1; 95% CI, 2.8 to 9.2; p < 0.0001). Significant treatment effects for both coprimary measures were identified at week 1, the earliest time point measured. The most commonly reported adverse events were somnolence (XP13512 27%, placebo 7%) and dizziness (XP13512 20%, placebo 5%), which were mild to moderate in intensity and generally remitted. CONCLUSIONS: XP13512 1,200 mg, taken once daily, significantly improved restless legs syndrome (RLS) symptoms compared with placebo and was generally well tolerated in adults with moderate to severe primary RLS.

An individual bioequivalence approach to compare the intrasubject variability of two ciclosporin formulations, SangCya and Neoral.

A novel bioequivalence testing approach was used to determine intrasubject variability and switchability of two ciclosporin formulations, SangCya (test) and Neoral (reference). Twenty healthy volunteers were enrolled into a single-dose, randomized, open-label, 4-period, 2-sequence study with a crossover replicate design. Subject-by-formulation interaction variances were compared using a mixed effects linear model. Intrasubject variability for ln AUC(0-infinity) and ln C(max) of SangCya and Neoral were not significantly different. The 95% confidence intervals of the intrasubject variability of AUC(0-infinity) (0.94) and C(max) (1.28) as determined using the bootstrap nonparametric percentile method (n = 2,000) were below the individual bioequivalence limit estimated at 2.25. We concluded equivalent intrasubject variability of ciclosporin pharmacokinetics and switchability between SangCya and Neoral.

Expression of intercellular adhesion molecule-1 in rat inner ear due to bacterial otitis media.

Expressions of anti-Streptococcus pneumoniae antibody and anti-intercellular adhesion molecule-1 (ICAM-1) antibody in the inner ear were studied immunohistochemically in rats following inoculation of S pneumoniae type 6A into the middle ear cavity. Positive staining with anti-S pneumoniae antibody was detected in the marginal cells of the stria vascularis of rats sacrificed 3 days after S pneumoniae inoculation, but almost no staining was detected in those sacrificed at 14 days. Strong ICAM-1 expression was detected in the basal cell layer of the stria vascularis of rats sacrificed 3 days after inoculation, but the intensity of the staining had decreased by 14 days. These results suggest that the stria vascularis may be a site of the inner ear damage that follows bacterial inoculation into the middle ear cavity. The up-regulated expression of ICAM-1 in the basal cell layer may represent a reaction of the inner ear to the bacterial otitis media.

A limited sampling strategy for the estimation of 12-hour SangCya and neoral AUCs in renal transplant recipients.

Neoral and SangCya are new cyclosporine formulations with more consistent pharmacokinetic profiles than the older formulation of cyclosporine, Sandimmune. Limited sampling strategies have been derived to estimate the full area under the curve (AUC) for both Neoral and Sandimmune. In addition, no limited sampling strategy has been derived for SangCya, and no rigorous prospective testing has been done on any of these formulas. The authors studied 32 renal transplant patients who received Neoral and then SangCya during a formulation conversion study. Full AUCs were drawn on all patients (twice while on Neoral, once while on SangCya). Abbreviated formulas were derived using linear regression models and then tested for the prediction error. The authors found that several abbreviated formulas offer excellent estimations of the full AUC for both SangCya and Neoral. The generated formulas worked equally well with either formulation. In addition, the authors found that limited sampling strategies using a 1.5-hour sample may predict a full AUC more accurately than those that use a 2-hour sample. The use of these abbreviated formulas allows for a convenient and accurate estimate of CsA exposure.

Amoxicillin middle ear fluid penetration and pharmacokinetics in children with acute otitis media.

BACKGROUND: Acute otitis media (AOM) is a common childhood infectious disease. The efficacy of antibiotic dosing regimens is usually assessed by antibiotic plasma pharmacokinetics or middle ear fluid (MEF) concentration at one or two time points. Viral coinfection in AOM reduced antibacterial efficacy of antibiotics. OBJECTIVE: To determine amoxicillin MEF penetration and pharmacokinetics in bacterial and combined bacterial and viral AOM. METHODS: Thirty-four children with AOM were enrolled, and MEF was collected by tympanocentesis for bacterial culture and viral studies. Nasal wash and venous blood were also obtained for viral culture and serologic studies, respectively. Subjects were treated with amoxicillin 40 mg/kg/day orally, divided in equal doses every 8 h. During the second visit (48 to 72 h later) the subjects, with the regular morning amoxicillin dose withheld, were given an oral amoxicillin dose of 25 mg/kg. Thereafter two blood samples and one MEF sample by tympanocentesis were collected from each child at selected times between 0.5 and 4.0 h after dosing for bacterial and viral studies and amoxicillin concentration determination by high performance liquid chromatography. RESULTS: Eleven (37%) children had only bacterial infection, 6 (20%) had viral infection only, 6 (20%) had both bacterial and viral infections and in 7 (23%) neither bacterial nor viral pathogens were recovered. MEF bacterial culture was positive in 23 of 40 ears (57.5%) before treatment with amoxicillin (40 mg/kg/day) and was still positive in 4 of 38 ears (10.5%) after 2 to 3 days of treatment. Amoxicillin plasma concentration reached its peak at 1.0 to 1.5 h after a 25-mg/kg oral dose. The estimated MEF concentration peak occurred 3.0 h after the dose with MEF concentrations ranging from undetectable to 20.6 microg/ml and a mean of approximately 9.5 microg/ml. Geometric mean amoxicillin concentrations were lowest in virus-infected children (2.7 microg/ml), nearly the same in culture-negative samples from children without viral infection (2.9 microg/ml), higher in children with combined bacterial and viral infection (4.1 microg/ml) and highest in children with bacterial-only infection (5.7 microg/ml). CONCLUSIONS: MEF amoxicillin penetration tended to be lower in children with viral infection. The current amoxicillin dosing recommendation of 40 mg/kg/day in three divided dose is inadequate to effectively eradicate resistant Streptococcus pneumoniae, particularly during viral coinfection. A dosing regimen of 75 to 90 mg/kg/day is recommended for AOM.

Effect of early cyclosporine levels on kidney allograft rejection.

Acute rejection is the greatest risk factor for development of biopsy-proven chronic rejection and late kidney allograft loss. We previously noted that low cyclosporine (CsA) levels were a risk factor for early acute rejection in pediatric recipients (1). In our current study, we used logistic regression to identify risk factors for acute rejection in 726 adult kidney transplant recipients on triple therapy (prednisone, azathioprine, CsA). Variables considered for logistic regression analysis were donor organ source (cadaver vs. living), degree of HLA mismatch (1 to 6 vs. 0 antigen mismatch), transplant number (primary vs. retransplant), CsA levels (< 125 vs. > or = 125 ng/ml, < 150 ng/ml vs. > or = 150 ng/ml, and < 175 vs. > or = 175 ng/ml), and acute rejection episodes (0 vs. > or = 1). Of 726 recipients, 401 (55%) received cadaver kidneys; 325 (45%), living related. Overall, 572 (79%) had a primary transplant; 154 (21%), a retransplant. The vast majority of acute rejection episodes occurred within the first 2 months posttransplant; 68% of recipients had no acute rejection episodes by 2 months and 58% had none by 60 months posttransplant. Logistic regression analysis revealed that a cadaver donor kidney (vs. living) (p = 0.004), a 1 to 6 antigen mismatch (vs. 0 mismatch) (p = 0.001), and CsA levels < 150 ng/ml (vs. > or = 150 ng/ml) correlated with biopsy-proven acute rejection. The correlation for CsA levels < 150 ng/ml (vs. > or = 150 ng/ml) held true for levels at 1 wk (p < 0.05), 1 month (p = 0.0001), 2 months (p = 0.01), and 3 months (p = 0.02) posttransplant. Similar correlation was found for CsA levels < 125 ng/ml (vs. > or = 125 ng/ml) and < 175 ng/ml (vs. > or = 175 ng/ml). Comparative analyses were made (by Chi-square) of acute and chronic rejection rates when recipients were divided into 3 groups by CsA level (< 125 ng/ml, > or = 125 to < 150 ng/ml, and > or 150 ng/ml). At each time point (1 wk, 2 wk, 1 month, 2 months, 3 months), CsA levels < 125 ng/ml (vs. > or = 125 to < 150 ng/ml and > or = 150 ng/ml) were associated with the greatest increased risk of acute rejection--for both cadaver and living related recipients (all p < 0.05). CsA levels < 125 ng/ml at each time point (1 wk, 2 wk, 1 month, 2 months, 3 months) were also associated with a significantly increased risk of chronic rejection (all p < 0.001). The incidence of both acute and chronic rejection was reduced in the group with CsA levels > or = 125 to < 150 ng/ml and further reduced in the > or = 150 ng/ml group. Our data indicate that maintaining CsA levels > or = 150 ng/ml as part of triple therapy reduces the incidence of both acute and chronic rejection. Because chronic rejection is the leading cause of late allograft loss, maintaining adequate CsA levels should improve long-term graft survival. Based on this analysis, we have modified our own immunosuppressive regimens to achieve higher CsA levels earlier posttransplant.

High-performance liquid chromatographic analysis of amoxicillin in human and chinchilla plasma, middle ear fluid and whole blood.

We extended the application of a sensitive high-performance liquid chromatography assay of amoxicillin developed in this laboratory for human plasma and middle ear fluid (MEF) to other sample matrices including chinchilla plasma or MEF and human and chinchilla whole blood with minor modification and validated the limit of quantitation at 0.25 microg/ml with a 50-microl sample size for human and chinchilla plasmas or MEFs. Amoxicillin and cefadroxil, the internal standard, were extracted from 50 microl of the samples with Bond Elut C18 cartridges. The extract was analyzed on a Keystone MOS Hypersil-1 (C8) column with UV detection at 210 nm. The mobile phase was 6% acetonitrile in 5 mM phosphate buffer, pH 6.5 and 5 mM tetrabutylammonium. The within-day coefficients of variation were 2.7-9.9 (n=4) and 1.7-7.2% (n=3) for chinchilla plasma and MEF samples, respectively; 2.8-8.1% (n=3) and 2.9-4.7% (n=3) for human and chinchilla whole blood, respectively. An alternative mobile phase composition for chinchilla plasma and MEF samples reduced the analysis time significantly.

Sensitive assay for measuring amoxicillin in human plasma and middle ear fluid using solid-phase extraction and reversed-phase high-performance liquid chromatography.

We developed a sensitive assay to measure amoxicillin in human plasma and middle ear fluid (MEF) using solid-phase extraction and reversed-phase HPLC. Amoxicillin and cefadroxil, the internal standard, were extracted from 50-200 microliters of sample with Bond Elut C18 cartridges. The extract was analyzed on a 15 cm x 2 mm, 5 micron Keystone MOS Hypersil-1 (C8) column with UV detection at 210 nm. The mobile phase was 6% acetonitrile in 5 mM phosphate buffer (pH = 6.5) and 5 mM tetrabutylammonium. The average absolute recovery of amoxicillin and cefadroxil were 91.2 +/- 16.6% and 91.0 +/- 6.8%, respectively. The limit of quantitation was 0.125 microgram/ml with 200 microliters sample size. The linear range was from 0.125 to 35.0 micrograms/ml with correlation coefficients greater than 0.999. These analytic conditions produced a highly sensitive amoxicillin assay in human body fluids without derivatization.

Important interactions of drugs with immunosuppressive agents used in transplant recipients.

Solid organ transplant recipients depend on multiple immunosuppressive drugs, given in combination, to prevent rejection of their allografts. These patients often require many other therapeutic agents to treat underlying illnesses or concurrent diseases. Whenever a new medication is administered to a transplant patient, the potential exists for increasing or decreasing the tissue concentrations of immunosuppressive agents. This can lead to serious complications, such as over-immunosuppression and infection, under-immunosuppression and acute rejection, or additive toxicities, including nephrotoxicity. New immunosuppressants are under development and in clinical use, such as FK506, deoxyspergualin, OG 37-325, rapamycin, brequinar, and mycophenolate mofetil, thereby creating the possibility of many new drug-drug interactions.

Optimizing the use of cyclosporine in renal transplantation.

OBJECTIVE: To review the existing data on the use of cyclosporine (CsA) in kidney transplantation, particularly with respect to therapeutic drug monitoring. DATA SOURCES: A literature search was conducted of applicable articles related to therapeutic drug monitoring of cyclosporine in renal transplantation. Previous consensus guidelines were examined. Discussions on issues related to this topic convened in Toronto, ON, on June 15-16, 1994. DATA SYNTHESIS: The literature was analyzed to examine patient factors and drug interactions affecting CsA concentrations, the effect of CsA concentrations on patient outcome, current methods of analysis, pharmacodynamic monitoring, and new immunosuppressants. CONCLUSIONS: CsA has improved the success of kidney transplantation, reducing the incidence and severity of acute rejection and improving short-term patient and graft survival. The rate of graft loss after the first year (primarily due to chronic rejection) has remained largely unchanged. Sandimmune Neoral offers promise due to its better bioavailability and limited dependence on bile flow for absorption. Long-term studies are underway to determine its effectiveness and safety. Indications for therapeutic drug monitoring for CsA are provided.