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Biomedical subjects

Gopal Krishna

Publications and source records attributed to Gopal Krishna.

12 recordsLinked to original sources
PubMed2007

Posaconazole plasma concentrations in juvenile patients with invasive fungal infection.

Posaconazole is an orally bioavailable triazole antifungal agent for the treatment and prophylaxis of invasive fungal infection. We evaluated plasma posaconazole concentration data from juvenile (younger than 18 years; n = 12) and adult (18 to 64 years; n = 194) patients who participated in a multicenter, phase 3, open-label study that assessed the efficacy and safety of posaconazole treatment for persons who were intolerant of or had invasive fungal infection refractory to standard antifungal therapies. With the exception of one juvenile patient who received 400 mg/day as a divided dose on the day of sample collection, all patients received posaconazole at 800 mg/day as an oral suspension in divided doses. Plasma samples were analyzed through a validated liquid chromatographic-tandem mass spectrometric method with a lower limit of quantitation of 1 ng/ml. Because plasma posaconazole concentrations are relatively constant at steady state, the average of all plasma concentrations (C(av)) for each patient was calculated to provide a single steady-state plasma posaconazole concentration. A blinded data review committee reviewed all treatment outcomes. Variable posaconazole plasma concentrations were observed within both the juvenile and adult populations. Mean (median [range]) C(av) values for juvenile and adult patients were 776 ng/ml (579 ng/ml [85.3 to 2,891 ng/ml]) and 817 ng/ml (626 ng/ml [0 to 3,710 ng/ml]), respectively. Overall success rates and adverse event profiles were comparable. In conclusion, posaconazole concentrations in plasma were similar for juvenile and adult patients, suggesting that clinical outcomes are expected to be similar in adults and children with refractory invasive fungal infection.

Adolescent↗
PubMed2006

Treatment of invasive aspergillosis with posaconazole in patients who are refractory to or intolerant of conventional therapy: an externally controlled trial.

BACKGROUND: Invasive aspergillosis is an important cause of morbidity and mortality in immunocompromised patients. Current treatments provide limited benefit. Posaconazole is an extended-spectrum triazole with in vitro and in vivo activity against Aspergillus species. METHODS: We investigated the efficacy and safety of posaconazole oral suspension (800 mg/day in divided doses) as monotherapy in an open-label, multicenter study in patients with invasive aspergillosis and other mycoses who were refractory to or intolerant of conventional antifungal therapy. Data from external control cases were collected retrospectively to provide a comparative reference group. RESULTS: Cases of aspergillosis deemed evaluable by a blinded data review committee included 107 posaconazole recipients and 86 control subjects (modified intent-to-treat population). The populations were similar and balanced with regard to prespecified demographic and disease variables. The overall success rate (i.e., the data review committee-assessed global response at the end of treatment) was 42% for posaconazole recipients and 26% for control subjects (odds ratio, 4.06; 95% confidence interval, 1.50-11.04; P=.006). The differences in response between the modified intent-to-treat treatment groups were preserved across additional, prespecified subsets, including infection site (pulmonary or disseminated), hematological malignancy, hematopoietic stem cell transplantation, baseline neutropenia, and reason for enrollment (patient was refractory to or intolerant of previous antifungal therapy). An exposure-response relationship was suggested by pharmacokinetic analyses. CONCLUSIONS: Although the study predates extensive use of echinocandins and voriconazole, these findings demonstrate that posaconazole is an alternative to salvage therapy for patients with invasive aspergillosis who are refractory to or intolerant of previous antifungal therapy.

Antifungal Agents↗
PubMed2006

Effects of age, gender, and race/ethnicity on the pharmacokinetics of posaconazole in healthy volunteers.

Posaconazole is a triazole antifungal for prophylaxis of invasive fungal infection and treatment of oropharyngeal candidiasis. We evaluated the effects of gender, age, and race/ethnicity (black or white) on the steady-state pharmacokinetics of posaconazole in two studies on healthy adult subjects (>or=18 years of age). Additionally, we explored the effect of P-glycoprotein expression and MDR1 genotype on posaconazole pharmacokinetics in black and white subjects. Age, gender, and race/ethnicity had no clinically relevant effects on posaconazole pharmacokinetics. No association was observed between any MDR1 single-nucleotide polymorphism and the area under the concentration-time curve for posaconazole. Posaconazole was safe and well tolerated regardless of age, gender, or race/ethnicity. In conclusion, age, gender, and race/ethnicity have no clinically relevant effects on the steady-state pharmacokinetics of posaconazole in healthy adults; therefore, dosage adjustments based on these covariates are unnecessary.

Adult↗
PubMed2006

A sensitive liquid chromatography and mass spectrometry method for the determination of posaconazole in human plasma.

Posaconazole is a novel extended-spectrum triazole that has favorable in vitro, in vivo and clinical activity against a number of yeasts and moulds. Posaconazole is available as an oral suspension. The dosage found to result in monitored plasma levels that correlate with clinical evidence of good antifungal activity is 800 mg/day in divided doses. A liquid chromatographic/mass spectrometric method (LC-MS/MS) that can be used by clinicians wishing to quantitate, and thereby monitor, plasma levels of posaconazole in certain patients was validated. The method utilized semi-automated 96-well protein precipitation with gradient chromatographic separation of analytes using a Varian Polaris C-18A (2.0 mm x 50 mm, 5-microm particle size) column. The approximate retention time of posaconazole was 2.0 min. Analytes were detected by using tandem mass spectrometry. Sample introduction and ionization was performed by atmospheric pressure chemical ionization in the positive-ion mode. This method has been proven suitable for routine quantitation of posaconazole over the concentration range of 5.00-5000 ng/mL. Inter-run precision based on percent relative deviation for replicate quality controls was < or = 6.2%. Inter-run accuracy expressed as %DIFF was +/-4.0%. Posaconazole quality controls were stable in human plasma for up to five freeze-thaw cycles, when frozen at -20 degrees C for at least 105 days and when kept at room temperature for 24 h. The lower limit of quantitation was 5.00 ng/mL for a 100-microL sample aliquot. These data indicate that the LC-MS/MS method described is suitable for the rapid measurement of posaconazole over the concentration range of 5.00-5000 ng/mL.

Antifungal Agents↗
PubMed2006

Pharmacokinetics and safety of oral posaconazole in neutropenic stem cell transplant recipients.

The pharmacokinetics of posaconazole oral suspension in neutropenic patients undergoing high-dose chemotherapy and stem cell transplantation were evaluated, and the association of plasma posaconazole exposure with the presence and severity of oral mucositis was explored in this nonrandomized, open-label, parallel-group, multiple-dose pharmacokinetic study. Thirty patients were enrolled and received one of three regimens (group I, 200 mg once daily; group II, 400 mg once daily; group III, 200 mg four times daily) for the duration of neutropenia. The mean total exposure for day 1, as shown by the area under the concentration-time curve from 0 to 24 h (AUC(0-24)), was 1.96 mg . h/liter in group I and was 51% higher in group II and in group III. Increases in AUC(0-24) and maximum plasma concentration (C(max)) in groups II and III were dose related. The AUC(0-24) and C(max) values on day 1 were similar between groups II and III. There was interpatient variability of up to 68% in the pharmacokinetic values for our study population. Steady state was attained by days 5 to 6. Average steady-state plasma posaconazole trough values were 192, 219, and 414 ng/ml in groups I, II, and III, respectively. The AUC(0-24) and apparent oral clearance increased by increasing dose and dosing frequency. Mucositis appeared to reduce exposure but did not significantly affect mean total posaconazole exposure (AUC and C(max)) at steady state (P = 0.1483). Moreover, this reduction could be overcome by increasing the total dose and dosing frequency. Posaconazole was safe and well tolerated.

Antifungal Agents↗
PubMed2006

Effect of a nutritional supplement on posaconazole pharmacokinetics following oral administration to healthy volunteers.

We conducted a randomized, crossover study in healthy adults to examine the effects of a nutritional supplement (Boost Plus) on posaconazole pharmacokinetics. In this study, coadministration of posaconazole with Boost Plus increased the maximum concentration of posaconazole in serum and area under the concentration-time curve from 0 to 72 h values 3.4- and 2.6-fold, respectively, compared to those for the fasted state.

Administration, Oral↗
PubMed2005

Nano-assembly of manganese peroxidase and lignin peroxidase from P. chrysosporium for biocatalysis in aqueous and non-aqueous media.

Development, characterization, and activity studies of nano-assemblies of lignin peroxidase (LiP), and manganese peroxidase (MnP) from Phanerochaete chrysosporium on flat surfaces as well as colloidal particles have been investigated. These assemblies of LiP and MnP were fabricated with polyelectrolytes-poly(ethylenimine) (PEI), poly(dimethyldiallylammonium chloride) (PDDA), and poly(allylamine) (PAH)-using a layer-by-layer self-assembly technique (LbL). Characterization of these assemblies on flat surfaces was monitored using quartz crystal microbalance (QCM), while assemblies on microparticles such as melamine formaldehyde (MF) were carried out with zeta potential analyzer (ZPA). A unique dynamic adsorption-desorption of the enzyme layers is observed during the assembly. All the nano-assemblies of LiP and MnP can effectively oxidize veratryl alcohol (VA) to its aldehyde for an extended period of time. The effect of different polyions and the number of polyion layers on the activities of LiP and MnP nano-assembly was also examined. It is observed that drying of enzyme layer during the assembly and the use of non-aqueous media, such as acetone can significantly reduce the activity of the enzymes. Enzyme activity reaches a minimum when the concentration of acetone is increased to 30%; however, the activity can be restored to its original value by increasing the concentration of aqueous media. Preliminary studies using assemblies of LiP and MnP on MF microparticles further demonstrate the feasibility of developing potential systems for degradation of environmental pollutants.

Adsorption↗
PubMed2005

Oral bioavailability of posaconazole in fasted healthy subjects: comparison between three regimens and basis for clinical dosage recommendations.

BACKGROUND AND OBJECTIVE: Posaconazole is a potent, extended-spectrum triazole antifungal agent currently in clinical development for the treatment of invasive fungal infections. This study was conducted to compare the bioavailability and resulting serum concentrations of posaconazole 800 mg following administration of three different dose regimens to fasting adults. STUDY DESIGN: This was a randomised, open-label, three-way crossover study. METHODS: Subjects fasted 12 hours before and 48 hours after the administration of posaconazole oral suspension (800 mg) given as a single dose (regimen A), 400 mg every 12 hours (regimen B) or 200 mg every 6 hours (regimen C). Plasma posaconazole concentrations were determined for 48 hours after the initial dose and subjects completed a 1-week washout period between treatment regimens. A one-compartment oral model with first-order rate of absorption and first-order rate of elimination was fitted to the plasma concentration-time data. Differences in exposure were investigated by allowing the bioavailability fraction to vary among regimens. STUDY PARTICIPANTS: A total of 18 healthy men were enrolled in and completed the study. MAIN OUTCOME MEASURES AND RESULTS: Posaconazole relative bioavailability was estimated to be significantly different among regimens (p < 0.0001) and increased with the number of doses, such that regimen B/regimen A = 1.98 +/- 0.35, representing a 98% increase, and regimen C/regimen A = 3.20 +/- 0.69, or a 220% increase. With use of the one-compartment model, the population steady-state values for area under the concentration-time curve over 24 hours were predicted to be 3900, 7700 and 12 400 microg.h/L, with average plasma concentrations of 162, 320 and 517 microg/L for regimens A, B and C, respectively. CONCLUSION: These data suggest that divided daily dose administration (every 12 or 6 hours) significantly increases posaconazole exposure under fasted conditions.

Administration, Oral↗
PubMed2004

Neonatal anesthesia.

The physiology of the preterm and term neonate is characterized by a high metabolic rate, limited pulmonary, cardiac and thermoregulatory reserve, and decreased renal function. Multisystem immaturity creates important developmental differences in drug handling and response when compared to the older child or adult. Neonatal anesthetic management requires an understanding of the pharmacophysiologic limitations of the neonate as well as the pathophysiology of coexisting surgical disease. This review addresses the pertinent aspects of neonatal physiology and pharmacology, general considerations in the anesthetic care of surgical neonates, and concludes with a brief review of the anesthetic management of neonates with necrotizing enterocolitis, diaphragmatic hernia, and tracheoesophageal fistula.

Anesthesia↗
PubMed2004

Pharmacodynamics of a new triazole, posaconazole, in a murine model of disseminated candidiasis.

Previous in vivo studies have characterized the pharmacodynamic characteristics of two triazole compounds, fluconazole and ravuconazole. These investigations demonstrated that the 24-h area under the concentration-time curve (AUC)/MIC ratio is the critical pharmacokinetic-pharmacodynamic (PK-PD) parameter associated with treatment efficacy. Further analysis demonstrated that a free-drug triazole 24-h AUC/MIC ratio of 20 to 25 was predictive of treatment success in both experimental models and clinical trials. We used a neutropenic murine model of disseminated Candida albicans infection to similarly characterize the time course activity of the new triazole, posaconazole. The PK-PD parameters (percent time above MIC, AUC/MIC ratio, and peak serum drug level/MIC ratio) were correlated with in vivo efficacy, as measured by organism number in kidney cultures after 48 h of therapy. Kinetics and protein binding following oral posaconazole dosing were performed in neutropenic infected mice. Peak levels and AUC from 0 h to infinity values were nonlinear over the 16-fold dose range studied. Serum drug elimination half-life ranged from 12.0 to 17.7 h. Protein binding was 99%. Single dose postantifungal effect studies demonstrated prolonged suppression of organism regrowth after serum posaconazole levels had fallen below the MIC. Treatment efficacy with the four dosing intervals studied was similar, supporting the AUC/MIC ratio as the PK-PD parameter predictive of efficacy. Nonlinear regression analysis also suggested that the AUC/MIC ratio was strongly predictive of treatment outcomes (AUC/MIC ratio R(2) = 83%; peak serum drug/MIC ratio R(2) = 85%; time that serum levels of posaconazole remained above the MIC R(2) = 65%). Similar studies were conducted with 11 additional C. albicans isolates with various posaconazole susceptibilities (MIC, 0.015 to 0.12 micro g/ml) to determine if a similar 24-h AUC/MIC ratio was associated with efficacy. The posaconazole free-drug AUC/MIC ratios were similar for all of the organisms studied (6.12 to 26.7, mean +/- SD = 16.9 +/- 7.8, P value, 0.42). These free-drug AUC/MIC ratios are similar to those observed for other triazoles in this model.

Animals↗
PubMed2002

The use of in vitro metabolic stability for rapid selection of compounds in early discovery based on their expected hepatic extraction ratios.

PURPOSE: The in vivo hepatic extraction ratio of cynomolgus monkeys was correlated with the corresponding in vitro extraction ratios that were determined in monkey microsomal incubations. METHOD: For compounds that are eliminated mainly through liver phase I metabolism, the extraction ratio calculated from liver microsomal stability studies should correlate with their in vivo hepatic extraction ratios and also with their oral bioavailability in monkey. We used both well-stirred and parallel tube models of intrinsic clearance for the correlation. We also calculated extraction ratios for compounds within a given therapeutic area from fraction absorbed values that were estimated from the Caco-2 absorption model. RESULT: The present data show that in vitro extraction ratios in monkey microsomes are predictive of the in vivo hepatic extraction ratios in monkeys. All compounds with high extraction ratio (>70%) in vivo were successfully classified as high-extraction-ratio compounds based on the in vitro monkey microsomal stability data. From the results of this study, it appears that the parallel tube model provided a slightly better classification than the well-stirred model. CONCULUSIONS: The present method appears to be a valuable tool to rapidly screen and prioritize compounds with respect to liver first-pass metabolism in monkeys at an early phase of drug discovery.

Animals↗