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H Kastrissios

Publications and source records attributed to H Kastrissios.

At least 19 recordsLinked to original sources
PubMed2006

Development of a predictive pharmacokinetic model for a novel cyclooxygenase-2 inhibitor.

A predictive population pharmacokinetic model was developed for a novel cyclooxygenase-2 (COX-2) inhibitor CS-706, using data from 130 subjects in 3 phase 1 trials after single or multiple doses of CS-706 (2- to 800-mg doses daily, up to 14 days) and validated using sparse data from a separate study. A 2-compartment model described the data. Typical apparent clearance (CL/F) was 47.2 L/h and was reduced by 43% at doses greater than 200 mg. Apparent clearance was decreased by 38% in female subjects and by 64% and 15%, respectively, in poor/intermediate CYP 2D6 and poor CYP 2C9 metabolizers. Typical apparent volume of the central compartment was 166 L and increased with body weight. Bioavailability increased by 42% after nighttime doses and decreased saturably with increasing dose (50% reduction at 221 mg). Predicted exposures in Japanese subjects were reduced relative to whites because of a lower frequency of poor metabolizers. The model may aid in optimizing the design of future studies and predicting exposures in other subpopulations.

Adult↗
PubMed2003

A phase I and pharmacokinetic study of irinotecan in patients with hepatic or renal dysfunction or with prior pelvic radiation: CALGB 9863.

BACKGROUND: To ascertain if hepatic or renal dysfunction or prior pelvic radiation (XRT) leads to increased toxicity at a given dose of irinotecan and to characterize the pharmacokinetics of irinotecan and its major metabolites in patients with hepatic or renal dysfunction. PATIENTS AND METHODS: Adults with tumors appropriate for irinotecan therapy and who had abnormal liver or renal function tests or had prior radiation to the pelvis were eligible. Patients were assigned to one of four treatment cohorts: I, aspartate aminotransferase (AST) > or = 3x upper limit of normal and direct bilirubin <1.0 mg/dl; II, direct bilirubin 1.0-7.0 mg/dl; III, creatinine 1.6-5.0 mg/dl with normal liver function; IV, prior pelvic XRT with normal liver and renal function. Starting with reduced doses of either 145 or 225 mg/m(2), irinotecan was administered every 3 weeks to at least three patients within each cohort. Irinotecan and its metabolites in the blood were measured in all patients. RESULTS: Thirty-five patients were evaluable for toxicity. No dose-limiting toxicity was seen in cohort I, although only three patients were treated and at a dose of 225 mg/m(2). Patients with elevations of direct bilirubin had dose-limiting toxicities, even though the starting dose was 145 mg/m(2). These same patients appeared to have comparable exposure to the active metabolite SN-38 as normal patients treated with full-dose irinotecan. Patients with elevations of creatinine or with prior pelvic radiotherapy did not appear to have increased risk of toxicity at the doses explored in this study. CONCLUSIONS: Patients with elevated bilirubin treated with irinotecan have an increased risk of toxicity and a dose reduction is recommended. Patients with elevated AST, creatinine or prior pelvic radiation do not appear to have increased sensitivity to irinotecan, but the data are not adequate to support a specific dosing recommendation.

Adult↗
PubMed2001

Pharmacokinetics of diaspirin cross-linked haemoglobin in a rat model of hepatic cirrhosis.

The aim of the study was to evaluate the effect of cirrhosis on the disposition of the haemoglobin-based oxygen carrier, diaspirin cross-linked haemoglobin (DCLHb). Cirrhosis was induced in male Sprague-Dawley rats (200-250 g) by inhalational exposure to carbon tetrachloride (CCl4), over a period of 6 weeks. Pharmacokinetic evaluation was performed after a single intravenous bolus administration of DCLHb (400 mg kg(-1)). Serum biochemistry, including aspartate transaminase, alkaline phosphatase, bile acids, serum albumin, and serum creatinine, were measured in CCl4-treated (n = 6) and age-matched control (n = 6) rats. After 6 weeks, the jugular vein and carotid artery were cannulated for bolus DCLHb administration (400 mg kg(-1)) and blood sampling, respectively, in both groups of rats. Cirrhosis produced significant (P < 0.05) elevations in alkaline phosphatase (497.4 +/- 84.8 U L(-1) vs 241.2 +/- 5.1 U L(-1)), aspartate transaminase (920.5 +/- 190.9 U L(-1) vs 238.2 +/- 118.1 U L(-1)) and bile acids (333.8 +/- 77.3 mg dL(-1) vs 43.8 +/- 4.2 mg dL(-1)) compared with the control group. No significant renal dysfunction was observed as a result of CCl4 exposure. Plasma DCLHb concentrations declined approximately log-linearly. Systemic clearance of DCLHb was estimated to be 2.2 +/- 0.7 mL h(-1) in the treatment group and was slightly, but not significantly, less in the control group (3.6 +/- 1.7 mL h(-1)). There was also a trend toward a longer elimination half-life in the treatment group (4.7 +/- 2.2 h) compared with the control group (3.8 +/- 0.8 h), although this difference was not statistically significant. Cirrhosis does not significantly alter the disposition of DCLHb perhaps due to increased extra-hepatic metabolism by the reticulo-endothelial system.

Animals↗
PubMed2000

Phase I and pharmacokinetic study of irinotecan and docetaxel in patients with advanced solid tumors: preliminary evidence of clinical activity.

PURPOSE: The goals of this study were to determine the maximum-tolerated dose and describe the toxicities of the combination of irinotecan and docetaxel administered every 3 weeks to patients with advanced malignancies and, also, to evaluate the effect of irinotecan on the disposition of docetaxel and describe preliminary evidence of antitumor activity. PATIENTS AND METHODS: Eighteen patients received 85 courses (median, two courses; range, one to 15 courses) of treatment with irinotecan, administered over 90 minutes by intravenous infusion, followed by docetaxel, administered over 60 minutes by intravenous infusion. Four escalating dose levels of irinotecan/docetaxel (160/50 mg/m(2), 160/65 mg/m(2), 200/65 mg/m(2), and 200/75 mg/m(2)) were studied. Pharmacokinetic analyses were performed to evaluate the effect of irinotecan on the disposition of docetaxel. RESULTS: The most common and dose-limiting toxicity was myelosuppression, which consisted of neutropenia that was severe (National Cancer Institute common toxicity criteria [NCI CTC] grade 4) but brief (< 5 days) in 11 patients, with three episodes of febrile neutropenia. Nonhematologic toxicities of anorexia, nausea, and stomatitis were mild to moderate (NCI CTC grades 1 and 2), but there was one incidence each of both CTC grade 3 anorexia and nausea. All patients had total alopecia. Diarrhea was dose-dependent and severe in four patients who failed to take adequate antidiarrhea therapy. Five out of 16 assessable patients, one with cholangiocarcinoma, one with leiomyosarcoma, and three with non-small-cell lung cancer, achieved partial remissions. CONCLUSION: The combination of irinotecan and docetaxel causes significant reversible myelosuppression, which was dose limiting but led to no serious sequelae. There was no evidence of a clinically significant interaction using these two agents in this sequence. The combination showed antitumor activity at all the dose levels tested and should be further studied in a number of tumor types. The recommended phase II dose on this schedule is irinotecan 160 mg/m(2) and docetaxel 65 mg/m(2).

Adult↗
PubMed1998

Characterizing patterns of drug-taking behavior with a multiple drug regimen in an AIDS clinical trial.

OBJECTIVE: To characterize drug-taking behavior using continuous electronic monitoring in an AIDS clinical trial. SETTING: This was a substudy of AIDS Clinical Trials Group (ACTG) protocol 175, a phase II/III study of dideoxynucleoside monotherapy versus combination therapy in asymptomatic HIV-positive subjects. Participants were required to comply with regimens containing zidovudine, zalcitabine and didanosine, or matching placebos; the total daily pill count was 16. DESIGN: For participants at two ACTG 175 sites, electronic devices were used to monitor drug-taking behavior of all study medications over a period of approximately 90 days. MEASUREMENTS: Four indices of drug-taking behavior were calculated and their distributions and relationship to the prescribed regimen were examined. RESULTS: Data from 41 subjects were analyzed. Of the prescribed doses of zidovudine, zalcitabine and didanosine, 88, 84 and 82%, respectively, were taken. Of these, 55, 66 and 79%, respectively, were taken at the prescribed dosing frequency. The median percentage of days on which participants failed to take any of the doses was 2-5%. There was a trend towards lower adherence in the combination therapy arms compared with those assigned to receive monotherapy. In this analysis, older patients demonstrated better adherence, although patient characteristics, in general, were poorly predictive of adherence. CONCLUSION: Drug-taking behavior for all three active study medications differed from that prescribed. One result of this erratic adherence was that study participants sustained little antiretroviral effect during more than 25% of the monitoring period.

Acquired Immunodeficiency Syndrome↗
PubMed1998

The extent of non-adherence in a large AIDS clinical trial using plasma dideoxynucleoside concentrations as a marker.

OBJECTIVES: To assess adherence to study medications in an AIDS clinical trial, to evaluate whether study participants adhered to only one component of a multidrug regimen ('differential adherence'), and to determine whether there was evidence of non-uniform adherence to study medications among treatment groups. SETTING: This was a substudy of AIDS Clinical Trials Group protocol 175, a large, double-blind, randomized study of monotherapy versus combination dideoxynucleoside therapy. Participants were required to adhere to a complex regimen of zidovudine, zalcitabine and didanosine, or their matching placebos. DESIGN: Between October 1992 and January 1994, study sites were selected at random, and a 1-week period was designated during which study participants attending routine clinic visits provided a blood sample and dosing history. Participants were not informed of the purpose of the substudy. MEASUREMENTS: Adherence was assessed using plasma drug concentrations and defined by the presence of detectable drug in a plasma sample obtained within a specified analysis window. RESULTS: Of 722 plasma samples analyzed, approximately 75% contained detectable concentrations of the assigned drugs and 5-14.5% contained no detectable drugs. Approximately 7 and 13% of samples from participants assigned to monotherapy arms contained non-prescribed dideoxynucleosides, and 14 and 19% assigned to combination therapies contained only one drug. CONCLUSIONS: Various non-adherence behaviors were observed, including patterns of underdosing and taking non-prescribed drugs. Non-adherence was moderate but uniform amongst the treatment groups and may have contributed to a marginal reduction in the power of the primary intent-to-treat analysis to detect differences in efficacy amongst the assigned treatments.

Acquired Immunodeficiency Syndrome↗
PubMed1998

A Markov mixed effect regression model for drug compliance.

Patient compliance (adherence) with prescribed medication is often erratic, while clinical outcomes are causally linked to actual, rather than nominal medication dosage. We propose here a hierarchical Markov model for patient compliance. At the first stage, conditional upon individual random effects and a set of individual-specific nominal daily dose times, we assume that (i) the subject-specific probability of taking zero, one, or more than one dose associated with a given nominal dose time depends on the value of certain covariates, and on the number of doses associated with the immediate previous time, but is independent of any other previous or future dosing events (the Markov hypothesis); and (ii) the set of 'errors' between actual dose times associated with each nominal time is multivariate normally distributed, conditional on covariates and the number of such actual dose times, as in (i). At the second stage, a multivariate normal distribution is assumed for the individual random effects. We fit this model by maximum likelihood to data collected over three months using an electronic system for recording actual dose times in HIV-positive patients assigned to a regimen of zidovudine thrice daily. Beyond its value for describing and quantifying compliance behaviour, as illustrated here, the model may prove useful for explanatory analyses of clinical trials.

Anti-HIV Agents↗
PubMed1997

Pharmacokinetics of saquinavir, zidovudine, and zalcitabine in combination therapy.

We investigated the pharmacokinetics of zidovudine, zalcitabine, and saquinavir in AIDS Clinical Trial Group protocol 229. Patients received either saquinavir, zalcitabine, or a combination of both, together with zidovudine three times a day. Approximately 100 patients were enrolled in each treatment arm, and intensive pharmacokinetic studies were performed on about 25 patients per arm at weeks 1 and 12. We estimated the pharmacokinetic parameters of all three drugs by using parametric and nonparametric methods. The mean values of the pharmacokinetic parameters of zidovudine (clearance [CL]/bioavailability [F], 168 liters/h; volume of distribution [V]/F, 185 liters; half-life, 0.76 h) and zalcitabine (CL/F, 25 liters/h; V/F, 92.2 liters; half-life, 2.7 h) were similar to those reported previously. For saquinavir, the mean pharmacokinetic parameter estimates using parametric methods were as follows: maximum concentration of drug in serum [Cmax], 70.8 ng/ml; time to Cmax, 3.11 h; area under the curve, 809 ng x h/ml; CL/F, 989 liters/h; V/F, 1,503 liters; half-life, 1.38 h. For all three drugs, clearance decreased with age. Weight did not influence the clearance of zidovudine, but the clearance of zalcitabine and saquinavir increased with weight. There were no differences in pharmacokinetic parameters between study weeks and arms, suggesting that there is no change in kinetics with chronic administration and that there are no significant pharmacokinetic interactions among these three drugs.

Adult↗
PubMed1997

Medication compliance as a feature in drug development.

Well-designed clinical trials maximize the information that can be obtained regarding the clinical pharmacology of a drug and, in turn, can streamline and enhance the drug development process. Until recently, little emphasis has been placed on integrating the role of variability in individual patterns of drug-taking into the drug development process. With the use of electronic monitoring, the temporal relationship between an individual's pattern of dosing and the prescribed regimen may be examined, and individual drug exposure may be estimated based on the actual history of dosing. As a result, accurate estimation of exposure-response relationships (or surrogate markers of response) can be obtained. Considerations in the design of clinical trials must therefore be expanded to include appropriate methods to measure compliance, sufficient frequency of monitoring to allow the time course of response to be mapped, and the use of statistically valid methods of data analysis.

Clinical Trials as Topic↗
PubMed1996

Do we need full compliance data for population pharmacokinetic analysis?

For population pharmacokinetic analysis of multiple oral doses one of the key issues is knowing as precisely as possible the dose inputs in order to fit a model to the input-output (dose-concentration) relationship. Recently developed electronic monitoring devices, placed on pill containers, permit precise records to be obtained over months, of the time/date opening of the container. Such records are reported to be the most reliable measurement of drug taking behavior for ambulatory patients. To investigate strategies for using and summarizing this new abundant information, a Markov chain process model was developed, that simulates compliance data from real data from electronically monitored patients, and data simulations and analyses were conducted. Results indicate that traditional population pharmacokinetic analysis methods that ignore actual dosing information tend to estimate biased clearance and volume and markedly overestimate random interindividual variability. The best dosing information summarization strategies consist of initially estimating population pharmacokinetic parameters, using no covariates and only a limited number of dose records, the latter chosen based on an a priori estimate of the half-life of the drug in the compartment of interest; then resummarizing the dose records using either population or individual posterior Bayes parameter estimates from the first population fit; and finally reestimating the population parameters using the newly summarized dose records. Such summarization strategies yield the same parameter estimates as using full dosing information records while reducing by at least 75% the CPU time needed for a population pharmacokinetic analysis.

Administration, Oral↗
PubMed1996

Pharmacokinetics of high-dose oral CCNU in bone marrow transplant patients.

PURPOSE: CCNU (lomustine) and other nitrosourea compounds are rapidly metabolized to alkylating moieties, which are active against various malignancies. In humans, CCNU undergoes biotransformation to the geometric isomers of 4'-hydroxyCCNU. The pharmacokinetics of trans-and cis-4'-hydroxyCCNU were determined in five patients with Hodgkin's or non-Hodgkin's lymphoma receiving sequential doses of CCNU (15 mg/kg), etoposide (60 mg/kg) and cyclophosphamide (100 mg/kg) prior to autologous bone marrow transplantation. METHODS: Plasma concentrations of the isomeric forms of the metabolites were determined by high-performance liquid chromatography. Data were analysed using noncompartmental pharmacokinetic methods. RESULTS: Formation of the trans-isomer predominated over that of the cis-isomer, with an average exposure ratio of 1.4 (range 1.0-2.1). Peak plasma concentrations occurred between 1 and 4.1 h postdosing and averaged 1.56 mg/l for the trans-isomer and 1.10 mg/l for cis isomer. Peak plasma concentrations and systemic exposures varied approximately six- and ninefold, respectively, reflecting significant interindividual variability in alkylating activity after high doses of CCNU. Plasma half-lives of the metabolites were 3.1 h (range 1.1-4.5 h) for the trans-isomer and 3.5 h (range 1.3-6.4 h) for the cis- isomer, and varied linearly with increasing patient body weight. There was no significant difference in plasma half-lives after high-dose CCNU administration observed in this study and those reported previously after the administration of substantially lower doses of CCNU. CONCLUSION: Despite linearity in the pharmacokinetics of the isomeric forms of 4'-hydroxyCCNU at high doses, large interindividual variability in exposure to the CCNU metabolites was observed. Potential saturation of metabolic pathways to the isomers at these doses may manifest as toxic symptoms since alkylating moieties formed directly from the parent, CCNU, may be associated with greater toxicity than those formed from the isomeric forms of the 4'-hydroxylated metabolite.

Administration, Oral↗
PubMed1996

Introducing medical students to medication noncompliance.

Medical students were introduced to issues relating to medication noncompliance in a simulated clinical setting. Compliance with either a twice-a-day or a three-times-a-day regimen was monitored with use of electronic monitoring devices for a 2-week interval. Compliance with the twice-a-day regimen was higher than compliance with the three-times-a-day regimen, although the difference was not significantly different. Overall, 71% of the prescribed doses were taken by the medical student participants; however, only 46.5% of the doses were taken at the prescribed dosing frequency and 28.5% were taken at the prescribed intervals. The majority of students linked dose taking with routine daily activities and reported that their hectic lifestyles adversely influenced compliance. Similar factors might be expected to influence compliance in patient populations. The goal of this exercise was to demonstrate to future physicians the difficulties that patients have with compliance to prescribed medications.

California↗
PubMed1995

A new preparatory regimen for autologous bone marrow transplantation for patients with lymphoma.

BACKGROUND: This trial studied the feasibility and efficacy of a new preparatory regimen for autologous bone marrow transplantation for patients with advanced lymphoid malignancies. METHODS: Twenty-one patients with Hodgkin's disease (n = 12) and non-Hodgkin's lymphoma (n = 9) were treated in this study. Lomustine was substituted for carmustine) in a dose-escalation study with an initial dose of 6 mg/kg and increasing by 3 mg/kg in groups of four patients. The preparatory regimen consisted of lomustine (6-15 mg/kg) orally on Day -6, etoposide (60 mg/kg) intravenously (i.v.) on Day -4, and cyclophosphamide (100 mg/kg) i.v. on Day -2. Peripheral blood progenitor cells and/or bone marrow were infused on Day 0. RESULTS: Lomustine was well tolerated in all patients with no significant toxicity specific to this drug. Engraftment was prompt: the time to achieving greater than or equal to 500 granulocytes/microliters was 12 days (range, 9-16 days) and the time to achieving greater than or equal to 25,000 platelets/microliters without transfusion support was 16 days (range, 9-22 days). Five patients experienced interstitial pneumonitis, three of whom had active or recent interstitial pneumonitis before bone marrow transplantation, and one who just completed mantle irradiation. Three patients died from this preparatory regimen, one of progressive interstitial pneumonitis, one of Legionella pneumonia, and one of multiorgan failure. Three patients with non-Hodgkin's lymphoma relapsed. Fourteen patients are currently alive and disease free to date. The actuarial are currently alive and disease free to date. The actuarial disease free survival was 57%, with a median follow-up of 23 months (range, 1-48 months). CONCLUSION: The preparatory regimen consisting of lomustine/etoposide/cyclophosphamide is active in treating patients with lymphomas. Further trials with high doses of lomustine are warranted.

Adolescent↗
PubMed1993

Plasma concentrations of bupivacaine after wound infiltration of an 0.5% solution after inguinal herniorrhaphy: a preliminary study.

After routine inguinal herniorrhaphy we gave 12 patients a wound infiltration regimen of bolus doses of 20 ml of 0.5% bupivacaine via a catheter within the wound and rectally administered indomethacin (100 mg). Peak venous plasma bupivacaine concentrations ranged from 0.07 mg.l-1 to 1.14 mg.l-1 (mean (SD) 0.47 (0.33) mg.l-1), and occurred at between 0.25 and 2 h after the first dose. Plasma concentrations were well below the toxic threshold of 4 mg.l-1 and there was no accumulation. The regimen provided satisfactory analgesia. There were no wound infections nor signs of toxicity.

Adult↗
PubMed1992

High-performance liquid chromatographic method for the quantitation of bupivacaine, 2,6-pipecoloxylidide and 4'-hydroxybupivacaine in plasma and urine.

A high-performance liquid chromatographic method with ultraviolet detection at 210 nm for quantitation of bupivacaine and two of its metabolites from plasma and urine is described. The compounds are extracted into n-hexane-isopropanol (5:1), evaporated and the reconstituted residue injected onto a reversed phase C18 column. Standard curves for all compounds were linear (r2 greater than 0.999) in the range 20-2000 ng/ml, with a limit of detection of 10 ng/ml. The inter-day coefficients of variation ranged between 2.7 and 12.2%. The method was applied to analyse bupivacaine and metabolite concentrations in patients on long-term epidural bupivacaine-fentanyl infusions.

Bupivacaine↗
PubMed1991

The disposition of bupivacaine following a 72 h interpleural infusion in cholecystectomy patients.

The disposition of bupivacaine and degree of analgesia following a 72 h interpleural infusion was investigated in 12 adult patients undergoing elective cholecystectomy. The infusion regimen of an initial interpleural bolus dose of 20 ml of 0.5% bupivacaine HCl with adrenaline (1:200,000) followed by continuous infusion at a rate of 8 ml h-1 of 0.25% plain bupivacaine HCl was designed to achieve continuous post-operative pain relief for 72 h. In practice an additional bolus dose (identical to the first) administered 5 h after infusion commencement was required to achieve adequate pain relief on the first postoperative day. The mean measured steady-state plasma bupivacaine concentration was 2.1 mg l-1 (s.d. +/- 0.54, range 1.3-3.2 mg l-1). Disposition parameters for bupivacaine measured for the infusion were calculated by non-compartmental methods and compared with previous values obtained after single and multiple interpleural bolus dose administration. No statistically significant differences were noted and, in particular, the systemic clearance of bupivacaine (mean 10.2 l h-1 s.d +/- 3.0; range 6.3-16.0 1 h-1) remained unchanged following the long-term interpleural infusion. Analgesia was deemed satisfactory throughout the entire post-operative period.

Adult↗