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David OJ, Behrje R, Pal P, Hara H, Lates CD, Schmouder R. Pharmacokinetic Interaction Between Fingolimod and Carbamazepine in Healthy Subjects. Clin Pharmacol Drug Dev 2018; 7:575-586. [PMID: 29694732 PMCID: PMC6099239 DOI: 10.1002/cpdd.459] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 02/13/2018] [Indexed: 01/26/2023]
Abstract
This open‐label, single‐sequence study in healthy subjects investigated the effects of steady‐state carbamazepine on the pharmacokinetic (PK) profile of a single 2‐mg dose of fingolimod. In period 1, a single oral dose of fingolimod 2 mg (day 1) was followed by PK and safety assessments up to 36 days. In period 2, carbamazepine was administered in flexible, up‐titrated doses (600 mg twice daily maximum) for 49 days. Fingolimod was administered on day 35, followed by a study completion evaluation (day 71). The PK analysis included 23 of 26 of the enrolled subjects (88.5%). Coadministration of fingolimod at steady‐state carbamazepine concentrations resulted in increased fingolimod CL/F by 67% through the induction of CYP3A4, a cytochrome with negligible involvement in fingolimod clearance in an uninduced state. Fingolimod Cmax was reduced by 18% and AUCinf by 40%, as was T1/2 (106 vs 163 hours). A similar trend was observed for fingolimod‐P. Models linking fingolimod‐P blood concentrations to lymphocyte count or annual relapse rate suggest that such a decrease would have a low impact on the treatment effect. However, in the absence of efficacy data of fingolimod at doses lower than the therapeutic dose, their coadministration should be used with caution.
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Affiliation(s)
| | - Rhett Behrje
- Novartis Pharmaceuticals Corporation, East Hanover, NJ, USA
| | - Parasar Pal
- Novartis Healthcare Private Limited, Hyderabad, India
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Time-dependent pharmacokinetics of dexamethasone and its efficacy in human breast cancer xenograft mice: a semi-mechanism-based pharmacokinetic/pharmacodynamic model. Acta Pharmacol Sin 2018; 39:472-481. [PMID: 29119968 DOI: 10.1038/aps.2017.153] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 06/30/2017] [Indexed: 12/19/2022] Open
Abstract
Dexamethasone (DEX) is the substrate of CYP3A. However, the activity of CYP3A could be induced by DEX when DEX was persistently administered, resulting in auto-induction and time-dependent pharmacokinetics (pharmacokinetics with time-dependent clearance) of DEX. In this study we investigated the pharmacokinetic profiles of DEX after single or multiple doses in human breast cancer xenograft nude mice and established a semi-mechanism-based pharmacokinetic/pharmacodynamic (PK/PD) model for characterizing the time-dependent PK of DEX as well as its anti-cancer effect. The mice were orally given a single or multiple doses (8 mg/kg) of DEX, and the plasma concentrations of DEX were assessed using LC-MS/MS. Tumor volumes were recorded daily. Based on the experimental data, a two-compartment model with first order absorption and time-dependent clearance was established, and the time-dependence of clearance was modeled by a sigmoid Emax equation. Moreover, a semi-mechanism-based PK/PD model was developed, in which the auto-induction effect of DEX on its metabolizing enzyme CYP3A was integrated and drug potency was described using an Emax equation. The PK/PD model was further used to predict the drug efficacy when the auto-induction effect was or was not considered, which further revealed the necessity of adding the auto-induction effect into the final PK/PD model. This study established a semi-mechanism-based PK/PD model for characterizing the time-dependent pharmacokinetics of DEX and its anti-cancer effect in breast cancer xenograft mice. The model may serve as a reference for DEX dose adjustments or optimization in future preclinical or clinical studies.
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Lee D, Kalu U, Halford JJ, Biton V, Cloyd J, Klein P, Bekersky I, Peng G, Dheerendra S, Tolbert D. Intravenous carbamazepine as short-term replacement therapy for oral carbamazepine in adults with epilepsy: Pooled tolerability results from two open-label trials. Epilepsia 2015; 56:906-14. [PMID: 25912051 DOI: 10.1111/epi.12991] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/06/2015] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To report tolerability findings and maintenance of seizure control from a pooled analysis of phase I open-label trial OV-1015 (NCT01079351) and phase III study 13181A (NCT01128959). METHODS Patients receiving a stable oral dosage of carbamazepine were switched to an intravenous (IV) carbamazepine formulation solubilized in a cyclodextrin matrix (at a 70% dosage conversion) for either a 15- or a 30-min infusion every 6 h for up to 7 days and then switched back. A subset of patients who tolerated 15-min infusions also received 2- to 5-min (rapid) infusions. Assessments included physical and laboratory evaluations, electrocardiography (ECG) studies, as well as adverse event (AE) monitoring for tolerability. Convulsion/seizure AE terms and data from seizure diaries were used as proxies for the assessment of consistency of seizure control between formulations. RESULTS Of the 203 patients exposed to IV carbamazepine (30 min, n = 43; 15 min, n = 160), 113 received 149 rapid infusions. During infusion, the most commonly reported AEs (≥ 5%) were dizziness (19%), somnolence (6%), headache (6%), and blurred vision (5%). IV carbamazepine was not associated with clinically relevant cardiac AEs. The tolerability profile appeared similar between patients who received <1,600 mg/day (n = 174) and ≥ 1,600 mg/day (n = 29) carbamazepine. Cyclodextrin exposure was not associated with clinically relevant changes in AEs or renal biomarkers. Seizure control was maintained as patients transitioned between oral and IV carbamazepine. SIGNIFICANCE IV carbamazepine administered as multiple 30- or 15-min infusions every 6 h, and as a single rapid infusion, was well tolerated as a short-term replacement in adults with epilepsy receiving stable dosages of oral carbamazepine. Infusion site reactions, which were generally mild, were the only unique AEs identified; seizure control was generally unchanged when patients were switching between formulations.
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Affiliation(s)
| | - Uwa Kalu
- Lundbeck LLC, Deerfield, Illinois, U.S.A
| | - Jonathan J Halford
- Comprehensive Epilepsy Center, Medical University of South Carolina, Charleston, South Carolina, U.S.A
| | - Victor Biton
- Arkansas Epilepsy Program, Little Rock, Arkansas, U.S.A
| | - James Cloyd
- Center for Orphan Drug Research, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota, U.S.A
| | - Pavel Klein
- Mid-Atlantic Epilepsy and Sleep Center, Bethesda, Maryland, U.S.A
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Maheswari E, Saraswathy GRL, Santhranii T. Hepatoprotective and antioxidant activity of N-acetyl cysteine in carbamazepine-administered rats. Indian J Pharmacol 2014; 46:211-5. [PMID: 24741196 PMCID: PMC3987193 DOI: 10.4103/0253-7613.129321] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 09/01/2013] [Accepted: 02/03/2014] [Indexed: 12/20/2022] Open
Abstract
Objectives: The present study evaluates the hepatoprotective activity of N-acetyl cysteine (NAC) against carbamazepine (CBZ)-induced hepatotoxicity. Materials and Methods: Rats were treated with CBZ (50 mg/kg p.o.) and CBZ supplemented with NAC 50, 100 and 200 mg/kg for 45 days, after which blood samples were collected and subjected to liver function tests. Animals were killed, liver was separated, weighed and the levels of antioxidants and liver enzymes were estimated. In addition, histopathological investigation was also performed. Results: Serum glutamate pyruvate transaminase (SGPT), serum glutamate oxaloacetate (SGOT) transaminase, alkaline phosphatase (ALP), bilirubin, lipid peroxidation, absolute and relative liver weights were significantly (P < 0.05) elevated, whereas serum levels of albumin, total protein and body weight were decreased in the CBZ-treated animals. CBZ also produced vacuolar degeneration, centrilobular congestion and hepatic necrosis as evidenced from histopathological report. NAC significantly reduced the levels of serum transaminase, ALP, bilirubin and liver weight and increased the levels of total protein, albumin and body weight. Conclusion: It was observed that NAC increased the glutathione (GSH) content, reduced lipid peroxidation and reversed the CBZ-induced histopathological abnormalities. CBZ-induced hepatotoxicity may be due its toxic epoxide metabolite-induced oxidative stress.
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Affiliation(s)
- Eswaran Maheswari
- Department of Pharmacology, M.S. Ramaiah College of Pharmacy, Rajiv Gandhi University of Health Sciences, Bangalore, Karnataka, India
| | - Ganesan Raja Lekshmi Saraswathy
- Department of Pharmacology, M.S. Ramaiah College of Pharmacy, Rajiv Gandhi University of Health Sciences, Bangalore, Karnataka, India
| | - Thakur Santhranii
- Department of Pharmacology, Institute of Pharmaceutical Technology, Sri Padmavathi Mahila Visvavidyalayam (Women's University), Tirupati, Andhra Pradesh, India
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Šíma M, Netíková I, Slanař O. Pregnane xenobiotic receptors and their effect on drug elimination from the organism. Prague Med Rep 2014; 114:205-13. [PMID: 24485337 DOI: 10.14712/23362936.2014.9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Nuclear receptors are intracellular proteins which, having been activated by their more or less specific ligands, regulate (usually increase) the transcription of target genes. They thus participate in a regulation of a number of physiologic functions. Some of them - especially pregnane xenobiotic receptors - serve primarily as protection of the organism from the xenobiotic intoxication. This is because many xenobiotics activate their function which consists in increasing the gene expression of enzymes involved in the metabolism of xenobiotics and detoxication drug transporters. Clarification of these mechanisms enabled the understanding of the substance of many drug-drug interactions observed in the clinical practice. Polymorphism of the nuclear receptors appears to be one of the causes of the interindividual variability in response to drug administration.
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Affiliation(s)
- M Šíma
- Institute of Pharmacology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - I Netíková
- Institute of Pharmacology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - O Slanař
- Institute of Pharmacology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech RepublicInstitute of Pharmacology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
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6
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Fan J, de Lannoy IA. Pharmacokinetics. Biochem Pharmacol 2014; 87:93-120. [DOI: 10.1016/j.bcp.2013.09.007] [Citation(s) in RCA: 169] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 09/06/2013] [Accepted: 09/09/2013] [Indexed: 11/29/2022]
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Lin Z, Fisher JW, Wang R, Ross MK, Filipov NM. Estimation of placental and lactational transfer and tissue distribution of atrazine and its main metabolites in rodent dams, fetuses, and neonates with physiologically based pharmacokinetic modeling. Toxicol Appl Pharmacol 2013; 273:140-58. [DOI: 10.1016/j.taap.2013.08.010] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 08/07/2013] [Accepted: 08/10/2013] [Indexed: 11/27/2022]
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The interactions of atorvastatin and fluvastatin with carbamazepine, phenytoin and valproate in the mouse maximal electroshock seizure model. Eur J Pharmacol 2012; 674:20-6. [DOI: 10.1016/j.ejphar.2011.10.030] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2011] [Revised: 09/12/2011] [Accepted: 10/15/2011] [Indexed: 11/21/2022]
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Cawello W, Nickel B, Eggert-Formella A. No pharmacokinetic interaction between lacosamide and carbamazepine in healthy volunteers. J Clin Pharmacol 2009; 50:459-71. [PMID: 19841161 DOI: 10.1177/0091270009347675] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Lacosamide is a new antiepileptic drug for adjunctive treatment of adult partial-onset seizures. Two open-label, multiple-dose clinical trials were conducted to evaluate the potential for pharmacokinetic interaction between lacosamide and carbamazepine. The influence of carbamazepine on lacosamide pharmacokinetics (trial A) and lacosamide on carbamazepine pharmacokinetics (trial B) was investigated in 19 (trial A) and 18 (trial B) healthy male participants. Trial A participants received lacosamide 200 mg bid alone and with carbamazepine 200 mg bid. Trial B participants received carbamazepine 200 mg bid alone and with lacosamide 200 mg bid. Pharmacokinetic parameters, area under the concentration-time curve during a dosage interval at steady state (AUC(tau,ss)), and maximum steady-state plasma drug concentration during a dosage interval (C(max,ss)) of lacosamide, carbamazepine, and carbamazepine-10,11-epoxide were measured and compared for each drug alone and together. The AUC(tau,ss) and C(max,ss) point estimates (combined vs sole treatment) showed relative bioavailability of approximately 100% for both drugs. All 90% confidence intervals of AUC(tau,ss) and C(max,ss) were within the generally accepted bioequivalence ranges of 80% to 125%. No changes in rate or extent of absorption or terminal half-life were observed. These results suggest that lacosamide and carbamazepine have a low potential for pharmacokinetic drug-drug interaction in clinical use.
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Affiliation(s)
- Willi Cawello
- SCHWARZ BIOSCIENCES GmbH, A Member of the UCB Group, Global Exploratory Development, Pharmacometrics, Alfred-Nobel-Strasse 10, D-40789 Monheim, Germany.
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Eyer F, Jung N, Neuberger H, Witte A, Poethko T, Henke J, Zilker T. Seromucosal Transport of Intravenously Administered Carbamazepine Is Not Enhanced by Oral Doses of Activated Charcoal in Rats. Basic Clin Pharmacol Toxicol 2008; 102:337-46. [DOI: 10.1111/j.1742-7843.2007.00193.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Ahmed SN, Siddiqi ZA. Antiepileptic drugs and liver disease. Seizure 2006; 15:156-64. [PMID: 16442314 DOI: 10.1016/j.seizure.2005.12.009] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2004] [Revised: 12/11/2005] [Accepted: 12/28/2005] [Indexed: 12/11/2022] Open
Abstract
Antiepileptic drugs (AEDs) are no longer restricted to the treatment of epilepsy. These are widely used in a broad spectrum of psychiatric and neurological disorders. Liver plays a major role in the metabolism of a majority of these drugs. Hepatotoxicity is rare, but a real concern when initiating therapy. Likewise, liver disease can adversely affect the biotransformation of some of these drugs. This manuscript addresses the significance of elevated liver enzymes associated with AED use, the role of therapeutic drug monitoring, pharmacokinetics during liver disease and potential risk of hepatotoxicity.
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Affiliation(s)
- Syed Nizamuddin Ahmed
- University of Alberta, 2E3.12 Walter C. Mackenzie Centre, 8440-112 Street, Edmonton, Alta., Canada T6G 2B7.
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Huitema AD, Mathôt RA, Tibben MM, Rodenhuis S, Beijnen JH. A mechanism-based pharmacokinetic model for the cytochrome P450 drug-drug interaction between cyclophosphamide and thioTEPA and the autoinduction of cyclophosphamide. J Pharmacokinet Pharmacodyn 2001; 28:211-30. [PMID: 11468938 DOI: 10.1023/a:1011543508731] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cyclophosphamide (CP) is widely used in high-dose chemotherapy regimens in combination with thioTEPA. CP is a prodrug and is activated by cytochrome P450 to 4-hydroxycyclophosphamide (HCP) which yields the final cytotoxic metabolite phosphoramide mustard (PM). The metabolism of CP into HCP exhibits autoinduction but is inhibited by thioTEPA. The aim of this study was to develop a population pharmacokinetic model for the bioactivation route of CP incorporating the phenomena of both autoinduction and the drug-drug interaction between CP and thioTEPA. Plasma samples were collected from 34 patients who received high-dose CP, thioTEPA and carboplatin in short infusions during 4 consecutive days. Elimination of CP was described by a noninducible route and an inducible route leading to HCP. The latter route was mediated by a hypothetical amount of enzyme. Autoinduction leads to a zero-order increase in amount of this enzyme during treatment. Inhibition by thioTEPA was modeled as a reversible, competitive, concentration-dependent inhibition. PM pharmacokinetics were described by first-order formation from HCP and first-order elimination. The final models for CP, HCP, and PM provided an adequate fit of the experimental data. The volume of distribution, noninducible and initial inducible clearances of CP were 31.0 L, 1.58 L/hr and 4.76 L/hr, respectively. The enzyme amount increased with a zero-order rate constant of 0.041 amount * hr-1. After each thioTEPA infusion, however, approximately 80% of the enzyme was inhibited. This inhibition was reversible with a half-life of 6.5 hr. The formation and elimination rate constants of PM were 1.58 and 0.338 hr-1, respectively. The developed model enabled the assessment of the complex pharmacokinetics of CP in combination with thio TEPA. This model provided an adequate description of enzyme induction and inhibition and can be used for treatment optimization in this combination.
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Affiliation(s)
- A D Huitema
- Department of Pharmacy and Pharmacology, The Netherlands Cancer Institute/Slotervaart Hospital, Louwesweg 6, 1066 EC, Amsterdam, The Netherlands
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13
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Hassan M, Svensson US, Ljungman P, Björkstrand B, Olsson H, Bielenstein M, Abdel-Rehim M, Nilsson C, Johansson M, Karlsson MO. A mechanism-based pharmacokinetic-enzyme model for cyclophosphamide autoinduction in breast cancer patients. Br J Clin Pharmacol 1999; 48:669-77. [PMID: 10594468 PMCID: PMC2014348 DOI: 10.1046/j.1365-2125.1999.00090.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS This study investigated the pharmacokinetics of cyclophosphamide (CP) and its main metabolite 4-hydroxycyclophosphamide (4-OH-CP) in patients with breast cancer undergoing high dose chemotherapy prior to autologous stem cell transplantation. An enzyme turn-over model was also developed to study the time course of cyclophosphamide induction. METHODS Fourteen patients received a combination of CP (6 g m-2 ), thiotepum (500 mg m-2 ) and carboplatin (800 mg m-2 ) as a 96 h infusion. Plasma concentrations of CP and 4-OH-CP were determined with h.p.l.c. and a pharmacokinetic and enzyme turn-over model applied to data using NONMEM. RESULTS CP plasma concentrations were described by a two-compartment model with a noninducible and an inducible pathway, the latter forming 4-OH-CP. In the final enzyme model, CP affects the amount of enzymes by increasing the enzyme production rate. CP concentrations decreased during the infusion with no subsequent change in 4-OH-CP concentrations. CP inducible and noninducible clearance were estimated to 1.76 l h-1 (90% C.I. 0.92-2.58) and 1.14 l h-1 (0.31-1.85), respectively. The induction resulted in an approximately doubled CP clearance through the inducible pathway at the end of treatment. The model predicted the enzyme turn-over half-life to be 24 h. CONCLUSIONS The presented mechanism-based enzyme induction model where the pharmacokinetics of the inducer and the enzyme pool counterbalance each other successfully described CP autoinduction. It is reasonable to believe that CP affects its own elimination by increasing the enzyme production rate and thereby increasing the amount of enzyme by which CP is eliminated.
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Affiliation(s)
- M Hassan
- Department of Hematology, Huddinge University Hospital, Huddinge; Department of Medical Laboratory Science and Technology, Division of Clinical Pharmacology, Huddinge University Hospital, Huddinge; Karolinska Pharmacy, Sweden.
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van Agtmael MA, Cheng-Qi S, Qing JX, Mull R, van Boxtel CJ. Multiple dose pharmacokinetics of artemether in Chinese patients with uncomplicated falciparum malaria. Int J Antimicrob Agents 1999; 12:151-8. [PMID: 10418761 DOI: 10.1016/s0924-8579(99)00063-1] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Multiple dose pharmacokinetics of artemether and dihydroartemisinin were investigated in chinese patients treated for malaria. They received over 2 days either 4 x 80 mg artemether orally (n = 48) or 4 x 80-480 mg co-artemether (n = 40), a combination of artemether and lumefantrine (benflumetol). Lag time = 0.48 h (mean), Cmax after first dose = 157 ng/ml, t(max) = 1.73 h and elimination half-life = 1.16 h. The lag and absorption times were 0.5 h longer for co-artemether compared with artemether. Dihydroartemisinin paralleled artemether pharmacokinetics. Artemether Cmax after the last dose was one-third of the Cmax after the first dose while, inversely, dihydroartemisinin Cmax increased over time. We suggest that auto-induction of gut mucosa enzymes and/or liver enzymes causes a time-dependent increase in first-pass metabolisation of artemether.
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Affiliation(s)
- M A van Agtmael
- Department of Clinical Pharmacology and Pharmacotherapy, Academic Medical Center, Amsterdam, The Netherlands
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15
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Falcão AC, de Almeida AM, Leitão F, Santos J, Sales F, Caramona MM. Predictive capacity of carbamazepine pharmacokinetic parameters in a Portuguese outpatient population. Ther Drug Monit 1999; 21:224-30. [PMID: 10217344 DOI: 10.1097/00007691-199904000-00014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The individualization of anticonvulsant therapy regimens can contribute to the implementation of appropriate carbamazepine (CBZ) maintenance doses in epileptic patients. An accurate method for the prediction of concentrations based on a determination of parameters and serum concentrations could be of clinical relevance in the management of epilepsy. In this study, we retrospectively evaluated the predictive performance in an adult outpatient population of six different methods, representing six sets of CBZ pharmacokinetic parameters selected according to the literature using a Bayesian computer program (PKS System; Abbott Laboratories, Abbott Park, IL, USA). The study involved 50 patients with two or more available concentrations selected under several inclusion criteria. The patients were taking CBZ (between 200 and 1600 mg/d) in monotherapy or polytherapy regimens and had no hepatic or renal disease. Steady state concentrations were predicted according to the use of prior information and using one and two feedback patient concentrations. Accuracy and precision were assessed by mean prediction error (ME), mean squared prediction error (MSE) and root mean squared prediction error (RMSE). The analysis showed CL = 0.067 L/hour/kg and Vd = 1.19 L/kg as the most accurate and precise set of pharmacokinetic parameters, presenting the highest percentage of clinically acceptable estimates (error < 2 microg/mL). Additionally, predictions based on one measured feedback concentration were found to be more accurate and precise than prior population-based predictions; the use of two previous patient concentrations further improved predictive capacity but failed to show a significant difference when compared with predictions based on one measured feedback concentration. In conclusion, the adoption of the previously mentioned set of parameters as population estimates and the use of at least one feedback concentration through the Bayesian approach seems to be essential for a better CBZ use in clinical practice. Finally, despite the obtained results, we believe that the Portuguese pharmacokinetic parameter determination of antiepileptics should be carried out to improve the rationale and cost-effectiveness of anticonvulsant therapy.
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Affiliation(s)
- A C Falcão
- Pharmacy Department, University of Coimbra, Portugal
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McLeod HL, Sludden J, Hardy SC, Lock RE, Hawksworth GM, Cassidy J. Autoregulation of 5-fluorouracil metabolism. Eur J Cancer 1998; 34:1623-7. [PMID: 9893640 DOI: 10.1016/s0959-8049(98)00175-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
5-Fluorouracil (5-FU) is a commonly used anticancer agent for the treatment of gastrointestinal, head and neck, and breast tumours. This study determined the influence of 5-FU on dihydropyrimidine dehydrogenase (DPD) activity, the enzyme responsible for its in vivo degradation. DPD activity was measured in mononuclear cells obtained prior to and after the administration of 5-FU in 20 patients with colorectal cancer. Following the results from the human studies, DPD activity was measured in Sprague-Dawley rat liver up to 72 h after administration of 5-FU 200 mg/kg as a single injection. Total liver P450 content and the production of testosterone metabolites (indicative of CYP3A activity) were also analysed to determine the specificity of 5-FU-associated alteration in rat liver metabolism. Human mononuclear cell DPD activity decreased by a median of 38.7% following the administration of 5-FU (P = 0.001). 5-FU-induced alterations in rat liver DPD were also observed, with the lowest activity occurring 48 h after injection (50% of control activity; P = 0.009). Rat liver DPD activity returned to near control values by 72 h postinjection. Rat liver total P450 content and CYP3A activity were not significantly different in 5-FU treated or control tissues. Thus, 5-FU demonstrates autoregulation of its metabolism through inhibition of DPD activity. Although this inhibition appears to be specific for DPD, the mechanism for enzyme inhibition is not clear. These findings may aid in the design of 5-FU treatment regimens and provide the basis for further studies into the regulation of DPD.
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Affiliation(s)
- H L McLeod
- Department of Medicine, University of Aberdeen, Foresterhill, U.K
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Almeida AM, Falcão AC, Sales F, Leitão F, Santos J, Costa IM, Caramona MM. Kinetic profile of carbamazepine in an adult Portuguese outpatient population. J Clin Pharm Ther 1998; 23:315-21. [PMID: 9867316 DOI: 10.1046/j.1365-2710.1998.00166.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE The aim of our work was to define the kinetic profile of carbamazepine (CBZ), in order to improve on dosing schedules through a Bayesian approach. METHOD Carbamazepine dose/steady-state trough concentrations data pairs and associated information were collected retrospectively on a population of adult epileptic patients. RESULTS Fifty patients (index population) with two or more available concentrations (total of 174 determinations) met our inclusion criteria. Patients were taking CBZ (200-1800 mg/day) in mono- or polytherapy regimens. The analysis assumed a one-compartmental model with first-order absorption and elimination. Due to the data source (only trough concentrations were measured as part of hospital routine), the volume of distribution was fixed at 1.19 l/kg. The final estimates for CL were: 0.075 +/- 0.027 (mono- and polytherapy), 0.069 +/- 0.020 (monotherapy), and 0.106 +/- 0.037 l/h/kg (polytherapy). In order to validate these results, we assessed their predictive capacity using 18 new patients (validation population), submitted to the same inclusion criteria and using Prediction-Error analysis. The results suggested a different CL value for our population compared to earlier published clearance values. The results also pointed to an increased metabolic rate associated with polytherapy. The prediction capacity of the optimization method derived from a Portuguese population made in an a priori evaluation indicated a low error (-0.04 microg/ml), close to the theoretical zero value. CONCLUSION Our results provide specific data on CBZ disposition in a Portuguese population and given the wide variability in the literature values, our data may help improve dosing of CBZ in Portuguese patients.
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Affiliation(s)
- A M Almeida
- Laboratory of Pharmacology, Faculty of Pharmacy, University of Coimbra, Portugal
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Brewster ME, Anderson WR, Meinsma D, Moreno D, Webb AI, Pablo L, Estes KS, Derendorf H, Bodor N, Sawchuk R, Cheung B, Pop E. Intravenous and oral pharmacokinetic evaluation of a 2-hydroxypropyl-beta-cyclodextrin-based formulation of carbamazepine in the dog: comparison with commercially available tablets and suspensions. J Pharm Sci 1997; 86:335-9. [PMID: 9050802 DOI: 10.1021/js9602913] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Complexation of carbamazepine with 2-hydroxypropyl-beta-cyclodextrin was performed to provide improved formulations of this widely used antiepileptic drug. Based on this approach, liquid dosage forms were configured for both parenteral and oral use. Intravenous administration of an aqueous carbamazepine x 2-hydroxypropyl-beta-cyclodextrin (CBZ x HPbetaCD) complex at a CBZ dose of 20 mg/kg was well tolerated and generated high initial drug levels that fell monoexponentially as a function of time, yielding a plasma elimination half-life of 38 min. Oral studies were completed with three preparations: a commercially available tablet and suspension, as well as a CBZ x HPbetaCD oral solution. Oral administration of tablets gave erratic and slow absorption, leading to maximum CBZ concentrations (C(max)) of <2 microg/mL, which were manifested only at 2.5 h after drug dosing. The absolute bioavailability of CBZ from the tablets was approximately 25%. Both the suspension and CBZ x HPbetaCD solution gave a significantly improved profile. Thus, the liquid oral dosage forms approximately doubled the oral bioavailability of CBZ compared with the tablets.
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