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Population Pharmacokinetic Models of Tacrolimus in Adult Transplant Recipients: A Systematic Review. Clin Pharmacokinet 2021; 59:1357-1392. [PMID: 32783100 DOI: 10.1007/s40262-020-00922-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
BACKGROUND AND OBJECTIVES Numerous population pharmacokinetic (PK) models of tacrolimus in adult transplant recipients have been published to characterize tacrolimus PK and facilitate dose individualization. This study aimed to (1) investigate clinical determinants influencing tacrolimus PK, and (2) identify areas requiring additional research to facilitate the use of population PK models to guide tacrolimus dosing decisions. METHODS The MEDLINE and EMBASE databases, as well as the reference lists of all articles, were searched to identify population PK models of tacrolimus developed from adult transplant recipients published from the inception of the databases to 29 February 2020. RESULTS Of the 69 studies identified, 55% were developed from kidney transplant recipients and 30% from liver transplant recipients. Most studies (91%) investigated the oral immediate-release formulation of tacrolimus. Few studies (17%) explained the effect of drug-drug interactions on tacrolimus PK. Only 35% of the studies performed an external evaluation to assess the generalizability of the models. Studies related variability in tacrolimus whole blood clearance among transplant recipients to either cytochrome P450 (CYP) 3A5 genotype (41%), days post-transplant (30%), or hematocrit (29%). Variability in the central volume of distribution was mainly explained by body weight (20% of studies). CONCLUSION The effect of clinically significant drug-drug interactions and different formulations and brands of tacrolimus should be considered for any future tacrolimus population PK model development. Further work is required to assess the generalizability of existing models and identify key factors that influence both initial and maintenance doses of tacrolimus, particularly in heart and lung transplant recipients.
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2
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Germovsek E, Barker CIS, Sharland M, Standing JF. Pharmacokinetic-Pharmacodynamic Modeling in Pediatric Drug Development, and the Importance of Standardized Scaling of Clearance. Clin Pharmacokinet 2020; 58:39-52. [PMID: 29675639 PMCID: PMC6325987 DOI: 10.1007/s40262-018-0659-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Pharmacokinetic/pharmacodynamic (PKPD) modeling is important in the design and conduct of clinical pharmacology research in children. During drug development, PKPD modeling and simulation should underpin rational trial design and facilitate extrapolation to investigate efficacy and safety. The application of PKPD modeling to optimize dosing recommendations and therapeutic drug monitoring is also increasing, and PKPD model-based dose individualization will become a core feature of personalized medicine. Following extensive progress on pediatric PK modeling, a greater emphasis now needs to be placed on PD modeling to understand age-related changes in drug effects. This paper discusses the principles of PKPD modeling in the context of pediatric drug development, summarizing how important PK parameters, such as clearance (CL), are scaled with size and age, and highlights a standardized method for CL scaling in children. One standard scaling method would facilitate comparison of PK parameters across multiple studies, thus increasing the utility of existing PK models and facilitating optimal design of new studies.
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Affiliation(s)
- Eva Germovsek
- Infection, Inflammation and Rheumatology Section, UCL Great Ormond Street Institute of Child Heath, University College London, London, UK. .,Pharmacometrics Research Group, Department of Pharmaceutical Biosciences, Uppsala University, PO Box 591, 751 24, Uppsala, Sweden.
| | - Charlotte I S Barker
- Infection, Inflammation and Rheumatology Section, UCL Great Ormond Street Institute of Child Heath, University College London, London, UK.,Paediatric Infectious Diseases Research Group, Institute for Infection and Immunity, St George's, University of London, London, UK.,St George's University Hospitals NHS Foundation Trust, London, UK
| | - Mike Sharland
- Paediatric Infectious Diseases Research Group, Institute for Infection and Immunity, St George's, University of London, London, UK.,St George's University Hospitals NHS Foundation Trust, London, UK
| | - Joseph F Standing
- Infection, Inflammation and Rheumatology Section, UCL Great Ormond Street Institute of Child Heath, University College London, London, UK.,Paediatric Infectious Diseases Research Group, Institute for Infection and Immunity, St George's, University of London, London, UK
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3
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Population Pharmacokinetics of the Antituberculosis Agent Pretomanid. Antimicrob Agents Chemother 2019; 63:AAC.00907-19. [PMID: 31405856 PMCID: PMC6761531 DOI: 10.1128/aac.00907-19] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 08/05/2019] [Indexed: 11/20/2022] Open
Abstract
A population pharmacokinetic (PopPK) model for pretomanid was developed using data from 14 studies in the pretomanid development program: six phase 1 studies, six phase 2 studies, and two phase 3 studies. The final analysis data set contained 17,725 observations from 1,054 subjects, including healthy subjects and subjects with drug-sensitive, multidrug-resistant, or extensively drug-resistant pulmonary tuberculosis dosed pretomanid in monotherapy or combination therapy for up to 6 months. Pretomanid pharmacokinetic behavior was described by a one-compartment model that at a given dose was linear in its absorption and clearance processes but where the rate of absorption and extent of bioavailability changed with dose. Clearance and volume of distribution scaled allometrically with weight. Apparent clearance in females was 18% less than in males. Among HIV-positive subjects, absent the effect of CYP3A4-inducing antiretrovirals, apparent clearance was 6% higher. Some effects of total bilirubin and albumin were found, but the impacts on exposure were small. Bioavailability in the fasted condition was about half that in the fed condition. Relative bioavailability decreased with increasing dose in the fasted condition, but not for doses of ≤200 mg in the fed condition. HIV-positive subjects taking efavirenz and lopinavir/ritonavir had exposures that were reduced by 46 and 17%, respectively. There was little evidence for noteworthy effects of regimen partners on pretomanid. Standard diagnostics indicated that the model described the voluminous, diverse data well, so that the model could be used to generate exposure metrics for exposure/response analyses to be reported elsewhere.
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Hennig S, Hannam JA, Kirkpatrick CMJ, Staatz CE, Holford S, Duffull SB, Al-Sallami HS, Charles BG, Holford N, Foster DJR. Pharmacometrics in Australasia-Twenty Years of Population Approach Group of Australia and New Zealand. CPT Pharmacometrics Syst Pharmacol 2019; 8:701-704. [PMID: 31449742 PMCID: PMC6813165 DOI: 10.1002/psp4.12460] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 07/19/2019] [Indexed: 11/09/2022] Open
Affiliation(s)
- Stefanie Hennig
- School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia
| | - Jacqueline A Hannam
- School of Pharmacology and Clinical Pharmacology, The University of Auckland, Auckland, New Zealand
| | - Carl M J Kirkpatrick
- Centre for Medicine Use and Safety, Monash University, Melbourne, Victoria, Australia
| | - Christine E Staatz
- School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia
| | - Sam Holford
- Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | | | | | - Bruce G Charles
- School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia
| | - Nick Holford
- School of Pharmacology and Clinical Pharmacology, The University of Auckland, Auckland, New Zealand
| | - David J R Foster
- School of Pharmacy and Medical Sciences, The University of South Australia, Adelaide, South Australia, Australia
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5
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Alves IA, Staudt KJ, Carreño FO, de Araujo Lock G, de Miranda Silva C, Rates SMK, Dalla Costa T, De Araujo BV. Population Pharmacokinetic Modeling to Describe the Total Plasma and Free Brain Levels of Fluconazole in Healthy and Cryptococcus neoformans Infected Rats: How Does the Infection Impact the Drug's Levels on Biophase? Pharm Res 2018; 35:132. [PMID: 29704215 DOI: 10.1007/s11095-018-2402-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 04/05/2018] [Indexed: 01/04/2023]
Abstract
PURPOSE The present work aimed to evaluate the influence of experimental meningitis caused by C. neoformans on total plasma and free brain concentrations of fluconazole (FLC) in Wistar rats. METHOD The infection was induced by the administration of 100 μL of inoculum (1.105 CFU) through the tail vein. Free drug in the brain was assessed by microdialisys (μD). Blood and μD samples were collected at pre-determined time points up to 12 h after intravenous administration of FLC (20 mg/kg) to healthy and infected rats. The concentration-time profiles were analyzed by non-compartmental and population pharmacokinetics approaches. RESULTS A two-compartmental popPK model was able to simultaneously describe plasma and free drug concentrations in the brain for both groups investigated. Analysis of plasma and μD samples showed a better FLC distribution on the brain of infected than healthy animals (1.04 ± 0.31 vs 0.69 ± 0.14, respectively). The probability of target attainment was calculated by Monte Carlo simulations based on the developed popPK model for 125 mg/kg dose for rats and 400-2000 mg for humans. CONCLUSIONS FLC showed a limited use in monotherapy to the treatment of criptoccocosis in rats and humans to value of MIC >8 μg/mL.
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Affiliation(s)
- Izabel Almeida Alves
- Pharmaceutical Sciences Graduate Program of Federal University of Rio Grande do Sul, Av. Ipiranga, 2752, Porto Alegre, RS, 90610-000, Brazil
| | - Keli Jaqueline Staudt
- Medical Sciences Graduate Program of Federal University of Rio Grande do Sul, Av. Ipiranga 2752, office 407, Porto Alegre, RS, 90610-000, Brazil
| | - Fernando Olinto Carreño
- Pharmaceutical Sciences Graduate Program of Federal University of Rio Grande do Sul, Av. Ipiranga, 2752, Porto Alegre, RS, 90610-000, Brazil
| | - Graziela de Araujo Lock
- Pharmaceutical Sciences Graduate Program of Federal University of Rio Grande do Sul, Av. Ipiranga, 2752, Porto Alegre, RS, 90610-000, Brazil
| | - Carolina de Miranda Silva
- Pharmaceutical Sciences Graduate Program of Federal University of Rio Grande do Sul, Av. Ipiranga, 2752, Porto Alegre, RS, 90610-000, Brazil
| | - Stela Maris Kuze Rates
- Pharmaceutical Sciences Graduate Program of Federal University of Rio Grande do Sul, Av. Ipiranga, 2752, Porto Alegre, RS, 90610-000, Brazil
| | - Teresa Dalla Costa
- Pharmaceutical Sciences Graduate Program of Federal University of Rio Grande do Sul, Av. Ipiranga, 2752, Porto Alegre, RS, 90610-000, Brazil
| | - Bibiana Verlindo De Araujo
- Pharmaceutical Sciences Graduate Program of Federal University of Rio Grande do Sul, Av. Ipiranga, 2752, Porto Alegre, RS, 90610-000, Brazil. .,Medical Sciences Graduate Program of Federal University of Rio Grande do Sul, Av. Ipiranga 2752, office 407, Porto Alegre, RS, 90610-000, Brazil.
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Nedelman J, Fisch R, Hu K, Paule I, Zhou J. Population Pharmacokinetics of Subcutaneous Pasireotide in Healthy Volunteers and Cushing's Disease Patients. Clin Pharmacokinet 2017; 57:855-866. [PMID: 29032486 DOI: 10.1007/s40262-017-0600-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND AND OBJECTIVE Pasireotide (SOM230, Signifor®) is a somatostatin analog approved in a subcutaneous formulation for the treatment of Cushing's disease. This analysis characterizes the population pharmacokinetics (PopPK) of subcutaneous pasireotide jointly in healthy volunteers (HVs) and Cushing's disease patients (CDPs), evaluating the effects of age, body size, and population on pasireotide pharmacokinetics. METHODS The analysis dataset included five phase I studies and one each from phase II and phase III. A three-compartment, linear structural pharmacokinetic model was used. Models were specified a priori that varied in the relationship between HVs and CDPs, and the model with the lowest value of the Bayes Information Criterion (BIC) was selected. It was then used to illustrate various features of pasireotide pharmacokinetics. RESULTS AND CONCLUSIONS In the final model, the estimated values of apparent clearance (CL/F), central volume of distribution, and deep peripheral volume of distribution of pasireotide in CDP were 59, 43, and 225% those of HVs at the same age and body size. Clearance increased with body size and decreased with age similarly for CDPs and HVs. The estimated CL/F for a typical CDP (40 years old, lean body weight [LBW] 49 kg) was 3.72 L/h, and for a typical HV (29 years old, LBW 61 kg) was 7.96 L/h. The model was judged adequate by visual predictive checks and diagnostic plots separately for HVs and CDPs and can be used for simulations for deriving exposure-response metrics for pharmacokinetic/pharmacodynamic analyses.
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Affiliation(s)
- Jerry Nedelman
- Oncology Clinical Pharmacology, Novartis Pharmaceuticals Corporation, One Health Plaza, East Hanover, NJ, 07936, USA.,TB Alliance, 40 Wall St # 24, New York, NY, 10005, USA
| | - Roland Fisch
- Modeling and Simulation, Novartis Pharma AG, Postfach, CH-4002, Basel, Switzerland.,Im Rotländ 21, CH-4112, Flüh, Switzerland
| | - Ke Hu
- Oncology Clinical Pharmacology, Novartis Pharmaceuticals Corporation, One Health Plaza, East Hanover, NJ, 07936, USA.,Rafael Pharmaceuticals, 520 Broad St, Newark, NJ, 07102, USA
| | - Ines Paule
- Modeling and Simulation, Novartis Pharma AG, Postfach, CH-4002, Basel, Switzerland
| | - Jocelyn Zhou
- Oncology Clinical Pharmacology, Novartis Pharmaceuticals Corporation, One Health Plaza, East Hanover, NJ, 07936, USA. .,Novartis Sandoz Division, 100 College Road West, Princeton, NJ, USA.
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7
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Imbert B, Alvarez JC, Simon N. Anticraving Effect of Baclofen in Alcohol-Dependent Patients. Alcohol Clin Exp Res 2015. [DOI: 10.1111/acer.12823] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Bruce Imbert
- Department of Addictology; Allauch Hospital Center; Allauch France
- INSERM U912 (SESSTIM); Aix-Marseille University; Marseille France
| | - Jean-Claude Alvarez
- Laboratoire de Pharmacologie-Toxicologie; Hôpital Raymond Poincaré; Garches France
- Université Versailles Saint-Quentin; UFR Sciences de la Santé Simone Veil; Montigny-Le-Bretonneux France
| | - Nicolas Simon
- Service d'addictologie; Hôpital Sainte Marguerite; Marseille France
- INSERM U912 (SESSTIM); Aix-Marseille University; Marseille France
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8
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Affiliation(s)
- Ian R Cox
- Department of Anaesthesia and Pain Management; Concord Repatriation and General Hospital; Concord New South Wales
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9
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Perera V, Dolton MJ, McLachlan AJ, Carr VJ, Day RO. Pharmacometrics: an underused resource in Australian clinical research. Med J Aust 2014; 200:82-3. [PMID: 24484099 DOI: 10.5694/mja13.10663] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 08/14/2013] [Indexed: 11/17/2022]
Affiliation(s)
- Vidya Perera
- Department of Pharmacy and Pharmaceutical Sciences, State University of New York at Buffalo, Buffalo, NY, USA.
| | - Michael J Dolton
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | | | | | - Richard O Day
- University of New South Wales, Sydney, NSW, Australia
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10
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Population pharmacokinetics of inhaled tobramycin powder in cystic fibrosis patients. CPT-PHARMACOMETRICS & SYSTEMS PHARMACOLOGY 2014; 3:e99. [PMID: 24522146 PMCID: PMC3944114 DOI: 10.1038/psp.2013.76] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 11/27/2013] [Indexed: 11/16/2022]
Abstract
Tobramycin powder for inhalation (TOBI Podhaler or TIP) is approved for the treatment of Pseudomonas aeruginosa airway infection in patients with cystic fibrosis (CF). A population pharmacokinetic model for tobramycin inhalation powder (TIP) in CF patients was developed to characterize the effect of covariates including body mass index (BMI) and lung function (forced expiratory volume in 1 s as percent of the predicted value (FEV1% predicted) at baseline) on the serum exposure parameters. A two-compartment model with first-order elimination and first-order absorption was developed. Across a range of baseline demographic values in the study population, the predicted mean values for the maximum (Cmax) and trough (Ctrough) plasma concentrations at steady state were at least 7.5 and 5-fold lower, respectively, than the recommended thresholds for tobramycin toxicity (12 µg/ml for Cmax and 2 µg/ml for Ctrough). This model adequately described the tobramycin serum concentration–time course in CF patients following inhalation of TIP. The results indicate that no BMI- or FEV1-based dose adjustment is needed for use of TIP in CF patients.
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11
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Ing Lorenzini K, Daali Y, Dayer P, Desmeules J. Pharmacokinetic-Pharmacodynamic Modelling of Opioids in Healthy Human Volunteers. A MiniReview. Basic Clin Pharmacol Toxicol 2011; 110:219-26. [DOI: 10.1111/j.1742-7843.2011.00814.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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12
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Abstract
The role of drug assays for screening, diagnosis, and guiding treatment decisions in overdose patients remains unclear. The use of drug concentration data in clinical toxicology research is more problematic, with studies using drug concentrations to simply confirm ingestion in observational studies or others report drug concentration time profiles with simplified pharmacokinetics. The reasons for the lack of more substantial pharmacokinetic and/or pharmacodynamic analysis in overdose patients include problems with uncertainty in dose, uncertainty in the time of ingestion, and limited sampling in the absorption phase. Many of these can be overcome by using population pharmacokinetic and pharmacokinetic-pharmacodynamic analysis in prospective studies of overdose patients to understand dose-concentration-effect relationships. Uncertainty in dose and dose time can be included using population analysis techniques, which may involve a clinical assessment of the veracity of the patient history. The pharmacokinetic-pharmacodynamic model can then be used as the basis for predicting toxicity and clinical outcomes from historical information such as dose and early clinical effects. Using such an approach means that the use of drug concentration data in research will improve the risk assessment in overdose patients, without requiring these assays to be rapidly available in the acute health setting.
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13
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Population pharmacokinetics of tacrolimus in pediatric hematopoietic stem cell transplant recipients: new initial dosage suggestions and a model-based dosage adjustment tool. Ther Drug Monit 2010; 31:457-66. [PMID: 19531982 DOI: 10.1097/ftd.0b013e3181aab02b] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The population pharmacokinetics of tacrolimus was described in 22 pediatric hematopoietic stem cell transplant recipients, and a model-based dosage adjustment tool that may assist with therapy in new patients was developed. Patients received tacrolimus by continuous intravenous (IV) infusion (0.03 mg x kg(-1) x d(-1)) starting 2 days before transplantation, with conversion to oral therapy 2-3 weeks after transplant. Population pharmacokinetic analysis was performed using NONMEM. A Bayesian dosage adjustment tool that searches for individual parameter estimates to describe concentration measurements, counterbalanced by the final population model, was created in Excel. Typical clearance was 106 mL x h(-1) x kg(-0.75), typical distribution volume was 3.71 L/kg, and typical bioavailability was 15.7%. Tacrolimus clearance decreased with increasing serum creatinine, and bioavailability decreased with postoperative day. A Bayesian dosage adjustment tool capable of suggesting an initial infusion rate based on patient covariate values and devising a further individualized dosage regimen as drug concentration measures become available was developed. Predictions from the model showed that current IV dose recommendations of 0.03 mg x kg(-1) x d(-1) may potentially produce toxic drug concentrations in this patient population, whereas current oral conversion of 4 times the adjusted IV dose may lead to subtherapeutic concentrations. A more suitable infusion rate to obtain a steady state concentration of 12 ng/mL was predicted to be 0.035 mg x kg(-0.75) x (-1)d. An additional loading dose of 0.07 mg x kg(-1) x d(-1) (total dose: 0.07 mg x kg(-1) x d(-1) + 0.035 mg x kg(-0.75) x d(-1)) during the first 24 hours of therapy should allow rapid achievement of steady state concentrations. A conversion factor of 6 from IV to enteric therapy may be more suitable. Such dosage recommendations may be site specific. The appropriateness of targets was not investigated in this study. The Bayesian dosing adjustment tool and suggested dose recommendations need to be evaluated in a prospective study before they can be applied in the clinical setting.
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Rubino CM, Ambrose P, Cirincione B, Arguedas A, Sher L, Lopez E, Sáez-Llorens X, Grasela DM. Pharmacokinetics and pharmacodynamics of gatifloxacin in children with recurrent otitis media: application of sparse sampling in clinical development. Diagn Microbiol Infect Dis 2007; 59:67-74. [PMID: 17875453 DOI: 10.1016/j.diagmicrobio.2007.04.015] [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] [Received: 01/26/2007] [Revised: 04/20/2007] [Accepted: 04/23/2007] [Indexed: 01/02/2023]
Abstract
Gatifloxacin is a 4th-generation fluoroquinolone previously under investigation for the treatment of otitis media in infants and children. These analyses were designed to evaluate the extent of drug exposure relative to adult populations and to examine the relationship between drug exposure and response to therapy in children with recurrent otitis media or early treatment failures of acute otitis media. The patient population included 187 patients from an open-label, multicenter, noncomparative study using gatifloxacin 10 mg/kg once daily. Gatifloxacin exposure was estimated using a single steady-state blood sample in conjunction with a pharmacostatistical model developed using a separate pediatric data set. Gatifloxacin exposure was equivalent to that in adults given 400 mg daily. Of the 41 patients who had Streptococcus pneumoniae from middle ear culture, there were only 3 bacteriologic failures; there was no relationship between plasma fu AUC(0-24):MIC ratio and outcome. In conclusion, population pharmacokinetic/pharmacodynamic methods allowed estimation of drug exposure using one sample per patient.
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Affiliation(s)
- Christopher M Rubino
- Institute for Clinical Pharmacodynamics, Ordway Research Institute, Albany, NY 12206, USA.
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Rubino CM, Capparelli EV, Bradley JS, Blumer JL, Kearns GL, Reed M, Jacobs RF, Cirincione B, Grasela DM. Population pharmacokinetic model for gatifloxacin in pediatric patients. Antimicrob Agents Chemother 2007; 51:1246-52. [PMID: 17220409 PMCID: PMC1855513 DOI: 10.1128/aac.00685-06] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The broad spectrum of antimicrobial activity, oral bioavailability, extensive tissue distribution, and once-daily intravenous or oral dosing of gatifloxacin, an expanded-spectrum 8-methoxy fluoroquinolone, make it a potentially useful agent for the treatment of pediatric infections. A population pharmacokinetic model was developed to describe the pharmacokinetics of gatifloxacin in children. Data for analysis were obtained from a single-dose safety/pharmacokinetic study utilizing intensive blood sampling in patients aged 6 months to 16 years. Each subject received a single oral dose of gatifloxacin as a suspension, at doses of 5, 10, or 15 mg/kg of body weight. A total of 845 samples were obtained from 82 patients. A one-compartment model with first-order absorption and elimination was the most appropriate to describe the gatifloxacin concentrations. Covariate analysis using forward selection and backward elimination found that apparent clearance was related to body surface area, and apparent volume of distribution was related to body weight. No effect of age on drug clearance could be identified once clearance was corrected for body surface area. Based on pharmacokinetic simulations, the 10-mg/kg (maximum, 400 mg) once-daily dose of gatifloxacin is expected to provide drug exposure similar to that in healthy adults. The population pharmacokinetic model described herein will be used for Bayesian analyses of sparse pharmacokinetic sampling in phase II/III clinical trials and for Monte Carlo simulation experiments. The success of this strategy provides a model for future pediatric drug development programs.
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16
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Bonate PL. Recommended reading in population pharmacokinetic pharmacodynamics. AAPS JOURNAL 2005; 7:E363-73. [PMID: 16353916 PMCID: PMC2750974 DOI: 10.1208/aapsj070237] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Developing the skills or expertise to create useful population pharmacokinetic-pharmacodynamic models can be a daunting task-the level of mathematical and statistical complexity is such that newcomers to the field are frequently overwhelmed. A good place to start in learning the field is to read articles in the literature. However, the number of articles dealing with population pharmacokinetic pharmacodynamics is exponentially increasing on a yearly basis, so choosing which articles to read can be difficult. The purpose of this review is to provide a recommended reading list for newcomers to the field. The list was chosen based on perceived impact of the article in the field, the quality of the article, or to highlight some important detail contained within the article. After reading the articles in the list, it is believed that the reader will have a broad overview of the field and have a sound foundation for more-detailed reading of the literature.
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Affiliation(s)
- Peter L Bonate
- Genzyme Corporation, 4545 Horizon Hill Blvd., San Antonio, TX, USA.
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Payen S, Zhang D, Maisin A, Popon M, Bensman A, Bouissou F, Loirat C, Gomeni R, Bressolle F, Jacqz-Aigrain E. Population pharmacokinetics of mycophenolic acid in kidney transplant pediatric and adolescent patients. Ther Drug Monit 2005; 27:378-88. [PMID: 15905811 DOI: 10.1097/01.ftd.0000159784.25872.f6] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Current data on mycophenolate mofetil (MMF) suggest that there is a pharmacokinetic/pharmacodynamic relationship between the mycophenolic acid (MPA) area under the curve (AUC) during treatment and both the risk of acute rejection and the occurrence of side effects. The aim of this study was to characterize the population pharmacokinetics of MPA in kidney transplant patients between the ages of 2 and 21 years and to propose a limited sampling strategy to estimate individual MPA AUCs. Forty-one patients received long-term oral MMF continuous therapy as part of a triple immunosuppressive regimen, which also included cyclosporine or tacrolimus (n=3) and corticosteroids. Therapy was initiated at a dose of 600 mg/m twice daily. The population parameters were calculated from an initial group of 32 patients. The data were analyzed by nonlinear mixed-effect modeling using a 2-compartment structural model with first-order absorption and a lag time. The interindividual variability in the initial volume of distribution was partially explained by the fact that this parameter was weight-dependent. Fifteen concentration-time profiles from 13 patients were used to evaluate the predictive performance of the Bayesian approach and to devise a limited sampling strategy. The protocol, involving two sampling times, 1 and 4 hours after oral administration, allows the precise and accurate determination of MPA AUCs (bias -0.9 microg.h/mL; precision 6.02 microg.h/mL). The results of this study combine the relationships between the pharmacokinetic parameters of MPA and patient covariates, which may be useful for dose adjustment, with a convenient sampling procedure that may aid in optimizing pediatric patient care.
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Affiliation(s)
- S Payen
- Clinical Pharmacokinetics Laboratory, Faculty of Pharmacy, University Montpellier I, Montpellier, France
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Abstract
Relaxation of the upper age limits for solid organ transplantation coupled with improvements in post-transplant survival have resulted in greater numbers of elderly patients receiving immunosuppressant drugs such as tacrolimus. Tacrolimus is a potent agent with a narrow therapeutic window and large inter- and intraindividual pharmacokinetic variability. Numerous physiological changes occur with aging that could potentially affect the pharmacokinetics of tacrolimus and, hence, patient dosage requirements. Tacrolimus is primarily metabolised by cytochrome P450 (CYP) 3A enzymes in the gut wall and liver. It is also a substrate for P-glycoprotein, which counter-transports diffused tacrolimus out of intestinal cells and back into the gut lumen. Age-associated alterations in CYP 3A and P-glycoprotein expression and/or activity, along with liver mass and body composition changes, would be expected to affect the pharmacokinetics of tacrolimus in the elderly. However, interindividual variation in these processes may mask any changes caused by aging. More investigation is needed into the impact aging has on CYP and P-glycoprotein activity and expression. No single-dose, intense blood-sampling study has specifically compared the pharmacokinetics of tacrolimus across different patient age groups. However, five population pharmacokinetic studies, one in kidney, one in bone marrow and three in liver transplant recipients, have investigated age as a co-variate. None found a significant influence for age on tacrolimus bioavailability, volume of distribution or clearance. The number of elderly patients included in each study, however, was not documented and may have been only small. It is likely that inter- and intraindividual pharmacokinetic variability associated with tacrolimus increase in elderly populations. In addition to pharmacokinetic differences, donor organ viability, multiple co-morbidity, polypharmacy and immunological changes need to be considered when using tacrolimus in the elderly. Aging is associated with decreased immunoresponsiveness, a slower body repair process and increased drug adverse effects. Elderly liver and kidney transplant recipients are more likely to develop new-onset diabetes mellitus than younger patients. Elderly transplant recipients exhibit higher mortality from infectious and cardiovascular causes than younger patients but may be less likely to develop acute rejection. Elderly kidney recipients have a higher potential for chronic allograft nephropathy, and a single rejection episode can be more devastating. There is a paucity of information on optimal tacrolimus dosage and target trough concentration in the elderly. The therapeutic window for tacrolimus concentrations may be narrower. Further integrated pharmacokinetic-pharmacodynamic studies of tacrolimus are required. It would appear reasonable, based on current knowledge, to commence tacrolimus at similar doses as those used in younger patients. Maintenance dose requirements over the longer term may be lower in the elderly, but the increased variability in kinetics and the variety of factors that impact on dosage suggest that patient care needs to be based around more frequent monitoring in this age group.
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Affiliation(s)
- Christine E Staatz
- School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia.
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Staatz CE, Tett SE. Clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplantation. Clin Pharmacokinet 2004; 43:623-53. [PMID: 15244495 DOI: 10.2165/00003088-200443100-00001] [Citation(s) in RCA: 629] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The aim of this review is to analyse critically the recent literature on the clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplant recipients. Dosage and target concentration recommendations for tacrolimus vary from centre to centre, and large pharmacokinetic variability makes it difficult to predict what concentration will be achieved with a particular dose or dosage change. Therapeutic ranges have not been based on statistical approaches. The majority of pharmacokinetic studies have involved intense blood sampling in small homogeneous groups in the immediate post-transplant period. Most have used nonspecific immunoassays and provide little information on pharmacokinetic variability. Demographic investigations seeking correlations between pharmacokinetic parameters and patient factors have generally looked at one covariate at a time and have involved small patient numbers. Factors reported to influence the pharmacokinetics of tacrolimus include the patient group studied, hepatic dysfunction, hepatitis C status, time after transplantation, patient age, donor liver characteristics, recipient race, haematocrit and albumin concentrations, diurnal rhythm, food administration, corticosteroid dosage, diarrhoea and cytochrome P450 (CYP) isoenzyme and P-glycoprotein expression. Population analyses are adding to our understanding of the pharmacokinetics of tacrolimus, but such investigations are still in their infancy. A significant proportion of model variability remains unexplained. Population modelling and Bayesian forecasting may be improved if CYP isoenzymes and/or P-glycoprotein expression could be considered as covariates. Reports have been conflicting as to whether low tacrolimus trough concentrations are related to rejection. Several studies have demonstrated a correlation between high trough concentrations and toxicity, particularly nephrotoxicity. The best predictor of pharmacological effect may be drug concentrations in the transplanted organ itself. Researchers have started to question current reliance on trough measurement during therapeutic drug monitoring, with instances of toxicity and rejection occurring when trough concentrations are within 'acceptable' ranges. The correlation between blood concentration and drug exposure can be improved by use of non-trough timepoints. However, controversy exists as to whether this will provide any great benefit, given the added complexity in monitoring. Investigators are now attempting to quantify the pharmacological effects of tacrolimus on immune cells through assays that measure in vivo calcineurin inhibition and markers of immunosuppression such as cytokine concentration. To date, no studies have correlated pharmacodynamic marker assay results with immunosuppressive efficacy, as determined by allograft outcome, or investigated the relationship between calcineurin inhibition and drug adverse effects. Little is known about the magnitude of the pharmacodynamic variability of tacrolimus.
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Affiliation(s)
- Christine E Staatz
- School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia
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Tranchand B, Laporte S, Glehen O, Freyer G. Pharmacology of cytotoxic agents: a helpful tool for building dose adjustment guidelines in the elderly. Crit Rev Oncol Hematol 2003; 48:199-214. [PMID: 14607383 DOI: 10.1016/j.critrevonc.2003.05.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Aging is associated with multidimensional changes, including alterations in physiological functions, co-morbidities and poly-medications. These changes may lead to modifications in the absorption, distribution, metabolism and excretion of drugs. The lack of a scientific basis for optimal drug dosing in the elderly is a major problem. The development and validation of guidelines are therefore essential to improve treatment administration and monitoring in elderly patients. Even though it has been widely demonstrated that standard therapies used in adults may be of great benefit in the elderly, there may be a higher incidence of toxicity. This could be avoided by using dosage individualization based on a sound knowledge of the physiological factors implicated in the pharmacokinetic (PK) characteristics of the drugs administered and in their observed pharmacodynamic (PD) effects in each patient. The so-called "population modeling" approach renders such studies feasible by allowing the analysis of PK-PD relationships from sparse observational data.
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Staatz CE, Willis C, Taylor PJ, Lynch SV, Tett SE. Toward better outcomes with tacrolimus therapy: population pharmacokinetics and individualized dosage prediction in adult liver transplantation. Liver Transpl 2003; 9:130-7. [PMID: 12548506 DOI: 10.1053/jlts.2003.50023] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Patient outcomes in transplantation would improve if dosing of immunosuppressive agents was individualized. The aim of this study is to develop a population pharmacokinetic model of tacrolimus in adult liver transplant recipients and test this model in individualizing therapy. Population analysis was performed on data from 68 patients. Estimates were sought for apparent clearance (CL/F) and apparent volume of distribution (V/F) using the nonlinear mixed effects model program (NONMEM). Factors screened for influence on these parameters were weight, age, sex, transplant type, biliary reconstructive procedure, postoperative day, days of therapy, liver function test results, creatinine clearance, hematocrit, corticosteroid dose, and interacting drugs. The predictive performance of the developed model was evaluated through Bayesian forecasting in an independent cohort of 36 patients. No linear correlation existed between tacrolimus dosage and trough concentration (r(2) = 0.005). Mean individual Bayesian estimates for CL/F and V/F were 26.5 +/- 8.2 (SD) L/hr and 399 +/- 185 L, respectively. CL/F was greater in patients with normal liver function. V/F increased with patient weight. CL/F decreased with increasing hematocrit. Based on the derived model, a 70-kg patient with an aspartate aminotransferase (AST) level less than 70 U/L would require a tacrolimus dose of 4.7 mg twice daily to achieve a steady-state trough concentration of 10 ng/mL. A 50-kg patient with an AST level greater than 70 U/L would require a dose of 2.6 mg. Marked interindividual variability (43% to 93%) and residual random error (3.3 ng/mL) were observed. Predictions made using the final model were reasonably nonbiased (0.56 ng/mL), but imprecise (4.8 ng/mL). Pharmacokinetic information obtained will assist in tacrolimus dosing; however, further investigation into reasons for the pharmacokinetic variability of tacrolimus is required.
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Affiliation(s)
- Christine E Staatz
- School of Pharmacy, University of Queensland, Princess Alexandra Hospital, Queensland, Australia.
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Staatz CE, Taylor PJ, Tett SE. Comparison of an ELISA and an LC/MS/MS method for measuring tacrolimus concentrations and making dosage decisions in transplant recipients. Ther Drug Monit 2002; 24:607-15. [PMID: 12352932 DOI: 10.1097/00007691-200210000-00005] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
This study compared an enzyme-linked immunosorbent assay (ELISA) to a liquid chromatography-tandem mass spectrometry (LC/MS/MS) technique for measurement of tacrolimus concentrations in adult kidney and liver transplant recipients, and investigated how assay choice influenced pharmacokinetic parameter estimates and drug dosage decisions. Tacrolimus concentrations measured by both ELISA and LC/MS/MS from 29 kidney (n = 98 samples) and 27 liver (n = 97 samples) transplant recipients were used to evaluate the performance of these methods in the clinical setting. Tacrolimus concentrations measured by the two techniques were compared via regression analysis. Population pharmacokinetic models were developed independently using ELISA and LC/MS/MS data from 76 kidney recipients. Derived kinetic parameters were used to formulate "typical dosing" regimens for concentration targeting. Dosage recommendations for the two assays were compared. The relation between LC/MS/MS and ELISA measurements was best described by the regression equation ELISA = 1.02. (LC/MS/MS) + 0.14 in kidney recipients, and ELISA = 1.12. (LC/MS/MS) - 0.87 in liver recipients. ELISA displayed less accuracy than LC/MS/MS at lower tacrolimus concentrations. Population pharmacokinetic models based on ELISA and LC/MS/MS data were similar with residual random errors of 4.1 ng/mL and 3.7 ng/mL, respectively. Assay choice gave rise to dosage prediction differences ranging from 0% to 30%. ELISA measurements of tacrolimus are not automatically interchangeable with LC/MS/MS values. Assay differences were greatest in adult liver recipients, probably reflecting periods of liver dysfunction and impaired biliary secretion of metabolites. While the majority of data collected in this study suggested assay differences in adult kidney recipients were minimal, findings of ELISA dosage underpredictions of up to 25% in the long term must be investigated further.
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Affiliation(s)
- Christine E Staatz
- School of Phamacy, University of Queensland, Princess Alexandra Hospital, Queensland, Australia.
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Staatz CE, Taylor PJ, Lynch SV, Willis C, Charles BG, Tett SE. Population pharmacokinetics of tacrolimus in children who receive cut-down or full liver transplants. Transplantation 2001; 72:1056-61. [PMID: 11579300 DOI: 10.1097/00007890-200109270-00013] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The aim of this study was to investigate the population pharmacokinetics of tacrolimus in pediatric liver transplant recipients and to identify factors that may explain pharmacokinetic variability. METHODS Data were collected retrospectively from 35 children who received oral immunosuppressant therapy with tacrolimus. Maximum likelihood estimates were sought for the typical values of apparent clearance (CL/F) and apparent volume of distribution (V/F) with the program NONMEM. Factors screened for influence on the pharmacokinetic parameters were weight, age, gender, postoperative day, days since commencing tacrolimus therapy, transplant type (whole child liver or cut-down adult liver), liver function tests (bilirubin, alkaline phosphatase [ALP], aspartate aminotransferase [AST], gamma-glutamyl transferase [GGT], alanine aminotransferase [ALT]), creatinine clearance, hematocrit, corticosteroid dose, and concurrent therapy with metabolic inducers and inhibitors of tacrolimus. RESULTS No clear correlation existed between tacrolimus dosage and blood concentrations (r2=0.003). Transplant type, age, and liver function test values were the most important factors (P<0.01) that influenced the pharmacokinetics of tacrolimus. CL/F estimates were greater in whole liver recipients, decreased with increasing patient age and AST values, and increased with increasing GGT values. Average parameter estimates were CL/F=5.75 L/h (cut-down liver), CL/F=44 L/h (whole liver), and V/F=617 L. Marked intersubject variability (CV%=110% to 297%) and residual variability (CV%=42%) was observed. CONCLUSIONS Pharmacokinetic information obtained in this study may assist physicians in making individualized dosage decisions in regard to tacrolimus in pediatric liver transplant recipients. Children who received a whole child's liver appeared to retain "pediatric" clearance, whereas those who received a cut-down adult liver had "adult" clearances (on average 7-fold less).
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Affiliation(s)
- C E Staatz
- School of Pharmacy, University of Queensland, Brisbane, Queensland 4072, Australia.
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Ozdemir V, Shear NH, Kalow W. What will be the role of pharmacogenetics in evaluating drug safety and minimising adverse effects? Drug Saf 2001; 24:75-85. [PMID: 11235820 DOI: 10.2165/00002018-200124020-00001] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
In the US, adverse drug reactions (ADRs) rank between the fourth to sixth leading cause of death, ahead of pneumonia and diabetes mellitus. An important reason for the high incidence of serious and fatal ADRs is that the existing drug development paradigms do not generate adequate information on the mechanistic sources of marked variability in pharmacokinetics and pharmacodynamics of new therapeutic candidates, precluding treatments from being tailored for individual patients. Pharmacogenetics is the study of the hereditary basis of person-to-person variations in drug response. The focus of pharmacogenetic investigations has traditionally been unusual and extreme drug responses resulting from a single gene effect. The Human Genome Project and recent advancements in molecular genetics now present an unprecedented opportunity to study all genes in the human genome, including genes for drug metabolism, drug targets and postreceptor second messenger machinery, in relation to variability in drug safety and efficacy. In addition to sequence variations in the genome, high throughput and genome-wide transcript profiling for differentially regulated mRNA species before and during drug treatment will serve as important tools to uncover novel mechanisms of drug action. Pharmacogenetic-guided drug discovery and development represent a departure from the conventional approach which markets drugs for broad patient populations, rather than smaller groups of patients in whom drugs may work more optimally. Pharmacogenetics provides a rational framework to minimise the uncertainty in outcome of drug therapy and clinical trials and thereby should significantly reduce the risk of drug toxicity.
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Affiliation(s)
- V Ozdemir
- Department of Pharmacology, University of Toronto, Ontario, Canada
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Hughes DA, Walley T. Economic evaluations during early (phase II) drug development: a role for clinical trial simulations? PHARMACOECONOMICS 2001; 19:1069-1077. [PMID: 11735674 DOI: 10.2165/00019053-200119110-00001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Faced with increasing demands on demonstrating cost effectiveness, pharmaceutical companies are required to conduct pharmacoeconomic evaluations throughout the drug development programme. At present, there is particular emphasis in the literature on burden-of-illness studies and on economic evaluations conducted alongside phase III clinical trials but not on those conducted during phase II clinical trials. This article describes modelling techniques, namely clinical trial simulations (CTS), which are gaining popularity in the clinical research community, but which might also prove to be beneficial during the conduct of these early pharmacoeconomic evaluations. The basic concepts and structure of CTS are described by using published examples of simulations of antipsychotic and anticancer drugs. With the use of an illustrative example of a hypothetical cholinesterase inhibitor for Alzheimer's disease, an integrated CTS-based pharmacoeconomic evaluation is presented. The results demonstrate how the modelling may be of value in 'go/no-go' decisions during the drug development programme.
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Affiliation(s)
- D A Hughes
- Prescribing Research Group, Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, UK.
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Abstract
We propose a framework for considering the role of pharmacokinetic/pharmacodynamic modeling in drug development and an appraisal of its current and potential impact on that activity. After some introduction, definitions, and background information on drug development, we discuss subject-matter models that underlie pharmacokinetic/pharmacodynamic modeling and show how they determine appropriate statistical models. We discuss the broad role modeling can play in drug development, enhancing primarily the "learning" steps, i.e. acquiring the information needed for the label and for planning efficient confirmatory clinical trials. Examples of past applications of modeling to drug development are presented in tabular form, followed by a discussion of some practical issues in application. Modeling will not reach its potential utility until it is manifest as a visible and separate work unit within a drug development program. We suggest that that work unit is the "in numero" study: a protocol-driven exercise designed to extract additional information, and/or answer a specific drug-development question, through an integrated model-based (meta-) analysis of existent raw data, often pooled across separate (clinical) studies.
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Affiliation(s)
- L B Sheiner
- Department of Laboratory Medicine, University of California San Francisco 94143, USA.
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Ozdemir V, Kalow W, Tang BK, Paterson AD, Walker SE, Endrenyi L, Kashuba AD. Evaluation of the genetic component of variability in CYP3A4 activity: a repeated drug administration method. PHARMACOGENETICS 2000; 10:373-88. [PMID: 10898107 DOI: 10.1097/00008571-200007000-00001] [Citation(s) in RCA: 287] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The CYP3A4 enzyme contributes to the disposition of more than 60 therapeutically important drugs and displays marked person-to-person variability of the catalytic function. However, the extent of genetic contribution to variability in CYP3A4 activity remains elusive. Recently, we showed that a comparison of between- (SDb2) and within-person (SDW2) variances provides an estimate of the genetic component of variability in drug disposition. The aim of the present analysis was to assess the genetic control of CYP3A4 activity in vivo. A computerized literature search was conducted covering 1966 to September 1999 to identify studies reporting repeated administration of CYP3A4 substrates. The genetic contribution (rGC) to disposition of each CYP3A4 substrate was obtained by the formula (SDb2-SDW2)/SDb2. The rGC values approaching 1.0, point to overwhelming genetic control, whereas those close to zero suggest that environmental factors dominate. A total of 16 studies with 10 different CYP3A4 substrates were identified (n = 161 subjects). The rGC for hepatic CYP3A4 activity as measured by midazolam plasma clearance or the erythromycin breath test was 0.96 (0.92-0.98) (95% Cl) and 0.89 (0.65-0.98), respectively (P < 0.05). The point estimates of rGC for composite (hepatic + intestinal) CYP3A4 activity measured after oral administration of cyclosporine, ethinylestradiol, ethylmorphine, nifedipine and nitrendipine, ranged from 0.66-0.98 (median: 0.83) (P < 0.05). Cyclosporine data suggested a higher genetic control of CYP3A4 at night than during the day. These data indicate that further molecular genetic investigations are warranted to identify genetic variants at CYP3A4 or elsewhere in the genome which contribute to regulation of CYP3A4 activity.
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Affiliation(s)
- V Ozdemir
- Department of Pharmacology and Pharmaceutical Sciences, University of Toronto, Ontario, Canada
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Thomson AH, Vasey PA, Murray LS, Cassidy J, Fraier D, Frigerio E, Twelves C. Population pharmacokinetics in phase I drug development: a phase I study of PK1 in patients with solid tumours. Br J Cancer 1999; 81:99-107. [PMID: 10487619 PMCID: PMC2374352 DOI: 10.1038/sj.bjc.6690657] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Doxorubicin pharmacokinetics were determined in 33 patients with solid tumours who received intravenous doses of 20-320 mg m(-2) HPMA copolymer bound doxorubicin (PK1) in a phase I study. Since assay constraints limited the data at lower doses, conventional analysis was not feasible and a 'population approach' was used. Bound concentrations were best described by a biexponential model and further analyses revealed a small influence of dose or weight on V1 but no identifiable effects of age, body surface area, renal or hepatic function. The final model was: clearance (Q) 0.194 I h(-1); central compartment volume (V1) 4.48 x (1+0.00074 x dose (mg)) I; peripheral compartment volume (V2) 7.94 I; intercompartmental clearance 0.685 I h(-1). Distribution and elimination half-lives had median estimates of 2.7 h and 49 h respectively. Free doxorubicin was present at most sampling times with concentrations around 1000 times lower than bound doxorubicin values. Data were best described using a biexponential model and the following parameters were estimated: apparent clearance 180 I h-(-1); apparent V1 (I) 1450 x (1+0.0013 x dose (mg)), apparent V2 (I) 21 300 x (1-0.0013 x dose (mg)) x (1+2.95 x height (m)) and apparent Q 6950 I h(-1). Distribution and elimination half-lives were 0.13 h and 85 h respectively.
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Affiliation(s)
- A H Thomson
- Department of Medicine & Therapeutics, University of Glasgow, UK
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Abstract
We review the role of cross-over trials in pharmacokinetic and pharmacodynamic studies, in particular as applied in phase I. Design and analysis considerations are covered. We also consider the use of pharmacokinetic and pharmacodynamic theories in planning cross-over trials. Finally some practical considerations are covered.
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Affiliation(s)
- S Senn
- Department of Statistical Science, University College London, UK.
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30
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Charles BG. Fundamentals of Population Modelling Opportunities for Hospital Pharmacy Practice. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/jppr199929288] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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