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DeMaagd GA, DeMaagd DR, Philip A. Delirium and its Pharmacological Causes in Older People, Part Two. Sr Care Pharm 2021; 36:534-547. [PMID: 34717785 DOI: 10.4140/tcp.n.2021.534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Delirium is a syndrome that can arise from many causes or underlying conditions, and though it has been reported in younger patients, it is more prevalent in older people, though it can occur in other age groups as well. Identifying delirium is challenging in older people because of the coexistence of underlying dementia or depression, which may further complicate the presentation. Drug-induced delirium is one of the major causes of delirium, and evaluation of this potential cause or contribution is an important component of the evaluation process, since it can lead to poor patient outcomes. Part one of this three part series reviewed the epidemiology, pathophysiology, evaluation, diagnostic process, and causes of delirium in older people, with a focus on the pharmacological causes. Part two of this series continues to review drugs and drug classes that can cause or contribute to delirium in older people.
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Affiliation(s)
| | | | - Ashok Philip
- Union University College of Pharmacy, Jackson, Tennessee
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Li Z, Gao Y, Yang C, Xiang Y, Zhang W, Zhang T, Su R, Lu C, Zhuang X. Assessment and Confirmation of Species Difference in Nonlinear Pharmacokinetics of Atipamezole with Physiologically Based Pharmacokinetic Modeling. Drug Metab Dispos 2019; 48:41-51. [PMID: 31699808 DOI: 10.1124/dmd.119.089151] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 10/24/2019] [Indexed: 11/22/2022] Open
Abstract
Atipamezole, an α 2-adrenoceptor antagonist, displayed nonlinear pharmacokinetics (PK) in rats. The aim of this study was to understand the underlying mechanisms of nonlinear PK in rats and linear PK in humans and develop physiologically based PK models (PBPK) to capture and validate this phenomenon. In vitro and in vivo data were generated to show that metabolism is the main clearance pathway of atipamezole and species differences exist. Where cytochrome P450 (P450) was responsible for the metabolism in rats with a low Michaelis constant, human-specific UDP-glucuronosyltransferase 2B10- and 1A4-mediated N-glucuronidation was identified as the leading contributor to metabolism in humans with a high V max capacity. Saturation of metabolism was observed in rats at pharmacologically relevant doses, but not in humans at clinically relevant doses. PBPK models were developed using GastroPlus software to predict the PK profile of atipamezole in rats after intravenous or intramuscular administration of 0.1 to 3 mg/kg doses. The model predicted the nonlinear PK of atipamezole in rats and predicted observed exposures within 2-fold across dose levels. Under the same model structure, a human PBPK model was developed using human in vitro metabolism data. The PBPK model well described human concentration-time profiles at 10-100 mg doses showing dose-proportional increases in exposure. This study demonstrated that PBPK is a useful tool to predict human PK when interspecies extrapolation is not applicable. The nonlinear PK in rat and linear PK in human were characterized in vitro and allowed the prospective human PK via intramuscular dosing to be predicted at the preclinical stage. SIGNIFICANCE STATEMENT: This study demonstrated that PBPK is a useful tool for predicting human PK when interspecies extrapolation is not applicable due to species unique metabolism. Atipamezole, for example, is metabolized by P450 in rats and by N-glucuronidation in humans that were hypothesized to be the underlying reasons for a nonlinear PK in rats and linear PK in humans. This was testified by PBPK simulation in this study.
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Affiliation(s)
- Zheng Li
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China (Z.L., Y.G., C.Y., Y.X., W.Z., T.Z., R.S., X.Z.); and Department of DMPK, Sanofi Company, Waltham, Massachusetts (C.L.)
| | - You Gao
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China (Z.L., Y.G., C.Y., Y.X., W.Z., T.Z., R.S., X.Z.); and Department of DMPK, Sanofi Company, Waltham, Massachusetts (C.L.)
| | - Chunmiao Yang
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China (Z.L., Y.G., C.Y., Y.X., W.Z., T.Z., R.S., X.Z.); and Department of DMPK, Sanofi Company, Waltham, Massachusetts (C.L.)
| | - Yanan Xiang
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China (Z.L., Y.G., C.Y., Y.X., W.Z., T.Z., R.S., X.Z.); and Department of DMPK, Sanofi Company, Waltham, Massachusetts (C.L.)
| | - Wenpeng Zhang
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China (Z.L., Y.G., C.Y., Y.X., W.Z., T.Z., R.S., X.Z.); and Department of DMPK, Sanofi Company, Waltham, Massachusetts (C.L.)
| | - Tianhong Zhang
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China (Z.L., Y.G., C.Y., Y.X., W.Z., T.Z., R.S., X.Z.); and Department of DMPK, Sanofi Company, Waltham, Massachusetts (C.L.)
| | - Ruibin Su
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China (Z.L., Y.G., C.Y., Y.X., W.Z., T.Z., R.S., X.Z.); and Department of DMPK, Sanofi Company, Waltham, Massachusetts (C.L.)
| | - Chuang Lu
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China (Z.L., Y.G., C.Y., Y.X., W.Z., T.Z., R.S., X.Z.); and Department of DMPK, Sanofi Company, Waltham, Massachusetts (C.L.)
| | - Xiaomei Zhuang
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, China (Z.L., Y.G., C.Y., Y.X., W.Z., T.Z., R.S., X.Z.); and Department of DMPK, Sanofi Company, Waltham, Massachusetts (C.L.)
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Guk J, Lee SG, Chae D, Kim JH, Park K. Optimal Dosing Regimen of Phenytoin for Korean Epilepsy Patients: From Premature Babies to the Elderly. J Pharm Sci 2019; 108:2765-2773. [DOI: 10.1016/j.xphs.2019.03.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 02/24/2019] [Accepted: 03/14/2019] [Indexed: 12/20/2022]
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Fukuchi Y, Toshimoto K, Mori T, Kakimoto K, Tobe Y, Sawada T, Asaumi R, Iwata T, Hashimoto Y, Nunoya KI, Imawaka H, Miyauchi S, Sugiyam Y. Analysis of Nonlinear Pharmacokinetics of a Highly Albumin-Bound Compound: Contribution of Albumin-Mediated Hepatic Uptake Mechanism. J Pharm Sci 2017; 106:2704-2714. [PMID: 28465151 DOI: 10.1016/j.xphs.2017.04.052] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 04/20/2017] [Accepted: 04/20/2017] [Indexed: 12/20/2022]
Abstract
The cause of nonlinear pharmacokinetics (PK) (more than dose-proportional increase in exposure) of a urea derivative under development (compound A: anionic compound [pKa: 4.4]; LogP: 6.5; and plasma protein binding: 99.95%) observed in a clinical trial was investigated. Compound A was metabolized by CYP3A4, UGT1A1, and UGT1A3 with unbound Km of 3.3-17.8 μmol/L. OATP1B3-mediated uptake of compound A determined in the presence of human serum albumin (HSA) showed that unbound Km and Vmax decreased with increased HSA concentration. A greater decrease in unbound Km than in Vmax resulted in increased uptake clearance (Vmax/unbound Km) with increased HSA concentration, the so-called albumin-mediated uptake. At 2% HSA concentration, unbound Km was 0.00657 μmol/L. A physiologically based PK model assuming saturable hepatic uptake nearly replicated clinical PK of compound A. Unbound Km for hepatic uptake estimated from the model was 0.000767 μmol/L, lower than the in vitro unbound Km at 2% HSA concentration, whereas decreased Km with increased concentration of HSA in vitro indicated lower Km at physiological HSA concentration (4%-5%). In addition, unbound Km values for metabolizing enzymes were much higher than unbound Km for OATP1B3, indicating that the nonlinear PK of compound A is primarily attributed to saturated OATP1B3-mediated hepatic uptake of compound A.
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Affiliation(s)
- Yukina Fukuchi
- Pharmacokinetic Research Laboratories, Ono Pharmaceutical Company, Ltd., Ibaraki, Japan
| | - Kota Toshimoto
- Sugiyama Laboratory, RIKEN Innovation Center, RIKEN, Kanagawa, Japan
| | - Takanori Mori
- Pharmacokinetic Research Laboratories, Ono Pharmaceutical Company, Ltd., Ibaraki, Japan
| | - Keisuke Kakimoto
- Pharmacokinetic Research Laboratories, Ono Pharmaceutical Company, Ltd., Ibaraki, Japan
| | - Yoshifusa Tobe
- Pharmacokinetic Research Laboratories, Ono Pharmaceutical Company, Ltd., Ibaraki, Japan
| | - Takeshi Sawada
- Pharmacokinetic Research Laboratories, Ono Pharmaceutical Company, Ltd., Ibaraki, Japan
| | - Ryuta Asaumi
- Pharmacokinetic Research Laboratories, Ono Pharmaceutical Company, Ltd., Ibaraki, Japan
| | - Takeyuki Iwata
- Oncology Clinical Development Planning, Ono Pharmaceutical Company, Ltd., Osaka, Japan
| | - Yoshitaka Hashimoto
- Translational Medicine Center, Ono Pharmaceutical Company, Ltd., Osaka, Japan
| | - Ken-Ichi Nunoya
- Pharmacokinetic Research Laboratories, Ono Pharmaceutical Company, Ltd., Ibaraki, Japan
| | - Haruo Imawaka
- Pharmacokinetic Research Laboratories, Ono Pharmaceutical Company, Ltd., Ibaraki, Japan.
| | - Seiji Miyauchi
- Sugiyama Laboratory, RIKEN Innovation Center, RIKEN, Kanagawa, Japan
| | - Yuichi Sugiyam
- Sugiyama Laboratory, RIKEN Innovation Center, RIKEN, Kanagawa, Japan
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Abstract
Minimizing toxicity while maximizing efficacy is a common goal in the treatment of any condition but its importance is underscored in the discipline of oncology because of the serious nature of many chemotherapeutic toxicities and the risk of cancer recurrence or disease progression. The challenge of achieving an optimal therapeutic index is especially augmented in the elderly population because of age-related metabolism changes and interacting concurrent medications. Additional factors, such as germline mutations in drug-metabolizing enzymes and other pharmacogenomic alterations, may have more pronounced effects in elderly patients, given their predisposition to altered pharmacokinetics and pharmacodynamics with resulting increased risk of toxicity. Examples of the possible interplay of these factors will be discussed using tamoxifen, paclitaxel, codeine, and fluorouracil as starting points. Limited participation of the elderly in many cancer trials, especially trials assessing drug exposure, makes much knowledge on the interaction of these patient and environmental factors speculative in nature but presents an opportunity for future research to achieve better optimization of chemotherapeutic agents in the elderly.
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Linares OA, Daly D, Linares AD, Stefanovski D, Boston RC. Personalized Oxycodone Dosing: Using Pharmacogenetic Testing and Clinical Pharmacokinetics to Reduce Toxicity Risk and Increase Effectiveness. PAIN MEDICINE 2014; 15:791-806. [DOI: 10.1111/pme.12380] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Wright DFB, Begg EJ. The 'apparent clearance' of free phenytoin in elderly vs. younger adults. Br J Clin Pharmacol 2011; 70:132-8. [PMID: 20642556 DOI: 10.1111/j.1365-2125.2010.03673.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT The clearance of many drugs is reduced in the elderly, but the data regarding phenytoin are conflicting. Most studies have estimated phenytoin metabolic clearance using total drug concentrations (bound plus unbound), which may be confounded by protein binding effects. Free phenytoin concentrations are independent of protein binding and should more accurately reflect true metabolic clearance changes in elderly patients. WHAT THIS STUDY ADDS The two studies reported in this paper suggest a trend towards reduced free phenytoin 'apparent clearance' in the elderly, although statistically significant results were not found. Other published studies have largely found similar trends, suggesting an age effect. AIMS To test the hypothesis that the 'apparent clearance' of free phenytoin is reduced in elderly patients. METHODS Two separate studies were conducted comparing free phenytoin 'apparent clearance' in elderly vs. younger adults. The first study was a retrospective analysis of free phenytoin concentrations measured at Christchurch Hospital from 1997 to 2006. In the second study free phenytoin concentrations were measured prospectively in ambulatory subjects who were taking phenytoin regularly. RESULTS In the retrospective study (n= 29), free phenytoin 'apparent clearance' was 0.27 +/- 0.04 l kg(-1) day(-1) (95% CI 0.19, 0.34) in the elderly cohort vs. 0.37 +/- 0.06 l kg(-1) day(-1) (95% CI 0.22, 0.52) in younger adults, but the difference was not statistically significant. In the prospective study, free phenytoin 'apparent clearance' showed a non-significant trend to being reduced in the elderly patients (0.12 +/- 0.02 l kg(-1) day(-1), 95% CI 0.07, 0.17) compared with the younger cohort (0.18 +/- 0.07 l kg(-1) day(-1), 95% CI 0.09, 0.26) in those not taking interacting drugs (n= 21). CONCLUSIONS This research does not prove the hypothesis that the 'apparent clearance' of free phenytoin is reduced in the elderly. However, the trends found in these two studies are supported by trends in the same direction in other published studies, suggesting an age effect.
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Affiliation(s)
- Daniel F B Wright
- Department of Clinical Pharmacology, Christchurch Hospital, Christchurch, New Zealand
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Gareri P, De Fazio P, Russo E, Marigliano N, De Fazio S, De Sarro G. The safety of clozapine in the elderly. Expert Opin Drug Saf 2008; 7:525-38. [PMID: 18759705 DOI: 10.1517/14740338.7.5.525] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Clozapine was the first atypical 'broad spectrum' antipsychotic drug to be marketed and the first agent approved for the treatment of schizophrenia refractory to other medications. It is also effective for the treatment of aggressive behaviour in schizophrenic and demented patients and in the management of psychosis and aggression in Parkinson's disease and Lewy body dementia. OBJECTIVE The aim of this review is to study the safety of clozapine for use in elderly patients. METHODS An extensive Medline search was made. Some studies that were referenced in reports from our pharmacovigilance centre and from regulatory agencies such as the FDA, EMEA and WHO were included. CONCLUSIONS Clozapine treatment in the elderly requires a careful geriatric assessment. However, its use is strongly limited by the possibility of onset of severe adverse effects such as potentially fatal agranulocytosis, myocarditis and others such as seizures, weight gain and metabolic adverse effects.
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Affiliation(s)
- Pietro Gareri
- University "Magna Graecia" of Catanzaro, "Mater Domini" University Hospital, Clinical Pharmacology and Pharmacovigilance Unit, Faculty of Medicine and Surgery, Department of Experimental and Clinical Medicine, Catanzaro, Italy.
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Schwartz JB. The Current State of Knowledge on Age, Sex, and Their Interactions on Clinical Pharmacology. Clin Pharmacol Ther 2007; 82:87-96. [PMID: 17495875 DOI: 10.1038/sj.clpt.6100226] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Pharmacokinetic and pharmacodynamic changes occur with increasing age. Sex differences in pharmacokinetics and pharmacodynamics exist and persist at older age. The issue for the clinician is how to best treat the older patient with currently available knowledge. This communication highlights age- and sex-related differences in pharmacokinetics that should influence clinical practice and prescribing guidelines to optimize clinical responses. The most compelling data for sex-specific medication dosing guidelines for older patients are related to volume of distribution differences, or size differences, between the sexes and to differences in glomerular filtration rates.
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Affiliation(s)
- J B Schwartz
- Jewish Home of San Francisco, University of California San Francisco, San Francisco, California, USA.
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Perucca E. Age‐Related Changes in Pharmacokinetics: Predictability and Assessment Methods. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2007; 81:183-99. [PMID: 17433924 DOI: 10.1016/s0074-7742(06)81011-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Although there have been relatively few studies of the pharmacokinetics of antiepileptic drugs (AEDs) in old age, available evidence indicates that the clearance of most old and new generation AEDs is reduced on average by about 20-40% in elderly patients compared with nonelderly adults. Depending on the pharmacokinetic characteristics of the drug, the reduction in clearance can be ascribed to a physiological reduction in rate of drug metabolism, to a decrease in renal excretion rate, or to both. Studies have consistently demonstrated that interindividual pharmacokinetic variability in old age is particularly prominent, due not only to the influence of aging-related physiological changes, but also to the impact of comorbidities and drug-drug interactions. For extensively metabolized drugs, there are no reliable tools to predict with a high degree of accuracy the pharmacokinetic behavior of an AED in an individual patient. With renally eliminated drugs, determination of creatinine clearance may provide a useful clue in predicting individual changes in drug clearance and the consequent need for dosage adjustment. In the therapeutic setting, measurement of serum AED concentrations can be valuable in individualizing dosage in an elderly person, even though it should be remembered that in the case of drugs that are highly bound to plasma proteins the total serum concentration may underestimate the level of unbound, pharmacologically active drug. Because aging is also associated with important pharmacodynamic changes that may alter the relationship between serum drug concentration and pharmacological effects, pharmacokinetic measurements alone are not a substitute for the need to monitor clinical response carefully and to adjust dosage accordingly.
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Affiliation(s)
- Emilio Perucca
- Clinical Pharmacology Unit, Department of Internal Medicine and Therapeutics, University of Pavia, Pavia, Italy
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Perucca E, Aldenkamp A, Tallis R, Krämer G. Role of valproate across the ages. Treatment of epilepsy in the elderly. Acta Neurol Scand 2006; 184:28-37. [PMID: 16776494 DOI: 10.1111/j.1600-0404.2006.00668.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
In June 2005, a team of experts participated in a workshop with the objective of reaching agreement on several important aspects of valproate in the treatment of elderly patients with epilepsy. Epilepsy in the elderly is relatively common and its incidence increases for each decade after age 60. The aetiology and manifestations of epilepsies in the elderly are complex because of comorbidity and other underlying risk factors. A consensus was reached that elderly patients who present with a seizure disorder should be referred rapidly to a specialist and that diagnosis should be improved by using a multidisciplinary team of cardiologists, neurologists and epilepsy experts (syncope, falls and seizure specialists). This is especially important to avoid mistreatment with antiepileptic drugs (AEDs). There was consensus that the elderly are generally more susceptible to the adverse effects of AEDs than younger adults. For these reasons, in older persons AEDs should be started at low dosages, and titrated slowly according to clinical response. Some of the most troublesome side effects of AEDs in the elderly include sedation and cognitive side effects, as well as osteoporosis. Drug-drug interactions should be given special consideration. There was consensus that the pharmacokinetics of all AEDs are altered in the elderly, and that the most significant change common to all AEDs is a moderate reduction in renal and metabolic clearance. Predicting pharmacokinetic changes in the individual, however, can be very difficult because multiple factors contribute to a high inter-patient variability. There was agreement on the advantages and disadvantages of the use of valproate in the elderly, and consensus that valproate is a useful option in this population. There was no consensus, however, on whether valproate should be considered among the preferred first-line treatments in the elderly.
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Affiliation(s)
- E Perucca
- Institute of Neurology IRCCS C. Mondino Foundation, and Clinical Pharmacology Unit, Department of Internal Medicine and Therapeutics, University of Pavia, Piazza Botta 10, 27100 Pavia, Italy.
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Perucca E, Berlowitz D, Birnbaum A, Cloyd JC, Garrard J, Hanlon JT, Levy RH, Pugh MJ. Pharmacological and clinical aspects of antiepileptic drug use in the elderly. Epilepsy Res 2006; 68 Suppl 1:S49-63. [PMID: 16207524 DOI: 10.1016/j.eplepsyres.2005.07.017] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2005] [Revised: 07/27/2005] [Accepted: 07/27/2005] [Indexed: 11/23/2022]
Abstract
In this article, epidemiological and clinical aspects related to the use of antiepileptic drugs (AEDs) in the elderly are highlighted. Studies have shown that people with epilepsy receiving AED treatment show important deficits in physical and social functioning compared with age-matched people without epilepsy. To what extent these deficits can be ascribed to epilepsy per se or to the consequences of AED treatment remains to be clarified. The importance of characterizing the effects of AEDs in an elderly population is highlighted by epidemiological surveys indicating that the prevalence of AED use is increased in elderly people, particularly in those living in nursing homes. Both the pharmacokinetics and the pharmacodynamics of AEDs may be altered in old age, which may contribute to the observation that AEDs are among the drug classes most commonly implicated as causing adverse drug reactions in an aged population. Age alone is one of several contributors to alterations in AED response in the elderly; other factors include physical frailty, co-morbidities, dietary influences, and drug interactions. Individualization of dosage, avoidance of unnecessary polypharmacy, and careful observation of clinical response are essential for an effective and safe utilization of AEDs in an elderly population.
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Affiliation(s)
- E Perucca
- Institute of Neurology IRCCS C. Mondino Foundation and Clinical Pharmacology Unit, University of Pavia, Piazza Botta 10, 27100 Pavia, Italy.
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Messina S, Battino D, Croci D, Mamoli D, Ratti S, Perucca E. Phenobarbital Pharmacokinetics in Old Age: A Case-matched Evaluation Based on Therapeutic Drug Monitoring Data. Epilepsia 2005; 46:372-7. [PMID: 15730534 DOI: 10.1111/j.0013-9580.2005.47504.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE To assess the influence of aging on the pharmacokinetics of phenobarbital (PB) at steady state in patients receiving long-term therapy. METHODS Serum PB concentrations from the database of the therapeutic drug monitoring service of a large neurological hospital were used to calculate apparent clearance values (CL/F) in 224 patients aged 65 years and older (mean, 73 +/- 6.1 years). CL/F values in these patients were compared with those determined in an equal number of controls aged 20 to 50 years (mean, 35.7 +/- 7.9 years) and matched for gender, body weight, and type of anticonvulsant comedication. Correlations of CL/F with age, body weight, gender, and comedication also were explored within each age group. RESULTS PB CL/F values were significantly lower in elderly patients than in controls (3.2 +/- 0.8 vs. 4.1 +/- 1.2 ml/h/kg; p < 0.0001). Age was identified as a statistically significant predictor of CL/F at multiple regression analysis, but it accounted for only a modest component of the interindividual pharmacokinetic variation. Comedication with carbamazepine (CBZ) and phenytoin (PHT) was associated with a moderate decrease in PB CL/F, which reached statistical significance in the elderly group (p < 0.01 for CBZ comedication; p < 0.001 for PHT comedication). CONCLUSIONS Aging is associated with a significant decrease in PB clearance, which might be related to a reduction in glomerular filtration rate or diminished drug-metabolizing capacity in the liver or both. Because of this, older patients will require lower dosages to achieve serum PB concentrations comparable with those found in nonelderly adults.
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Affiliation(s)
- Sara Messina
- Carlo Besta National Neurological Institute, Milan, Italy
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Abstract
Drug dosage in the elderly requires an understanding of the age-dependent changes in drug disposition and sensitivity. The most important pharmacokinetic alteration is a decline in renal function, the elderly should therefore be treated as renally insufficient patients. Metabolic clearance is primarily reduced with drugs that display high hepatic extraction, whereas the metabolism of drugs with low hepatic extraction usually is not diminished. The reduction of metabolic clearance is especially pronounced in malnourished or frail patients. The water content of the aging body decreases, the fat content rises. Hence the distribution volume of hydrophilic drugs may be reduced in the elderly, resulting in increased plasma concentrations. In contrast, the distribution volume of liphophilic drugs is increased, their plasma concentrations may decrease. Intestinal absorption of most drugs is not altered in the elderly. Aside of these pharmacokinetic changes, one of the characteristics of old age is a progressive decline in counterregulatory (homeostatic) mechanisms. Therefore, drug effects are attenuated less, the responses are usually stronger than in younger subjects, the rate and intensity of adverse effects are higher. Examples of drug actions augmented is this manner are postural hypotension with agents that lower blood pressure, dehydration and electrolyte disturbances in response to diuretics, bleeding complications with oral anticoagulants, hypoglycemia with antidiabetics, and gastrointestinal irritation with non-steroidal anti-inflammatory drugs. The brain is an especially sensitive drug target in old age. Psychotropic drugs, anticonvulsants, and centrally acting antihypertensives may impede intellectual function and motor coordination. Hence drugs should be used restrictively in geriatric patients.
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Affiliation(s)
- Klaus Turnheim
- Institut für Pharmakologie, Medzinische Universität Wien, Währinger Str. 13a, Vienna A-1090, Austria.
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Battino D, Croci D, Mamoli D, Messina S, Perucca E. Influence of aging on serum phenytoin concentrations: a pharmacokinetic analysis based on therapeutic drug monitoring data. Epilepsy Res 2004; 59:155-65. [PMID: 15246117 DOI: 10.1016/j.eplepsyres.2004.04.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2003] [Revised: 04/03/2004] [Accepted: 04/05/2004] [Indexed: 10/26/2022]
Abstract
The influence of aging on the pharmacokinetics of phenytoin at steady-state was evaluated retrospectically by comparing apparent oral clearance values (CL/F) in 75 patients aged 65-90 years (mean, 71.7 +/- 5.3 years) receiving phenytoin alone (n = 58) or in combination with phenobarbital (n = 17) and in an equal number of control patients aged 20-50 years (mean, 36.7 +/- 8.5 years) matched for gender, body weight, and comedication. All data were derived from the database of the therapeutic drug monitoring service (TDMS) of an academic neurological hospital. On average, elderly patients were found to exhibit slightly higher CL/F values compared with controls (14.6 +/- 4.7 ml h(-1) kg(-1) versus 13.1 +/- 4.2 ml h(-1) kg(-1), P < 0.05), the difference being probably related to the dose-dependent nature of phenytoin metabolism and the fact that elderly patients received lower dosages (4.4 +/- 1.1 mg kg(-1)day(-1) versus 5.3 +/- 1.1 mg kg(-1) day(-1), P < 0.001) and had lower serum phenytoin concentrations (14.1 +/- 5.7 microg ml(-1) versus 18.6 +/- 6.8 microg ml(-1), P < 0.0001). Gender and phenobarbital comedication were not found to exert any statistically significant influence on phenytoin CL/F. By contrast, in the elderly group, CL/F values were negatively correlated with age. On average, CL/F values decreased by about one-third between 65 and 85 years of age, but interindividual variability was considerable and age explained only 7.8% of the variation in CL/F in the elderly group. Overall, these findings indicate that aging is associated with a progressive decline in phenytoin clearance, presumably as a result of decreased drug metabolizing capacity. Because assessment was based on total serum phenytoin concentrations and the unbound fraction of phenytoin is known to decrease in old age, the influence of aging as quantified in this study may underestimate the magnitude of changes in the clearance of unbound, pharmacologically active drug. Based on these data, it is prudent to utilize initially smaller phenytoin dosages in old patients, and to make subsequent dose adjustments based on clinical response and serum drug level measurements. Interpretation of the latter, however, should take into account the possibility of an increase in the fraction of unbound drug.
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Affiliation(s)
- Dina Battino
- Carlo Besta National Neurological Institute, Via Celoria 11, 20133 Milan, Italy.
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Wagner GL, Wilms EB, Van Donselaar CA, Vecht CJ. Levetiracetam: preliminary experience in patients with primary brain tumours. Seizure 2003; 12:585-6. [PMID: 14630498 DOI: 10.1016/s1059-1311(03)00096-7] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Affiliation(s)
- G L Wagner
- Department of Neurology, Medical Center Haaglanden Westeinde, Den Haag, The Netherlands
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Abstract
The age-related changes in the functions and composition of the human body require adjustments of drug selection and dosage for old individuals. Drug excretion via the kidneys declines with age, the elderly should therefore be treated as renally insufficient patients. The metabolic clearance is primarily reduced with drugs that display high hepatic extraction ('blood flow-limited metabolism'), whereas the metabolism of drugs with low hepatic extraction ('capacity-limited metabolism') usually is not diminished. Reduction of metabolic drug elimination is more pronounced in malnourished or frail subjects. The water content of the aging body decreases, the fat content rises, hence the distribution volume of hydrophilic compounds is reduced in the elderly, whereas that of lipophilic drugs is increased. Intestinal absorption of most drugs is not altered in the elderly. Aside of these pharmacokinetic changes, one of the characteristics of old age is a progressive decline in counterregulatory (homeostatic) mechanisms. Therefore drug effects are mitigated less, the reactions are usually stronger than in younger subjects, the rate and intensity of adverse effects are higher. Examples of drug effects augmented is this manner are postural hypotension with agents that lower blood pressure, dehydration, hypovolemia, and electrolyte disturbances in response to diuretics, bleeding complications with oral anticoagulants, hypoglycemia with antidiabetics, and gastrointestinal irritation with non-steroidal anti-inflammatory drugs. The brain is an especially sensitive drug target in old age. Psychotropic drugs but also anticonvulsants and centrally acting antihypertensives may impede intellectual functions and motor coordination. The antimuscarinic effects of some antidepressants and neuroleptic drugs may be responsible for agitation, confusion, and delirium in elderly. Hence drugs should be used very restrictively in geriatric patients. If drug therapy is absolutely necessary, the dosage should be titrated to a clearly defined clinical or biochemical therapeutic goal starting from a low initial dose.
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Affiliation(s)
- Klaus Turnheim
- Institut für Pharmakologie, Universität Wien, Währinger Str. 13a, Vienna A-1090, Austria.
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Battino D, Croci D, Rossini A, Messina S, Mamoli D, Perucca E. Serum carbamazepine concentrations in elderly patients: a case-matched pharmacokinetic evaluation based on therapeutic drug monitoring data. Epilepsia 2003; 44:923-9. [PMID: 12823575 DOI: 10.1046/j.1528-1157.2003.62202.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To assess the influence of aging on the steady-state pharmacokinetics of carbamazepine (CBZ) in a large population of patients evaluated in a therapeutic drug monitoring (TDM) setting. METHODS The database of a large TDM service was used to identify retrospectively steady-state serum CBZ concentrations in 157 elderly patients with epilepsy (65 years and older) treated with CBZ alone or in combination with phenobarbital (PB). CBZ apparent oral clearance (CL/F) values were calculated and compared with those determined in an equal number of controls aged 20 to 50 years, and matched for gender, body weight, and comedication. RESULTS Compared with corresponding controls, mean CBZ CL/F values were 23% and 24% lower, respectively, in the groups of elderly patients receiving monotherapy (57.1 +/- 20.6 vs. 74.6 +/- 28.3 ml/h/kg; p < 0.0001) and PB comedication (74.7 +/- 25.5 vs. 98.7 +/- 34.9 ml/h/kg; p < 0.01). Within each age group, patients comedicated with PB showed significantly higher CBZ CL/F values than those on monotherapy. A negative correlation between CL/F and age was found both within the monotherapy and the PB comedicated groups. In addition, CL/F values showed a positive relation with the administered daily dosage, which persisted within subgroups homogeneous for age and comedication. The independent influence of age, CBZ dosage, and comedication on CBZ CL/F was confirmed by multiple regression analysis. CONCLUSIONS CBZ CL/F is decreased in an age-dependent manner in elderly patients compared with younger subjects, presumably because a reduction in the rate of CYP3A4-mediated drug metabolism. Elderly patients retain their sensitivity to dose-dependent autoinduction and to heteroinduction by enzyme-inducing AEDs, but their metabolic rates remain considerably below those observed in matched controls. As a result of this, patients in old age will require lower CBZ dosages to achieve serum concentrations comparable with those found in nonelderly adults.
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Affiliation(s)
- Dina Battino
- Carlo Besta National Neurological Institute, Milan, Italy.
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