Showing papers in "Clinical Pharmacology & Therapeutics in 2008"
TL;DR: Nanomaterials have unique physicochemical properties, such as ultra small size, large surface area to mass ratio, and high reactivity, which are different from bulk materials of the same composition, which can be used to overcome some of the limitations found in traditional therapeutic and diagnostic agents.
Abstract: Nanotechnology is the understanding and control of matter generally in the 1-100 nm dimension range. The application of nanotechnology to medicine, known as nanomedicine, concerns the use of precisely engineered materials at this length scale to develop novel therapeutic and diagnostic modalities. Nanomaterials have unique physicochemical properties, such as ultra small size, large surface area to mass ratio, and high reactivity, which are different from bulk materials of the same composition. These properties can be used to overcome some of the limitations found in traditional therapeutic and diagnostic agents.
2,202 citations
TL;DR: This article attempts to provide a brief overview of the main determinants of antibody pharmacokinetics and pharmacodynamics.
Abstract: More than 20 monoclonal antibodies have been approved as therapeutic drugs by the US Food and Drug Administration, and it is quite likely that the number of approved antibodies will double in the next 7-10 years. Antibody drugs show several desirable characteristics, including good solubility and stability, long persistence in the body, high selectivity and specificity, and low risk for bioconversion to toxic metabolites. However, many antibody drugs demonstrate attributes that complicate drug development, including very poor oral bioavailability, incomplete absorption following intramuscular or subcutaneous administration, nonlinear distribution, and nonlinear elimination. In addition, antibody administration often leads to an endogenous antibody response, which may alter the pharmacokinetics and efficacy of the therapeutic antibody. Antibodies have been developed for a wide range of disease conditions, with effects produced through a complex array of mechanisms. This article attempts to provide a brief overview of the main determinants of antibody pharmacokinetics and pharmacodynamics. Clinical Pharmacology & Therapeutics (2008); 84, 5, 548-558 doi:10.1038/clpt.2008.170.
884 citations
TL;DR: A “opt‐out” model was implemented after significant review and revision to develop a DNA biobank linked to phenotypic data derived from an electronic medical record (EMR) system.
Abstract: Our objective was to develop a DNA biobank linked to phenotypic data derived from an electronic medical record (EMR) system. An "opt-out" model was implemented after significant review and revision. The plan included (i) development and maintenance of a de-identified mirror image of the EMR, namely, the "synthetic derivative" (SD) and (ii) DNA extracted from discarded blood samples and linked to the SD. Surveys of patients indicated general acceptance of the concept, with only a minority ( approximately 5%) opposing it. As a result, mechanisms to facilitate opt-out included publicity and revision of a standard "consent to treatment" form. Algorithms for sample handling and procedures for de-identification were developed and validated in order to ensure acceptable error rates (<0.3 and <0.1%, respectively). The rate of sample accrual is 700-900 samples/week. The advantages of this approach are the rate of sample acquisition and the diversity of phenotypes based on EMRs.
815 citations
TL;DR: The goal was to develop and validate a pharmacogenetic algorithm that explained 53–54% of the variability in the warfarin dose in the derivation and validation cohorts.
Abstract: Initiation of warfarin therapy using trial-and-error dosing is problematic. Our goal was to develop and validate a pharmacogenetic algorithm. In the derivation cohort of 1,015 participants, the independent predictors of therapeutic dose were: VKORC1 polymorphism -1639/3673 G>A (-28% per allele), body surface area (BSA) (+11% per 0.25 m(2)), CYP2C9(*)3 (-33% per allele), CYP2C9(*)2 (-19% per allele), age (-7% per decade), target international normalized ratio (INR) (+11% per 0.5 unit increase), amiodarone use (-22%), smoker status (+10%), race (-9%), and current thrombosis (+7%). This pharmacogenetic equation explained 53-54% of the variability in the warfarin dose in the derivation and validation (N= 292) cohorts. For comparison, a clinical equation explained only 17-22% of the dose variability (P < 0.001). In the validation cohort, we prospectively used the pharmacogenetic-dosing algorithm in patients initiating warfarin therapy, two of whom had a major hemorrhage. To facilitate use of these pharmacogenetic and clinical algorithms, we developed a nonprofit website, http://www.WarfarinDosing.org.
798 citations
TL;DR: The utility of an “activity score” (AS) system to simplify genotype interpretation and improve phenotype prediction was evaluated and was most accurate if ethnicity was considered; among subjects with genotypes containing a CYP2D6*2 allele, CYP1D6 activity was significantly slower in African Americans compared to Caucasians.
Abstract: Inferring CYP2D6 phenotype from genotype is increasingly challenging, considering the growing number of alleles and their range of activity. This complexity poses a challenge in translational research where genotyping is being considered as a tool to personalize drug therapy. To simplify genotype interpretation and improve phenotype prediction, we evaluated the utility of an "activity score" (AS) system. Over 25 CYP2D6 allelic variants were genotyped in 672 subjects of primarily Caucasian and African-American heritage. The ability of genotype and AS to accurately predict phenotype using the CYP2D6 probe substrate dextromethorphan was evaluated using linear regression and clustering methods. Phenotype prediction, given as a probability for each AS group, was most accurate if ethnicity was considered; among subjects with genotypes containing a CYP2D6*2 allele, CYP2D6 activity was significantly slower in African Americans compared to Caucasians. The AS tool warrants further prospective evaluation for CYP2D6 substrates and in additional ethnic populations.
680 citations
TL;DR: Human pharmacology studies of nicotine and smoking behavior provide a basis for assessing the benefits and risks of long‐term nicotine use for harm reduction and for a potential cigarette regulatory strategy that includes reducing nicotine content of cigarettes to nonaddictive levels.
Abstract: Understanding the basic and clinical pharmacology of nicotine provides a basis for improved prevention and treatment of tobacco addiction. Nicotine acts on nicotinic cholinergic receptors in the brain to release dopamine and other neurotransmitters that sustain addiction. Neuroadaptation and tolerance involve changes in both nicotinic receptors and neural plasticity. Nicotine addiction can occur in the context of physical dependence characterized by self-medication to modulate negative affect and/or to relieve withdrawal symptoms, as well as, in light or occasional smokers, primarily for positive reinforcement in specific situations. Nicotine is metabolized primarily by CYP2A6. Its clearance exhibits considerable individual variability that is determined by genetic, racial, and hormonal (sex) factors. Genetically slow metabolism of nicotine appears to be associated with a lower level of dependence. Nicotine dependence is highly heritable and appears to be influenced by genes coding for some nicotine receptor subtypes, some neurotransmitter genes, and genes involved in neural connectivity. Novel pharmacotherapies for nicotine dependence include partial agonists for nicotinic receptors and nicotine vaccines. Pharmacogenetic studies suggest various candidate genes and a nicotine metabolism phenotype that influence outcome. Human pharmacology studies of nicotine and smoking behavior also provide a basis for assessing the benefits and risks of long-term nicotine use for harm reduction and for a potential cigarette regulatory strategy that includes reducing nicotine content of cigarettes to nonaddictive levels.
490 citations
TL;DR: The studies suggest that OCT1 genotype is a determinant of metformin pharmacokinetics, possibly reflecting species differences in hepatic expression level of the transporter.
Abstract: The goal of this study was to determine the effects of genetic variation in the organic cation transporter 1, OCT1, on the pharmacokinetics of the antidiabetic drug, metformin. Twenty healthy volunteers with known OCT1 genotype agreed to participate in the study. Each subject received two oral doses of metformin followed by collection of blood and urine samples. OCT1 genotypes had a significant (P<0.05) effect on metformin pharmacokinetics, with a higher area under the plasma concentration-time curve (AUC), higher maximal plasma concentration (Cmax), and lower oral volume of distribution (V/F) in the individuals carrying a reduced function OCT1 allele (R61C, G401S, 420del, or G465R). The effect of OCT1 on metformin pharmacokinetics in mice was less than in humans possibly reflecting species differences in hepatic expression level of the transporter. Our studies suggest that OCT1 genotype is a determinant of metformin pharmacokinetics.
448 citations
TL;DR: Drug development should seek to ensure that a clinical pharmacologic evaluation includes a population that is representative of the target therapeutic population, because ethnic diversity in drug response with respect to safety and efficacy and the resulting differences in recommended doses have been well described.
Abstract: Ethnicity is one factor that may account for the observed differences in both pharmacokinetics (PK) and pharmacodynamics (PD) of drugs, resulting in variability in response to drug therapy. Given that the applicability of clinical study results to the treatment of an individual patient is a critical consideration in a physician's choice of drug therapy, drug development should seek to ensure that a clinical pharmacologic evaluation includes a population that is representative of the target therapeutic population. Ethnic diversity in drug response with respect to safety and efficacy and the resulting differences in recommended doses have been well described for some drugs. Some of these differential responses may be related to the pharmacogenomics of a particular drug. Pharmacogenomic techniques have recently enjoyed widespread use in studies of drug exposure and response. The clinical relevance of variability in drug response due to pharmacogenomics of drug-metabolizing enzymes was considered at a September 2004 workshop cosponsored by the US Food and Drug Administration (FDA), Johns Hopkins University, and the Pharmaceutical Research and Manufacturers of America (http://www.fda.gov/cder/Offices/OCPB/workshops.htm).
365 citations
TL;DR: YP2C9 genotype‐guided warfarin therapy is more efficient and safer than the “average‐dose” protocol and future research should focus on construction of algorithms that incorporate other polymorphisms (VKORC1), host factors, and environmental influences.
Abstract: Warfarin anticoagulation effect is characterized by marked variability, some of which has been attributed to CYP2C9 polymorphisms. This study prospectively examines whether a priori knowledge of CYP2C9 genotype may improve warfarin therapy. Patients were randomly assigned to receive warfarin by a validated algorithm ("control", 96 patients) or CYP2C9 genotype-adjusted algorithms ("study", 95 patients). The first therapeutic international normalized ratio and stable anticoagulation were reached 2.73 and 18.1 days earlier in the study group, respectively (P<0.001). The faster rate of initial anticoagulation was driven by a 28% higher daily dose in the study group (P<0.001). Study group patients spent more time within the therapeutic range (80.4 vs 63.4%, respectively, P<0.001) and experienced less minor bleeding (3.2 vs 12.5%, P<0.02, respectively). In conclusion, CYP2C9 genotype-guided warfarin therapy is more efficient and safer than the "average-dose" protocol. Future research should focus on construction of algorithms that incorporate other polymorphisms (VKORC1), host factors, and environmental influences.
357 citations
TL;DR: Combining the extreme genotypes of both genes, the association between patient polymorphism and pain relief improved, allowing the detection of three groups: strong responders, responders, and non‐responders, with sensitivity close to 100% and specificity more than 70%.
Abstract: The pharmacokinetics and pharmacodynamics of morphine are under the control of several polymorphic genes, which can account for part of the observed interindividual variation in pain relief. We focused on two such genes: ABCB1/MDR1, a major determinant of morphine bioavailability, and OPRM1, which encodes for the mu-opioid receptor, the primary site of action for morphine. One hundred and forty-five patients of Italian origin undergoing morphine therapy were genotyped for the single-nucleotide polymorphism (SNP) C3435T of ABCB1/MDR1 and for the A80G SNP of OPRM1. Pain relief variability was significantly (P<0.0001) associated with both polymorphisms. Combining the extreme genotypes of both genes, the association between patient polymorphism and pain relief improved (P<0.00001), allowing the detection of three groups: strong responders, responders, and non-responders, with sensitivity close to 100% and specificity more than 70%. This study provides a good example of the possible clinical use of pharmacogenetics.
318 citations
TL;DR: Investigation of the expression of imatinib uptake transporter and efflux transporters using real‐time quantitative reverse transcription‐polymerase chain reaction in chronic myeloid leukemia patients found that pretreatment hOCT1 expression was the most powerful predictor of CCR achievement at 6 months.
Abstract: Some chronic myeloid leukemia (CML) patients do not respond to imatinib, whereas others lose an initial response. Toidentify potential imatinib failures, we investigated the expression of imatinib uptake transporter (human organic cationtransporter 1; hOCT1) and efflux transporters (ATP-binding cassette transporters ABCB1, ABCG2, and ABCC1) using real-time quantitative reverse transcription-polymerase chain reaction in 70 CML patients. Patients with high pretreatmenthOCT1 expression had superior complete cytogenetic response (CCR) rates (P¼0.008), progression-free and overallsurvival (P¼0.01 and 0.004). Pretreatment ABCB1, ABCG2, and ABCC1 levels did not correlate with treatment outcome.Regression analysis demonstrated that pretreatment hOCT1 expression was the most powerful predictor of CCRachievement at 6 months (P¼0.002). Imatinib uptake into a CML cell line with high hOCT1 expression was greater thaninto those with modest or low expression (P¼0.002). The expression of hOCT1, but not efflux transporters, is importantin determining the clinical response to imatinib.Chronic myeloid leukemia (CML) is a serious disorder of thehemopoietic stem cell, which is likely to be initiated by thefusion oncoprotein breakpoint cluster region-Abelson (BCR-ABL). Imatinib mesylate, which targets the ATP bindingpocket of the ABL kinase domain, has undoubtedly saved andimproved the quality of the lives of many thousands of CMLpatients. It has an excellent toxicity profile,
TL;DR: It is clear that the CYP2C19 genotype affects the plasma levels of clopidogrel and modulates the antiplatelet effect of clopsinogrel.
Abstract: We evaluated the effect of the CYP2C19 genotype on the pharmacokinetics and pharmacodynamcis of clopidogrel. Twenty-four subjects were divided into three groups on the basis of their CYP2C19 genotype: homozygous extensive metabolizers (homoEMs, n = 8), heterozygous EMs (heteroEMs, n = 8), and poor metabolizers (PMs, n = 8). After a single 300-mg loading dose of clopidogrel on day 1, followed by a 75-mg daily maintenance dose from days 2 to 7, we measured the plasma levels of clopidogrel and assessed the antiplatelet effect as pharmacodynamics. The mean clopidogrel area under the curve (AUC) for PMs was 1.8- and 2.9-fold higher than that for heteroEMs and homoEMs, respectively (P = 0.013). The mean peak plasma concentration in PMs was 1.8- and 4.7-fold higher than that of heteroEMs and homoEMs, respectively (P = 0.008). PMs exhibited a significantly lower antiplatelet effect than heteroEMs or homoEMs (P < 0.001). From these findings it is clear that the CYP2C19 genotype affects the plasma levels of clopidogrel and modulates the antiplatelet effect of clopidogrel.
TL;DR: Because drug development has been stagnant in terms of innovation, there exists huge potential for innovation and failure to innovate drug development will render the “big pharma” model unsustainable.
Abstract: The pharmaceutical industry is facing tremendous pressure, not only from payers but as a result of public perception, regulatory hurdles, and the intricacies of research and development (R&D). The latter two are significant in that they affect the number of drugs that may be registered by regulatory authorities, the time to discover and develop drugs, and the cost of drug development. Because drug development has been stagnant in terms of innovation, there exists huge potential for innovation. Failure to innovate drug development will render the "big pharma" model unsustainable.
TL;DR: Genetic variants of the organic cation transporter 2 (protein, OCT2; gene, SLC22A2) showed significant differences in metformin pharmacokinetics when compared with the reference genotype, with higher peak plasma concentration and area under the curve (AUC) and lower renal clearance (Clrenal), suggesting that a decrease in transport function associated with the SLC 22A2 variants results in reduced Clrenal of met formin and consequently leads to increased plasma concentrations.
Abstract: Genetic variants of the organic cation transporter 2 (protein, OCT2; gene, SLC22A2) were evaluated for their contribution to the variations in the pharmacokinetics of metformin, especially to its renal elimination. Genetic variants of SLC22A2 (c.596C>T, c.602C>T, and c.808G>T) showed significant differences in metformin pharmacokinetics when compared with the reference genotype, with higher peak plasma concentration (C(max)) and area under the curve (AUC) and lower renal clearance (Cl(renal)), thereby suggesting that a decrease in transport function associated with the SLC22A2 variants results in reduced Cl(renal) of metformin and consequently leads to increased plasma concentrations.
TL;DR: Several lines of emerging evidence indicate that kidney disease differentially affects uptake and efflux transporters and metabolic enzymes in the liver and gastrointestinal tract, and uremic toxins have been implicated as the cause.
Abstract: Several lines of emerging evidence indicate that kidney disease differentially affects uptake and efflux transporters and metabolic enzymes in the liver and gastrointestinal (GI) tract, and uremic toxins have been implicated as the cause. In patients with kidney disease, even drugs that are eliminated by nonrenal transport and metabolism could lead to important unintended consequences if they are administered without dose adjustment for reduced renal function. This is particularly so in the case of drugs with narrow therapeutic windows and may translate into clinically significant variations in exposure and response.
TL;DR: The variant CYP2C9 genotype is associated with an increased risk of major hemorrhage, which persists even after stabilization of therapy, and this association was evaluated using Cox proportional hazard regression with adjustment for demographics, comorbidity, and time‐varying covariates.
Abstract: The association of CYP2C9 and VKORC1 1173C/T genotype and risk of hemorrhage among African Americans and European Americans is presented. This association was evaluated using Cox proportional hazard regression with adjustment for demographics, comorbidity, and time-varying covariates. Forty-four major and 203 minor hemorrhages occurred over 555 person-years among 446 patients (60.6+/-15.6 years, 50% men, 227 African Americans). The variant CYP2C9 genotype conferred an increased risk for major (hazard ratio (HR) 3.0; 95% confidence interval (CI): 1.1-8.0) but not minor (HR 1.3; 95% CI: 0.8-2.1) hemorrhage. The risk of major hemorrhage was 5.3-fold (95% CI: 0.4-64.0) higher before stabilization of therapy, 2.2-fold (95% CI: 0.7-6.5) after stabilization, and 2.4-fold (95% CI: 0.8-7.4) during all periods when anticoagulation was not stable. The variant VKORC1 1173C/T genotype did not confer a significant increase in risk for major (HR 1.7; 95% CI: 0.7-4.4) or minor (HR 0.8; 95% CI: 0.5-1.3) hemorrhage. The variant CYP2C9 genotype is associated with an increased risk of major hemorrhage, which persists even after stabilization of therapy.
TL;DR: A homozygous CYP2C19*17 genotype is associated with lower serum concentration of escitalopram, which might imply increased risk of therapeutic failure.
Abstract: Recently, a novel allelic variant of cytochrome P450 2C19 encoding ultrarapid enzyme activity was described (denoted CYP2C19*17). The objective of this study was to evaluate the impact of CYP2C19*17 on serum concentration of escitalopram in psychiatric patients. One hundred and sixty-six patients treated with escitalopram were divided into the following subgroups according to CYP2C19 genotype: CYP2C19*17/*17 (n=7), CYP2C19*1/*17 (n=43), CYP2C19*1/*1 (n=60), CYP2C19*17/def (n=16), CYP2C19*1/def (n=34), and CYP2C19def/def (n=6) (def=defective allele, i.e., CYP2C19*2 or *3). Dose-adjusted serum concentrations of escitalopram were compared using the CYP2C19*1/*1 subgroup as reference. Geometric mean of the escitalopram serum concentration was 42% lower in patients homozygous for CYP2C19*17 (P<0.01) and 5.7-fold higher in subjects homozygous for defective CYP2C19 alleles (P<0.001). Of the heterozygous subgroups, only CYP2C19*1/def was significantly different from CYP2C19*1/*1 (P<0.001). In conclusion, a homozygous CYP2C19*17 genotype is associated with lower serum concentration of escitalopram, which might imply increased risk of therapeutic failure.
TL;DR: Data from this study are consistent with increased hepatic and/or intestinal CYP3A and renal P‐gp activities during pregnancy, as measured by disposition of midazolam and digoxin.
Abstract: The objectives of the study were to evaluate the effects of pregnancy on CYP3A and P-glycoprotein (P-gp) activities, as measured by disposition of midazolam and digoxin, respectively. Thirteen women received digoxin (0.25 mg p.o.) and midazolam (2 mg p.o.) in random order, separated by 1–2 weeks at 28–32 weeks gestation, and the same order was repeated at 6–10 weeks postpartum. Plasma and urine concentrations were determined by liquid chromatography–mass spectrometry and analyzed by noncompartmental methods. Midazolam CL/Funbound (593 ± 237 l/min vs. 345 ± 103 l/min; P = 0.007), digoxin CLRenal, unbound (272 ± 45 ml/min vs. 183 ± 37 ml/min; P < 0.002) and digoxin CLsecretion, unbound (109 ± 34 ml/min vs. 58 ± 22 ml/min; P < 0.002) were higher during pregnancy than postpartum. These data are consistent with increased hepatic and/or intestinal CYP3A and renal P-gp activities during pregnancy.
Clinical Pharmacology & Therapeutics (2008); 84, 2, 248–253 doi:10.1038/clpt.2008.1
TL;DR: The use of pharmacogenetics has remained limited to investigation in only a few clinical fields such as oncology and psychiatry as mentioned in this paper, and the main reason is the paucity of scientific evidence to show that pharmacogenetic testing leads to improved clinical outcomes.
Abstract: Despite initial enthusiasm, the use of pharmacogenetics has remained limited to investigation in only a few clinical fields such as oncology and psychiatry. The main reason is the paucity of scientific evidence to show that pharmacogenetic testing leads to improved clinical outcomes. Moreover, for most pharmacogenetic tests (such as tests for genetic variants of cytochrome P450 enzymes) a detailed knowledge of pharmacology is a prerequisite for application in clinical practice, and both physicians and pharmacists might find it difficult to interpret the clinical value of pharmacogenetic test results. Guidelines that link the result of a pharmacogenetic test to therapeutic recommendations might help to overcome these problems, but such guidelines are only sparsely available. In 2001, an early step was taken to develop such guidelines for the therapeutic use of antidepressants, and these included CYP2D6-related dose recommendations drawn from pharmacokinetic study data. However, the use of such recommendations in routine clinical practice remains difficult, because they are currently outside the ambit of the clinical environment and are not accessible during the decision-making process by physicians and pharmacists, namely the prescription and dispensing of drugs.
TL;DR: The effects of lopinavir/ritonavir on tenofovir renal clearance was consistent with a renal interaction between these drugs, and future studies should clarify the exact mechanism and whether there is an increased risk of nephrotoxicity.
Abstract: We determined the effects of lopinavir/ritonavir on tenofovir renal clearance. Human immunodeficiency virus-infected subjects taking tenofovir disoproxil fumarate (TDF) were matched on age, race, and gender and were enrolled into one of the following two groups: group 1: subjects taking TDF plus lopinavir/ritonavir plus other nucleoside reverse transcriptase inhibitors (NRTIs); group 2: subjects taking TDF plus NRTIs and/or non-NRTIs but no protease inhibitors. Twenty-four-hour blood and urine collections were carried out in subjects for tenofovir quantification. Drug transporter genotype associations with tenofovir pharmacokinetics were examined. In 30 subjects, median (range) tenofovir apparent oral clearance, renal clearance, and fraction excreted in urine were 34.6 l/h (20.6-89.5), 11.3 l/h (6.2-22.6), and 0.33 (0.23-0.5), respectively. After adjusting for renal function, tenofovir renal clearance was 17.5% slower (P=0.04) in subjects taking lopinavir/ritonavir versus those not taking a protease inhibitor, consistent with a renal interaction between these drugs. Future studies should clarify the exact mechanism and whether there is an increased risk of nephrotoxicity.
TL;DR: It is demonstrated that MSC therapy in patients with MSA was safe and delayed the progression of neurological deficits with achievement of functional improvement in the follow‐up period.
Abstract: We evaluated the feasibility and safety of therapy with mesenchymal stem cells (MSCs) through consecutively intra-arterial and three repeated intravenous injections and compared the long-term prognosis between MSC-treated (n=11) and control multiple system atrophy (MSA) patients (n=18). The MSC-treated patients showed significantly greater improvement on the unified MSA rating scale (UMSARS) than the control patients at all visits throughout the 12-month study period. Orthostasis in UMSARS I items and cerebellar dysfunction-related items of UMSARS II items were significantly different in favor of MSC treatment compared to controls. Serial positron emission tomography scan in the MSC-treated group showed that increased fluorodeoxyglucose uptake from baseline was noted in cerebellum and frontal white matters. No serious adverse effects related to MSC therapy occurred. This study demonstrated that MSC therapy in patients with MSA was safe and delayed the progression of neurological deficits with achievement of functional improvement in the follow-up period.
Clinical Pharmacology & Therapeutics (2008); 83, 5, 723–730. doi:10.1038/sj.clpt.6100386
TL;DR: It is concluded that equivalent plasma drug concentrations and metabolic profiles can be expected for native Japanese, first‐ and third‐generation Japanese, Koreans, and Chinese for compounds handled through these six CYP enzymes.
Abstract: Application of foreign clinical data across geographic regions can accelerate drug development. Drug disposition can be variable, and identification of factors influencing responsible pharmacokinetic/pharmacogenomic approaches could facilitate the universal application of foreign data and reduce the total amount of phase III clinical trials evaluating risks in different populations. Our objective was to establish and compare genotype (major cytochrome P450 (CYP) enzymes)/phenotype associations for Japanese (native and first- and third-generation Japanese living abroad), Caucasian, Chinese, and Korean populations using a standard drug panel. The mean metabolic ratios (MRs) for the four ethnic groups were similar except for a lower activity of CYP2D6 in Caucasians and CYP2C19 in Asians. Genotype, not ethnicity, impacted the MR for CYP2C9, CYP2C19, and CYP2D6; neither affected CYP1A2, CYP2E1, and CYP3A4/5 activities. We conclude that equivalent plasma drug concentrations and metabolic profiles can be expected for native Japanese, first- and third-generation Japanese, Koreans, and Chinese for compounds handled through these six CYP enzymes.
TL;DR: The a priori knowledge of the pharmacogenetic variation known to abrogate CYP2D6 enzyme activity may provide a means by which the hormonal therapy of breast cancer can be individualized.
Abstract: Tamoxifen continues to be a standard endocrine therapy for the prevention and treatment of estrogen receptor (ER)-positive breast cancer. Tamoxifen can be considered a classic "pro-drug," requiring metabolic activation to elicit pharmacological activity. CYP2D6 is the rate-limiting enzyme catalyzing the conversion of tamoxifen into metabolites with significantly greater affinity for the ER and greater ability to inhibit cell proliferation. Both genetic and environmental (drug-induced) factors that alter CYP2D6 enzyme activity directly affect the concentrations of the active tamoxifen metabolites and the outcomes of patients receiving adjuvant tamoxifen. The a priori knowledge of the pharmacogenetic variation known to abrogate CYP2D6 enzyme activity may provide a means by which the hormonal therapy of breast cancer can be individualized.
TL;DR: The Integrating Family Medicine and Pharmacy to Advance Primary Care Therapeutics (IMPACT) project was designed to provide a real‐world demonstration of the feasibility of integrating the pharmacist into primary care office practice.
Abstract: The prevalence of suboptimal prescribing of medications is well documented. Patients are often undertreated or not offered therapeutic treatments that are likely to confer benefit. As a result, drug-related hospital admissions are common and often preventable. Improvements to the health-care system are clearly needed in order to maximize the benefits that can be derived from medications. Many countries are changing their primary health-care systems to improve the quality of health-care delivery. One main transformation is the use of multidisciplinary care teams to provide care in a coordinated manner often from the same location or by using the common medical record of the patients. It has been demonstrated that pharmacists can improve prescribing, reduce health-care utilization and medication costs, and contribute to clinical improvements in many chronic medical conditions, such as cardiovascular disease, diabetes, and psychiatric illness. However, the effect of integrating a pharmacist providing general services into a primary care group has not been extensively studied. The Integrating Family Medicine and Pharmacy to Advance Primary Care Therapeutics (IMPACT) project was designed to provide a real-world demonstration of the feasibility of integrating the pharmacist into primary care office practice. This article provides a description of the IMPACT project participants; the IMPACT practice model and the concepts incorporated in its development; some initial results from the program evaluation; sustainability of the model; and some reflections on the implementation of the practice model.
TL;DR: Cathepsin K inhibitors represent a novel target for developing agents to treat osteoporosis and other disorders characterized by increased bone resorption.
Abstract: Osteoporosis is characterized by low bone mass with skeletal fragility and an increased risk of fracture. This bone loss is brought about by an imbalance between bone resorption and formation. Cathepsin K is the most abundant cysteine protease expressed in the osteoclast and is believed to be instrumental in bone matrix degradation necessary for bone resorption. Cathepsin K inhibitors represent a novel target for developing agents to treat osteoporosis and other disorders characterized by increased bone resorption.
TL;DR: A pretreatment assessment of NMR may identify smokers who are most and least likely to benefit from treatment with bupropion for smoking cessation.
Abstract: We examined whether a pretreatment phenotypic marker of nicotine metabolism rate (NMR) predicts successful smoking cessation with bupropion. Smokers (N = 414) were tested for pretreatment NMR, based on the ratio of 3′-hydroxycotinine/cotinine derived during smoking, before entering a placebo-controlled randomized trial of bupropion plus counseling. At the end of the 10-week treatment phase, slow metabolizers (1st NMR quartile) had equivalent quit rates with placebo or bupropion (32%). Fast metabolizers (4th NMR quartile) had low quit rates with placebo (10%), and these were enhanced significantly by bupropion (34%). Smokers in the 2nd quartile (placebo: 25%, bupropion: 30%) and the 3rd quartile (placebo: 20%, bupropion: 30%) did not benefit significantly from bupropion. At the 6-month follow-up, the relationship between the NMR and quitting remained similar, but was no longer statistically significant. A pretreatment assessment of NMR may identify smokers who are most and least likely to benefit from treatment with bupropion for smoking cessation.
Clinical Pharmacology & Therapeutics (2008); 84, 3, 320–325 doi:10.1038/clpt.2008.57
TL;DR: Raltegravir is generally well tolerated at doses of up to 1,600 mg/day given for up to 10 days and exhibits a pharmacokinetic profile supportive of twice‐daily dosing with multiple doses of 100 mg and greater achieving trough levels >33 nM.
Abstract: Raltegravir is a novel human immunodeficiency virus-1 integrase inhibitor with potent in vitro activity (95% inhibitory concentration (IC95)=33 nM in 50% human serum). Three double-blind, randomized, placebo-controlled, pharmacokinetic, safety, and tolerability studies were conducted: (1) single-dose escalation study (10-1,600 mg), (2) multiple-dose escalation study (100-800 mg q12 h x 10 days), and (3) single-dose female study (400 mg). Raltegravir was rapidly absorbed with a terminal half-life (t1/2) approximately 7-12 h. Approximately 7-14% of raltegravir was excreted unchanged in urine. Area under the curve (AUC)(0-infinity) was similar between male and female subjects. After multiple-dose administration, steady state was achieved within 2 days; there was little to modest accumulation of raltegravir. Trough levels were >33 nM for dose levels of 100 mg and greater. Raltegravir is generally well tolerated at doses of up to 1,600 mg/day given for up to 10 days and exhibits a pharmacokinetic profile supportive of twice-daily dosing with multiple doses of 100 mg and greater achieving trough levels >33 nM.
TL;DR: The cascades that are often altered in cancer cells during cancer progression that may contribute in a crucial manner to drug resistance and disease relapse are described.
Abstract: This review summarizes the recent knowledge obtained on the molecular mechanisms involved in the intrinsic and acquired resistance of cancer cells to current cancer therapies. We describe the cascades that are often altered in cancer cells during cancer progression that may contribute in a crucial manner to drug resistance and disease relapse. The emphasis is on the implication of ATP-binding cassette (ABC) multidrug efflux transporters in drug disposition and antiapoptotic factors, including epidermal growth factor receptor cascades and deregulated enzymes in ceramide metabolic pathways. The altered expression and activity of these signaling elements may have a critical role in the resistance of cancer cells to cytotoxic effects induced by diverse chemotherapeutic drugs and cancer recurrence. Of therapeutic interest, new strategies for reversing the multidrug resistance and developing more effective clinical treatments against the highly aggressive, metastatic, and recurrent cancers, based on the molecular targeting of the cancer progenitor cells and their further differentiated progeny, are also described.
TL;DR: The risk associated with exposure of vulnerable older women to drugs with anticholinergic properties, and to a lesser extent those with sedative properties, implies that such drugs should not be used in this patient group without compelling clinical indication.
Abstract: Polypharmacy, common in older people, confers both risk of adverse outcomes and benefits. We assessed the relationship of commonly prescribed medications with anticholinergic and sedative effects to physical and cognitive performance in older individuals. The study population comprised 932 moderately to severely disabled community-resident women aged 65 years or older who were participants in the Women's Health and Aging Study I. A scale based on pharmacodynamic principles was developed and utilized as a measure of drug burden. This was related to measures of physical and cognitive function. After adjusting for demographics and comorbidities, anticholinergic drug burden was independently associated with greater difficulty in four physical function domains with adjusted odds ratios (95% confidence interval (CI)) of 4.9 (2.0-12.0) for balance difficulty; 3.2 (1.5-6.9) for mobility difficulty; 3.6 (1.6-8.0) for slow gait; 4.2 (2.0-8.7) for chair stands difficulty; 2.4 (1.1-5.3) for weak grip strength; 2.7 (1.3-5.4) for upper extremity limitations; 3.4 (1.7-6.9) for difficulty in activities of daily living; and 2.4 (95% CI, 1.1-5.1) for poor performance on the Mini-Mental State Examination. Sedative burden was associated only with impaired grip strength (3.3 (1.5-7.3)) and mobility difficulty (2.4 (1.1-5.3)). The burden of multiple drugs can be quantified by incorporating the recommended dose regimen and the actual dose and frequency of drug taken. Anticholinergic drug burden is strongly associated with limitations in physical and cognitive function. Sedative burden is associated with impaired functioning in more limited domains. The risk associated with exposure of vulnerable older women to drugs with anticholinergic properties, and to a lesser extent those with sedative properties, implies that such drugs should not be used in this patient group without compelling clinical indication.
TL;DR: The data indicate that SASP is a candidate probe of BCRP, particularly in its role in intestinal absorption, and the pharmacokinetics of SASP, SP, and N ‐acetylsulfapyridine (AcSP are described simultaneously by nonlinear mixed‐effects modeling (NONMEM) analysis with regard to both gene polymorphisms.
Abstract: The role of breast cancer resistance protein (BCRP), an efflux ABC transporter, in the pharmacokinetics of substrate drugs in humans is unknown. We investigated the impact of genetic polymorphisms of ABCG2 (421C>A) and NAT2 on the pharmacokinetics of sulfasalazine (SASP), a dual substrate, in 37 healthy volunteers, taking 2,000 mg of conventional SASP tablets. In ABCG2, SASP AUC(0-48) of C/C, C/A, and A/A subjects was 171 +/- 85, 330 +/- 194, and 592 +/- 275 microg h/ml, respectively, with significant differences among groups. In contrast, AUC(0-48) of sulfapyridine (SP) tended to be lower in subjects with the ABCG2-A allele as homozygosity. In NAT2, AUC(AcSP)/AUC(SP) was significantly higher in rapid than in intermediate and slow acetylator (SA) genotypes. We successfully described the pharmacokinetics of SASP, SP, and N -acetylsulfapyridine (AcSP) simultaneously by nonlinear mixed-effects modeling (NONMEM) analysis with regard to both gene polymorphisms. The data indicate that SASP is a candidate probe of BCRP, particularly in its role in intestinal absorption.