Effect Of Comedication Research Articles

The effect of age and comedication on lamotrigine clearance, tolerability, and efficacy

To compare pharmacokinetics, tolerability, and efficacy of lamotrigine (LTG) in older versus younger adults. We studied 686 adult outpatients seen at our center over 5 years. We compared apparent clearance (CL) of LTG in the youngest (16-36 years; n = 247) and oldest (55-92 years; n = 155) tertiles. We analyzed one-year retention for younger and older adults newly started on LTG, frequency of adverse effects causing intolerability, and rates of specific adverse effects. We also investigated 6-month seizure freedom. Median LTG CL of older adults taking LTG in monotherapy was approximately 22% lower compared to younger adults (28.8 vs. 36.5 ml/h/kg; p < 0.001). LTG CL in older adults was lower compared to younger adults in patients on polytherapy and on polytherapy without enzyme inducers or valproate. One-year retention for LTG was comparable in older (78.1%, 121/155) and younger (72.4%, 179/247) adults. Intolerability to LTG was higher in older (34.8%) versus younger adults (24.2%; p = 0.005). Imbalance, drowsiness, and dizziness were common intolerable side effects in both groups. Older patients had higher rates of intolerability due to imbalance (16% vs. 4%), drowsiness (13% vs. 7%), and tremor (5% vs. 2%) compared with younger patients. Rates of 6-month seizure freedom were comparable, and small numbers of each group benefited from very high levels of LTG (>15 μg/ml). LTG CL in monotherapy in older adults is approximately 20% lower than in younger adults. For a given serum LTG level, older adults are twice as likely to have significant adverse effects compared to younger adults. Older patients are more likely to experience imbalance, drowsiness, and tremor than younger patients. Younger adults tolerate LTG better than older adults, but one-year retention is comparable. Some patients may benefit from high serum levels of LTG.

Absolute Quantification of [11C]docetaxel Kinetics in Lung Cancer Patients Using Positron Emission Tomography

Tumor resistance to docetaxel may be associated with reduced drug concentrations in tumor tissue. Positron emission tomography (PET) allows for quantification of radiolabeled docetaxel ([(11)C]docetaxel) kinetics and might be useful for predicting response to therapy. The primary objective was to evaluate the feasibility of quantitative [(11)C]docetaxel PET scans in lung cancer patients. The secondary objective was to investigate whether [(11)C]docetaxel kinetics were associated with tumor perfusion, tumor size, and dexamethasone administration. Thirty-four lung cancer patients underwent dynamic PET-computed tomography (CT) scans using [(11)C]docetaxel. Blood flow was measured using oxygen-15 labeled water. The first 24 patients were premedicated with dexamethasone. For quantification of [(11)C]docetaxel kinetics, the optimal tracer kinetic model was developed and a noninvasive procedure was validated. Reproducible quantification of [(11)C]docetaxel kinetics in tumors was possible using a noninvasive approach (image derived input function). Thirty-two lesions (size ≥4 cm(3)) were identified, having a variable net influx rate of [(11)C]docetaxel (range, 0.0023-0.0229 mL·cm(-3)·min(-1)). [(11)C]docetaxel uptake was highly related to tumor perfusion (Spearman's ρ = 0.815;P < 0.001), but not to tumor size (Spearman's ρ = -0.140; P = 0.446). Patients pretreated with dexamethasone showed lower [(11)C]docetaxel uptake in tumors (P = 0.013). Finally, in a subgroup of patients who subsequently received docetaxel therapy, relative high [(11)C]docetaxel uptake was related with improved tumor response. Quantification of [(11)C]docetaxel kinetics in lung cancer was feasible in a clinical setting. Variable [(11)C]docetaxel kinetics in tumors may reflect differential sensitivity to docetaxel therapy. Our findings warrant further studies investigating the predictive value of [(11)C]docetaxel uptake and the effects of comedication on [(11)C]docetaxel kinetics in tumors.

The in vitro effect of the new antithrombotic drug candidate ALX-0081 on blood samples of patients undergoing percutaneous coronary intervention

Compound ALX-0081 is a bivalent humanised Nanobody® that binds the A1-domain of von Willebrand factor (VWF) with high affinity. Consequently, it can block the interaction between VWF and its platelet-receptor-glycoprotein Ib, which leads inevitably to formation of arterial thrombi. It was the objective of this study to assess the in vitro effects of ALX-0081 on platelet adhesion and aggregation in coronary artery disease (CAD) patients to determine the optimal concentration of ALX-0081 and the effect of co-medication. We included nine CAD patients, who were scheduled for elective percutaneous coronary intervention (PCI), and 11 healthy volunteers. At admission all patients received aspirin, clopidogrel and heparin. Blood was drawn 24 hours (h) before and 1 h after start of the PCI procedure and was subsequently spiked with different concentrations of ALX-0081 or buffer. The efficacy of ALX-0081 was assessed by in vitro experiments: flow chamber experiments, ristocetin-induced platelet aggregation (RIPA), and the platelet function analyser (PFA-100™). VWF levels in CAD patients were significantly higher than in healthy controls. During PCI VWF levels did not rise. In all in vitro experiments, ALX-0081 led to complete inhibition of platelet adhesion and aggregation. However, the required effective concentration was higher in patients than in controls and was related to plasma VWF levels. In conclusion, ALX-0081 is able to completely inhibit in vitro platelet adhesion and aggregation in CAD patients scheduled for elective PCI. The efficacy of ALX-0081 is not influenced by PCI or co-medication. However, due to higher VWF levels in CAD patients a higher effective concentration of ALX-0081 was required than in healthy individuals.

Television depictions about dermatology and skin diseases in Seinfeld

The iconic television situation comedy Seinfeld frequently referenced dermatologists and topics involving the integument, using satire for comedic effect. However, selecting satire to portray an already misunderstood and unknown subject matter may perpetuate incorrect public beliefs and stereotypes about those with skin diseases and diminish cultural sensitivity towards people who have dermatologic conditions and their caregivers.

Genotyping, Clopidogrel Metabolism, and the Search for the Therapeutic Window of Thienopyridines

It is somewhat remarkable to note that not until recently, nearly 12 years and tens of millions of treated patients after its initial approval, has the metabolism of clopidogrel, an inactive prodrug, begun to be more fully understood. Although this lack of knowledge may not be unique among common cardiovascular drugs, there are 4 characteristics of clopidogrel therapy that make this gap in understanding disconcerting: The potential for life-threatening complications (bleeding or thrombosis) at both ends of its therapeutic spectrum; the fact that 1 dose is supposed to fit all; the lack of a measureable, proven end point (such as blood pressure for antihypertensive drugs) that allows for titration to a target response; and the nearly mandatory need by many patients for clopidogrel, with no acceptable alternative until recently. Article see p 512 Historically, understanding the metabolism of a drug has been critical in identifying those patients most likely to benefit from and, more important, potentially be harmed by that drug. This is especially true for drugs with relatively narrow therapeutic windows, such as phenytoin, warfarin, and others. Although it seems safe to assume, on the basis of our extensive clinical experience, that the therapeutic window of clopidogrel is unlikely to be narrow, this certainly does not represent the depth of knowledge we would hope for after so much clinical experience and research. What we do know is that P2Y12 inhibition with thienopyridines is beneficial in preventing arterial thrombotic events, presumably requiring the achievement of some minimal level of receptor inhibition that may or may not vary on the basis of the patient and clinical scenario. We also know that it is associated with a significant increase in serious bleeding events, with higher levels of inhibition associated with greater bleeding. In the present and future practice environment, with a growing …

Effect of comedication with proton pump inhibitors (PPIs) on post-interventional residual platelet aggregation in patients undergoing coronary stenting treated by dual antiplatelet therapy

Introduction Currently, there is an intense debate about whether comedication with proton pump inhibitors (PPIs) weakens the antiplatelet effect of clopidogrel in patients undergoing coronary stent implantation. Competing mechanisms on the hepatic cytochrome 2C19 level are proposed. The aim of this study was to assess the impact of PPI treatment on clopidogrel response by measuring the ex vivo platelet aggregation in patients with coronary intervention. Methods 1425 consecutive patients with symptomatic coronary artery disease undergoing percutaneous coronary intervention were enrolled in this single centre study. PPI comedication was defined as PPI intake ≥ 1 week prior to a 600 mg clopidogrel loading dose. PPI treatment was based on physician preference. Residual platelet aggregation (RPA) was measured by optical aggregometry. To correct for potential selection bias, propensity score matching was applied. Results RPA was significantly higher in PPI-treated patients compared with non-PPI-users (final aggregation 34.0% vs. 29.8%, p < 0.001). Low responder defined as RPA in the upper tertile were more often found in PPI-users. After adjustment for relevant confounders, PPI treatment was independently associated with higher RPA-levels. Discussion We demonstrated that peri-procedural co-administration of PPIs significantly decreases the effect of clopidogrel on RPA. To assess if clopidogrel-PPI interaction results in a higher susceptibility for cardiovascular events remains subject to further investigations.

Effects of age, gender, smoking and co-medication on the pharmacokinetics of venlafaxine and O-desmethylvenlafaxine in everyday clinical practice

Venlafaxine (VEN) exerts both serotonin and norepinephrine reuptake inhibition and is widely used as an antidepressant. In a retrospective study, we aimed to examine the influence of age, gender, smoking habits and comedication on the pharmacokinetics of VEN and its main metabolite O-desmethylvenlafaxine (OD-VEN) by therapeutic drug monitoring (TDM). We evaluated all TDM-analyses of VEN during the years 2004–2006 in an unselected sample of patients in the psychiatric university hospitals of Mainz, Regensburg, and Würzburg. To avoid multiple assessments of the same individual only one sample per patient was included. The determination of the serum concentrations of VEN and OD-VEN was performed by a virtually identical HPLC method in the three participating hospitals. Women had higher dose-corrected concentrations than men, and patients over 60 years showed higher concentrations than the younger ones. In smokers lower serum levels were observed than in non-smokers. Comedication with other antidepressants, antipsychotics and mood stabilizers was generally associated with a significantly lowered OD-VEN/VEN ratio. This indicates a delayed metabolism of VEN via CYP2D6, which was observable also in patients receiving a concomitant medication with the known CYP2D6 inhibitor melperone. Altogether our findings confirm that TDM is a useful tool to control pharmacokinetic factors during treatment with VEN and can thus help to avoid inadequate dosage and to recognize drug interactions.

Effect of proton pump inhibitor co-medication on imatinib disposition: A healthy volunteer study

2503 Background: Imatinib mesylate, a potent inhibitor of Bcr-Abl and c-kit tyrosine kinases, is widely used to treat gastrointestinal stromal tumors and Philadelphia chromosome-positive leukemias. Imatinib often causes gastric upset and is therefore frequently administered with a proton pump inhibitor (PPI). Yet, the resulting elevated gastric pH, delayed gastric emptying, and inhibition of ABC transporters in the gut could change imatinib absorption, thereby affecting the therapeutic effectiveness of imatinib. To test this hypothesis, we sought to define the effect of PPI on the plasma pharmacokinetics of imatinib. Methods: 11 healthy subjects (6 M, 5 F; 21–56 years) were enrolled in a 2-period, open-label, randomized cross-over, fixed- sequence study. In one period, they received a single 400 mg dose of imatinib p.o., in the other, 40 mg omeprazol daily for five days followed by a single 400 mg dose of imatinib p.o.. The periods were separated by a wash-out period of ≥ 14 days. Plasma samples from 0–72 h after dosing were obtained. Plasma concentrations of imatinib and its active metabolite CGP74588 were determined with an LC-MS assay and data were analyzed non-compartmentally. The study was powered to detect a 30% difference in imatinib AUC with 80% power and a 5% type I error. Results: See Table . Conclusions: This study demonstrates that the use of PPI to treat imatinib-induced gastric upset does not significantly affect imatinib plasma AUC. Support: Novartis; NIH/NCRR/CTSA Grant UL1 RR024153 [Table: see text] [Table: see text]

Muscarinic receptor antagonists for overactive bladder treatment: does one fit all?

To review evidence and regulatory dosing recommendations for muscarinic receptor antagonists used in the treatment of overactive bladder symptom complex (darifenacin, fesoterodine, oxybutynin, propiverine, solifenacin, tolterodine, trospium) in special patient populations. Growing evidence demonstrates effects of renal impairment, hepatic impairment, genetics and/or comedications on the pharmacokinetics of muscarinic antagonists. They may cause greater exposure in the respective population, which may translate into greater risks for side effects. These possible risks lead to drug-specific regulatory dosing recommendations or even contraindications in certain patient populations. Physicians should be aware of pharmacokinetic alterations in special patient populations and possible associated risks. The evidence-based choice of a muscarinic antagonist in such patients should be guided by its specific pharmacokinetic profile.

P.8.a.015 The effect of lamotrigine co-medication on seizure occurrence: basal versus ictal serum levels

P.8.a.015 The effect of lamotrigine co-medication on seizure occurrence: basal versus ictal serum levels

Factors Influencing Efavirenz and Nevirapine Plasma Concentration: Effect of Ethnicity, Weight and Co-Medication

The aim of this study was to examine factors influencing plasma concentration of efavirenz and nevirapine. Data from the Liverpool Therapeutic Drug Monitoring (TDM) registry were linked with the UK Collaborative HIV Cohort (CHIC) Study. For each patient, the first measurement of efavirenz (600 or 800 mg/day) or nevirapine (400 mg/day) plasma concentration was included. Linear regression was used to evaluate the association of dose, gender, age, weight, ethnicity and concomitant antiretroviral drugs or rifampicin with log-transformed drug concentration, adjusted for time since last intake. Data from 339 patients on efavirenz (34% black, 17% rifampicin) and 179 on nevirapine (27% black, 6% rifampicin) were included. Multivariable models revealed the following predictors for efavirenz concentration: black ethnicity (59% higher; P<0.001), weight (10% lower per additional 10 kg; P=0.002), 800 mg/day (52% higher; P=0.027), rifampicin (35% lower; P=0.039), and zidovudine (25% lower; P=0.010). Notably, without adjustment for other factors, patients on rifampicin had 48% higher efavirenz concentration, as these patients were mostly black and on 800 mg/day. For nevirapine the predictors were black ethnicity (39% higher; P=0.002), rifampicin (40% lower; P=0.002), protease inhibitor (28% higher; P=0.008) and tenofovir (22% higher; P=0.024). We observed clear associations between ethnicity and concentrations of nevirapine and efavirenz. Our analyses confirm that concomitant rifampicin substantially decreases concentration of both efavirenz and nevirapine; however, for efavirenz this effect was more than counterbalanced by the effect of ethnicity and increased efavirenz dose. There was also an additional impact of weight, which should be considered when determining optimal dosage. Other associations from our analysis (between tenofovir or protease inhibitor and nevirapine, and zidovudine and efavirenz), require confirmation in formal pharmacokinetic studies.

ECNP consensus meeting. Bipolar depression. Nice, March 2007

ECNP consensus meeting. Bipolar depression. Nice, March 2007

Effect of antacid co-medication on imatinib disposition: A healthy volunteer study

2547 Background: Imatinib mesylate, a potent inhibitor of Bcr-Abl and c-kit tyrosine kinases, is widely used to treat gastrointestinal stromal tumors and Philadelphia chromosome-positive leukemias. Imatinib often causes gastric upset and is therefore frequently administered with an antacid (AA). Yet, the resulting elevated gastric pH, delayed gastric emptying, or introduction of Mg2+ and Al3+ could change imatinib absorption, thereby affecting the therapeutic effectiveness of imatinib. To test this hypothesis, we sought to define the effect of AA on the plasma pharmacokinetics of imatinib. Methods: 12 healthy subjects (6 M, 6 F; 20–51 years) were enrolled in a 2- period, open-label, randomized cross-over, fixed-sequence study. In one period, they received 400 mg imatinib p.o., in the other 20 mL Maximum Strength Maalox Max Antacid/Anti-gas (1.6 g Al(OH)3 + 1.6 g Mg(OH)2) 15 min prior to 400 mg imatinib p.o. The periods were separated by a wash-out period of ≥ 14 days. Plasma samples from 0–72 h after dosing were obtained. Plasma concentrations of imatinib and its active metabolite CGP74588 were determined with an LC-MS assay and data were analyzed non-compartmentally. The study was powered to detect a 30% difference in imatinib AUC with 80% power and a 5% type I error. Results: See table. Conclusions: This study demonstrates that the use of Mg2+-Al3+ based AA to treat imatinib-induced gastric upset does not significantly affect imatinib plasma AUC. The small difference in imatinib half-life, detected by an unplanned statistical test, should not affect the average steady-state concentration achieved after multiple doses, and therefore is not likely to be clinically significant. Support: Novartis; NIH/NCRR/CTSA Grant UL1 RR024153 Analyte Arm AUC0-inf Cmax tmax t1/2 V/F Cl/F (ug/mL*h) (ug/mL) (h) (h) (L) (L/h) Imatinib Alone 32.6 (8.0) 2.12 (0.43) 2.8 (0.9) 14.3 (1.5) 267 (75) 13.1 (3.7) Imatinib +AA 33.1 (6.0) 2.10 (0.45) 3.4 (0.7) 15.1 (1.8) 273 (72) 12.6 (3.1) p-value 0.73 0.85 0.08 0.03 0.68 0.40 CGP74588 Alone 6.04 (1.43) 0.27 (0.06) 2.5 (0.9) 30.5 (5.3) 3077 (945) 69.9 (17.1) CGP74588 +AA 6.45 (1.67) 0.26 (0.09) 3.1 (0.5) 33.3 (9.4) 3012 (1295) 61.2 (25.1) p-value 0.078 0.85 0.11 0.35 0.84 0.10 Mean (SD) Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Novartis Novartis Novartis

Estimating the effects of co-medications on plasma olanzapine concentrations by using a mixed model

The purpose of this study was to estimate the effect sizes of drug interactions on plasma olanzapine concentrations while adjusting for potentially confounding factors such as smoking. The estimation was performed by using a mixed model, data from a series of previously published studies of lamotrigine, oxcarbazepine, topiramate, and mirtazapine, and unpublished data from patients under clinical therapeutic drug monitoring (TDM). The total sample included 163 adult patients (age ≥ 18 years) who provided both steady-state plasma olanzapine concentrations and smoking information. They provided a total of 360 olanzapine concentrations (1 to 11 measures per patient). Smoking and concomitant carbamazepine or lamotrigine use were found to have significant effects on median plasma olanzapine concentrations. The effects of lamotrigine on plasma olanzapine concentrations were modified by smoking. After adjusting for olanzapine dose and carbamazepine intake, plasma olanzapine concentrations were 10% lower in non-smokers who were taking lamotrigine than in non-smokers who were not taking lamotrigine; olanzapine concentrations were 35% higher in smokers who were taking lamotrigine than in smokers who were not taking lamotrigine; olanzapine concentrations were 41% lower in smokers who were not taking lamotrigine than in non-smokers who were not taking lamotrigine; and olanzapine concentrations were 11% lower in smokers who were taking lamotrigine than in non-smokers who were taking lamotrigine. After adjusting for olanzapine dose and taking carbamazepine, the correction factor comparing smokers taking lamotrigine versus non-smokers who were not taking lamotrigine was 1.3. Gender, age, and concomitant use of mirtazapine, valproic acid, lamotrigine, topiramate, lorazepam, citalopram or oxcarbazepine did not have significant effects on olanzapine concentrations. The main limitation of this clinical design is the unavoidable substantial “noise” that characterizes (uncontrolled) clinical environments, which may make it difficult to detect the effects of some variables. Other limitations were the small sample size of some drug sub-samples and the lack of testing for plasma olanzapine metabolites.

Estimating the Size of the Effects of Co-Medications on Plasma Clozapine Concentrations using a Model that Controls for Clozapine Doses and Confounding Variables

The purpose of this study was to estimate the effect sizes of drug interactions on plasma clozapine concentrations, adjusting for potentially confounding factors such as smoking. The estimation was performed by using a mixed model, and a combination of unpublished (N=83) and published (N=172) data that included patients taking phenobarbital, valproic acid, fluvoxamine, fluoxetine, paroxetine, sertraline, citalopram and reboxetine, and patients not taking co-medications. The 255 patients provided a total of 415 steady-state trough plasma clozapine concentrations. Each patient provided 1 to 15 measures of plasma clozapine concentrations. Total plasma clozapine concentration, defined as the sum of plasma clozapine and norclozapine concentrations, was also investigated. A random intercept linear model of the natural log of plasma clozapine concentration with the natural log of dose and other variables as independent variables was built. The model confirmed that phenobarbital induces clozapine metabolism (effect size, E=-28%), and that fluoxetine (E=+42%), fluvoxamine (E=+263%) and paroxetine (E=+30%) inhibit it. Valproic acid appeared to inhibit clozapine metabolism in non-smokers (effect size, E=+16%), whereas it appeared to induce clozapine metabolism in smokers (E=-22%). The effect sizes of smoking on plasma clozapine concentration were -20% in patients not taking valproic acid, and -46% in patients taking valproic acid. Thus, smoking induces clozapine metabolism, and this induction may be stronger when the patient is taking valproic acid. The effect sizes allowed the computation of clozapine dose-correction factors for phenobarbital, 1.4 [95% confidence interval, CI, (1.1, 1.7)]; paroxetine, 0.77 (0.67, 0.89); fluoxetine, 0.70 (0.64, 0.78); fluvoxamine, 0.28 (0.22, 0.35); and valproic acid [0.86 (0.75, 1.0) in non-smokers, and 1.3 (0.96, 1.73) in smokers]. Sertraline, reboxetine and citalopram had no obvious effects. The results for total plasma clozapine concentrations are similar to those for plasma clozapine concentrations. The main limitations of this study were that the computed effect sizes reflect only the doses and treatment-durations of the co-medications studied, and that the substantial "noise" of the clinical environment may make it difficult to detect the effects of some variables, particularly those with small effect sizes. Gender was not significant probably due to its relatively small effect size in the studied population, and age was not significant probably due to the limited age variability. This article contributes to the clozapine literature by describing a possible interaction between taking valproic acid and smoking, which modifies plasma clozapine concentrations, by estimating the effect sizes of other compounds on plasma clozapine concentrations after correcting for confounders, and by providing dose-correction factors for clinicians.

Determinants of Steady-State Torasemide Pharmacokinetics

Torasemide is frequently used for the treatment of hypertension and heart failure. However, the determinants of torasemide pharmacokinetics in patients during steady-state conditions are largely unknown. We therefore explored the impact of genetic polymorphisms of cytochrome P450 (CYP) 2C9 (CYP2C9) and organic anion transporting polypeptide (OATP) 1B1 (SLCO1B1), gender, and the effects of losartan and irbesartan comedication on the interindividual variability of steady-state pharmacokinetics of torasemide. Twenty-four patients receiving stable medication with torasemide 10 mg once daily and with an indication for additional angiotensin II receptor blocker (ARB) treatment to control hypertension or to treat heart failure were selected. Blood samples were taken before torasemide administration and 0.5, 1, 2, 4, 8, 12 and 24 hours after administration. After this first study period, patients received either irbesartan 150 mg (five female and seven male patients aged 69+/-8 years) or losartan 100 mg (two female and ten male patients aged 61+/-8 years) once daily. After 3 days of ARB medication, eight blood samples were again collected at the timepoints indicated above. The patients' long-term medications, which did not include known CYP2C9 inhibitors, were maintained at a constant dose during the study. All patients were genotyped for CYP2C9 (*1/*1 [n=15]; *1/*2 [n = 4]; *1/*3 [n=5]) as well as for SLCO1B1 (c.521TT [n=13]; c.521TC [n=11]). Factorial ANOVA revealed an independent impact of the CYP2C9 genotype (dose-normalized area under the plasma concentration-time curve during the 24-hour dosing interval at steady state [AUC(24,ss)/D]: *1/*1 375.5+/-151.4 microg x h/L/mg vs *1/*3 548.5+/-271.6 microg x h/L/mg, p=0.001), the SLCO1B1 genotype (AUC(24,ss)/D: TT 352.3+/-114 microg x h/L/mg vs TC 487.6+/-218.4 microg x h/L/mg, p<0.05) and gender (AUC(24,ss)/D: males 359.5+/-72.2 microg x h/L/mg vs females 547.3+/-284 microg x h/L/mg, p<0.01) on disposition of torasemide. Coadministration of irbesartan caused a 13% increase in the AUC(24,ss)/D of torasemide (p=0.002), whereas losartan had no effect. This study shows that the CYP2C9*3 and SLCO1B1 c.521TC genotype and female gender are significant and independent predictors of the pharmacokinetics of torasemide. Coadministration of irbesartan yields moderate but significant increases in the torasemide plasma concentration and elimination half-life.

Cardiac Safety of Central Nervous System Stimulants in Children and Adolescents With Attention-Deficit/Hyperactivity Disorder

Case reports have raised concerns about the risk of cardiac events associated with central nervous system stimulants for the treatment of attention-deficit/hyperactivity disorder. This was a retrospective cohort study that used 10 years (July 1994 to June 2004) of Florida Medicaid claims data cross-linked to Vital Statistics Death Registry data. The cohort was composed of all youth 3 to 20 years old who were newly diagnosed with attention-deficit/hyperactivity disorder. Each month of follow-up was classified according to stimulant claims (methylphenidate, amphetamines, and pemoline) as current use (active stimulant claim), former use (time after periods of current use), or nonuse (time preceding the first stimulant claim, including follow-up of youth who were never exposed to stimulants). The study's end points were (1) cardiac death, (2) first hospital admission for cardiac causes or (3) first emergency department visit for cardiac causes. Risks were compared with time-dependent Cox regression analysis adjusting for various cardiac risk factors. During 124,932 person-years of observation (n = 55,383), 73 youth died, 5 because of cardiac causes. No cardiac death occurred during 42,612 person-years of stimulant use. Hospital admissions for cardiac cause occurred for 27 children (8 during stimulant use, 11 during 35,671 person-years of former use, and 8 during 46,649 person-years of nonuse); and 1091 children visited the emergency department for cardiac causes (8.7 per 1000 person-years). Current stimulant use was associated with a 20% increase in the hazard for emergency department visits when compared with nonuse. No increased risk was found for periods of former use when compared with nonuse. Incidence rates of cardiac events requiring hospitalization were small and similar to national background rates. Stimulants were associated with an increase in cardiac emergency department visits. More evidence is needed that addresses the long-term risk/benefit of the various treatment options and the effect of other cardiac risk factors and comedications.

Quetiapine and Drug Interactions

The objective of the present study was to investigate the effect of age, gender, and various comedications on the pharmacokinetics of quetiapine in a naturalistic setting. In total, 2111 serum samples analyzed for quetiapine during the period from June 2001 to December 2004 were included in the study. The samples had been collected for routine therapeutic drug monitoring purposes from 1179 patients treated with quetiapine. A log-linear mixed model was used to identify factors influencing the dose-corrected quetiapine serum concentration, expressed as the quetiapine concentration-to-dose (C/D) ratio. Variables included in the analysis were age, gender, and concomitant treatment with a total of 41 drugs most often used in combination with quetiapine. Age >or= 70 years (p = .001) and comedication with alimemazine (p = .002), fluvoxamine (p = .001), citalopram/escitalopram (p = .041), or clozapine (p < .001) significantly increased the serum concentrations of quetiapine, while age < 18 years (p = .044) and comedication with lamotrigine (p = .024), levomepromazine (p = .011), oxazepam (p < .001), or carbamazepine (p < .001) significantly decreased the serum concentrations. The effects were most pronounced for fluvoxamine (+159%), clozapine (+82%), age >or= 70 years (+67%), and carbamaze-pine (-86%). In 18% of the samples, the daily dose exceeded the currently recommended maximum of 800 mg/day. Due to the increased serum levels of quetiapine, a lower dose than usual should be considered when quetiapine is administered to elderly patients and to patients comedicated with clozapine or fluvoxamine. As the inducing effect of carbamazepine on quetiapine metabolism is very potent, cotreatment with carbamazepine cannot be recommended. On the basis of our data and pharmacokinetic considerations, the majority of drugs commonly used in psychiatry can safely be given in combination with quetiapine.

Effect of Age and Comedication on Levetiracetam Pharmacokinetics and Tolerability

To compare pharmacokinetics and tolerability of levetiracetam (LEV) in older versus younger adults. As part of the Columbia Antiepileptic Drug Database, we retrospectively studied the pharmacokinetics and tolerability of LEV in patients who had been seen as an outpatient at our center during a 4-year period. We compared apparent clearance (CL) of LEV in the youngest (16-31 years; n=151) and oldest (55-88 years; n=157) quartile of 629 adult outpatients who had taken LEV. We also analyzed the frequency of adverse effects leading to dose change or discontinuation ("intolerability") and specific adverse effects in the younger versus older adults. One-year retention was determined for younger and older adults newly started on LEV at our center. Mean LEV CL differed significantly between older (46.5 ml/h/kg) and younger adults (78.3 ml/h/kg). On average, older patients had a 40% lower LEV CL than younger patients. Comedication with an enzyme-inducing antiepileptic drug (EIAED; mostly carbamazepine) was associated with a 24% higher clearance of LEV compared to those who were not on EIAEDs. This difference was 37% in a subgroup of patients whose LEV CL was compared while they were on and off EIAEDs. Stepwise linear regression identified younger age and comedication with an EIAED as significant predictors of increased LEV CL. A total of 34.3% of the 629 patients (31.7% of younger vs. 40.7% of older patients; p=0.16) reported intolerability to LEV on at least one occasion. This difference in tolerability reached significance in the group of patients newly started on LEV (26.3% vs. 41.0%; p=0.017). Drowsiness and psychiatric/behavioral side effects were the most common adverse effects associated with LEV use in both age groups. One-year retention was 72% in the older group vs. 54% in the younger group (not significant). Older adults have lower CL than younger adults and require a mean 40% lower dose of LEV to achieve the same serum level. Comedication with an EIAED increases LEV CL by 24-37%. Younger adults tolerate LEV better than older adults, but 1-year retention was (nonsignificantly) higher in the older group.

Effects of Comedication on the Serum Levels of Aripiprazole: Evidence from a Routine Therapeutic Drug Monitoring Service

The objective of the study was to compare the serum concentrations of the atypical antipsychotic aripiprazole in monotherapy with the concentrations found during concomitant therapy with other drugs. Samples analyzed for aripiprazole by a liquid chromatography-mass spectrometry method in a routine therapeutic drug monitoring setting were collected consecutively. Samples from 81 patients were included in the study. Comedication with the CYP3A4 inducer carbamazepine lowered the dose-adjusted aripiprazole concentration by 88%. Comedication with CYP2D6 inhibitors gave a mean concentration 44% higher than in the monotherapy group. Subjects comedicated with valproate had lower aripiprazole concentrations, while subjects comedicated with lamotrigine, citalopram/escitalopram and lithium had higher concentrations than the subjects in the monotherapy group. Although the study is small and the results should be interpreted very cautiously, it indicates that comedication with drugs inhibiting or inducing CYP2D6 or CYP3A4 affects the serum concentrations of aripiprazole. The other findings should be considered as preliminary and have to be replicated in a larger setting before firm conclusions can be drawn.