Neuropathic pain symptoms on the modified painDETECT correlate with signs of central sensitization in knee osteoarthritis.

OBJECTIVE: Clinical tools are needed to identify and target a neuropathic-like phenotype, which may be associated with central sensitization (CS), in osteoarthritis (OA). The modified painDETECT questionnaire (mPD-Q) has face and content validity for identifying neuropathic-like symptoms in knee OA. To further validate the mPD-Q, this study assessed the unknown relationship between mPD-Q scores and signs of CS on quantitative sensory testing (QST) in knee OA. DESIGN: 36 Individuals were recruited with chronic, symptomatic, knee OA without other pain/neurological conditions. Reference QST data were obtained from 18 controls/32 eligible knees, enabling identification of sensory abnormalities/CS among case knees. A standardized questionnaire assessed psychological factors (depressive symptoms and pain catastrophizing), and for individual knees, mPD-Q and pain intensity scores. A standardized/comprehensive QST protocol was conducted for each knee. QST signs of CS were defined as: mechanical hyperalgesia and/or enhanced temporal summation and/or allodynia. The relationship between the presence of CS (yes/no) and a pre-selected mPD-Q score (≤12 or >12), by knees, was assessed using generalized estimating equations. RESULTS: Among 57 eligible case knees, 45.6% had ≥1 sign of CS. Controlling for age, knees with higher mPD-Q scores (>12.0) had higher odds of having QST signs of CS (adjusted odds ratio (OR) = 5.6; 95% confidence interval (CI), 1.3-22.9). This relationship was unaffected by controlling for depression and pain intensity, but was attenuated by pain catastrophizing. CONCLUSIONS: Among painful OA knees, higher mPD-Q scores were associated with greater odds of having signs of CS. Thus, the mPD-Q may aid the identification of CS in people with chronic knee OA.

Genetic testing in patients with acute coronary syndrome undergoing percutaneous coronary intervention: a cost-effectiveness analysis.

BACKGROUND: The CYP2C19 genotype is a predictor of adverse cardiovascular events in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) treated with clopidogrel. OBJECTIVES: We aimed to evaluate the cost-effectiveness of a CYP2C19*2 genotype-guided strategy of antiplatelet therapy in ACS patients undergoing PCI, compared with two 'no testing' strategies (empiric clopidogrel or prasugrel). METHODS: We developed a Markov model to compare three strategies. The model captured adverse cardiovascular events and antiplatelet-related complications. Costs were expressed in 2010 US dollars and estimated using diagnosis-related group codes and Medicare reimbursement rates. The net wholesale price for prasugrel was estimated as $5.45 per day. A generic estimate for clopidogrel of $1.00 per day was used and genetic testing was assumed to cost $500. RESULTS: Base case analyses demonstrated little difference between treatment strategies. The genetic testing-guided strategy yielded the most QALYs and was the least costly. Over 15 months, total costs were $18 lower with a gain of 0.004 QALY in the genotype-guided strategy compared with empiric clopidogrel, and $899 lower with a gain of 0.0005 QALY compared with empiric prasugrel. The strongest predictor of the preferred strategy was the relative risk of thrombotic events in carriers compared with wild-type individuals treated with clopidogrel. Above a 47% increased risk, a genotype-guided strategy was the dominant strategy. Above a clopidogrel cost of $3.96 per day, genetic testing was no longer dominant but remained cost-effective. CONCLUSIONS: Among ACS patients undergoing PCI, a genotype-guided strategy yields similar outcomes to empiric approaches to treatment, but is marginally less costly and more effective.

Neuropathic pain symptoms in a community knee OA cohort.

OBJECTIVE: A neuropathic pain (NP) questionnaire may facilitate the identification of a neuropathic component to osteoarthritis (OA) pain. An existing questionnaire, the painDETECT, was modified for use in knee OA and administered to measure the prevalence and correlates of NP symptoms among adults with this condition. METHOD: Sensibility of the modified painDETECT (mPD-Q) was assessed in 20 OA subjects followed by mail administration in an established knee OA cohort. NP symptoms were defined using a previously established, painDETECT cut-point. Correlates of NP symptoms, including OA severity (Western Ontario and McMaster Universities Osteoarthritis Index, Von Korff Chronic Pain Grade pain subscale score), psychological factors (Centre for Epidemiological Studies Depression Scale, Pain Catastrophizing Scale), and concomitant medical conditions, were evaluated using logistic regression. Construct validity of the mPD-Q was evaluated through co-administration with another NP questionnaire (S-LANSS). RESULTS: The mPD-Q had face and content validity. Of 259 eligible cohort members, 171 (66%) completed the questionnaire; 28% had NP symptoms on the mPD-Q (19% among those without neurological conditions). Independent correlates of NP symptoms were: pain intensity (adjusted odds ratio [OR]=2.1 per 10 unit increase, P<0.0001), the presence of referred back/hip pain (adjusted OR=2.9, P=0.024), number of painful joints (OR=1.2, P=0.20) and one or more self-reported neurological condition (OR=3.0, P=0.026). CONCLUSIONS: Among older adults with chronic symptomatic knee OA, over one-quarter had NP symptoms localized to their knees using the mPD-Q. The mPD-Q may facilitate the identification of a neuropathic component to pain in adults with knee OA who may benefit from further evaluation and/or treatment for NP.

Hormone replacement therapy in women with systemic lupus erythematosus and risk of cardiovascular disease.

We sought to determine the impact of hormone replacement therapy (HRT) on the occurrence of coronary artery disease (CAD) in women with systemic lupus erythematosus (SLE). Women in the University of Toronto lupus database who had taken HRT with no history of CAD were compared with all post-menopausal female patients with no history of HRT or CAD. Chi-squared and t-tests were used to compare the risk factors of CAD and Kaplan-Meier curve, log rank test and proportional hazard model with time-dependent covariates were used to compare the time from entry into the clinic to occurrence of CAD. A total of 114 HRT-user patients with no history of CAD were compared with 227 post-menopausal non-HRT user SLE controls. The groups were similar with respect to lupus anticoagulant, antiphospholipid antibody, cumulative steroid dose and classic cardiac risk factors. A similar percentage of patients developed CAD in the control (13.7%) and HRT (11.4%) groups. There was no difference in the time to development of CAD. In the multivariate analysis, HRT was not a risk factor for CAD. Only age (P = 0.0001, HR = 1.11, 95% CI = 1.05, 1.17) and SLEDAI-2K (P = 0.0001, HR = 1.10, 95% CI = 1.05, 1.16) were significantly associated with the risk of CAD. In this small group of patients with SLE, HRT alone did not appear to predispose to CAD.

Cardiovascular outcomes in high risk patients with osteoarthritis treated with ibuprofen, naproxen or lumiracoxib.

BACKGROUND: Evidence suggests that both selective cyclooxygenase (COX)-2 inhibitors and non-selective non-steroidal anti-inflammatory drugs (NSAIDs) increase the risk of cardiovascular events. However, evidence from prospective studies of currently available COX-2 inhibitors and non-selective NSAIDs is lacking in patients at high cardiovascular risk who are taking aspirin. OBJECTIVE: To determine the cardiovascular outcomes in high risk patients with osteoarthritis treated with ibuprofen, naproxen or lumiracoxib. METHODS: The Therapeutic Arthritis Research and Gastrointestinal Event Trial (TARGET) of 18 325 patients with osteoarthritis comprised two parallel substudies, comparing lumiracoxib (COX-2 inhibitor) with either ibuprofen or naproxen. A post hoc analysis by baseline cardiovascular risk, treatment assignment, and low-dose aspirin use was performed. The primary composite end point was cardiovascular mortality, non-fatal myocardial infarction, and stroke at 1 year; a secondary end point was the development of congestive heart failure (CHF). RESULTS: In high risk patients among aspirin users, patients in the ibuprofen substudy had more primary events with ibuprofen than lumiracoxib (2.14% vs 0.25%, p = 0.038), whereas in the naproxen substudy rates were similar for naproxen and lumiracoxib (1.58% vs 1.48%, p = 0.899). High risk patients not taking aspirin had fewer primary events with naproxen than with lumiracoxib (0% vs 1.57%, p = 0.027), but not for ibuprofen versus lumiracoxib (0.92% vs 0.80%, p = 0.920). Overall, CHF developed more often with ibuprofen than lumiracoxib (1.28% vs 0.14%; p = 0.031), whereas no difference existed between naproxen and lumiracoxib. CONCLUSIONS: These data suggest that ibuprofen may confer an increased risk of thrombotic and CHF events relative to lumiracoxib among aspirin users at high cardiovascular risk. The study indicates that naproxen may be associated with lower risk relative to lumiracoxib among non-aspirin users. This study is subject to inherent limitations, and therefore should be interpreted as a hypothesis-generating study.

Effects of fibrates on human organic anion-transporting polypeptide 1B1-, multidrug resistance protein 2- and P-glycoprotein-mediated transport.

The effects of different fibric acid derivatives (bezafibrate, clofibrate, clofibric acid, fenofibrate, fenofibric acid and gemfibrozil) on human organic anion transporting-polypeptide 1B1 (OATP2, OATP-C, SLC21A6), multidrug resistance protein 2 (MRP2/ABCC2) and MDR1-type P-glycoprotein (P-gp/ABCB1) were examined in vitro. Cyclosporin A (a known inhibitor of OATP1B1 and P-gp), MK-571 (a known inhibitor of MRP2) and cimetidine (an organic cation) were also tested. Bezafibrate, fenofibrate, fenofibric acid and gemfibrozil showed concentration-dependent inhibition of estradiol 17-beta-D-glucuronide uptake by OATP1B1-stably transfected HEK cells, whereas clofibrate and clofibric acid did not show any significant effects up to 100 microM. Inhibition kinetics of gemfibrozil, which exhibited the most significant inhibition on OATP1B1, was shown to be competitive with a Ki = 12.5 microM. None of the fibrates showed any significant inhibition of MRP2-mediated transport, which was evaluated by measuring the uptake of ethacrynic acid glutathione into MRP2-expressing Sf9 membrane vesicles. Only fenofibrate showed moderate P-gp inhibition as assessed by measuring cellular accumulation of vinblastine in a P-gp overexpressing cell-line. Cyclosporin A significantly inhibited OATP1B1 and P-gp, whereas only moderate inhibition was observed on MRP2. The rank order of inhibitory potency of MK-571 was determined as OATP1B1 (IC50: 0.3 microM) > MRP2 (4 microM) > P-gp (25 microM). Cimetidine did not show any effects on these transporters. In conclusion, neither MRP2- nor P-gp-mediated transport is inhibited significantly by the fibrates tested. Considering the plasma protein binding and IC50 values for OATP1B1, only gemfibrozil appeared to have a potential to cause drug-drug interactions by inhibiting OATP1B1 at clinically relevant concentrations.

First experience with direct, selective factor Xa inhibition in patients with non-ST-elevation acute coronary syndromes: results of the XaNADU-ACS Trial.

BACKGROUND: Unfractionated heparin is widely used in patients with non-ST-elevation acute coronary syndromes but has important limitations. Anticoagulants with predictable kinetics and anticoagulant effects, better efficacy, and greater safety are needed. OBJECTIVE: To investigate the efficacy and safety of a direct, selective factor Xa inhibitor, DX-9065a (Daiichi Pharmaceuticals LTD, Inc.) compared with heparin, in patients with non-ST-elevation acute coronary syndromes. PATIENTS AND METHODS: Patients (n = 402) from the USA, Canada, and Japan were randomized to blinded, weight-adjusted heparin, low-dose DX-9065a, or high-dose DX-9065a. RESULTS: The primary efficacy endpoint of death, myocardial infarction, urgent revascularization, or ischemia on continuous ST-segment monitoring occurred in 33.6%, 34.3%, and 31.3% of patients assigned to heparin, low-dose DX-9065a, and high-dose DX-9065a (P = 0.91 for heparin vs. combined DX-9065a). The composite of death, myocardial infarction, or urgent revascularization occurred in 19.5%, 19.3%, and 11.9% (P = 0.125 for heparin vs. high-dose DX-9065a) of patients; major or minor bleeding occurred in 7.7%, 4.2%, and 7.0% of patients; and major bleeding in 3.3%, 0.8%, and 0.9% of patients. Higher concentrations of DX-9065a were associated with a lower likelihood of ischemic events (P = 0.03) and a non-significant tendency toward a higher likelihood of major bleeding (P = 0.32). CONCLUSIONS: In this small phase II trial, there was a non-significant tendency toward a reduction in ischemic events and bleeding with DX-9065a compared with heparin in patients with acute coronary syndromes. The absence of an effect on ST-monitor ischemia warrants further investigation. These data provide the rationale for adequately powered studies of DX-9065a in acute coronary syndromes or percutaneous intervention.

Initial experience with factor-Xa inhibition in percutaneous coronary intervention: the XaNADU-PCI Pilot.

BACKGROUND: Direct factor (F)Xa inhibition is an attractive method to limit thrombotic complications during percutaneous coronary intervention (PCI). OBJECTIVES: To investigate drug levels achieved, effect on coagulation markers, and preliminary efficacy and safety of several doses of DX-9065a, an intravenous, small molecule, direct, reversible FXa inhibitor during PCI. PATIENTS AND METHODS: Patients undergoing elective, native-vessel PCI (n = 175) were randomized 4 : 1 to open-label DX-9065a or heparin in one of four sequential stages. DX-9065a regimens in stages I-III were designed to achieve concentrations of > 100 ng mL-1, > 75 ng mL-1, and > 150 ng mL-1. Stage IV used the stage III regimen but included patients recently given heparin. RESULTS: At 15 min median (minimum) DX-9065a plasma levels were 192 (176), 122 (117), 334 (221), and 429 (231) ng mL-1 in stages I-IV, respectively. Median whole-blood international normalized ratios (INRs) were 2.6 (interquartile range 2.5, 2.7), 1.9 (1.8, 2.0), 3.2 (3.0, 4.1), and 3.8 (3.4, 4.6), and anti-FXa levels were 0.36 (0.32, 0.38), 0.33 (0.26, 0.39), 0.45 (0.41, 0.51), and 0.62 (0.52, 0.65) U mL-1, respectively. Stage II enrollment was stopped (n = 7) after one serious thrombotic event. Ischemic and bleeding events were rare and, in this small population, showed no clear relation to DX-9065a dose. CONCLUSIONS: Elective PCI is feasible using a direct FXa inhibitor for anticoagulation. Predictable plasma drug levels can be rapidly obtained with double-bolus and infusion DX-9065a dosing. Monitoring of DX-9065a may be possible using whole-blood INR. Direct FXa inhibition is a novel and potentially promising approach to anticoagulation during PCI that deserves further study.

Renal elimination of a novel and potent alphavbeta3 integrin antagonist in animals.

Compound A (3-{2-oxo-3-[3-(5,6,7,8-tetrahydro-[1,8]napthyridin-2-yl)propyl]-imidazolidin-1-yl}-3(S)-(6-methoxy-pyridin-3-yl)propionic acid), a hydrophilic zwitter-ion, is a potent and selective alphavbeta3 integrin antagonist currently under clinical development for the treatment of osteoporosis. The mechanism of renal excretion of compound A was investigated using a combination of in vivo and in vitro approaches. In rats, renal excretion of compound A involved tubular secretion; ratios between renal clearance, corrected for unbound fraction in plasma (CLr,u) and glomerular filtration rate (GFR) were greater than unity (2-5). The tubular secretion of compound A was saturable at high plasma levels (> 26 microM), and was inhibited significantly, although modestly (about twofold) by relatively high plasma concentrations of the organic anion PAH (160 microM) and the cation cimetidine (about 400 microM), but not by the P-gp inhibitor quinidine (about 50 microM). However, compound A (about 100 microM) had a minimal effect on CLr/GFRs for cimetidine and PAH. In rhesus monkeys, renal elimination of compound A also involved tubular secretion, with a CLr,u/GFR ratio of about 30. The renal secretion of compound A was not affected by either cimetidine (about 120 microM) or PAH (about 80 microM). Similarly, compound A (about 40 microM) had a minimal effect on the renal tubular secretion of both cimetidine and PAH. At the doses studied, neither rat nor monkey plasma protein binding of compound A, cimetidine or PAH was affected in the presence of each other. In vitro transport studies showed that compound A was not a substrate for P-gp in the Caco-2, human MDR1 and mouse mdr1a transfected LLC-PK1 cell lines. In an uptake study using rOAT1 and rOAT3 transfected HEK cell lines, compound A was shown to be a substrate for rat OAT3 (Km= 15 microM), but not rat OAT1. The results suggest that the tubular secretion of compound A is not mediated by P-gp, but rather is mediated, at least in part, via the organic anion transporter OAT3, the renal transporter shown to be capable of transporting both the organic anion PAH and the organic cation cimetidine. Although there is a possibility for pharmacokinetic interactions between compound A and substrates or inhibitors of OAT3, at the renal excretion level, the magnitude of interaction would likely be modest in humans at clinically relevant doses.

Early revascularization is associated with improved survival in elderly patients with acute myocardial infarction complicated by cardiogenic shock: a report from the SHOCK Trial Registry.

AIMS: The SHould we emergently revascularize Occluded Coronaries in cardiogenic shocK (SHOCK) Trial showed no benefit of early revascularization in patients aged >/=75 years with acute myocardial infarction and cardiogenic shock. We examined the effect of age on treatment and outcomes of patients with cardiogenic shock in the SHOCK Trial Registry. METHODS AND RESULTS: We compared clinical and treatment factors in patients in the SHOCK Trial Registry with shock due to pump failure aged <75 years (n=588) and >/=75 years (n=277), and 30-day mortality of patients treated with early revascularization <18 hours since onset of shock and those undergoing a later or no revascularization procedure. After excluding early deaths covariate-adjusted relative risk and 95% confidence intervals were calculated to compare the revascularization strategies within the two age groups. Older patients more often had prior myocardial infarction, congestive heart failure, renal insufficiency, other comorbidities, and severe coronary anatomy. In-hospital mortality in the early vs. late or no revascularization groups was 45 vs. 61% for patients aged <75 years (p=0.002) and 48 vs. 81% for those aged >/=75 years (p=0.0003). After exclusion of 65 early deaths and covariate adjustment, the relative risk was 0.76 (0.59, 0.99; p=0.045) in patients aged <75 years and 0.46 (0.28, 0.75; p=0.002) in patients aged >/=75 years. CONCLUSIONS: Elderly patients with myocardial infarction complicated by cardiogenic shock are less likely to be treated with invasive therapies than younger patients with shock. Covariate-adjusted modeling reveals that elderly patients selected for early revascularization have a lower mortality rate than those receiving a revascularization procedure later or never.

Differences in the absorption, metabolism and biliary excretion of a diastereomeric pair of alphavbeta3-antagonists in rat: limited role of P-glycoprotein.

1. The study investigated mechanisms underlying the pharmacokinetic differences of two zwitterionic diastereomers ((3S)-3-[(3R or 3S)-2-oxo-3-[3-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)propyl]pyrrolidin-1-yl]-3-quinolin-3-ylpropanoic acid) with different lipophilicities using a combination of in vivo and in vitro approaches. 2. In rat, both isomers possessed comparable plasma clearances (CL). However, the more lipophilic diastereomer I exhibited a higher metabolic clearance (>2-fold higher than II), whereas the hydrophilic zwitterion II exhibited a higher biliary clearance (approximately 5-fold higher than I). Following oral administration, the bioavailability (F) of I (17%) was much higher than that of II (1%). 3. Consistent with these in vivo observations and the expectation based on their lipophilicity differences, the metabolism in rat liver microsomes was faster and the permeability in Caco-2 and LLC-PK1 cells and in situ rat intestinal loop was better for I than for II. 4. Only the absorption of the more lipophilic diastereomer I was subjected to an efflux system in the Caco-2 and in situ rat intestinal loop models. I was a good substrate for P-glycoprotein (P-gp) in both the human MDR1 and mouse mdr1a transfected cell lines, and in the wild-type mdr1a (-/-) mouse when compared with the P-gp-deficient mdr1a (-/-) mouse. Concomitant administration of I with verapamil in rat caused significant increases in oral AUC, F and Cmax of I without affecting its CL, further supporting the effect of P-gp in limiting the intestinal absorption of I in vivo in this animal model. 5. Since the findings that the lipophilic diastereomer I, but not II, was a good P-gp substrate were not in line with the observations that I was excreted to bile much slower than II and that I was absorbed better than II, the results suggested that P-gp played a minor role to the observed differences in the biliary excretion and intestinal absorption of the diastereomers I and II in rat.

Absence of gender differences in clinical outcomes in patients with cardiogenic shock complicating acute myocardial infarction. A report from the SHOCK Trial Registry.

OBJECTIVES: The aim of this study was to assess the impact of gender on clinical course and in-hospital mortality in patients with cardiogenic shock (CS) complicating acute myocardial infarction (AMI). BACKGROUND: Previous studies have demonstrated higher mortality for women compared with men with ST elevation myocardial infarctions and higher rates of CS after AMI. The influence of gender and its interaction with various treatment strategies on clinical outcomes once CS develops is unclear. METHODS: Using the SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK? (SHOCK) Registry database of 1,190 patients with suspected CS in the setting of AMI, we examined shock etiologies by gender. Among the 884 patients with predominant left ventricular (LV) failure, we compared the patient demographics, angiographic and hemodynamic findings, treatment approaches as well as the clinical outcomes of women versus men. This study had a 97% power to detect a 10% absolute difference in mortality by gender. RESULTS: Left ventricular failure was the most frequent cause of CS for both gender groups. Women in the SHOCK Registry had a significantly higher incidence of mechanical complications including ventricular septal rupture and acute severe mitral regurgitation. Among patients with predominant LV failure, women were, on average, 4.6 years older, had a higher incidence of hypertension, diabetes and a lower cardiac index. The overall mortality rate for the entire cohort was high (61%). After adjustment for differences in patient demographics and treatment approaches, there was no significant difference in in-hospital mortality between the two gender groups (odds ratio = 1.03, 95% confidence interval of 0.73 to 1.43, p = 0.88). Mortality was also similar for women and men who were selected for revascularization (44% vs. 38%, p = 0.244). CONCLUSIONS: Women with CS complicating AMI had more frequent adverse clinical characteristics and mechanical complications. Women derived the same benefit as men from revascularization, and gender was not independently associated with in-hospital mortality in the SHOCK Registry.

The late open artery hypothesis--a decade later.

BACKGROUND: Early reperfusion after myocardial infarction has been proved to preserve left ventricular function and reduce mortality. However, a significant number of patients have persistent occlusion of the infarct-related artery late (days to weeks) after myocardial infarction because of ineligibility for thrombolytic therapy, failure of reperfusion, or reocclusion. METHODS: In this report we review the data on the potential mechanisms and benefits of late reperfusion and present prospective data on the incidence of and current practice patterns for the management of persistently occluded infarct-related arteries late after myocardial infarction. RESULTS: Although several studies have associated late patency of the infarct-related artery with improved long-term clinical outcome, they were nonrandomized and reflect selection bias. Furthermore, data on late patency from the largest study, Global Utilization of Steptokinase and Tissue Plasminogen Activator for Occluded Arteries (GUSTO-I), failed to confirm independent benefits of an open infarct-related artery 1 year after myocardial infarction. The randomized data on the effects of percutaneous transluminal coronary angioplasty for occluded infarct-related arteries late after myocardial infarction are limited and inconclusive. CONCLUSIONS: The hypothesis that late reperfusion by percutaneous coronary intervention days to weeks after myocardial infarction results in improved long-term clinical outcomes in asymptomatic patients with occluded infarct-related artery is currently being tested in the randomized, multicenter Occluded Artery Trial.

Entry routes of malignant lymphoma into the brain and eyes in a mouse model.

We have recently developed a novel mouse model for studying the infiltration of malignant lymphoma to the eye and brain. After i.p. inoculation of variant S49 mouse lymphoma cells into young mice (optimum: day 7 postnatal), specific homing of these cells (named Rev-2-T-6) to the brain and eyes took place. This model offers an opportunity to study the routes of infiltration to these sites and spread thereof, as well as the molecular mechanisms that govern this metastasis. By applying a time course histopathological analysis, we demonstrate that infiltration of the brain and eyes can be visualized as early as days 9 and 14 after inoculation, respectively. The lymphoma cells enter the brain preferentially through the choroid plexus and cranial nerves. Infiltration of the rostral part occurs before the caudal part of the brain. Once within the brain, the cells spread within it as well as migrate along the optic nerve sheath into the eyes, where they continue to migrate along the choroid, ciliary body, iris, and into the anterior chamber of the eye. The orbit is also infiltrated by the lymphoma cells. However, this occurs independent of the brain-optic nerve-intraocular route.

P-glycoprotein-mediated efflux of indinavir metabolites in Caco-2 cells expressing cytochrome P450 3A4.

The role of P-glycoprotein in secretion of indinavir metabolites produced by CYP3A4 was evaluated in Caco-2 cells expressing CYP3A4. Metabolism of indinavir by CYP3A4 expressing Caco-2 cells grown on filters resulted in the formation of N-dealkylation products (M5 and M6) and hydroxylation of indinavir, which were preferentially secreted into the apical compartment. Apical secretion of the metabolites was inhibited by cyclosporin A (CsA) with all three classes of metabolites showing similar sensitivity to CsA, suggesting that they are all secreted by the same pathway. M6 stimulated P-glycoprotein (Pgp)-ATPase activity in a concentration-dependent manner. This stimulation was inhibited by the Pgp-specific monoclonal antibody C219. A method was developed to specifically inhibit Pgp using the monoclonal antibody UIC2 to determine whether Pgp efflux accounts for a significant proportion of the apical secretion of indinavir metabolites. UIC2 recognizes an extracellular transient conformational epitope that is stabilized by some Pgp substrates or by ATP depletion. Incubation of Caco-2 cells with UIC2 in the presence of 1 microM CsA resulted in 50 to 80% inhibition of Pgp-mediated vinblastine efflux, with no significant inhibition observed by UIC2 or CsA alone. Inhibition of Pgp in CYP3A4-expressing Caco-2 cells by UIC2 and 1 microM CsA resulted in a significant decrease in the apical secretion of M6, M5, and OH-indinavir and an increase in the amount of the metabolites secreted in the basolateral compartment and retained in the cytosol. These results are consistent with a role of Pgp in elimination of CYP3A4-generated metabolites and indicate that even relatively polar metabolites may be secreted from the cell by Pgp.

New heparin dosing recommendations for patients with acute coronary syndromes.

Despite major innovations in antithrombotic and antiplatelet therapy, unfractionated intravenous heparin is widely used to treat acute coronary syndromes. Recommendations for unfractionated heparin dosing in acute myocardial infarction and unstable angina have been issued in two recent American College of Cardiology/American Heart Association guidelines. An initial heparin bolus of 60 U/kg (maximum, 4000 U) followed by a 12-U/kg/h infusion (maximum 1000 U/h) is recommended with alteplase for ST-elevation myocardial infarction. When intravenous heparin is administered for myocardial infarction with non-ST elevation and unstable angina, an initial bolus of 60 to 70 U/kg (maximum, 5000 U) followed by a 12- to 15-U/kg/h infusion is recommended. The goal is to achieve an activated partial thromboplastin time of 50 to 70 seconds. Here, we review these new dosing regimens and explain the rationale for their use. We also review the risk of bleeding with heparin, especially when administered concurrently with aspirin, thrombolytic agents, and glycoprotein IIb/IIIa antagonists, and the relationship between activated partial thromboplastin time and cardiac events.