A randomized, open-label, crossover study evaluating bioequivalence of two N-acetylcysteine 2% oral solution formulations in healthy subjects
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OBJECTIVE: N-acetylcysteine is a mucolytic agent used to treat bronchopulmonary diseases associated with airway mucus hypersecretion. The bioequivalence of a new oral N-acetylcysteine 2% formulation was evaluated relative to an appropriate reference product. MATERIALS AND METHODS: This open-label, randomized, crossover study assessed the bioequivalence of a new N-acetylcysteine 2% oral solution compared to an approved reference N-acetylcysteine 2% oral solution in healthy subjects in terms of pharmacokinetics, including area under the plasma concentration vs. time curve of N-acetylcysteine plasma concentrations from time 0 to the last measurable sampling time point and the maximum postdose concentration. Bioequivalence was concluded if the 90% confidence intervals for the ratio of the geometric means of the two pharmacokinetic parameters with baseline correction were entirely within the range of 80 - 125%. RESULTS: 46 participants were randomized. The ratios of the geometric means for the test vs. reference treatment, with baseline correction, were 1.0961 (90% confidence interval: 1.0228, 1.1746) for area under the plasma concentration curve of test N-acetylcysteine plasma concentrations and 1.0938 (90% confidence interval: 1.0142, 1.1796) for maximum postdose concentration; both were within the predefined range to demonstrate bioequivalence. Most treatment-emergent adverse events were mild or moderate and not considered study drug related. CONCLUSION: The new N-acetylcysteine 2% oral solution was found to be bioequivalent to the marketed reference formulation. Treatments were generally safe and well tolerated.
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Effect of Coadministered Water on the In Vivo Performance of Oral Formulations Containing N-Acetylcysteine: An In Vitro Approach Using the Dynamic Open Flow-Through Test Apparatus.

The drug plasma profile after oral administration of immediate release dosage forms can be affected by the human gastrointestinal physiology, the formulation, and the drug itself. In this work, we investigated the in vivo and in vitro performance of two formulations (granules vs. tablet) containing the highly soluble drug N-Acetylcysteine (BCS class I). Thereby, special attention was paid to the effect of the dosage form and the coadministration of water on drug release. Interestingly, the in vivo results from a pharmacokinetic study with 11 healthy volunteers indicated that the drug plasma concentrations were comparable for the tablet given with water as well as for the granules given with and without water. In order to mechanistically understand this outcome, we used a biorelevant dissolution test device, the dynamic open flow-through test apparatus. With the aid of this test apparatus, we were able to simulate biorelevant parameters, such as gastric emptying, hydrodynamic flow as well as physical stress. By this, it was possible to mimic the intake conditions of the clinical trial (i.e., drug intake with and without water). Whereas the experiments in the USP paddle apparatus revealed differences between the two formulations, we could not observe significant differences in the release profiles of the two formulations by using the dynamic open flow-through test apparatus. Even by considering the different intake conditions, drug release was slow and amounted to around 30% until simulated gastric emptying. These results suggest that dissolution was irrespective of coadministered water and the formulation. Despite the high aqueous solubility of N-Acetylcysteine, the limiting factor for drug release was the slow dissolution rate in relation to the gastric emptying rate under simulated gastric conditions. Thus, in case of administration together with water, large amounts of the drug are still present in the stomach even after complete gastric emptying of the water. Consequently, the absorption of the drug is largely controlled by the nature of gastric emptying of the remaining drug. The data of this study indicated that the water emptying kinetics are only determining drug absorption if drug release is rapid enough. If this is not the case, physiological mechanisms, such as the migrating motor complex, play an important role for oral drug delivery.

An assessment of the variation in the concentration of acetylcysteine in infusions for the treatment of paracetamol overdose.

BACKGROUND: Intravenous acetylcysteine is the treatment of choice for paracetamol poisoning. A previous UK study in 2001 found that 39% of measured acetylcysteine infusion concentrations differed by >20% from anticipated concentrations. In 2012, the UK Commission on Human Medicines made recommendations for the management of paracetamol overdose, including provision of weight-based acetylcysteine dosing tables. The aim of this study was to assess variation in acetylcysteine concentrations in administered infusions following the introduction of this guidance. METHODS: A 6-month single-centre prospective study was undertaken at a UK teaching hospital. After preparation, 5-ml samples were taken from the first, second and third/any subsequent acetylcysteine infusions. Acetylcysteine was measured in diluted (1:50) samples by high-performance liquid chromatography. Comparisons between measured and expected concentrations based on prescribed weight-based dose and volume were made for each infusion. RESULTS: Ninety samples were collected. There was a variation of ≤10% in measured compared to expected concentration for 45 (50%) infusions, of 10-20% for 27 (30%) infusions, 20.1-50% for 14 (16%) infusions and >50% for four (4%) infusions. There was a median (interquartile range) variation in measured compared to expected concentration of -3.6 mg ml-1 (-6.7 to -2.3) for the first infusion, +0.2 mg ml-1 (-0.9 to +0.4) for the second infusion and -0.3 mg ml-1 (-0.6 to +0.2) for third and fourth infusions. CONCLUSION: There has been a moderate improvement in the variation in acetylcysteine dose administered by infusion. Further work is required to understand the continuing variation and consideration should be given to simplification of acetylcysteine regimes to decrease the risk of administration errors.

Pharmacokinetic modelling of modified acetylcysteine infusion regimens used in the treatment of paracetamol poisoning.

PURPOSE: Paracetamol overdose is common and is treated with acetylcysteine to prevent the development of hepatotoxicity. N-acetyl-p-benzoquinone imine (NAPQI) is the toxic metabolite of paracetamol overdose. We aimed to assess the expected acetylcysteine concentration time profiles following delivery of modified acetylcysteine regimens proposed for those at high and low risk of hepatotoxicity. In addition, we will determine acetylcysteine concentrations post-cessation of abbreviated infusions. METHOD: We performed pharmacokinetic simulations using Berkeley Madonna (version 8.3.23.0) comparing the time course of acetylcysteine concentration during and after the cessation of an abbreviated 12-h regimen (250 mg/kg) using a two-bag infusion and compared this to the standard 21-h three-bag (300 mg/kg) regimen. We also simulated extended duration acetylcysteine regimens and other increased dosing strategies that have been recommended in specific paracetamol poisoning scenarios. RESULTS: A more sustained serum concentration is achieved when the acetylcysteine loading dose is delivered over 4 h using the two-bag compared to the 1-h loading dose of the three-bag regimen. When administering an abbreviated 12-h acetylcysteine regimen, circulating acetylcysteine is detectable for 8 h after cessation of the infusion. This may provide a continued hepatoprotective effect if NAPQI is still being generated after the infusion is ceased. CONCLUSION: This pharmacokinetic simulation study is an important step in determining plasma acetylcysteine concentrations that are likely to be achieved using various modified treatment regimens. Importantly, for patients at low risk of liver injury after acute overdose, acetylcysteine is likely to be detectable many hours post-cessation of a 12-h regimen. This should provide a safety factor against development of hepatotoxicity for any ongoing paracetamol metabolism after cessation of the acetylcysteine infusion.

Uptake of dendrimer-drug by different cell types in the hippocampus after hypoxic-ischemic insult in neonatal mice: Effects of injury, microglial activation and hypothermia.

Perinatal hypoxic-ischemic encephalopathy (HIE) can result in neurodevelopmental disability, including cerebral palsy. The only treatment, hypothermia, provides incomplete neuroprotection. Hydroxyl polyamidoamine (PAMAM) dendrimers are being explored for targeted delivery of therapy for HIE. Understanding the biodistribution of dendrimer-conjugated drugs into microglia, neurons and astrocytes after brain injury is essential for optimizing drug delivery. We conjugated N-acetyl-L-cysteine to Cy5-labeled PAMAM dendrimer (Cy5-D-NAC) and used a mouse model of perinatal HIE to study effects of timing of administration, hypothermia, brain injury, and microglial activation on uptake. Dendrimer conjugation delivered therapy most effectively to activated microglia but also targeted some astrocytes and injured neurons. Cy5-D-NAC uptake was correlated with brain injury in all cell types and with activated morphology in microglia. Uptake was not inhibited by hypothermia, except in CD68+ microglia. Thus, dendrimer-conjugated drug delivery can target microglia, astrocytes and neurons and can be used in combination with hypothermia for treatment of HIE.

Decreased cysteine uptake by EAAC1 gene deletion exacerbates neuronal oxidative stress and neuronal death after traumatic brain injury.

Excitatory amino acid carrier type 1 (EAAC1), a high-affinity glutamate transporter, can expend energy to move glutamate into neurons. However, under normal physiological conditions, EAAC1 does not have a great effect on glutamate clearance but rather participates in the neuronal uptake of cysteine. This process is critical to maintaining neuronal antioxidant function by providing cysteine for glutathione synthesis. Previous study showed that mice lacking EAAC1 show increased neuronal oxidative stress following transient cerebral ischemia. In the present study, we sought to characterize the role of EAAC1 in neuronal resistance after traumatic brain injury (TBI). Young adult C57BL/6 wild-type or EAAC1 (-/-) mice were subjected to a controlled cortical impact model for TBI. Neuronal death after TBI showed more than double the number of degenerating neurons in the hippocampus in EAAC1 (-/-) mice compared with wild-type mice. Superoxide production, zinc translocation and microglia activation similarly showed a marked increase in the EAAC1 (-/-) mice. Pretreatment with N-acetyl cysteine (NAC) reduced TBI-induced neuronal death, superoxide production and zinc translocation. These findings indicate that cysteine uptake by EAAC1 is important for neuronal antioxidant function and survival following TBI. This study also suggests that administration of NAC has therapeutic potential in preventing TBI-induced neuronal death.

[Effectiveness of N-acetylcysteine in the treatment of schizophrenia].

Oxidative stress and neuroinflammation have recently been focused on the pathological hypotheses of schizophrenia. N-acetylcysteine (NAC) is a precursor of endogenous antioxidant glutathione and has antioxidant, anti-inflammatory, and neuroprotective properties. NAC is widely available as an over-the-counter nutritional supplement. Increasing lines of evidence suggest that NAC is effective for various mental disorders. In randomized controlled trials, treatment with NAC as an add-on to antipsychotics showed beneficial effects and safety profiles in patients with chronic schizophrenia. The results of a recent preclinical study using a neurodevelopmental model of schizophrenia suggest that NAC may have promising effects in an early stage of schizophrenia and an at-risk mental state. However, there is little clinical evidence for the efficacy and safety of NAC at these stages of schizophrenia. In this review, we summarize the evidence regarding the effectiveness of NAC for the treatment of schizophrenia and its prodromal stage. We also introduce the preliminary results of our research on NAC.

Nanoparticles increase the efficacy of cancer chemopreventive agents in cells exposed to cigarette smoke condensate.

Lung cancer is a leading cause of death in developed countries. Although smoking cessation is a primary strategy for preventing lung cancer, former smokers remain at high risk of cancer. Accordingly, there is a need to increase the efficacy of lung cancer prevention. Poor bioavailability is the main factor limiting the efficacy of chemopreventive agents. The aim of this study was to increase the efficacy of cancer chemopreventive agents by using lipid nanoparticles (NPs) as a carrier. This study evaluated the ability of lipid NPs to modify the pharmacodynamics of chemopreventive agents including N-acetyl-L-cysteine, phenethyl isothiocyanate and resveratrol (RES). The chemopreventive efficacy of these drugs was determined by evaluating their abilities to counteract cytotoxic damage (DNA fragmentation) induced by cigarette smoke condensate (CSC) and to activate protective apoptosis (annexin-V cytofluorimetric staining) in bronchial epithelial cells both in vitro and in ex vivo experiment in mice. NPs decreased the toxicity of RES and increased its ability to counteract CSC cytotoxicity. NPs significantly increased the ability of phenethyl isothiocyanate to attenuate CSC-induced DNA fragmentation at the highest tested dose. In contrast, this potentiating effect was observed at all tested doses of RES, NPs dramatically increasing RES-induced apoptosis in CSC-treated cells. These results provide evidence that NPs are highly effective at increasing the efficacy of lipophilic drugs (RES) but are not effective towards hydrophilic agents (N-acetyl-L-cysteine), which already possess remarkable bioavailability. Intermediate effects were observed for phenethyl isothiocyanate. These findings are relevant to the identification of cancer chemopreventive agents that would benefit from lipid NP delivery.

Population pharmacokinetic-pharmacodynamic modelling to describe the effects of paracetamol and N-acetylcysteine on the international normalized ratio.

Paracetamol is one of the most common pharmaceutical agents taken in self-poisonings, and can increase the prothrombin time (PT) through liver injury, and in overdose without hepatic injury by reducing functional factor VII. PT is a measure of hepatic injury used to predict and monitor hepatotoxicity, reported as the international normalized ratio (INR). The antidote for paracetamol poisoning, N-acetylcysteine (NAC), has been reported to have an effect on the PT. This analysis included patients from a retrospective case series, a prospective inception cohort of paracetamol and psychotropic (control) overdoses, and a cross-over clinical trial. A population pharmacokinetic-pharmacodynamic model describing the pharmacodynamic effects of paracetamol and NAC on the INR was developed in Phoenix NLME. The dataset included 172 patients; the median age was 22 years (range 13-71 years). A one-compartment model with first-order input and linear disposition best described paracetamol pharmacokinetics. The population mean estimate of the concentration that induced a response halfway between the baseline and maximal pharmacological effect of paracetamol was 1302 µmol/L (242), the maximum effect of paracetamol was 0.534 (202; from baseline) and the maximum effect of NAC was 0.325 (9.03; from baseline). Both paracetamol and NAC contributed a pharmacological effect to the elevation of INR. The estimated paracetamol concentration that induced a response halfway between the baseline and maximal pharmacological effect was within the range of plasma paracetamol values studied, fivefold greater than the maximum therapeutic concentration, suggesting that an elevated INR would not be expected within the therapeutic range. Simulated 24 and 48 g paracetamol overdoses with NAC administration produced INR values (50th percentile) that reached the upper limit of, or exceeded, the reference range.

Antenatal pharmacokinetics and placental transfer of N-acetylcysteine in chorioamnionitis for fetal neuroprotection.

OBJECTIVE: To determine the pharmacokinetics (PK) and placental transfer of intravenous (i.v.) N-acetylcysteine (NAC) in mothers with a clinical diagnosis of chorioamnionitis (CA) and determine the PK of i.v. NAC in their infants. STUDY DESIGN: In this prospective, double-blind study i.v. NAC 100 mg/kg/dose or saline was administered within 4 hours of CA diagnosis to pregnant women ≥24 weeks' gestation and then every 6 hours until delivery. Maternal PK and placental transfer were determined with maternal blood and matched maternal and cord venous blood. Neonatal PK estimates were determined from i.v. NAC (12.5-25 mg/kg/dose) administered every 12 hours for 5 doses. Noncompartmental analyses were performed for maternal and neonatal PK estimates. RESULTS: Eleven mothers (5 preterm, 6 near-term) and 12 infants (1 set of twins) received NAC. Maternal clearance (CL) of NAC was faster than in nonpregnant adults, with a terminal elimination half-life of 1.2 ± 0.2 hours. The NAC cord to maternal ratio was 1.4 ± 0.8, suggesting rapid placental transfer and slower rate of fetal CL. Neonatal PK estimates for near-term compared with preterm infants showed a significantly shorter terminal elimination half-life (5.1 vs 7.5 hours, respectively) and greater CL (53.7 vs 45.0 mL/h/kg, respectively). CONCLUSIONS: Maternal CL and placental transfer of NAC was rapid, with umbilical cord concentrations frequently exceeding maternal concentrations. The administration of NAC to mothers with CA achieves predictable NAC plasma concentrations in the fetus, indicating that antenatal neuroprotection may be possible for these newborns at high risk for neuroinflammation.

Safety and Pharmacokinetics of a Combined Antioxidant Therapy against Myocardial Reperfusion Injury: A Phase 1 Randomized Clinical Trial in Healthy Humans.

Myocardial reperfusion injury (MRI) accounts for up to 50% of the final size in acute myocardial infarction and other conditions associated with ischemia-reperfusion. Currently, there is still no therapy to prevent MRI, but it is well known that oxidative stress has a key role in its mechanism. We previously reduced MRI in rats through a combined antioxidant therapy (CAT) of ascorbic acid, N-acetylcysteine, and deferoxamine. This study determines the safety and pharmacokinetics of CAT in a Phase I clinical trial. Healthy subjects (n = 18) were randomized 2:1 to CAT or placebo (NaCl 0.9% i.v.). Two different doses/infusion rates of CATs were tested in a single 90-minute intravenous infusion. Blood samples were collected at specific times for 180 minutes to measure plasma drug concentrations (ascorbic acid, N-acetylcysteine, and deferoxamine) and oxidative stress biomarkers. Adverse events were registered during infusion and followed for 30 days. Both CAT1 and CAT2 significantly increased the CAT drug concentrations compared to placebo (P < .05). Most of the pharmacokinetic parameters were similar between CAT1 and CAT2. In total, 6 adverse events were reported, all nonserious and observed in CAT1. The ferric-reducing ability of plasma (an antioxidant biomarker) increased in both CAT groups compared to placebo (P < .001). The CAT is safe in humans and a potential treatment for patients with acute myocardial infarction undergoing reperfusion therapy.

Pharmacological enhancement of α-glucosidase by the allosteric chaperone N-acetylcysteine.

Pompe disease (PD) is a metabolic myopathy due to the deficiency of the lysosomal enzyme α-glucosidase (GAA). The only approved treatment for this disorder, enzyme replacement with recombinant human GAA (rhGAA), has shown limited therapeutic efficacy in some PD patients. Pharmacological chaperone therapy (PCT), either alone or in combination with enzyme replacement, has been proposed as an alternative therapeutic strategy. However, the chaperones identified so far also are active site-directed molecules and potential inhibitors of target enzymes. We demonstrated that N-acetylcysteine (NAC) is a novel allosteric chaperone for GAA. NAC improved the stability of rhGAA as a function of pH and temperature without disrupting its catalytic activity. A computational analysis of NAC-GAA interactions confirmed that NAC does not interact with GAA catalytic domain. NAC enhanced the residual activity of mutated GAA in cultured PD fibroblasts and in COS7 cells overexpressing mutated GAA. NAC also enhanced rhGAA efficacy in PD fibroblasts. In cells incubated with NAC and rhGAA, GAA activities were 3.7-8.7-fold higher than those obtained in cells treated with rhGAA alone. In a PD mouse model the combination of NAC and rhGAA resulted in better correction of enzyme activity in liver, heart, diaphragm and gastrocnemia, compared to rhGAA alone.

Safety and pharmacokinetic studies of liposomal antioxidant formulations containing N-acetylcysteine, α-tocopherol or γ-tocopherol in beagle dogs.

The safety and pharmacokinetic profile of liposomal formulations containing combinations of the antioxidants α-tocopherol, γ-tocopherol or N-acetylcysteine in beagle dogs was examined. Each group consisted of beagle dogs of both genders with a control group receiving empty dipalmitoylphosphatidylcholine (DPPC) liposomes (330 mg/kg DPPC, EL), and test groups receiving liposomes prepared from DPPC lipids with (i) N-acetylcysteine (NAC) (60 mg/kg NAC [L-NAC]); (ii) NAC and α-tocopherol (αT) (60 mg/kg NAC and 25 mg/kg α-tocopherol [L-αT-NAC]) and (iii) NAC and γ-tocopherol (60 mg/kg NAC and 25 mg/kg γ-tocopherol (γT) [L-γT-NAC]). The dogs in the control group (EL) and three test groups exhibited no signs of toxicity during the dosing period or day 15 post treatment. Weight gain, feed consumption and clinical pathology findings (hematology, coagulation, clinical chemistry, urinalysis) were unremarkable in all dogs and in all groups. Results from the pharmacokinetic study revealed that the inclusion of tocopherols in the liposomal formulation significantly increased the area under the curve (AUC) and ß-half life for NAC; the tocopherols had greater impact on the clearance of NAC, where reductions of central compartment clearance (CL) ranged from 56% to 60% and reductions of tissue clearance (CL2) ranged from 73% to 77%. In conclusion, there was no treatment-related toxicity in dogs at the maximum feasible dose level by a single bolus intravenous administration while the addition of tocopherols to the liposomal formulation prolonged the circulation of NAC in plasma largely due to a decreased clearance of NAC.

Population Pharmacokinetic Model of N-Acetylcysteine During Periods of Recurrent Hypoglycemia in Healthy Volunteers.

Recurrent hypoglycemia leads to impaired awareness of hypoglycemia where the blood glucose threshold that elicits the counterregulatory response is lowered. Hypoglycemia-induced oxidative stress is hypothesized to contribute to impaired awareness of hypoglycemia development and hypoglycemia-associated autonomic failure. Our group conducted a randomized, double-blinded, placebo-controlled, crossover study in healthy individuals undergoing experimentally induced recurrent hypoglycemia to evaluate the impact of intravenous N-acetylcysteine (NAC) during experimental hypoglycemia to preserve the counterregulatory response to subsequent hypoglycemia. The work presented herein aimed to characterize the NAC pharmacokinetics and its effects on oxidative stress. Whole blood and plasma samples were collected at specified time points during separate NAC and placebo infusions from 10 healthy volunteers. Samples were analyzed for NAC, cysteine, and glutathione (GSH) concentrations. A 2-compartment population NAC pharmacokinetic model was developed. Estimates for central compartment clearance and volume of distribution were 19.8 L/h, and 12.2 L, respectively, for a 70-kg person. Peripheral compartment clearance and volume of distribution estimates were 34.9 L/h and 13.1 L, respectively, for a 70-kg person. The PK parameters estimated here were different from those reported in the literature, suggesting a higher NAC clearance during hypoglycemic episodes. NAC leads to a significant increase in circulating cysteine concentration in a NAC concentration-dependent manner, suggesting rapid biotransformation. A transient decrease in plasma GSH was observed, supporting the hypothesis that NAC can act as a reducing agent displacing glutathione from the disulfide bond allowing for increased clearance and/or distribution of GSH.

Phase I study of the pharmacokinetics and safety of single and multiple doses of intravenous N-acetylcysteine in healthy Chinese subjects.

OBJECTIVE: The aim of the study was to determine the pharmacokinetics (PK) and safety of single and repeat doses of intravenous (IV) N-acetylcysteine (NAC) in Chinese subjects. PATIENTS AND METHODS: A total of 24 healthy male and female Chinese subjects aged 19-40 years were enrolled in this open-label phase I study. All subjects received a single dose of NAC 600 mg IV on day 1 and, after a 3-day washout, received repeat doses of NAC 600 mg IV (twice daily on days 4 and 5 and once on day 6). RESULTS: Following a single dose, plasma NAC concentrations peaked rapidly, starting to fall at the end of the 5-minute infusion in a multiphasic manner. Mean Cmax was 83.30 µg/mL (CV% 30.7%), median Tmax was 0.083 h (range 0.08-0.25 h), and mean AUC(0-12 h) was 81.87 h*µg/mL (CV 14.0%). Following repeat dosing, Cmax was approximately 20% higher than after a single dose, with similar Tmax. Total exposure AUC(0-12) was 13% higher at steady state than after single dosing. The accumulation ratio was approximately 1.13, indicating only a slight accumulation with multiple dosing. NAC was eliminated with T1/2 of approximately 8 hours. Around 15% of the total NAC dose was excreted in the urine in the 32 hours post-dose, keeping with extensive NAC metabolism and transformation. Renal clearance of NAC was 995.2 mL/h (CV 50.2%). IV NAC was well tolerated after both single and multiple dosing. CONCLUSIONS: This is the first robust study evaluating the PK and safety of IV NAC 600 mg in Chinese subjects and provides important data if this agent is to be used IV as a mucolytic in this population.

Mechanisms of modified LDL-induced pericyte loss and retinal injury in diabetic retinopathy.

AIMS/HYPOTHESIS: In previous studies we have shown that extravasated, modified LDL is associated with pericyte loss, an early feature of diabetic retinopathy (DR). Here we sought to determine detailed mechanisms of this LDL-induced pericyte loss. METHODS: Human retinal capillary pericytes (HRCP) were exposed to 'highly-oxidised glycated' LDL (HOG-LDL) (a model of extravasated and modified LDL) and to 4-hydroxynonenal or 7-ketocholesterol (components of oxidised LDL), or to native LDL for 1 to 24 h with or without 1 h of pretreatment with inhibitors of the following: (1) the scavenger receptor (polyinosinic acid); (2) oxidative stress (N-acetyl cysteine); (3) endoplasmic reticulum (ER) stress (4-phenyl butyric acid); and (4) mitochondrial dysfunction (cyclosporin A). Oxidative stress, ER stress, mitochondrial dysfunction, apoptosis and autophagy were assessed using techniques including western blotting, immunofluorescence, RT-PCR, flow cytometry and TUNEL assay. To assess the relevance of the results in vivo, immunohistochemistry was used to detect the ER stress chaperon, 78 kDa glucose-regulated protein, and the ER sensor, activating transcription factor 6, in retinas from a mouse model of DR that mimics exposure of the retina to elevated glucose and elevated LDL levels, and in retinas from human participants with and without diabetes and DR. RESULTS: Compared with native LDL, HOG-LDL activated oxidative and ER stress in HRCP, resulting in mitochondrial dysfunction, apoptosis and autophagy. In a mouse model of diabetes and hyperlipidaemia (vs mouse models of either condition alone), retinal ER stress was enhanced. ER stress was also enhanced in diabetic human retina and correlated with the severity of DR. CONCLUSIONS/INTERPRETATION: Cell culture, animal, and human data suggest that oxidative stress and ER stress are induced by modified LDL, and are implicated in pericyte loss in DR.

Intravenous N-acetylcysteine in the prevention of contrast media-induced nephropathy.

OBJECTIVE: To define the clinical role of intravenous N-acetylcysteine for prophylaxis of contrast-induced nephropathy (CIN). DATA SOURCES: Randomized controlled clinical trials were identified using a search of MEDLINE (1990-September 2010) with the search terms acetylcysteine, N-acetylcysteine, NAC, intravenous, IV, nephropathy, nephrotoxic, radiocontrast, contrast, and media. The search was limited to studies published in English. Additional pertinent literature was retrieved by reviewing references of the articles obtained in the initial search. DATA SYNTHESIS: N-Acetylcysteine is a vasodilator and antioxidant that has been investigated for the prevention of CIN. In the majority of clinical trials, neither oral nor intravenous N-acetylcysteine has demonstrated clinical benefits at preventing CIN. The pharmacodynamic and pharmacokinetic profiles of intravenous N-acetylcysteine are significantly different from those of the oral product in that intravenous administration bypasses extensive first-pass metabolism. Studies have suggested that N-acetylcysteine directly affects serum creatinine levels in a way that is not associated with improvement of kidney function. Only intravenous N-acetylcysteine doses that were higher than the oral doses showed potential benefits, but they were associated with significant adverse events. Furthermore, the study populations were heterogeneous, including patients with various levels of kidney function and other risk factors, and the clinical definition of CIN was not well established. CONCLUSIONS: No conclusive evidence has shown that intravenous N-acetylcysteine is safe and effective in preventing CIN. Further clinical trials to define its role are warranted.

Liquid chromatography tandem mass spectrometry method for determination of N-acetylcysteine in human plasma using an isotope-labeled internal standard.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to determine total N-acetylcysteine in human plasma. Mass spectrometric detection was achieved in positive electrospray ionization and multiple reaction monitoring mode. The mass transition pairs of N-acetylcysteine and the isotope-labeled internal standard d3-N-acetylcysteine were 164 → 122 and 167 → 123, respectively. The method was linear over the range of 10-5000 ng/mL in human plasma. The adoption of trichloroacetic acid significantly enhanced the extraction recovery. The blank matrix was screened to minimize the influence of endogenous N-acetylcysteine. After being fully validated, the method was successfully applied to the pharmacokinetic and bioequivalent study of N-acetylcysteine after oral administration of 600 mg tablets to 24 healthy Chinese volunteers.

Population Pharmacokinetic Analysis of N-Acetylcysteine in Pediatric Patients With Inherited Metabolic Disorders Undergoing Hematopoietic Stem Cell Transplant.

N-acetylcysteine (NAC) has been used in patients with cerebral adrenoleukodystrophy as an antioxidant agent in association with hematopoietic stem cell transplant (HSCT). However, an understanding of the pharmacokinetic characteristics of intravenous NAC dosing in these patients is limited. If and how NAC pharmacokinetics change following the transplant is unknown. Toward that end, a total of 260 blood samples obtained from 18 pediatric patients with inherited metabolic disorders who underwent HSCT were included in a population pharmacokinetic analysis using nonlinear mixed-effects modeling. NAC clearance (CL) and volume of distribution (V) were explored on 3 occasions: -7, +7, and +21 days relative to transplant. Additionally, the effect of transplant procedure on NAC disposition was explored by accounting for between-occasion variability. The covariate OCC was modeled as a fixed-effect parameter on CL and/or V1. A 2-compartment model adequately described the pharmacokinetics of total NAC. Weight-based allometric scaling on pharmacokinetic parameters was assumed using standard coefficients. Estimates for CL, central (V1), and peripheral volume (V2), and intercompartment clearance were 14.7 L/h, 23.2 L, 17.1 L, 3.99 L/h, respectively, for a 70-kg person. The data only supported between-subject variability in CL (12%) and V1 (41%). Residual variability was estimated to be 16%. HSCT did not change CL and V1 significantly, and analysis across occasions did not reveal any trends. Pharmacokinetic parameter estimates were in general comparable to those reported previously in different populations. These results suggest that dosing of NAC does not need to be altered following HSCT.

Locus-Level Changes in Macular Sensitivity in Patients with Retinitis Pigmentosa Treated with Oral N-acetylcysteine.

PURPOSE: To identify characteristics of loci associated with locus-level sensitivity loss or improvement during treatment with N-acetylcysteine (NAC) in retinitis pigmentosa (RP). DESIGN: Retrospective analysis of prospectively collected data in the FIGHT RP clinical trial. METHODS: Patients (n = 30) were treated with 600, 1,200, or 1,800 mg of NAC twice daily for 3 months and then 3 times/day for 3 months. Microperimetry locus-level changes between baseline and month 6 were correlated with baseline characteristics of loci using regression models. The main outcome measurement was locus-level sensitivity change ≥6 dB. RESULTS: Baseline mean sensitivity (3,468 loci; 51 evaluable eyes) was 7.7 dB and for foveal, parafoveal, and perifoveal loci were 20.2, 11.8, and 5.8 dB. During treatment, 287 loci (8.28%) increased ≥6 dB, and 119 of 1,613 loci with baseline sensitivity ≥6 dB decreased ≥6 dB (7.38%). A higher dose of NAC was associated with lower likelihood of sensitivity loss ≥6 dB (P = .033). Loci with low baseline sensitivity were more likely to decrease ≥6 dB (P = .034) but also more likely to increase ≥6 dB (P < .001). Foveal versus perifoveal loci (P < .001) and superior versus inferior loci (P = .005) were more likely to increase ≥6 dB. CONCLUSIONS: Higher doses of NAC reduced risk of macular loci sensitivity loss in RP. Greater sensitivity depression reversibility in the fovea during treatment suggests that high foveal cone density protects cones from irreversible loss of function in RP making them more likely to show improved function during NAC treatment.