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.

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.

Design, development and in-vitro/in-vivo evaluation of intranasally delivered Rivastigmine and N-Acetyl Cysteine loaded bifunctional niosomes for applications in combinative treatment of Alzheimer's disease.

The present investigation explores the potential of novel dual drug-loaded niosomes for nasal delivery of Rivastigmine (RIV) and N-Acetyl Cysteine (NAC) to the brain. The dual niosomes showed a particle size of 162.4 nm and % entrapment efficiencies of 97.7% for RIV and 85.9% for NAC. The niosomes were statistically validated using Box-Behnken experimental design (BBD) with good significance. Ultrastructural and chemical characterization of the niosomes using various analytical techniques like Fourier Transform Infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), Transmission electron microscopy (TEM) showcased drug-excipient compatibility and robust stability of 6 months in a liquid state at 4-8 °C. The dual drug-loaded niosomes showed a sustained drug release pattern up to 2 days. Acetylcholinesterase (AChE) and DPPH (1, 1-diphenyl-2- picrylhydrazyl) enzyme inhibition assays showed a better combinative effect than the free drug solutions. A 2-day nasal permeation proved the effectiveness and biocompatibility of the niosomes. In-vivo pharmacokinetic and organ biodistribution studies revealed a better drug profile and greater distribution of the niosomes in the brain compared to other organs, thereby indicating a direct nose-to-brain delivery of the niosomes.

Improvement of the skeletal phenotype in a mouse model of diastrophic dysplasia after postnatal treatment with N-acetylcysteine.

Diastrophic dysplasia (DTD) is a recessive chondrodysplasia caused by mutations in the SLC26A2 gene encoding for a sulfate/chloride transporter. When SLC26A2 is impaired intracellular level of sulfate is reduced leading to the synthesis of undersulfated proteoglycans. In normal chondrocytes, the main source of intracellular sulfate is the extracellular uptake through SLC26A2, but a small amount comes from the catabolism of sulfur-containing amino acids and other thiols. Here N-acetylcysteine (NAC), an extensively used drug, is proposed as alternative source of intracellular sulfate in an animal model of DTD (dtd mouse). Mutant and wild type mice were treated twice a day with hypodermic injections of 250 mg NAC/kg body weight for one week after birth. At the end of the treatment, an improvement trend in cartilage proteoglycan sulfation and in the skeletal phenotype of treated dtd mice were observed. Thus, a longer treatment lasted three weeks starting from birth was performed. Treated mutant mice showed a significant increase of cartilage proteoglycan sulfation and a relevant improvement of the skeletal phenotype based on measurements of several bony elements and bone quality by DEXA and micro CT. Moreover, the amelioration of the overall growth plate morphology in treated dtd mice suggested a partial rescue of the endochondral ossification process. Overall, the results prove that NAC is an effective source of intracellular sulfate for dtd mice in the postnatal period. This finding paves the way for a potential pharmacological treatment of DTD patients taking advantage from a drug repositioning strategy.

Legacy Effect of Antioxidant N-acetylcysteine in Cellular Senescence of Diet-induced Obesity Mice.

BACKGROUND: Cellular senescence is a state of stable growth arrest triggered by mitogenic and metabolic stressors. Ageing and a high-fat diet (HFD) are proven inducers of senescence in various organs, presenting a challenge for ageing populations worldwide. Our previous study demonstrated that ROS scavenger N-acetylcysteine (NAC) can improve insulin resistance (IR) and chronic inflammation in diet-induced obesity mice, an effect better achieved through early intervention. We, herein, investigate whether NAC can improve cellular senescence in a diet-induced obesity mouse model, and whether a legacy effect is presented with early intervention. MATERIALS AND METHODS: For a twelve-month treatment course, all C57B/L6 mice were fed a chow diet (CD), high-fat high-sucrose diet (HFD), CD+NAC1-12 (NAC intervention 1st-12th month), HFD+NAC1-12, and HFD+NAC1-6 (NAC intervention 1st-6th month). Staticalanalysis was used to analyze the different markers of cellular senescence and inflammation. RESULTS: Throughout the study, the HFD group exhibited significantly increased body weight (BW) and body fat, markers of senescence, decreased motor activity (MA) and impaired glucose tolerance. Compared to the HFD group, the HFD+NAC1-12 group exhibited increased MA, decreased BW and body fat, improved glucose tolerance, and decreased senescence markers.The HFD+NAC1-6 group showed similar effects to the HFD+NAC1-12 group, despite discontinuing NAC for 6 months. Our study showed that NAC significantly increased MA in both HFD+NAC1-12 and HFD+NAC1-6 groups, and improved HFD-induced mitochondrial and intracellular ROS expression, DNA and protein oxidative damage, and adipose tissue inflammation. CONCLUSION: Legacy effect was indeed presented in HFD-induced cellular senescence with NAC intervention, with possible mechanisms being persistently increased motor activity and anti-oxidative stress effects.

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.

Intratympanic application of poloxamer 407 hydrogels results in sustained N-acetylcysteine delivery to the inner ear.

N-acetylcysteine is a thiol-containing antioxidant, which has shown otoprotective effects in in vitro as well as in vivo models of cisplatin-induced hearing loss. Systemic administration of antioxidants, however, is associated with the major potential drawback of interference with the tumoricidal effect of cisplatin. This therapeutic limitation can be overcome by local intratympanic injection of the antioxidant N-acetylcysteine, which results in very restricted systemic uptake of the drug, whilst intracochlear drug levels are substantially higher. Furthermore, osmolality and pH properties of formulations for intratympanic injection need to be controlled, as they impact the fraction of drug crossing the barriers of the inner ear and could potentially damage middle and inner ear structures. This study focused on (i) the evaluation of concentration-time profiles of N-acetylcysteine in perilymph, cerebrospinal fluid and plasma after intratympanic administration, (ii) the influence of the dosage form, i.e. a thermoreversible poloxamer 407 hydrogel versus a solution, on N-acetylcysteine pharmacokinetics, and (iii) the development of a pH- and osmolality-adjusted formulation for intratympanic N-acetylcysteine delivery. 49 female albino guinea pigs were randomized into two treatment groups, receiving either a single intratympanic injection of a 4% N-acetylcysteine poloxamer 407 hydrogel or a 4% N-acetylcysteine solution. 8 animals served as untreated controls. N-acetylcysteine levels in perilymph, cerebrospinal fluid and plasma were monitored over a period of 24 h. Samples were taken at 1, 3, 6, 12 and 24 h (poloxamer 407 hydrogel group) and 1, 6 and 24 h (solution group) post injection, and analysed by high performance liquid chromatography-tandem mass spectrometry. Intratympanic application of the 4% N-acetylcysteine poloxamer 407 hydrogel resulted in a 4-fold larger perilymph area under the concentration-time curve (0-24 h) than topical administration of the equally concentrated N-acetylcysteine solution but in similar plasma N-acetylcysteine levels. N-acetylcysteine concentrations in the cerebrospinal fluid were below the level of detection (5 ng/ml) in both treatment groups. N-acetylcysteine-containing formulations applied to the middle ear were isohydric and osmolality was reduced by up to 200 mosmol/kg compared to equally concentrated formulations used in previous studies. In summary, we were able to demonstrate that the intratympanic injection of thermoreversible poloxamer 407 hydrogels increases and sustains N-acetylcysteine delivery to the inner ear. Given the low plasma N-acetylcysteine levels after topical application and the physiological pH and osmolality of the hydrogel, the risk of compromising the antineoplastic effects of cisplatin therapy and of local side effects is minimal.

Pharmacokinetic profile of N-acetylcysteine amide and its main metabolite in mice using new analytical method.

N-acetylcysteine amide (NACA) is the amide derivative of N-acetylcysteine (NAC) that is rapidly converted to NAC after systemic administration. It has emerged as a promising thiol antioxidant for multiple indications; however, the pharmacokinetic property is yet unclear due to lack of an accurate quantification method. The present investigation aimed to develop an analytical method for simultaneous quantification of NACA and NAC in plasma. A new reagent (2-(methylsulfonyl)-5-phenyl-1,3,4-oxadiazole, MPOZ) was introduced for thiol stabilization during sample processing and storage. Further, we utilized tris (2-carboxyethyl) phosphine (TCEP) to reduce the oxidized forms of NACA and NAC. After derivatization, NACA-MPOZ and NAC-MPOZ were quantified using liquid chromatography-mass spectrometry (LC-MS). The new method was validated and found to have high specificity, linearity, accuracy, precision, and recovery for the quantification of NACA and NAC in plasma. Furthermore, the formed derivatives of NACA and NAC were stable for 48 h under different conditions. The method was utilized in pharmacokinetic study which showed that the bioavailability of NACA is significantly higher than NAC (67% and 15%, respectively). The pharmacokinetic of NACA obeyed a two-compartment open model. The glutathione (GSH)-replenishing capacity was found to be three to four-fold higher after the administration of NACA compared to that observed after the administration of NAC. In conclusion, the present method is simple, robust and reproducible, and can be utilized in both experimental and clinical studies. NACA might be considered as a prodrug for NAC. Furthermore, this is the first report describing the pharmacokinetics and bioavailability of NACA in mouse.

Metabolomics-based biomarker analysis of dihydroxypropyl mercapturic acid isomers from 3-monochloropropane-1,2-diol and glycidol for evaluation of toxicokinetics in rats and daily internal exposure in humans.

3-Monochloropropane-1,2-diol (3-MCPD), glycidol, and their esters are some major sources of risk factors during food processing. Here we showed the biomarker analysis of 2,3-dihydroxypropyl mercapturic acid (DHPMA) isomers which derived from the metabolism of 3-MCPD, glycidol, and their esters in urine of rats and humans. Iso-DHPMA, a novel urinary metabolite, was discovered and detected in urine of rats, which were orally administered with glycidol but not 3-MCPD. Using the quadrupole-orbitrap high-resolution mass spectrometry, we confirmed that iso-DHPMA appeared a specific biomarker which derived from glycidol. The limit of quantification (signal-to-noise ratio, 10:1) of the analytes in urine of rats and humans were 1.33 ng/mL and 1.56 ng/mL, respectively. Acceptable within-laboratory reproducibility (RSD<9.0%) and spiking recovery (94.7%-100.1%) substantially supported the use of current method for robust biomarker analysis, which was successfully applied to the toxicokinetic study of DHPMA in rats and short-term internal exposure to 3-MCPD and glycidol in humans.

N-Acetyl Cysteine Is Associated With Dopaminergic Improvement in Parkinson's Disease.

This study assessed the biological and clinical effects in patients with Parkinson's disease (PD) of N-acetyl-cysteine (NAC), the prodrug to l-cysteine, a precursor to the natural biological antioxidant glutathione. Forty-two patients with PD were randomized to either weekly intravenous infusions of NAC (50 mg/kg) plus oral doses (500 mg twice per day) for 3 months or standard of care only. Participants received prebrain and postbrain imaging with ioflupane (DaTscan) to measure dopamine transporter (DAT) binding. In the NAC group, significantly increased DAT binding was found in the caudate and putamen (mean increase from 3.4% to 8.3%) compared with controls (P < 0.05), along with significantly improved PD symptoms (P < 0.0001). The results suggest NAC may positively affect the dopaminergic system in patients with PD, with corresponding positive clinical effects. Larger scale studies are warranted.

A Double-Blind, Randomized, Placebo-Controlled Study of Aspirin and N-Acetylcysteine as Adjunctive Treatments for Bipolar Depression.

OBJECTIVE: Neuroinflammation has been implicated in the pathophysiology of bipolar disorder. Some evidence shows that nonsteroidal anti-inflammatory drugs (NSAIDs) have promising antidepressant effects. The antioxidant N-acetylcysteine (NAC) may enhance the effects of NSAIDs. No study has, however, tested the adjunctive therapeutic benefits of an NSAID and NAC in bipolar disorder. METHODS: The sample included 24 medicated patients diagnosed with DSM-IV-TR bipolar disorder who were aged 18-65 years and had a Montgomery-Asberg Depression Rating Scale (MADRS) score ≥ 20. Participants were randomly assigned to receive either aspirin (1,000 mg), NAC (1,000 mg), combined aspirin and NAC (1,000 mg each), or placebo. Data were collected between 2013 and 2017. The primary outcome was a ≥ 50% reduction in MADRS scores. Participants completed mood and global functioning questionnaires. They also underwent blood tests prior to and following 8 and 16 weeks of treatment. A Bayesian analytic method was adopted, and posterior probability distributions were calculated to determine the probability of treatment response. RESULTS: Following the first 8-week treatment phase, individuals on treatment with placebo and NAC + aspirin had a similar probability for successful treatment response (about 70%). Following a 16-week treatment period, NAC + aspirin was associated with higher probability of treatment response (67%) compared to placebo (55%), NAC (57%), and aspirin (33%). There was no treatment effect on interleukin-6 and C-reactive protein levels at either 8 or 16 weeks. CONCLUSIONS: The coadministration of NAC and aspirin during a period of 16 weeks was associated with a reduction in depressive symptoms. The adverse effects were minimal. These preliminary findings may serve as a starting point for future studies assessing the efficacy, tolerability, and safety of anti-inflammatory and antioxidant agents in the treatment of bipolar depression. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01797575.

N-acetylcysteine in dermatology.

N-acetylcysteine is a mucolytic drug which is commonly used as an antidote for acetaminophen toxicity. It is a thiol compound, which acts as a donor of cysteine, leading to replenishment of glutathione and thus acts as an antioxidant. It also has anti-inflammatory effects, alters the levels of neurotransmitters, inhibits proliferation of fibroblasts and keratinocytes and causes vasodilatation. Due to these actions, n-acetylcysteine has found use in several dermatologic conditions in systemic and topical form. The drug has been used as an adjuvant in the management of conditions such as toxic epidermal necrolysis, drug hypersensitivity syndrome, trichotillomania, skin picking disorders and onychotillomania, ichthyoses, contact dermatitis, atopic dermatitis, melasma, pseudoporphyria, connective tissue diseases, wound healing and alopecia. It also has a role in protection from radiation-induced skin damage including photo-ageing, photocarcinogenesis and radiation dermatitis. Most indications in dermatology are supported by case reports, small case series and small trials. Higher quality of evidence is needed for its wider use. The drug is cheap and is generally safe with few adverse effects. Thus a greater role is possible for use of n-acetylcysteine in various skin conditions. This review explores the various uses of n-acetylcysteine in the field of dermatology, the evidence supporting the same, the possible mechanisms of action and the adverse effects of the drug.

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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Pediatric oral formulation of dendrimer-N-acetyl-l-cysteine conjugates for the treatment of neuroinflammation.

N-Acetyl-l-cysteine (NAC) commonly used as an antidote in acetaminophen poisoning has shown promise in the treatment of neurological disorders such as cerebral palsy (CP). However, NAC suffers from drawbacks such as poor oral bioavailability and suboptimal blood-brain-barrier (BBB) permeability limiting its clinical success. It was previously demonstrated that intravenous administration of dendrimer-NAC (D-NAC) conjugates have shown significant promise in the targeted treatment of neuroinflammation, in multiple preclinical models. Development of an oral formulation of D-NAC may open new administrative routes for this compound. Here, we report the gastrointestinal stability, in vitro transepithelial permeability, and in vivo oral absorption and pharmacokinetics in rats of a pediatric formulation of D-NAC containing Capmul MCM (glycerol monocaprylate) as a penetration enhancer. D-NAC was stable for 6 h in all five simulated gastrointestinal fluids with no signs of chemical degradation. The apparent permeability (Papp) of D-NAC increased 9-fold in the formulation containing Capmul. The area under the curve [AUC]0-∞ of D-NAC with Capmul increased by 47% when compared to D-NAC alone. These results indicate that an oral pediatric formulation containing D-NAC and Capmul can be an effective option for the treatment of neuroinflammation.

Evaluation of the Neuroprotective Potential of N-Acetylcysteine for Prevention and Treatment of Cognitive Aging and Dementia.

Alzheimer's disease is a progressive neurodegenerative disease for which there is no cure and only a few treatments providing little relief. Increased oxidative stress that is associated with aging is strongly implicated in the pathogenesis and progression of Alzheimer's disease. Studies have shown that levels of the endogenous antioxidant glutathione decline at an early stage of Alzheimer's disease with decreased levels correlating with worse cognitive functions. N-acetylcysteine, a drug also widely available as a dietary supplement, is a precursor of L-cysteine, which in turn is a component of glutathione. Because cysteine availability is a limiting factor for glutathione synthesis, treatment with N-acetylcysteine may increase glutathione levels and thereby counter oxidative stress, promote redox -regulated cell signaling, and improve immune responses. In this review, we evaluate the existing literature and the potential of N-acetylcysteine in promoting cognitive health and alleviating cognitive decline associated with dementia. Discussion will also include possible mechanisms of action of N-acetylcysteine, its effects on aging biology, and safety of long-term use. Based on the available literature, a nutraceutical formulation containing N-acetylcysteine among other compounds has shown some pro-cognitive benefits in Alzheimer's patients and older adults, but the evidence for N-acetylcysteine alone is less robust. Although N-acetylcysteine crosses the blood-brain-barrier, low bioavailability is an obstacle. One promising avenue of research may be to explore derivatives of N-acetylcysteine such as N-acetylcysteine amide, which has been reported in preclinical studies to have higher permeability through cellular and mitochondrial membranes with increased central nervous system bioavailability compared to N-acetylcysteine.

Dose escalation study of intravenous and intra-arterial N-acetylcysteine for the prevention of oto- and nephrotoxicity of cisplatin with a contrast-induced nephropathy model in patients with renal insufficiency.

BACKGROUND: Cisplatin neuro-, oto-, and nephrotoxicity are major problems in children with malignant tumors, including medulloblastoma, negatively impacting educational achievement, socioemotional development, and overall quality of life. The blood-labyrinth barrier is somewhat permeable to cisplatin, and sensory hair cells and cochlear supporting cells are highly sensitive to this toxic drug. Several chemoprotective agents such as N-acetylcysteine (NAC) were utilized experimentally to avoid these potentially serious and life-long side effects, although no clinical phase I trial was performed before. The purpose of this study was to establish the maximum tolerated dose (MTD) and pharmacokinetics of both intravenous (IV) and intra-arterial (IA) NAC in adults with chronic kidney disease to be used in further trials on oto- and nephroprotection in pediatric patients receiving platinum therapy. METHODS: Due to ethical considerations in pediatric tumor patients, we used a clinical population of adults with non-neoplastic disease. Subjects with stage three or worse renal failure who had any endovascular procedure were enrolled in a prospective, non-randomized, single center trial to determine the MTD for NAC. We initially aimed to evaluate three patients each at 150, 300, 600, 900, and 1200 mg/kg NAC. The MTD was defined as one dose level below the dose producing grade 3 or 4 toxicity. Serum NAC levels were assessed before, 5 and 15 min post NAC. Twenty-eight subjects (15 men; mean age 72.2 ± 6.8 years) received NAC IV (N = 13) or IA (N = 15). RESULTS: The first participant to experience grade 4 toxicity was at the 600 mg/kg IV dose, at which time the protocol was modified to add an additional dose level of 450 mg/kg NAC. Subsequently, no severe NAC-related toxicity arose and 450 mg/kg NAC was found to be the MTD in both IV and IA groups. Blood levels of NAC showed a linear dose response (p < 0.01). Five min after either IV or IA NAC MTD dose administration, serum NAC levels reached the 2-3 mM concentration which seemed to be nephroprotective in previous preclinical studies. CONCLUSIONS: In adults with kidney impairment, NAC can be safely given both IV and IA at a dose of 450 mg/kg. Additional studies are needed to confirm oto- and nephroprotective properties in the setting of cisplatin treatment. Clinical Trial Registration URL: https://eudract.ema.europa.eu . Unique identifier: 2011-000887-92.

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.

Phase I randomized clinical trial of N-acetylcysteine in combination with an adjuvant probenecid for treatment of severe traumatic brain injury in children.

BACKGROUND: There are no therapies shown to improve outcome after severe traumatic brain injury (TBI) in humans, a leading cause of morbidity and mortality. We sought to verify brain exposure of the systemically administered antioxidant N-acetylcysteine (NAC) and the synergistic adjuvant probenecid, and identify adverse effects of this drug combination after severe TBI in children. METHODS: IRB-approved, randomized, double-blind, placebo controlled Phase I study in children 2 to 18 years-of-age admitted to a Pediatric Intensive Care Unit after severe TBI (Glasgow Coma Scale [GCS] score ≤8) requiring an externalized ventricular drain for measurement of intracranial pressure (ICP). Patients were recruited from November 2011-August 2013. Fourteen patients (n = 7/group) were randomly assigned after obtaining informed consent to receive probenecid (25 mg/kg load, then 10 mg/kg/dose q6h×11 doses) and NAC (140 mg/kg load, then 70 mg/kg/dose q4h×17 doses), or placebos via naso/orogastric tube. Serum and CSF samples were drawn pre-bolus and 1-96 h after randomization and drug concentrations were measured via UPLC-MS/MS. Glasgow Outcome Scale (GOS) score was assessed at 3 months. RESULTS: There were no adverse events attributable to drug treatment. One patient in the placebo group was withdrawn due to adverse effects. In the treatment group, NAC concentrations ranged from 16,977.3±2,212.3 to 16,786.1±3,285.3 in serum and from 269.3±113.0 to 467.9±262.7 ng/mL in CSF, at 24 to 72 h post-bolus, respectively; and probenecid concentrations ranged from 75.4.3±10.0 to 52.9±25.8 in serum and 5.4±1.0 to 4.6±2.1 µg/mL in CSF, at 24 to 72 h post-bolus, respectively (mean±SEM). Temperature, mean arterial pressure, ICP, use of ICP-directed therapies, surveillance serum brain injury biomarkers, and GOS at 3 months were not different between groups. CONCLUSIONS: Treatment resulted in detectable concentrations of NAC and probenecid in CSF and was not associated with undesirable effects after TBI in children. TRIAL REGISTRATION: ClinicalTrials.gov NCT01322009.

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.