Pharmacokinetics of N-acetylcysteine after oral and intravenous administration to healthy cats

LC-MS/MS determination of N-acetyl-l-cysteine in chicken plasma

N-acetyl-l-cysteine (NAC) shows beneficial effects in cases of aflatoxicosis and heat stress in poultry but little is known about its pharmacokinetics in chickens. Therefore, the study aimed to develop and validate a sensitive LC-MS/MS analytical method for quantitative analysis of NAC in chicken plasma. A split calibration curve approach was used for determination of NAC in chicken plasma. Standard curves for low (0.05-2.5 μg/ml) and high (2.5-100 μg/ml) ranges of concentrations were prepared. The standard curves for low (r2 = 0.9987) and high (r2 = 0.9899) concentrations were linear within the tested range. The limits of detection (LOD) and of quantification (LOQ) for the standard at low concentrations were 0.093 and 0.28 μg/ml, respectively. The accuracy was from 97.35 to 101.33%. The values of LOD and LOQ for the standard at high concentrations were 0.76 and 2.30 μg/ml, respectively. The accuracy was between 99.77 and 112.14%. The intra- and inter-day precisions for all concentrations from both standards did not exceed 8.57% and 10.69%, respectively. The recovery for all concentrations was between 92.45 and 105.52%. The validated method for determination of NAC in chicken plasma can be applied in future pharmacokinetic studies in chickens without dilution of samples and their repeated analysis.

N-Acetylcysteine and Its Immunomodulatory Properties in Humans and Domesticated Animals

N-acetylcysteine (NAC), an acetylated derivative of the amino acid L-cysteine, has been widely used as a mucolytic agent and antidote for acetaminophen overdose since the 1960s and the 1980s, respectively. NAC possesses antioxidant, cytoprotective, anti-inflammatory, antimicrobial, and mucolytic properties, making it a promising therapeutic agent for a wide range of diseases in both humans and domesticated animals. Oxidative stress and inflammation play a major role in the onset and progression of all these diseases. NAC's primary role is to replenish glutathione (GSH) stores, the master antioxidant in all tissues; however, it can also reduce levels of pro-inflammatory tumor necrosis factor-alpha (TNF-∝) and interleukins (IL-6 and IL-1β), inhibit the formation of microbial biofilms and destroy biofilms, and break down disulfide bonds between mucin molecules. Many experimental studies have been conducted on the use of NAC to address a wide range of pathological conditions; however, its effectiveness in clinical trials remains limited and studies often have conflicting results. The purpose of this review is to provide a concise overview of promising NAC usages for the treatment of different human and domestic animal disorders.

Effect of N-Acetyl-L-cysteine on Activity of Doxycycline against Biofilm-Forming Bacterial Strains

Biofilm-forming bacteria are associated with difficult-to-cure bacterial infections in veterinary patients. According to previous studies, N-acetyl-L-cysteine (NAC) showed an inhibitory effect on biofilm formation when it was applied in combination with beta-lactam antibiotics and fluoroquinolones. The lack of information about the effect of NAC on doxycycline activity against biofilm-forming strains was the reason for conducting this study. Staphylococcus aureus (S. aureus) ATCC 25923, Staphylococcus aureus O74, Escherichia coli (E. coli) ATCC 25922 and Pseudomonas aeruginosa (P. aeruginosa) ATCC 27853 were used to evaluate the activity of doxycycline with and without addition of NAC on planktonic bacteria and on biofilm formation. The minimum inhibitory concentrations (MICs) of doxycycline were not affected by NAC for Gram-negative strains and were found to be two times higher for the strains of S. aureus. The minimum biofilm inhibitory concentrations (MBICs) for Gram-negative bacteria (2 μg/mL for E. coli ATCC 25922 and 32 μg/mL for P. aeruginosa ATCC 27853), determined using a standard safranin colorimetric assay, were higher than the MICs (0.5 and 4 μg/mL, respectively). The data suggest that the combinations of doxycycline and NAC could stimulate the growth of planktonic cells of S. aureus and biofilm-forming E. coli ATCC 25922. NAC did not affect the strong inhibitory effect of doxycycline on the biofilm formation by the strains of S. aureus.

Absorption of N-acetylcysteine in Healthy and Mycoplasma gallisepticum-Infected Chickens

N-acetylcysteine (NAC) is widely used as a mucolytic agent in cases with inflammation of the lungs. NAC is applied in poultry with aflatoxin B1 intoxication as an antioxidant, but its pharmacokinetics are not known. The present study was conducted to characterize the population pharmacokinetics of orally administered NAC in broilers. It included 32 chickens, divided into four groups, treated with NAC at a dose rate of 100 mg/kg/day mixed with the feed: healthy broilers (n = 6); chickens infected with Mycoplasma gallisepticum (n = 10); healthy broilers (n = 6); and diseased chickens (n = 10) treated with NAC and doxycycline (via drinking water, 20 mg/kg body weight (b.w.)). Plasma concentrations were analyzed by Liquid Chromatography –Mass Spectrometry (MS)/MS. NAC was absorbed after oral administration in all four groups of chickens. In healthy chickens treated solely with NAC, maximum plasma concentrations of 2.26 ± 0.91 µg mL⁻¹ were achieved at 2.47 ± 0.45 h after dosing. The value of absorption half-life was 1.04 ± 0.53 h. The population pharmacokinetic analysis showed that dose adjustment of NAC is not required in M. gallisepticum-infected broilers or when it is combined with doxycycline.

N-Acetylcysteine Added to Local Anesthesia Reduces Scar Area and Width in Early Wound Healing-An Animal Model Study

The aim of the study was to evaluate if a pre-incisional N-acetylcysteine (NAC) treatment altered the process of wound healing in a rat model. The dorsal skin of 24 Sprague-Dawley rats was incised in six locations. Before the incisions were made, skin was injected either with lidocaine and epinephrine (one side) or with these agents supplemented with 0.015%, 0.03%, or 0.045% NAC (contralaterally). Photographic documentation of the wound healing process was made at 11 time points. Rats were sacrificed 3, 7, 14, or 60 days after incision to excise scars for histological analysis. They included: Abramov scale scoring, histomorphometry analysis, and collagen fiber arrangement assessment. Skin pretreated with 0.03% NAC produced the shortest scars at all analyzed time points, though this result was statistically insignificant. At this NAC concentration the scars had smaller areas on the third day and were narrower on the day 4 compared with all the other groups (p < 0.05). On day 7, at the same concentration of NAC, the scars had a higher superficial concentration index (p = 0.03) and larger dermal proliferation area (p = 0.04). NAC addition to pre-incisional anesthetic solution decreased wound size and width at an early stage of scar formation at all concentrations; however, with optimal results at 0.03% concentration.

Mitchell J, Lodzinska J, Cazzini P, Varjonen K, Gunn-Moore DA. Systemic Mycobacterium kansasii Infection in Two Related Cats

Mycobacterial infections are a major concern in veterinary medicine because of the difficulty achieving an etiological diagnosis, the challenges and concerns of treatment, and the potential zoonotic risk. Mycobacterium kansasii, a slow-growing non-tuberculous mycobacteria, causes disease in both humans and animals. While infections have been well described in humans, where it may be misdiagnosed as tuberculosis, there are fewer reports in animals. Only four cases have been reported in the domestic cat. This case report describes systemic M. kansasii infection in two sibling indoor-only cats that presented two and half years apart with cutaneous disease that was found to be associated with osteolytic and pulmonary pathology. Infection with M. kansasii was confirmed in both cats by polymerase chain reaction on fine-needle aspirate of a lumbosacral soft tissue mass in one cat and on a tissue punch biopsy of a skin lesion in the other; interferon-gamma release assay inferred M. avium-complex and M. tuberculosis-complex infection in the two cats, respectively. Both patients made a full recovery following antimicrobial therapy with rifampicin, azithromycin, and pradofloxacin (plus N-acetyl cysteine in cat 2). This report highlights successful treatment of systemic M. kansasii mycobacteriosis in the cat and the challenge of accurately diagnosing this infection.

Efficacy of N-acetylcysteine in the prevention of alcohol relapse-like drinking: Study in long-term ethanol-experienced male rats

Alcohol use disorders are chronic and highly relapsing disorders, thus alcoholic patients have a high rate of recidivism for drug use even after long periods of abstinence. The literature points to the potential usefulness of N-acetylcysteine (NAC) in the management of several substance use disorders probably due to its capacity to restore brain homeostasis of the glutamate system disrupted in addiction. However, there is little evidence in the case of alcohol. The aim of this study was to explore the potential anti-relapse efficacy of NAC using the alcohol deprivation effect (ADE) model in long-term experienced rats. Two experiments were performed in male Wistar rats to: (a) test the efficacy of NAC to prevent relapse and (b) discriminate the best administration schedule (intermittent vs. continuous) for NAC. In the first experiment, animals were implanted with mini-osmotic pumps delivering 0 or 1 mg/hr NAC during 14 days. In a second experiment, rats received 0, 60, or 100 mg/kg once daily by subcutaneous injection. The efficacy to prevent ADE was evaluated in both experiments. NAC subcutaneously administered, either by continuous infusion or by intermittent injections regimen, is able to block the ADE. The best results were obtained after using 60 mg/kg NAC dose. Our findings support the hypothesis that NAC may represent a valuable therapy in the management of alcohol relapse.

Drug-responsive autism phenotypes in the 16p11.2 deletion mouse model: a central role for gene-environment interactions

There are no current treatments for autism, despite its high prevalence. Deletions of chromosome 16p11.2 dramatically increase risk for autism, suggesting that mice with an equivalent genetic rearrangement may offer a valuable model for the testing of novel classes of therapeutic drug. 16p11.2 deletion (16p11.2 DEL) mice and wild-type controls were assessed using an ethological approach, with 24 h monitoring of activity and social interaction of groups of mice in a home-cage environment. The ability of the excitation/inhibition modulator N-acetyl cysteine (NAC) and the 5-HT_1B/1D/1F receptor agonist eletriptan to normalise the behavioural deficits observed was tested. 16p11.2 DEL mice exhibited largely normal behaviours, but, following the stress of an injection, showed hyperlocomotion, reduced sociability, and a strong anxiolytic phenotype. The hyperactivity and reduced sociability, but not the suppressed anxiety, were effectively attenuated by both NAC and eletriptan. The data suggest that 16p11.2 DEL mice show an autism-relevant phenotype that becomes overt after an acute stressor, emphasising the importance of gene-environmental interactions in phenotypic analysis. Further, they add to an emerging view that NAC, or 5-HT_1B/1D/1F receptor agonist treatment, may be a promising strategy for further investigation as a future treatment.

Beta-sarcoglycan-deficient muscular dystrophy presenting as chronic bronchopneumonia in a young cat

Case summary

A 5-month-old cat was evaluated for a 3 week history of cough, nasal discharge, decreased appetite and weight loss. Musculoskeletal examination was normal and serum creatine kinase (CK) activity was within the reference interval. The cat was treated during the next 10 months for chronic, persistent pneumonia. Weakness then became apparent, the cat developed dysphagia and was euthanized. Post-mortem evaluation revealed chronic aspiration pneumonia and muscular dystrophy associated with beta (β)-sarcoglycan deficiency.

Relevance and novel information

This is the first report of a cat with muscular dystrophy presenting for chronic pneumonia without obvious megaesophagus, dysphagia or prominent neuromuscular signs until late in the course of the disease. The absence of gait abnormalities, marked muscle atrophy or hypertrophy and normal serum CK activity delayed the diagnosis in this cat with β-sarcoglycan deficiency.

Biomarkers of oxidative stress as an assessment of the redox status of the liver in dogs

Background

Oxidative stress is associated with a diverse group of liver disorders across species.

Objectives

Determine whether glutathione (GSH) concentration in plasma and red blood cells correlates with liver GSH concentration in dogs and evaluate whether other markers of systemic oxidative stress, plasma vitamin E and urine 8‐isoprostanes/creatinine (F₂‐IsoPs/Cr) concentrations, correlate with liver GSH.

Animals

Thirty‐four client‐owned dogs undergoing clinically indicated liver biopsy and 15 healthy control dogs.

Methods

Prospective, observational cross‐sectional study. Urine and blood were collected before liver biopsy. Plasma, erythrocyte, and liver GSH were measured using high performance liquid chromatography (HPLC); vitamin E was measured by HPLC, and F₂‐IsoPs/Cr was measured by gas chromatography/mass spectrometry.

Results

All dogs were treated at the discretion of the attending clinician (24/34 received antioxidants; 4/34 fed therapeutic liver diet), which included dogs with primary or secondary liver disease (inflammatory (n = 21), metabolic (n = 9), vascular (n = 2), and neoplastic (n = 2)). Median GSH concentrations in plasma, erythrocyte, and liver were 0.18 mg/dL (range 0.14 to 0.56 mg/dL), 56.7 mg/dL (18.3 to 79.2 mg/dL), and 181 mg/dL (39.9 to 527 mg/dL), respectively. No significant correlations were found between liver GSH and erythrocyte GSH, plasma GSH, vitamin E, or F₂‐IsoPs/Cr. Dogs undergoing clinically indicated liver biopsy had significantly higher urine F₂‐IsoPs/Cr than did healthy controls (5.89 vs 2.98 ng/mg; P < .0001).

Conclusions and Clinical Importance

Erythrocyte and plasma GSH are not indicative of liver GSH concentration in dogs. In addition, dogs undergoing clinically indicated liver biopsy have evidence of increased systemic oxidative stress compared to healthy controls.

In vitro effect of 20% N-acetylcysteine on the viscosity of normal canine bile

OBJECTIVE To evaluate the in vitro effect of 20% N-acetylcysteine (NAC) on the viscosity of normal canine bile. ANIMALS Bile samples obtained from 10 adult dogs euthanized for reasons unrelated to biliary disease. PROCEDURES Each sample was centrifuged to remove particulates, then divided into 3 aliquots. One aliquot remained untreated (control). Each of the other aliquots was diluted 1:4 with 20% NAC or sterile water. The viscosity of all samples was measured with a rotational viscometer at 25°C. Viscosity of control samples was measured immediately after centrifugation and at 1 and 24 hours after treatment application to the diluted samples. Viscosity of diluted samples was measured at 1 and 24 hours after treatment application. RESULTS Mean viscosity differed significantly among the 3 groups at both 1 and 24 hours after treatment application. Relative to control samples, the addition of NAC and sterile water decreased the viscosity by approximately 3.35 mPa·s (95% confidence interval [CI], 1.58 to 5.12 mPa·s) and 2.74 mPa·s (95% CI, 1.33 to 4.14 mPa·s), respectively. Mean viscosity of the NAC-treated samples was approximately 0.61 mPa·s (95% CI, 0.21 to 1.01 mPa·s) less than that for the sterile water-treated samples. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that in vitro dilution of canine bile 1:4 with 20% NAC significantly decreased the viscosity of the resulting mixture. Further research is necessary to determine whether NAC is a safe and effective noninvasive treatment for dogs with persistent biliary sludge or gallbladder mucoceles.

Repeated-Dose Oral N-Acetylcysteine in Parkinson's Disease: Pharmacokinetics and Effect on Brain Glutathione and Oxidative Stress

Parkinson's disease (PD) is associated with oxidative stress and decreased nigral glutathione (GSH), suggesting that therapies that boost GSH may have a disease-modifying effect. Intravenous administration of a high dose of N-acetylcysteine (NAC), a well-known antioxidant and GSH precursor, increases blood and brain GSH in individuals with PD and with Gaucher disease and in healthy controls. To characterize the pharmacokinetics of repeated high oral doses of NAC and their effect on brain and blood oxidative stress measures, we conducted a 4-week open-label prospective study of oral NAC in individuals with PD (n = 5) and in healthy controls (n = 3). Brain GSH was measured in the occipital cortex using ¹ H-MRS at 3 and 7 tesla before and after 28 days of 6000 mg NAC/day. Blood was collected prior to dosing and at predetermined collection times before and after the last dose to assess NAC, cysteine, GSH, catalase, malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) concentrations and the reduced-to-oxidized GSH ratio (GSH/ glutathione disulfide [GSSG]). Symptomatic adverse events were reported by 3 of the 5 subjects with PD. NAC plasma concentration-time profiles were described by a first-order absorption, 1-compartment pharmacokinetic model. Although peripheral antioxidant measures (catalase and GSH/GSSG) increased significantly relative to baseline, indicators of oxidative damage, that is, measures of lipid peroxidation (4-HNE and MDA) were unchanged. There were no significant increases in brain GSH, which may be related to low oral NAC bioavailability and small fractional GSH/GSSG blood responses. Additional studies are needed to further characterize side effects and explore the differential effects of NAC on measures of antioxidant defense and oxidative damage.