Acetadote (Acetylcysteine Injection) - Summary

ACETADOTE SUMMARY

Acetylcysteine injection is an intravenous (I. V.) medication for the treatment of acetaminophen overdose. Acetylcysteine is the nonproprietary name for the N-acetyl derivative of the naturally occurring amino acid, L-cysteine (N-acetyl-L-cysteine, NAC). The compound is a white crystalline powder, which melts in the range of 104° to 110°C and has a very slight odor.

Acetadote, administered intravenously within 8 to 10 hours after ingestion of a potentially hepatotoxic quantity of acetaminophen, is indicated to prevent or lessen hepatic injury [ see Dosage and Administration (2) and Acetaminophen Assays – Interpretation and Methodology (1.1, 1.2) ].

On admission for suspected acetaminophen overdose, a serum blood sample should be drawn at least 4 hours after ingestion to determine the acetaminophen level and will serve as a basis for determining the need for treatment with acetylcysteine. If the patient presents after 4 hours post-ingestion, the serum acetaminophen sample should be determined immediately.

Acetadote should be administered within 8 hours from acetaminophen ingestion for maximal protection against hepatic injury for patients whose serum acetaminophen levels fall above the "possible" toxicity line on the Rumack-Matthew nomogram (line connecting 150 mcg/mL at 4 hours with 37.5 mcg/mL at 12 hours); [ see Acetaminophen Assays – Interpretation and Methodology (1.1, 1.2) ]. If the time of ingestion is unknown, or the serum acetaminophen level is not available, cannot be interpreted, or is not available within the 8 hour time interval from acetaminophen ingestion, Acetadote should be administered immediately if 24 hours or less have elapsed from the reported time of ingestion of an overdose of acetaminophen, regardless of the quantity reported to have been ingested.

The aspartate aminotransferase (AST, SGOT), alanine aminotranferase (ALT, SGPT), bilirubin, prothrombin time, creatinine, blood urea nitrogen (BUN), blood glucose, and electrolytes also should be determined in order to monitor hepatic and renal function and electrolyte and fluid balance.

NOTE: The critical ingestion-treatment interval for maximal protection against severe hepatic injury is between 0 – 8 hours. Efficacy diminishes progressively after 8 hours and treatment initiation between 15 and 24 hours post-ingestion of acetaminophen yields limited efficacy. However, it does not appear to worsen the condition of patients and it should not be withheld, since the reported time of ingestion may not be correct.

Acetaminophen Assays Interpretation and Methodology – Acute Ingestion

The acute ingestion of acetaminophen in quantities of 150 mg/kg or greater may result in hepatic toxicity. However, the reported history of the quantity of a drug ingested as an overdose is often inaccurate and is not a reliable guide to therapy of the overdose. Therefore, plasma or serum acetaminophen concentrations, determined as early as possible, but no sooner than four hours following an acute overdose, are essential in assessing the potential risk of hepatotoxicity. If an assay for acetaminophen cannot be obtained, it is necessary to assume that the overdose is potentially toxic.

Interpretation of Acetaminophen Assays

1. When results of the plasma acetaminophen assay are available, refer to the nomogram in Figure 1 to determine if plasma concentration is in the potentially toxic range. Values above the line connecting 200 mcg/mL at 4 hours with 50 mcg/mL at 12 hours (probable line) are associated with a probability of hepatic toxicity if an antidote is not administered.
2. If the predetoxification plasma level is above the line connecting 150 mcg/mL at 4 hours with 37.5 mcg/mL at 12 hours (possible line), continue with maintenance doses of acetylcysteine. It is better to err on the safe side and thus this line, defining possible toxicity, is plotted 25% below the line defining probable toxicity.
3. If the predetoxification plasma level is below the line connecting 150 mcg/mL at 4 hours with 37.5 mcg/mL at 12 hours (possible line), there is minimal risk of hepatic toxicity, and acetylcysteine treatment may be discontinued.

Estimating Potential for Hepatotoxicity: The following depiction of the Rumack-Matthew nomogram has been developed to estimate the probability that plasma levels in relation to intervals post-ingestion will result in hepatotoxicity.

Figure 1. Rumack-Matthew Nomogram: Plasma or Serum Acetaminophen Concentration vs. Time Post Acetaminophen Ingestion (Rumack BH, Matthew H. Acetaminophen poisoning and toxicity. Pediatrics. 1975;55:871-876 and Rumack BH, Peterson RC, Kock GG, Amara IA. Acetaminophen overdose. 662 cases with evaluation of oral acetylcysteine treatment. Arch Intern Med. 1981;141:380-385).

Acetaminophen Assays Interpretation and Methodology – Repeated Supratherapeutic Ingestion

Repeated Supratherapeutic Ingestion (RSI) is defined as ingestion of acetaminophen at doses higher than those recommended for extended periods of time. The nomogram does not apply to patients with RSI. Treatment is based on the acetaminophen and elevated AST/ALT levels indicative of potential toxicity due to acetaminophen. For specific treatment information regarding the clinical management of repeated supratherapeutic acetaminophen overdose, please contact your regional poison center at 1-800-222-1222, or alternatively, a special health professional assistance line for acetaminophen overdose at 1-800-525-6115.

Figure 2. Acetadote Treatment Flow Chart

*Acetaminophen levels drawn less than 4 hours post-ingestion may be misleading.

# With an extended-release preparation, an acetaminophen level drawn less than 8 hours post-ingestion may be misleading. Draw a second level at 4 to 6 hours after the initial level. If either falls above the toxicity line, acetylcysteine treatment should be initiated.

***Acetylcysteine may be withheld until acetaminophen assay results are available as long as initiation of treatment is not delayed beyond 8 hours post-ingestion. If more than 8 hours post-ingestion, start acetylcysteine treatment immediately.

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NEWS HIGHLIGHTS

Published Studies Related to Acetadote (Acetylcysteine Injection)

Potentially detrimental effects of N-acetylcysteine on renal function in knee arthroplasty. [2009.07]
Ischaemia/reperfusion induces systemic inflammation and oxidative stress and thereby remote organ injury in the kidney. In a double-blind, placebo-controlled clinical trial of 30 patients undergoing knee arthroplasty with tourniquet, this study evaluated the effect of N-acetylcysteine (NAC) infusion on renal function by measuring urine alpha-1-microglobulin, N-acetyl-beta-D-glucosaminidase (NAG), glutathione-S-transferase-alpha and -phi and serum creatinine and cystatin C concentrations up to 24 h post-operatively...

Nephrotoxic effects of iodixanol and iopromide in patients with abnormal renal function receiving N-acetylcysteine and hydration before coronary angiography and intervention: a randomized trial. [2009.01]
BACKGROUND: The use of contrast agents during coronary intervention can result in nephropathy, particularly in patients with renal dysfunction. We aimed to determine whether the use of iso-osmolar iodixanol is less nephrotoxic than that of low-osmolar iopromide when patients are adequately prehydrated and have received N-acetylcysteine... CONCLUSION: There remains a high incidence of CIN despite prehydration and routine use of N-acetylcysteine in patients with pre-existing renal dysfunction undergoing coronary interventional procedures. Although our study is underpowered, iodixanol was not associated with a statistically significant lower incidence of CIN when compared with iopromide.

Is treatment with N-acetylcysteine to prevent contrast-induced nephropathy when using bicarbonate hydration out of date? [2008.12]
AIMS: Chronic renal failure (CRF) is a major risk factor for contrast-induced nephropathy (CIN) and could be prevented by bicarbonate hydration. The effect of N-acetylcysteine (NAC) in preventing CIN in patients treated by bicarbonate hydration has never been investigated... CONCLUSION: In CRF patients undergoing cardiac angiography, the use of bicarbonate hydration is associated with a very low incidence of CIN. In these conditions, on the basis of our results, we cannot draw any meaningful conclusion on the effect of NAC on the prevention of CIN.

Improved estimation of glomerular filtration rate by serum cystatin C in preventing contrast induced nephropathy by N-acetylcysteine or zinc--preliminary results. [2008.04]
BACKGROUND: Prevention of contrast media (CM) induced nephropathy (CIN) by prophylaxis (e.g. N-acetylcysteine; NAC) is controversially discussed. Up to now, assessment of kidney function has been based on measurements of serum creatinine, although this biomarker has several limitations. We investigated NAC and zinc (Zn) for the prevention of CIN by monitoring creatinine and cystatin C... CONCLUSIONS: Cystatin C seems to reflect CM-induced changes in kidney function better than creatinine. NAC and Zn have no effect in preventing CIN by the standard definition, but based on cystatin C we can confirm a preventive effect of NAC. It appears mandatory to assess kidney function by cystatin C in CIN intervention trials, because relying on creatinine can be misleading.

I.v. N-acetylcysteine and emergency CT: use of serum creatinine and cystatin C as markers of radiocontrast nephrotoxicity. [2007.09]
CONCLUSION: On the basis of serum creatinine concentration only, i.v. administration of NAC appears protective against the nephrotoxicity of contrast medium. No effect is found when serum cystatin C concentration is used to assess renal function. The effect of NAC on serum creatinine level remains unclear and may not be related to a renoprotective action.

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Clinical Trials Related to Acetadote (Acetylcysteine Injection)

Mechanisms for the Effect of Acetylcysteine on Renal Function After Exposure to Radiographic Contrast Material [Recruiting]
Millions of people receive radiographic contrast material for investigations like CT and coronary angiography. While considered safe in healthy patients, it can cause acute renal impairment. This is termed radiocontrast-induced nephropathy (RCIN) and is generally defined as an increase in serum creatinine over baseline of more than 25% or 0. 5 mg/dL (44. 2 μmol/l) within 48 hrs. RCIN occurs in less than 2% of patients with normal renal function but is more common in patients with pre-existing renal damage.

The pathophysiology of RCIN is unclear. Possible mechanisms involve 1) reduced renal blood flow leading to acute tubular necrosis and 2) direct renal tubular injury by oxygen free radicals. Current prevention strategies focus on increasing renal blood flow and reducing oxidative stress. Patients at risk of RCIN currently receive fluids, a low dose of contrast, and variable and unproven doses of acetylcysteine.

The evidence for acetylcysteine administration is unclear. A RCIN consensus working group reported in the American Journal of Cardiology in September 2006 that "N-acetylcysteine is not consistently effective in reducing the risk for contrast-induced nephropathy". The perception of a benefit from acetylcysteine administration that is unproven has disadvantages as some clinicians report giving larger amounts of radio-contrast to patients who have received acetylcysteine since they believe that it prevents RCIN. There is a need to determine how acetylcysteine might prevent RCIN and to identify the appropriate dose and route of administration.

Since acetylcysteine is a vasodilator as well as an antioxidant, it may work in two distinct ways, by preventing reduction in renal blood flow (RBF) or contrast-induced oxidative damage. Previous studies have used changes in serum creatinine. In addition to being an insensitive marker of altered renal function, if contrast causes renal vasoconstriction and acetylcysteine vasodilatation, changes in serum creatinine will not be the ideal marker of effect. Finally the optimum dose and route of acetylcysteine administration is unclear, as illustrated by studies using a variety of doses and routes.

We propose to study the mechanism of effects of acetylcysteine on healthy and diseased kidneys, both unstressed and stressed by radiocontrast administration. We hypothesise that acetylcysteine may exert a renoprotective effect in RCIN by a renal vasodilatation and/or antioxidant mechanism.

Study of N-Acetylcysteine (NAC) and Continuous Renal Replacement Therapy (CRRT) for the Treatment of Rhabdomyolysis [Recruiting]
Rhabdomyolysis has many causes including trauma, muscle crush injuries, lack of blood supply to an arm or leg, burns, seizures, drugs and hereditary disorders. Rhabdomyolysis causes the breakdown of muscle cells and the release of a molecule called myoglobin. Myoglobin is very harmful to the kidneys and can lead to kidney failure.

Continuous dialysis has been shown to remove the myoglobin molecule from the blood in patients with rhabdomyolysis. N-Acetylcysteine (NAC) has been used in patients receiving contrast dye for x-rays and has shown less worsening of kidney function compared to patients not receiving NAC.

Early and aggressive treatment of patients with rhabdomyolysis with standard therapy, continuous dialysis and a drug called N-acetylcysteine (NAC) may prevent the development of acute kidney failure. Patients who develop kidney failure from this disorder are often critically ill and have a much higher chance of not surviving than those who do not develop kidney failure.

The purpose of this study is to determine if the use of NAC and Continuous Veno-Venous hemo(dia)filtration (CRRT)early in the course of rhabdomyolysis (in addition to standard therapy)decreases the chance of developing acute renal failure

A Study of Oral N-Acetylcysteine in Children With Autism Spectrum Disorders [Recruiting]
The purpose of this study is to determine whether treatment with oral N-acetylcysteine (NAC) will improve behavior problems often associated with autism spectrum disorders.

N-Acetylcysteine in Heart Failure With Coexistent Chronic Renal Failure [Recruiting]
Treatment with n-acetylcysteine in patients with heart failure and chronic renal failure leads to improvements in vascular function and in renal function.

Treatment of Systemic Lupus Erythematosus (SLE) With N-Acetylcysteine [Recruiting]
Systemic lupus erythematosus (SLE) is a chronic inflammatory disease which often has debilitating and potentially life-threatening consequences. The cause of SLE is unknown and current therapies lack specificity and carry significant side-effects. Existing data in the literature provide evidence that a natural antioxidant, glutathione, is depleted in T cells of patients with SLE. This may be a key factor underlying abnormal activation and predisposition of T lymphocytes to pro-inflammatory cell death via necrosis. Administration of N-acetylcysteine (NAC), that serves as a precursor of glutathione (GSH), improves the clinical outcome of murine lupus, and limits the toxicity of pro-oxidant/immunosuppressant medications commonly used in patients with SLE. NAC is widely available in health food stores and large doses (up to 8 g/day) can be safely administered to humans. In a one-year study of patients with inflammatory lung disease treated with prednisone and azathioprine, addition of NAC (1. 8 g/day) diminished disease severity and reduced drug toxicity in comparison to placebo. Moreover, oral NAC has been found to improve muscle fatigue which is reported to be the most disabling symptom in 53% of patients with SLE. Thus, establishing a dose ranging between 1. 2-9. 6 g/day that is well tolerated and capable of raising intracellular GSH in lupus patients and determining its immunological and therapeutic impact in SLE appears to be well justified.

The study will consist of two parts, Aim 1 and Aim 2.

AIM 1:

The purpose of Aim 1 is to establish the optimal daily oral dose of NAC that can be well tolerated without side effects and can normalize or moderate the depletion of GSH in lupus T cells.

50 SLE subjects and 50 healthy controls (matched by age and sex) will be studied.

The 50 SLE subjects will be divided into 5 groups of 10. Each group will receive a different dose of NAC (N-acetylcysteine)or placebo as follows:

Group 1- 8 will receive 600mg of NAC/Two times a Day, 2 will receive placebo Group 2- 8 will receive 1200mg of NAC/Two times a Day, 2 will receive placebo Group 3- 8 Will receive 2400mg of NAC/Two times a Day, 2 will receive placebo Group 4- 8 Will receive 3600mg of NAC/Two times a Day, 2 will receive placebo Group 5- 8 will receive 4800mg of NAC/Two times a Day, 2 will receive placebo

To account for attrition 12 subjects will be initially randomized in each group (9 active, 3 placebo).

At each subject visit, blood from a healthy donor will be drawn and used as control. The control blood will be used for flow cytometry measurements of GSH and in vitro immunological studies. In addition to GSH measurements and immunologic studies, routine labs and SLEDAI/BILAG will be performed for the SLE subjects. There will be a total of 5 visits per subject, including the screening visit, in a period of four months.

At the same time of their selection, the SLE subjects will be given a Krupp Fatigue Severity Scale (FSS) test. At each visit up to 100 ml of blood will be drawn from each subject. 20 ml are needed for routine labs. and up to 80 ml are needed for the GSH/Immunologic tests.

Dose comparisons will be based on continuous monitoring of adverse events and drug tolerance.

AIM 2:

Aim 2 will determine the impact of an optimal NAC dose on disease activity and prednisone use in 110 subjects with SLE in a double-blind placebo-controlled 12-month study. It is designed to detect clinically meaningful differences in disease activity in the patient population. It was determined by statistical analysis that each group must have 55 subjects. There will be 3 groups. Group 1 will consist of 110 controls, group 2 will consist of 55 SLE subjects assigned to placebo, and group 3 will consist of 55 SLE subjects assigned to the optimum dose of NAC/Day as determined in Aim 1. SLE subjects will be randomized into three strata according to their baseline SLEDAI scores (0-6, 7-12, 13+).

The inclusion and exclusion criteria will be the same as in Aim 1 and the same subjects may continue to participate. A new consent form will be required to participate in the second phase.

In addition to the routine and experimental blood test performed in Aim 1, Aim 2 will include muscle tests and fatigue testing for the SLE subjects at each visit. The study will last 13 months with a total of 7 visits, including the screening visit and a 1 month washout.

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