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. The molecular formula of the compound is C₅H₉NO₃S, and its molecular weight is 163.2.

Acetylcysteine has the following structural formula:

Acetadote is supplied as a sterile solution in vials containing 20% w/v (200 mg/mL) acetylcysteine. The pH of the solution ranges from 6.0 to 7.5. Acetadote contains the following inactive ingredients: 0.5 mg/mL disodium edetate, sodium hydroxide (used for pH adjustment), and Sterile Water for Injection, USP.

Last updated on RxList: 2/3/2009

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 and Acetaminophen Assays – Interpretation and Methodology].

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 50 mcg/mL at 12 hours); [see Acetaminophen Assays – Interpretation and Methodology]. 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.
4. 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.)

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 FlowChart

*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.

The total dose of Acetadote is 300 mg/kg administered over 21 hours. Please refer to the guidelines below for dose preparation based upon patient weight.

Administration Instructions (Three-Bag Method: Loading, Second and Third Dose) Patients ≥ 40 kg (Table1):

Loading Dose: 150mg/kg in 200mL of diluent administered over 60 min

Second Dose: 50mg/kg in 500mL of diluent administered over 4 hr

Third Dose: 100mg/kg in 1000mL of diluent administered over 16 hr

Table 1. Three-Bag Method Dosage Guide by Weight, patients ≥ 40 kg

BodyWeight		LOADING Dose 150 mg/kg in 200 mL diluent◊ over 60 min	SECOND Dose 50 mg/kg in 500mL diluent over 4 hours	THIRD Dose 100 mg/kg in 1000 mL diluent over 16 hours
(kg)	(lb)	Acetadote (mL)	Acetadote (mL)	Acetadote (mL)
100	220	75	25	50
90	198	67.5	22.5	45
80	176	60	20	40
70	154	52.5	17.5	35
60	132	45	15	30
50	110	37.5	12.5	25
40	88	30	10	20

The total volume administered should be adjusted for patients less than 40 kg and for those requiring fluid restriction:

Patients > 20 - < 40 kg (Table 2):

Loading Dose: 150mg/kg in 100mL of diluent administered over 60 min

Second Dose: 50mg/kg in 250mL of diluent administered over 4 hr

Third Dose: 100mg/kg in 500mL of diluent administered over 16 hr

Table 2. Three-Bag Method Dosage Guide by Weight, patients > 20 - < 40 kg

Body Weight		LOADING 150 mg/kg minutes	Dose over 60	SECOND 50 mg/kg hours	Dose over 4	THIRD 100 mg/kg hours	Dose over 16
(kg)	(lb)	Acetadote (mL)	Diluent◊ (mL)	Acetadote (mL)	Diluent (mL)	Acetadote (mL)	Diluent (mL)
30	66	22.5	100	7.5	250	15	500
25	55	18.75	100	6.25	250	12.5	500

Patients < 20 kg (Table 3):

Loading Dose: 150mg/kg in 3mL/kg of body weight of diluent administered over 60 min

Second Dose: 50mg/kg in 7mL/kg of body weight of diluent administered over 4 hr

Third Dose: 100mg/kg in 14mL/kg of body weight of diluent administered over 16 hr

Table 3. Three-Bag Method Dosage Guide by Weight, patients ≤ 20 kg

Body Weight		LOADING 150 mg/kg minutes	Dose over 60	SECOND 50 mg/kg hours	Dose over 4	THIRD 100 mg/kg hours	Dose over 16
(kg)	(lb)	Acetadote (mL)	Diluent◊ (mL)	Acetadote (mL)	Diluent (mL)	Acetadote (mL)	Diluent (mL)
20	44	15	60	5	140	10	280
15	33	11.25	45	3.75	105	7.5	210
10	22	7.5	30	2.5	70	5	140

◊ Acetadote is hyperosmolar (2600 mOsm/L) and is compatible with 5% Dextrose (D5W), ½ Normal Saline (0.45% Sodium Chloride Injection, ½ NS), and Water for Injection (WFI).

Single dose vial, preservative-free, discard unused portion. If vial was previously opened, do not use for I.V. administration.

Stability studies indicate that the diluted solution is stable for 24 hours at controlled room temperature.

Note: The color of Acetadote may turn from essentially colorless to a slight pink or purple once the stopper is punctured. The color change does not affect the quality of the product.

Renal Impairment

No data are available to determine if a dose adjustment in patients with moderate or severe renal impairment is required.

Hepatic Impairment

Although there was a threefold increase in acetylcysteine plasma concentrations in patients with hepatic cirrhosis, no data are available to determine if a dose adjustment in these patients is required. The published medical literature does not indicate that the dose of acetylcysteine in patients with hepatic impairment should be reduced.

Dosage Forms And Strengths

Acetadote (acetylcysteine) Injection is available as a 20% solution (200mg/mL) in 30 mL single dose glass vials. Acetadote is sterile and can be used for I.V. administration.

Storage And Handling

Acetadote (acetylcysteine) Injection is available as a 20% solution (200mg/mL) in 30 mL single dose glass vials. Acetadote is sterile and can be used for I.V. administration. It is available as follows:

30 mL vials, carton of 4 (NDC 66220-107-30)

Do not use previously opened vials for I.V. administration.

Note: The color of Acetadote may turn from essentially colorless to a slight pink or purple once the stopper is punctured. The color change does not affect the quality of the product.

The stopper in the Acetadote vial is formulated with a synthetic base-polymer and does not contain Natural Rubber Latex, Dry Natural Rubber, or blends of Natural Rubber.

Storage

Store unopened vials at controlled room temperature, 20° to 25° C (68° to 77° F) [See USP Controlled Room Temperature].

For all questions concerning adverse reactions associated with the use of this product or for inquiries concerning our products, please contact us at 1-877-484-2700.
For specific treatment information regarding the clinical management of 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.
Manufactured for: Cumberland Pharmaceuticals Inc. Nashville, TN 37203. FDA revision date: 12/12/2009

Last updated on RxList: 2/3/2009

Clinical Studies Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

In the literature the most frequently reported adverse reactions attributed to I.V. acetylcysteine administration were rash, urticaria, and pruritus. The frequency of adverse reactions has been reported to be between 0.2% and 20.8%, and they most commonly occur during the initial loading dose of acetylcysteine.

Loading Dose/Infusion Rate Study

The incidence of drug-related adverse reactions occurring within the first 2 hours following acetylcysteine administration reported in a randomized study in patients with acetaminophen poisoning is presented in Table 4 by preferred term. In this study patients were randomized to a 15-minute or a 60-minute loading dose regimen.

Within the first 2 hours following I.V. acetylcysteine administration, 17% developed an anaphylactoid reaction (18% in the 15-minute treatment group; 14% in the 60-minute treatment group) in this randomized, open-label, multi-center clinical study conducted in Australia to compare the rates of anaphylactoid reactions between two rates of infusion for the I.V. acetylcysteine loading dose. [see WARNINGS and Clinical Studies - Loading Dose/Infustion Rate Study].

Table 4. Incidence of Drug-Related Adverse Reactions Occurring Within the First 2 Hours Following Study Drug Administration by Preferred Term: Loading Dose/Infusion Rate Study

Treatment Group	15-min				60-min
Number of Patients	n=109				n=71
Cardiac disorders	5(5%)				2 (3%)
Severity:	Unkn	Mild	Moderate	Severe	Unkn	Mild	Moderate	Severe
Tachycardia NOS		4 (4%)	1 (1%)			2 (3%)
Gastrointestinal disorders	16(15%)				7(10%)
Severity:	Unkn	Mild	Moderate	Severe	Unkn	Mild	Moderate	Severe
Nausea	1 (1%)		6 (6%)			1 (1%)	1 (1%)
Vomiting NOS		2 (2%)	11 (10%)			2 (3%)	4 (6%)
Immune System Disorders	20 (18%)				10(14%)
Severity:	Unkn	Mild	Moderate	Severe	Unkn	Mild	Moderate	Severe
Anaphylactoid reaction	2 (2%)	6 (6%)	11 (10%)	1 (1%)		4 (6%)	5 (7%)	1 (1%)
Respiratory, thoracic and mediastinal disorders	2 (2%)				2 (3%)
Severity:	Unkn	Mild	Moderate	Severe	Unkn	Mild	Moderate	Severe
Pharyngitis			1 (1%)
Rhinorrhoea		1 (1%)
Rhonchi						1 (1%)
Throat tightness						1 (1%)
Skin & subcutaneous tissue disorders	6(6%)				5(7%)
Severity:	Unkn	Mild	Moderate	Severe	Unkn	Mild	Moderate	Severe
Pruritus		1 (1%)				2 (3%)
Rash NOS		3 (3%)	2 (2%)			3 (4%)
Vascular disorders	2(2%)				3(4%)
Severity:	Unkn	Mild	Moderate	Severe	Unkn	Mild	Moderate	Severe
Flushing		1 (1%)	1 (1%)			2 (3%)	1 (1%)
Unkn=Unknown

Postmarketing Safety Study

A large, multi-center study was performed in Canada where data were collected from patients who were treated with IV NAC for acetaminophen overdose between 1980 and 2005. This study evaluated 4709 adult cases and 1905 pediatric cases. The incidence of anaphylactoid reactions in adult (overall incidence 7.9%) and pediatric (overall incidence 9.5%) patients is presented in Tables 5 and 6.

Table 5. Distribution of reported reactions in adult patients receiving IV NAC

Reaction	Incidence (%)
	% of Patients (N=4709)
Urticaria/Facial Flushing	6.1%
Pruritus	4.3%
Respiratory Symptoms*	1.9%
Edema	1.6%
Hypotension	0.1%
Anaphylaxis	0.1%

Table 6. Distribution of reported reactions in pediatric patients receiving IV NAC

Reaction	Incidence (%)
	% of Patients (N=1905)
Urticaria/Facial Flushing	7.6%
Pruritus	4.1%
Respiratory Symptoms*	2.2%
Edema	1.2%
Anaphylaxis	0.2%
Hypotension	0.1%
*Respiratory symptoms are defined as presence of any of the following: cough, wheezing, stridor, shortness of breath, chest tightness, respiratory distress, or bronchospasm.

No drug-drug interaction studies have been conducted.

Last updated on RxList: 2/3/2009

Included as part of the PRECAUTIONS section.

Anaphylactoid Reactions

Serious anaphylactoid reactions, including death in a patient with asthma, have been reported in patients administered acetylcysteine intravenously.

Acute flushing and erythema of the skin may occur in patients receiving acetylcysteine intravenously. These reactions usually occur 30 to 60 minutes after initiating the infusion and often resolve spontaneously despite continued infusion of acetylcysteine. Anaphylactoid reactions (defined as the occurrence of an acute hypersensitivity reaction during acetylcysteine administration including rash, hypotension, wheezing, and/or shortness of breath) have been observed in patients receiving I.V. acetylcysteine for acetaminophen overdose and occurred soon after initiation of the infusion [see ADVERSE REACTIONS]. If a reaction to acetylcysteine involves more than simply flushing and erythema of the skin, it should be treated as an anaphylactoid reaction. This usually entails administering antihistaminic drugs and in severe cases may require administration of epinephrine. In addition, the acetylcysteine infusion may be interrupted until treatment of the anaphylactoid symptoms has been initiated and then carefully restarted. If the anaphylactoid reaction returns upon reinitiation of treatment or increases in severity, intravenous acetylcysteine should be discontinued and alternative patient management should be considered.

Monitoring patients with asthma

Acetadote should be used with caution in patients with asthma, or where there is a history of bronchospasm.

Volume Adjustment: Patients < 40kg and Requiring Fluid Restriction

The total volume administered should be adjusted for patients less than 40 kg and for those requiring fluid restriction. To avoid fluid overload, the volume of 5% dextrose should be reduced as needed [see DOSAGE AND ADMINISTRATION]. If volume is not adjusted fluid overload can occur, potentially resulting in hyponatremia, seizure, and death.

For specific treatment information regarding the clinical management of 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.

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term studies in animals have not been performed to evaluate the carcinogenic potential of acetylcysteine.

Acetylcysteine was not genotoxic in the Ames test or the in vivo mouse micronucleus test. It was, however, positive in the in vitro mouse lymphoma cell (L5178Y/TK+/-) forward mutation test.

Treatment of male rats with acetylcysteine at an oral dose of 250 mg/kg/day for 15 weeks (0.8 times the recommended human dose of 300 mg/kg) did not affect the fertility or general reproductive performance.

Reproductive and Developmental Toxicology

Reproduction studies were performed in rats at oral doses up to 2000 mg/kg/day (6.7 times the recommended human dose of 300 mg/kg) and in rabbits at oral doses up to 1000 mg/kg/day (3.3 times the recommended human dose of 300 mg/kg) and revealed no evidence of impaired fertility or harm to the fetus due to acetylcysteine [see Pregnancy].

Use In Specific Populations

Pregnancy

Pregnancy Category B

There are no adequate and well-controlled studies of Acetadote in pregnant women. However, limited case reports of pregnant women exposed to acetylcysteine during various trimesters did not report any adverse maternal, fetal, or neonatal outcomes.

There are published reports on four pregnant women with acetaminophen toxicity, who were treated with oral or intravenous acetylcysteine at the time of delivery. Acetylcysteine crossed the placenta and was measurable following delivery in serum and cord blood of three viable infants and in cardiac blood of a fourth infant at autopsy (22 weeks gestational age who died 3 hours after birth). No adverse sequelae developed in the three viable infants. All mothers recovered and none of the infants had evidence of acetaminophen poisoning.

Reproductive and developmental toxicity studies performed in rats at oral doses up to 6.7 times the recommended human intravenous dose and in rabbits at doses up to 3.3 times the recommended human intravenous dose revealed no evidence of impaired fertility or embryofetal toxicity. [see Reproductive and Developmental Toxicology]

Nursing mothers

It is not known whether Acetadote is present in human milk. Because many drugs are excreted in human milk, caution should be exercised when acetylcysteine is administered to a nursing woman. Based on the pharmacokinetics of acetylcysteine, it should be nearly completely cleared 30 hours after administration. Nursing women may consider resuming nursing 30 hours after administration.

Pediatric use

No adverse effects were noted during I.V. infusion with acetylcysteine at a mean rate of 4.2 mg/kg/h for 24 hours to 10 preterm newborns ranging in gestational age from 25 to 31 weeks and in weight from 500 to 1380 grams in one study or in 6 newborns ranging in gestational age from 26 to 30 weeks and in weight from 520 to 1335 grams infused with acetylcysteine at 0.1 to 1.3 mg/kg/h for 6 days. Elimination of acetylcysteine was slower in these infants than in adults; mean elimination half-life was 11 hours. There are no adequate and well-controlled studies in pediatric patients.

Geriatric use

The clinical studies do not provide a sufficient number of geriatric subjects to determine whether the elderly respond differently.

Last updated on RxList: 2/3/2009

Single intravenous doses of acetylcysteine at 1000 mg/kg in mice, 2445 mg/kg in rats, 1500 mg/kg in guinea pigs, 1200 mg/kg in rabbits and 500 mg/kg in dogs were lethal. Symptoms of acute toxicity were ataxia, hypoactivity, labored respiration, cyanosis, loss of righting reflex and convulsions.

Acetadote is contraindicated in patients with previous anaphylactoid reactions to acetylcysteine.

Last updated on RxList: 2/3/2009

Mechanism of action

Acetaminophen Overdose

Acetaminophen is absorbed from the upper gastrointestinal tract with peak plasma levels occurring between 30 and 60 minutes after therapeutic doses and usually within 4 hours following an overdose. It is extensively metabolized in the liver to form principally the sulfate and glucoronide conjugates which are excreted in the urine. A small fraction of an ingested dose is metabolized in the liver by isozyme CYP2E1 of the cytochrome P-450 mixed function oxidase enzyme system to form a reactive, potentially toxic, intermediate metabolite. The toxic metabolite preferentially conjugates with hepatic glutathione to form nontoxic cysteine and mercapturic acid derivatives, which are then excreted by the kidney. Recommended therapeutic doses of acetaminophen are not believed to saturate the glucuronide and sulfate conjugation pathways and therefore are not expected to result in the formation of sufficient reactive metabolite to deplete glutathione stores. However, following ingestion of a large overdose, the glucuronide and sulfate conjugation pathways are saturated resulting in a larger fraction of the drug being metabolized via the cytochrome P-450 pathway and therefore, the amount of acetaminophen metabolized to the reactive intermediate increases. The increased formation of the reactive metabolite may deplete the hepatic stores of glutathione with subsequent binding of the metabolite to protein molecules within the hepatocyte resulting in cellular necrosis.

Acetylcysteine I.V. Treatment

Acetylcysteine has been shown to reduce the extent of liver injury following acetaminophen overdose. It is most effective when given early, with benefit seen principally in patients treated within 8-10 hours of the overdose. Acetylcysteine likely protects the liver by maintaining or restoring the glutathione levels, or by acting as an alternate substrate for conjugation with, and thus detoxification of, the reactive metabolite.

Pharmacokinetics

Distribution

The steady-state volume of distribution (Vd_ss) and the protein binding for acetylcysteine were reported to be 0.47 liter/kg and 83%, respectively. Metabolism: Acetylcysteine may form cysteine, disulfides, and conjugates in vivo (N, N'-diacetylcysteine, N-acetylcysteine-cysteine, N-acetylcysteine-glutathione, N-acetylcysteine-protein, etc). Based on published data, it was reported that after an oral dose of ³⁵S-acetylcysteine, about 22% of total radioactivity was excreted in urine after 24 hours. No metabolites were identified.

Elimination

After a single intravenous dose of acetylcysteine, the plasma concentration of total acetylcysteine declined in a poly-exponential decay manner with a mean terminal half-life (T½) of 5.6 hours. The mean clearance (CL) for acetylcysteine was reported to be 0.11 liter/hr/kg and renal CL constituted about 30% of total CL.

Special Populations

Gender: Adequate information is not available to assess if there are differences in pharmacokinetics (PK) between males and females.

Pediatric: The mean elimination ^T1/2 of acetylcysteine is longer in newborns (11 hours) than in adults (5.6 hours). Pharmacokinetic information is not available in other age groups.

Pregnant Women: In four pregnant women with acetaminophen toxicity, oral or I.V. acetylcysteine was administered at the time of delivery. Acetylcysteine was detected in the cord blood of 3 viable infants and in cardiac blood of a fourth infant sampled at autopsy. [see Pregnancy]

Hepatic Impairment: In subjects with severe liver damage, i.e., cirrhosis due to alcohol (with Child-Pugh score of 7-13), or primary and/or secondary biliary cirrhosis (with Child-Pugh score of 5-7), mean T1/2 increased by 80% while mean CL decreased by 30% compared to the control group.

Renal Impairment: Pharmacokinetic information is not available in patients with renal impairment. Geriatric Patients: Adequate information on acetylcysteine PK in geriatric patients is not available.

Clinical Studies

Loading Dose/Infusion Rate Study

A randomized, open-label, multi-center clinical study was conducted in Australia to compare the rates of anaphylactoid reactions between two rates of infusion for the I.V. acetylcysteine loading dose. One hundred nine subjects were randomized to a 15 minute infusion rate and seventy-one subjects were randomized to a 60 minute infusion rate. The loading dose was 150 mg/kg followed by a maintenance dose of 50 mg/kg over 4 hours and then 100 mg/kg over 16 hours. Of the 180 patients, 27% were male and 73% were female. Ages ranged from 15 to 83 years, with the mean age being 29.9 years (± 13.0).

A subgroup of 58 subjects (33 in the 15-minute treatment group; 25 in the 60-minute treatment group) was treated within 8 hours of acetaminophen ingestion. No hepatotoxicity occurred within this subgroup; however with 95% confidence, the true hepatotoxicity rates could range from 0% to 9% for the 15-minute treatment group and from 0% to 12% for the 60-minute treatment group.

Observational Study

An open-label, observational database contained information on 1749 patients who sought treatment for acetaminophen overdose over a 16-year period. Of the 1749 patients, 65% were female, 34% were male and < 1% was transgender. Ages ranged from 2 months to 96 years, with 71.4% of the patients falling in the 16-40 year old age bracket. A total of 399 patients received acetylcysteine treatment. A post-hoc analysis identified 56 patients who (1) were at high or probable risk for hepatotoxicity (APAP > 150 mg/L at the four hours line according to the Australian nomogram) and (2) had a liver function test. Of the 53 patients who were treated with I.V. acetylcysteine (300 mg/kg I.V. acetylcysteine administered over 20-21 hours) within 8 hours, two (4%) developed hepatotoxicity (AST or ALT > 1000U/L). Twenty-one of 48 (44%) patients treated with acetylcysteine after 15 hours developed hepatotoxicity. The actual number of hepatotoxicity outcomes may be higher than what is reported here. For patients with multiple admissions for acetaminophen overdose, only the first overdose treated with I.V. acetylcysteine was examined. Hepatotoxicity may have occurred in subsequent admissions.

Evaluable data were available from a total of 148 pediatric patients (less than 16 years of age) who were admitted for poisoning following ingestion of acetaminophen, of whom 23 were treated with I.V. acetylcysteine. Of the 23 patients who received I.V. acetylcysteine treatment, 3 patients (13%) had an adverse reaction (anaphylactoid reaction, rash and flushing, transient erythema). There were no deaths of pediatric patients. None of the pediatric patients receiving I.V. acetylcysteine developed hepatotoxicity while two patients not receiving I.V. acetylcysteine developed hepatotoxicity. The number of pediatric patients is too small to provide a statistically significant finding of efficacy, however the results appear to be consistent to those observed for adults. Postmarketing Safety Study [see Clinical Studies Experience]

Last updated on RxList: 2/3/2009

Sensitivity to acetylcysteine: Patients should be advised to report to their physician any history of sensitivity to acetylcysteine [see CONTRAINDICATIONS].

Asthma: Patients should be advised to report to their physician any history of asthma [see WARNINGS AND PRECAUTIONS].

Last updated on RxList: 2/3/2009

IMPORTANT NOTE: This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your health care professional. Always seek the advice of your health care professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your health care professional. This information does not contain any assurances that this product is safe, effective, or appropriate for you.

ACETYLCYSTEINE - INJECTION

(a-SEET-il-SIS-teen)

COMMON BRAND NAME(S): Acetadote

USES: This medication is used as an antidote for acetaminophen overdose to prevent life-threatening liver damage. It is most effective if given within 8 to 10 hours after ingestion, but it can be used anytime up to 24 hours after an overdose. If acetaminophen overdose is suspected, but the exact time of ingestion is unknown, acetylcysteine may still be given.

HOW TO USE: Before and during use of this medication, acetaminophen blood levels will be taken. The first blood test should be done no later than 4 hours after the suspected ingestion. A repeat blood test may be necessary (e.g., in case of extended-release acetaminophen overdose). Additional blood tests will determine if treatment should be continued.

This medication is injected into a vein (intravenously-IV) by a healthcare professional, or as directed by your doctor. The dosage is based on your weight. This drug should be continued until your acetaminophen blood levels are below toxic levels.

Follow all instructions for proper mixing and dilution with the correct IV fluids. If you have any questions regarding the use of this medication, consult your pharmacist.

Before using, check this product visually for particles or discoloration. If either is present, do not use the liquid. Discard the remaining content of any open vials immediately after use.

SIDE EFFECTS: Nausea, vomiting, dizziness, flushing, stomach upset, cough, or increased sweating may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: eye pain, fainting, trouble walking.

A serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching, swelling (especially of the face, lips, tongue, or throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

Contact your doctor for medical advice about side effects. The following numbers do not provide medical advice, but in the US you may report side effects to the Food and Drug Administration (FDA) at 1-800-FDA-1088. In Canada, you may call Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking acetylcysteine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: breathing disorders (e.g., asthma, bronchospasm).

This drug may make you dizzy; use caution engaging in activities requiring alertness such as driving or using machinery. Avoid alcoholic beverages.

This medication should be used only when clearly needed during pregnancy. Discuss the risks and benefits with your doctor.

It is not known whether this drug passes into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with them first.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use.

Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

OVERDOSE: If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US national poison hotline at 1-800-222-1222. Canadian residents should call their local poison control center directly.

NOTES: Do not share this medication with others.

Laboratory and/or medical tests (e.g., acetaminophen blood levels, liver and kidney function tests, electrolytes) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

MISSED DOSE: To prevent liver damage, it is very important to take this medication as directed. If you miss a dose, contact your doctor or pharmacist immediately to establish a new dosing schedule.

STORAGE: Store at room temperature between 68-77 degrees F (20-25 degrees C) away from light and moisture. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

Information last revised July 2008 Copyright(c) 2008 First DataBank, Inc.