Acetylcysteine

RECENT MAJOR CHANGES Dosage and Administration (2.1, 2.2, 2.3, 2.4, 2.5) 11/2024

1 INDICATIONS AND USAGE Acetylcysteine Injection is an antidote for acetaminophen overdose indicated to prevent or lessen hepatic injury after ingestion of a potentially hepatotoxic quantity of acetaminophen. Overdose incidences are divided into two types; Acute Ingestion or Repeated Supratherapeutic Ingestion (RSI). [see Dosage and Administration ( 2 ) and Acetaminophen Assays – Interpretation and Methodology -(Acute or Repeated Supratherapeutic Ingestion) ( 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. Acetylcysteine Injection 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, Acetylcysteine Injection 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 to 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. Acetylcysteine Injection is an antidote for acetaminophen overdose indicated to prevent or lessen hepatic injury after ingestion of a potentially hepatotoxic quantity of acetaminophen (1) 1.1 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 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. 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. If the predetoxification plasma level is belo …

2 DOSAGE AND ADMINISTRATION Pre-Treatment Assessment Following Acute Ingestion ( 2.1 ) : Obtain a plasma or serum sample to assay for acetaminophen concentration at least 4 hours after ingestion. If the time of acetaminophen ingestion is unknown: Administer a loading dose of acetylcysteine injection immediately. Obtain an acetaminophen concentration to determine need for continued treatment. If the acetaminophen concentration cannot be obtained (or is unavailable or uninterpretable) within the 8-hour time interval after acetaminophen ingestion or there is clinical evidence of acetaminophen toxicity: Administer a loading dose of acetylcysteine injection immediately and continue treatment for a total of three doses over 21 hours. If the patient presents more than 8 hours after ingestion and the time of acute acetaminophen ingestion is known: Administer a loading dose of acetylcysteine injection immediately. Obtain acetaminophen concentration to determine need for continued treatment. If the patient presents less than 8 hours after ingestion and the time of acute acetaminophen ingestion is known and the acetaminophen concentration is known: Use the Rumack-Matthew nomogram ( Figure 1 ) to determine whether or not to initiate treatment with acetylcysteine injection ( 2.2 ). Nomogram for Estimating Potential for Hepatotoxicity from Acute Acetaminophen Ingestion ( 2.2 ): See Full Prescribing Information for instructions on how to use the nomogram to determine the need for dosing. Preparation and Storage of Diluted Solution Prior to Administration ( 2.3 ) : Acetylcysteine injection is hyperosmolar (2600 mOsmol/L), therefore acetylcysteine injection must be diluted in sterile water for injection, 0.45% sodium chloride injection, or 5% dextrose in water injection prior to intravenous administration. See Full Prescribing Information for examples of osmolarity depending on the type of solution and acetylcysteine injection concentration. Recommended Adult and Pediatric Dosage ( 2.4 ): Acetylcysteine injection is for intravenous administration only. Total dosage of acetylcysteine injection is 300 mg/kg given intravenously as 3 separate doses and total recommended infusion time for 3 doses is 21 hours. See Full Prescribing Information for weight-based dosage and weight-based dilution ( 2.4 ). See Full Prescribing Information for recommendations for continuing acetylcysteine injection treatment after 21 hours ( 2.2 ). Repeated Supratherapeutic Acetaminophen Ingestion ( 2.5 ): Obtain acetaminophen concentration and other laboratory tests to guide treatment; Rumack-Matthew nomogram does not apply. 2.1 Pre-Treatment Assessment and Testing Following Acute Acetaminophen Ingestion The following recommendations are related to acute acetaminophen ingestion. For recommendations related to repeated supratherapeutic exposure [see Dosage and Administration ( 2.5 )] . Assess the history and timing of acetaminophen ingestion as an overdose. The reported history of the quantity of acetaminophen ingested as an overdose is often inaccurate and is not a reliable guide to therapy. Obtain the following laboratory tests to monitor hepatic and renal function and electrolyte and fluid balance: aspartate aminotransferase (AST), alanine aminotransferase (ALT), bilirubin, international normalized ratio (INR), creatinine, blood urea nitrogen (BUN), blood glucose, and electrolytes. Obtain a plasma or serum sample to assay for acetaminophen concentration at least 4 hours after ingestion. Acetaminophen concentrations obtained earlier than 4 hours post-ingestion may be misleading as they may not represent maximum acetaminophen concentrations. If the time of acute acetaminophen ingestion is unknown: Administer a loading dose of acetylcysteine injection immediately [see Dosage and Administration ( 2.4 )]. Obtain an acetaminophen concentration to determine need for continued treatment [see Dosage and Administration ( 2.2 )]. If the acetaminophen concentration cannot be obtain …

3 DOSAGE FORMS AND STRENGTHS Each single dose vial contains 6g/30mL (200 mg/mL) of Acetylcysteine. Acetylcysteine Injection is sterile and can be used for intravenous administration. Each single dose vial contains 6 g/30 mL (200 mg/mL), Acetylcysteine Injection ( 3 )

4 CONTRAINDICATIONS Acetylcysteine Injection is contraindicated in patients with a previous hypersensitivity reaction to acetylcysteine [see Warnings and Precautions ( 5.1 )] . Patients with a previous hypersensitivity reaction to acetylcysteine ( 4 )

6 ADVERSE REACTIONS Most common adverse reactions (> 2%) are rash, urticaria/facial flushing and pruritus ( 6.1 ). To report SUSPECTED ADVERSE REACTIONS, contact Sagent Pharmaceuticals at 1-866-625-1618 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Studies Experience The following clinically significant adverse reactions are described elsewhere in labeling: Hypersensitivity Reactions [see Warnings and Precautions ( 5.1 .)] Fluid Overload [see Warnings and Precautions ( 5.2 )] 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 intravenous acetylcysteine administration were rash, urticaria and pruritus. The frequency of adverse reactions has been reported to be between 0.2% and 21%, and they most commonly occur during the initial loading dose of acetylcysteine. Loading Dose/Infusion Rate Study In a randomized, open-label, multi-center clinical study conducted in Australia in patients with acetaminophen poisoning, the rates of hypersensitivity reactions between a 15-minute and 60-minute intravenous infusion for the 150 mg/kg loading dose of acetylcysteine were compared. The incidence of drug-related adverse reactions occurring within the first 2 hours following acetylcysteine administration is presented in Table 4 . Overall, 17% of patients developed an acute hypersensitivity reaction (18% in the 15-minute infusion group; 14% in the 60-minute infusion group) [see Warnings and Precautions ( 5.1 ), Clinical Studies ( 14 )] . 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 Unkn=Unknown; NOS=not otherwise specified Treatment Group 15-minutes 60-minutes 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 Hypersensitivity 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%) Rhinorrhea 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%) Safety Study A large multi-center study was performed in Canada where data were collected from patients who were treated with intravenous acetylcysteine for acetaminophen overdose between 1980 and 2005. This study evaluated 4,709 adult cases and 1,905 pediatric cases. The incidence of hypersensitivity reactions in adult (overall incidence 8%) and pediatric (overall incidence 10%) patients is presented in Table 5 and Table 6 . Table 5. Distribution of Reported Hypersensitivity Reactions in Adult Patients Receiving Intravenous Acetylcysteine * Respiratory symptoms are defined as presence of any of the following: cough, wheezing, stridor, shortness of breath, chest tightness, respiratory distress, or bronchospasm. Reaction Incidence (%) n=4,709 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 Hypersensitivity Reactions in Pediatric Patients Receiving Int …

7 DRUG INTERACTIONS No drug-drug interaction studies have been conducted. No drug-drug interaction studies have been conducted ( 7 )

8 USE IN SPECIFIC POPULATIONS 8.1 Pregnancy Risk Summary Limited published case reports and case series of pregnant women exposed to acetylcysteine during various trimesters are not sufficient to inform any drug associated risk. Delaying treatment of acetaminophen overdose may increase the risk of maternal or fetal morbidity and mortality [see Clinical Considerations]. Reproduction studies in rats and rabbits following oral administration of acetylcysteine during the period of organogenesis at doses similar to the total intravenous dose (based on the body surface area) did not cause any adverse effects to the fetus. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. Clinical Considerations Disease-Associated Maternal and/or Embryo/Fetal Risk Acetaminophen and acetylcysteine cross the placenta. Delaying treatment in pregnant women with acetaminophen overdose and potentially toxic acetaminophen plasma levels may increase the risk of maternal and fetal morbidity and mortality. Data Animal Data Reproduction studies have been performed following administration of acetylcysteine during the period of organogenesis in rats at oral doses up to 2000 mg/kg/day (1.1 times the recommended total human intravenous dose of 300 mg/kg based on body surface area comparison) and in rabbits at oral doses up to 1000 mg/kg/day (1.1 times the recommended total human intravenous dose of 300 mg/kg based on body surface area comparison). No adverse developmental outcomes due to acetylcysteine were observed. 8.2 Lactation Risk Summary There are no data on the presence of acetylcysteine in human milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for Acetylcysteine injection and any potential adverse effects on the breastfed child from Acetylcysteine injection or from the underlying maternal condition. Clinical Considerations Based on the pharmacokinetic data, acetylcysteine should be nearly completely cleared 30 hours after administration. Breastfeeding women may consider pumping and discarding their milk for 30 hours after administration. 8.4 Pediatric Use Safety and effectiveness of Acetylcysteine injection in pediatric patients have not been established by adequate and well- controlled studies. Use of Acetylcysteine injection in pediatric patients 5 kg and greater is based on clinical practice [see Dosage and Administration ( 2.5 )].

12.1 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 Intravenous 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.

11 DESCRIPTION Acetylcysteine injection is an intravenous antidote 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,). 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 C 5 H 9 NO 3 S, and its molecular weight is 163.2. Acetylcysteine has the following structural formula: Acetylcysteine injection is supplied as a sterile solution in vials containing 20% w/v (200 mg/mL) acetylcysteine USP. The pH of the solution ranges from 6 to 7.5. Acetylcysteine injection contains the following inactive ingredients: 0.5 mg/mL edetate disodium, sodium hydroxide (used for pH adjustment), and Water for Injection, USP. The amount of sodium in acetylcysteine injection is approximately 30 mg/mL. Because acetylcysteine injection is administered based on a patient’s weight, the amount of sodium administered in a course of treatment will vary from approximately 225 mg to 4,500 mg. The use of 1⁄2 normal saline will contribute approximately an additional 1,770 mg of sodium per liter of diluent. Acetylcysteine Chemical Structure

10 OVERDOSAGE Fatal and life-threatening adverse events have been reported following acetylcysteine overdosage, including anaphylaxis, cerebral edema, and hemolytic-uremic syndrome (HUS). Stop acetylcysteine administration in the setting of suspected acetylcysteine overdosage and manage as clinically indicated. Anaphylaxis, including cases with a fatal outcome, has been reported following acetylcysteine overdosage. Patients who experienced anaphylaxis following acetylcysteine overdosage often became symptomatic during the loading dose and experienced hypotension, rash, angioedema, bronchospasm, or respiratory distress. Cases of anaphylaxis with acetylcysteine overdosage also described coagulopathy, renal failure, or respiratory failure. Cerebral edema, including cases with a fatal outcome, has been reported following acetylcysteine overdosage. Patients who experienced cerebral edema following acetylcysteine overdose presented with altered mental status, abnormal pupillary responses, seizures. Some cases of cerebral edema with acetylcysteine overdosage described brain herniation. HUS has been reported following acetylcysteine overdosage. Patients who experienced HUS presented with microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Removal of acetylcysteine via hemodialysis has been reported in the literature outside of the context of acetylcysteine overdosage. Studies of hemodialysis in acetaminophen overdose report significant extracorporeal removal of acetylcysteine during hemodialysis. Contact the Poison Center (1-800-222-1222) for overdosage management recommendations for Acetylcysteine injection including considerations for hemodialysis.

16 HOW SUPPLIED/STORAGE AND HANDLING Acetylcysteine Injection is available as a 20% solution (200 mg/mL) in 30 mL single dose glass vials. Each single dose vial contains 6 g/30 mL (200 mg/mL) of Acetylcysteine. Acetylcysteine Injection is sterile and can be used for intravenous administration. Acetylcysteine Injection is available as: Product Code Unit of Sale Strength Each PRX963030 NDC 63323-963-44 Unit of 4 20% (6 grams per 30 mL) (200 mg per mL) NDC 63323-963-41 30 mL Single Dose glass vial Do not use previously opened vials for intravenous administration. Note: The color of Acetylcysteine Injection 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 Acetylcysteine Injection 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].