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warnings and cautions
5 WARNINGS AND PRECAUTIONS Hypersensitivity Reactions: Fatal or life-threatening anaphylaxis, rash, hypotension, wheezing, shortness of breath, and/or bronchospasm have been observed. Observe patients during and after the infusion; immediately discontinue infusion if a serious reaction occurs and initiate appropriate treatment. Acetylcysteine infusion may be carefully restarted after treatment of hypersensitivity has been initiated and acute symptoms have resolved (5.1) . Fluid Overload : Total volume administered should be reduced for patients weighing less than 40 kg and for those requiring fluid restriction (5.2) . 5.1 Hypersensitivity Reactions Serious acute hypersensitivity reactions; including fatal or life-threatening anaphylaxis, rash, hypotension, wheezing, and/or shortness of breath; have been observed in patients receiving intravenous acetylcysteine for acetaminophen overdose and occurred soon after initiation of the infusion [see Adverse Reactions (6) ] . If a severe hypersensitivity reaction occurs, immediately stop the infusion of acetylcysteine and initiate appropriate treatment. Patients with asthma should be closely monitored during initiation of acetylcysteine therapy and throughout acetylcysteine therapy. 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. If a reaction to acetylcysteine involves more than simply flushing and erythema of the skin, it should be treated as a hypersensitivity reaction. Management of less severe hypersensitivity reactions should be based upon the severity of the reaction and include temporary interruption of the infusion and/or administration of antihistaminic drugs. The acetylcysteine infusion may be carefully restarted after treatment of the hypersensitivity symptoms has been initiated and acute symptoms have resolved; however, if the hypersensitivity reaction returns upon re-initiation of treatment or increases in severity, acetylcysteine should be discontinued and alternative patient management should be considered. 5.2 Fluid Overload The total volume of acetylcysteine administered should be adjusted for patients less than 40 kg and for those requiring fluid restriction. Intravenous administration of acetylcysteine can cause fluid overload, potentially resulting in hyponatremia, seizure, and death. To avoid fluid overload, use the recommended dilutions [see Dosage and Administration (2.5) ].
6 ADVERSE REACTIONS Most common adverse reactions (> 2%) are rash, urticaria/facial flushing and pruritus (6.1) . To report SUSPECTED ADVERSE REACTIONS, contact Eugia US LLC at 1-866-850-2876 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 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=1,905 Urticaria/Facial Flushing 7.6% Pruritus 4.1% Respiratory Symptoms* 2.2% Edema 1.2% Anaphylaxis 0.2% Hypotension 0.1% 6.2 Postmarketing Experience Adverse Reactions from Observational Studies Table 7 displays the incidence of hypersensitivity reactions in patients who received three-bag regimens of intravenous acetylcysteine admitted between 2009 to 2020. Table 7. Incidence of Hypersensitivity Reactions in Patients who Received Three-bag Regimens of Intravenous Acetylcysteine in Published Literature Study Hypersensitivity Reactions in Patients Receiving Three-Bag Regimen Study 1 (Three Danish hospitals) 16% (47/292) Study 2 (Four Australian hospitals) 14% (45/313) Study 3 (Nine Australian hospitals) 7% (65/911) Study 4 (One US hospital) 23% (34/150) Adverse Reactions from Postmarketing Spontaneous Reports The following adverse reactions have been identified during post-approval use of acetylcysteine. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Immune system disorders: fatal anaphylaxis