Metronidazole

INDICATIONS AND USAGE To reduce the development of drug-resistant bacteria and maintain the effectiveness of Metronidazole Injection and other antibacterial drugs, Metronidazole Injection should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy. Treatment of Anaerobic Infections Metronidazole Injection is indicated in the treatment of serious infections caused by susceptible anaerobic bacteria. Indicated surgical procedures should be performed in conjunction with Metronidazole Injection therapy. In a mixed aerobic and anaerobic infection, antibacterial drugs appropriate for the treatment of the aerobic infection should be used in addition to Metronidazole Injection. Metronidazole Injection is effective in Bacteroides fragilis infections resistant to clindamycin, chloramphenicol, and penicillin. • Intra-Abdominal Infections , including peritonitis, intra-abdominal abscess, and liver abscess, caused by Bacteroides species including the B. fragilis group (B. fragilis , B. distasonis , B. ovatus , B. thetaiotaomicron , B. vulgatus) , Clostridium species, Eubacterium species, Peptococcus species, and Peptostreptococcus species in adults and pediatric patients less than 4 months of age. • Skin and Skin Structure Infections caused by Bacteroides species including the B. fragilis group, Clostridium species, Peptococcus species, Peptostreptococcus species, and Fusobacterium species in adults. • Gynecologic Infections , including endometritis, endomyometritis, tubo-ovarian abscess, and post-surgical vaginal cuff infection, caused by Bacteroides species including the B. fragilis group, Clostridium species, Peptococcus species, and Peptostreptococcus species in adults. • Bacterial Septicemia caused by Bacteroides species including the B. fragilis group and Clostridium species in adults. • Bone and Joint Infections , as adjunctive therapy, caused by Bacteroides species including the B. fragilis group in adults. • Central Nervous System (CNS) Infections , including meningitis and brain abscess, caused by Bacteroides species including the B. fragilis group in adults. • Lower Respiratory Tract Infections , including pneumonia, empyema, and lung abscess, caused by Bacteroides species including the B. fragilis group in adults. • Endocarditis caused by Bacteroides species including the B. fragilis group in adults. Prophylaxis Indication The prophylactic administration of Metronidazole Injection preoperatively, intraoperatively, and postoperatively may reduce the incidence of postoperative infection in adult patients undergoing elective colorectal surgery which is classified as contaminated or potentially contaminated. Prophylactic use of Metronidazole Injection should be discontinued within 12 hours after surgery. If there are signs of infection, specimens for cultures should be obtained for the identification of the causative organism(s) so that appropriate therapy may be given (see DOSAGE AND ADMINISTRATION ). Usage To reduce the development of drug-resistant bacteria and maintain the effectiveness of metronidazole and other antibacterial drugs, metronidazole should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antimicrobial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

DOSAGE AND ADMINISTRATION Dosage, rate of administration, and duration of treatment are to be individualized and depend upon the indication for use, the patient’s age, weight, clinical condition and concomitant treatment, and on the patient’s clinical and laboratory response to the treatment. Recommended Dosage for the Treatment of Anaerobic Bacterial Infections The recommended dosage schedule for adults for the treatment of anaerobic infections is presented in the Table 1 : Table 1. Recommended Dosage Schedule for the Treatment of Anaerobic Bacterial Infections in Adults Loading Dose 15 mg/kg infused intravenously over one hour (approximately 1 gram for a 70-kg adult). Maintenance Dosage 7.5 mg/kg infused intravenously over one hour every six hours (approximately 500 mg for a 70-kg adult). The first maintenance dose should be instituted six hours following the initiation of the loading dose. Parenteral therapy may be changed to oral metronidazole therapy when conditions warrant, based upon the severity of the disease and the response of the patient to treatment with metronidazole injection. The usual adult oral dosage is 7.5 mg/kg every six hours (approximately 500 mg for a 70-kg adult). A maximum of 4 grams should not be exceeded during a 24-hour period. The usual duration of therapy is 7 days to 10 days; however, infections of the bone and joint, lower respiratory tract and endocardium may require longer treatment. Recommended Dosage for the Treatment of Intra-Abdominal Infections in Pediatric Patients Less than 4 Months of Age: The recommended dosage schedule for pediatric patients less than 4 months of age for the treatment of intra-abdominal infections is described in Table 2 below. These dosage schedules achieve drug exposures in pediatric patients similar to adults treated with Metronidazole Injection for this indication. Table 2. Recommended Dosage Schedule for the Treatment of Intra-Abdominal Infections in Pediatric Patients Less than 4 months of Age Post-menstrual age (Completed weeks) Loading Dose (mg/kg) Maintenance Dose* (mg/kg) Dosing interval (hours) 23 to 40 to 48 15 7.5 6 * The first maintenance dose is given 24 hours after the start of the loading dose. Recommended Dosage in Patients with Severe Hepatic Impairment For patients with severe hepatic impairment (Child-Pugh C), the metronidazole dose should be reduced by 50% (see CLINICAL PHARMACOLOGY and PRECAUTIONS ). Recommended Dosage in Patients Undergoing Hemodialysis Hemodialysis removes significant amounts of metronidazole and its metabolites from systemic circulation. The clearance of metronidazole will depend on the type of dialysis membrane used, the duration of the dialysis session, and other factors. If the administration of metronidazole cannot be separated from a hemodialysis session, supplementation of metronidazole dosage following a hemodialysis session should be considered, depending on the patient’s clinical situation (see CLINICAL PHARMACOLOGY ). Dosage Considerations in Geriatric Patients In elderly patients the pharmacokinetics of metronidazole may be altered and, therefore, monitoring of serum levels may be necessary to adjust the metronidazole dosage accordingly. Recommended Prophylaxis Dosage For surgical prophylactic use, to prevent postoperative infection in contaminated or potentially contaminated colorectal surgery, the recommended dosage schedule for adults is: a. 15 mg/kg infused over 30 minutes to 60 minutes and completed approximately one hour before surgery; followed by b. 7.5 mg/kg infused over 30 minutes to 60 minutes at 6 hours and 12 hours after the initial dose. It is important that (1) administration of the initial preoperative dose be completed approximately one hour before surgery so that adequate drug levels are present in the serum and tissues at the time of initial incision and (2) metronidazole injection be administered, if necessary, at 6-hour intervals to maintain effective drug levels. Prophylactic use of metronid …

CONTRAINDICATIONS • Hypersensitivity Metronidazole Injection is contraindicated in patients with a prior history of hypersensitivity to metronidazole or other nitroimidazole derivatives. • Psychotic Reaction with Disulfiram Use of oral metronidazole is associated with psychotic reactions in alcoholic patients who were using disulfiram concurrently. Do not administer metronidazole to patients who have taken disulfiram within the last two weeks (see PRECAUTIONS-Drug Interactions ). • Interaction with Alcohol Use of oral metronidazole is associated with a disulfiram-like reaction to alcohol, including abdominal cramps, nausea, vomiting, headaches, and flushing. Discontinue consumption of alcohol or products containing propylene glycol during and for at least three days after therapy with metronidazole (see PRECAUTIONS-Drug Interactions ). • Cockayne Syndrome Metronidazole Injection is contraindicated in patients with Cockayne syndrome. Severe irreversible hepatotoxicity/acute liver failure with fatal outcomes have been reported after initiation of metronidazole in patients with Cockayne syndrome (see ADVERSE REACTIONS ).

ADVERSE REACTIONS The following are the most serious adverse reactions reported in patients treated with metronidazole and are also described elsewhere in the labeling: convulsive seizures, encephalopathy, aseptic meningitis, optic and peripheral neuropathy (characterized mainly by numbness or paresthesia of an extremity) (see WARNINGS) . The following adverse reactions associated with the use of metronidazole products were identified in clinical studies or postmarketing reports or published literature. Because some of these reactions were 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. GASTROINTESTINAL: Nausea, anorexia, vomiting, abdominal discomfort, diarrhea, an unpleasant metallic taste, epigastric distress, abdominal cramping, constipation and pancreatitis. MOUTH: A sharp metallic taste. Furry tongue, glossitis, and stomatitis have occurred; these may be associated with a sudden overgrowth of Candida which may occur during therapy with metronidazole. HEMATOPOIETIC: Reversible neutropenia (leukopenia); thrombocytopenia, eosinophilia. HEPATOBILIARY DISORDERS: Hepatotoxicity and liver failure especially in patients with Cockayne syndrome (see CONTRAINDICATIONS ), jaundice. CARDIOVASCULAR: QT prolongation has been reported, particularly when metronidazole was administered with drugs with the potential for prolonging the QT interval. Flattening of the T-wave may be seen in electrocardiographic tracings. SKIN AND SUBCUTANEOUS DISORDERS: Toxic epidermal necrolysis, Stevens-Johnson syndrome, Fixed drug eruption, Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), erythematous rash, bullae, pruritus, swelling face, urticaria, and hyperhidrosis. CENTRAL NERVOUS SYSTEM: Encephalopathy, aseptic meningitis, convulsive seizures, optic neuropathy, peripheral neuropathy (mainly numbness or paresthesia of an extremity), dizziness, vertigo, incoordination, ataxia, confusion, psychosis, dysarthria, irritability, depression, weakness, headache, tinnitus, hearing impairment, hearing loss, and insomnia. LABORATORY INVESTIGATIONS: Hepatic enzymes increased. HYPERSENSITIVITY: Toxic epidermal necrolysis (TEN), Stevens-Johnson Syndrome (SJS), drug reaction with eosinophilia and systemic symptoms (DRESS), acute generalized exanthematous pustulosis (AGEP) (see WARNINGS ), anaphylaxis, angioedema, hypotension, flushing, nasal congestion, and dryness of mouth (or vagina or vulva). RENAL: Dysuria, cystitis, polyuria, incontinence, a sense of pelvic pressure, and darkened urine. HEPATIC: Cases of severe irreversible hepatotoxicity/acute liver failure, including cases with fatal outcomes with very rapid onset after initiation of systemic use of metronidazole, have been reported in patients with Cockayne Syndrome (latency from drug start to signs of liver failure as short as 2 days) (see CONTRAINDICATIONS ). LOCAL REACTIONS: Thrombophlebitis after intravenous infusion. This reaction can be minimized or avoided by avoiding prolonged use of indwelling intravenous catheters. OTHER ADVERSE REACTIONS: Fever, hiccup, proliferation of Candida in the vagina, dyspareunia, decrease of libido, proctitis, and fleeting joint pains sometimes resembling “serum sickness”. If patients receiving metronidazole drink alcoholic beverages, they may experience abdominal distress, nausea, vomiting, flushing, or headache. A modification of the taste of alcoholic beverages has also been reported. Patients with Crohn’s disease are known to have an increased incidence of gastrointestinal and certain extraintestinal cancers. There have been some reports in the medical literature of breast and colon cancer in Crohn’s disease patients who have been treated with metronidazole at high doses for extended periods of time. A cause and effect relationship has not been established. Crohn’s disease is not an approved indication for Metronidazole Injection. D …

Drug Interactions • Disulfiram Psychotic reactions and confusion have been reported in alcoholic patients who are using metronidazole and disulfiram concurrently. Do not administer Metronidazole Injection to patients who have taken disulfiram within the last two weeks (see CONTRAINDICATIONS ). • Alcoholic Beverages Abdominal cramps, nausea, vomiting, headaches, tachycardia and flushing may occur if alcoholic beverages or products containing propylene glycol are consumed during or following metronidazole therapy. Discontinue consumption of alcohol or products containing propylene glycol before, during and up to 72 hours after therapy with Metronidazole Injection (see CONTRAINDICATIONS ). • Warfarin and other Oral Anticoagulants Metronidazole has been reported to potentiate the anticoagulant effect of warfarin and other oral coumarin anticoagulants, resulting in a prolongation of prothrombin time and increased risk of hemorrhages. When Metronidazole Injection is prescribed for patients on this type of anticoagulant therapy, prothrombin time and international normalized ratio (INR) should be carefully monitored and their anticoagulant dose adjusted accordingly. Monitor patients for signs and symptoms of bleeding. • Lithium In patients stabilized on relatively high doses of lithium, short-term metronidazole therapy has been associated with elevation of serum lithium and, in a few cases, signs of lithium toxicity. Lithium toxicity may lead to renal damage. Frequent monitoring of serum lithium and serum creatinine levels is necessary. • Busulfan Metronidazole has been reported to increase plasma concentrations of busulfan, which can result in an increased risk for serious busulfan toxicity such as sinusoidal obstruction syndrome, gastrointestinal mucositis, and hepatic veno-occlusive disease. Metronidazole Injection should not be administered concomitantly with busulfan unless the benefit outweighs the risk. If no therapeutic alternatives to metronidazole are available, and concomitant administration with busulfan is medically needed, frequent monitoring of busulfan plasma concentration should be performed and the busulfan dose should be adjusted accordingly. • Drugs that Inhibit CYP450 Enzymes The simultaneous administration of drugs that decrease microsomal liver enzyme activity, such as cimetidine, may decrease metabolism and reduce plasma clearance of metronidazole which may result in metronidazole toxicity. • Drugs that Induce CYP450 Enzymes The simultaneous administration of drugs that induce microsomal liver enzyme activity, such as phenytoin or phenobarbital, may accelerate the elimination of metronidazole and therefore decrease its efficacy. • Cytochrome P450 3A4 (CYP3A4) substrates Concomitant use of Metronidazole Injection and CYP3A4 substrates (e.g., amiodarone, tacrolimus, cyclosporine, carbamazepine, phenytoin, and quinidine) may increase respective CYP3A4-substrate plasma levels. Monitoring of plasma concentrations of CYP3A4 substrates may be necessary. • 5-Fluorouracil Metronidazole Injection decreases the clearance of 5-fluorouracil and may therefore cause 5-fluorouracil toxicity. • Vecuronium Metronidazole Injection may potentiate the effects of vecuronium. • Drugs that Prolong the QT interval QT prolongation has been reported, particularly when metronidazole was administered with drugs with the potential for prolonging the QT interval. • Drug/Laboratory Test Interactions Metronidazole may interfere with certain types of determinations of serum chemistry values, such as aspartate aminotransferase (AST, SGOT), alanine aminotransferase (ALT, SGPT), lactate dehydrogenase (LDH), triglycerides and glucose hexokinase. Metronidazole causes an increase in ultraviolet absorbance at 340 nm resulting in falsely decreased values.

Mechanism of Action Metronidazole, a nitroimidazole, exerts antibacterial effects in an anaerobic environment against most obligate anaerobes. Once metronidazole enters the organism by passive diffusion and is activated in the cytoplasm of susceptible anaerobic bacteria, it is reduced; this process includes intra-cellular electron transport proteins such as ferredoxin, transfer of an electron to the nitro group of the metronidazole, and formation of a short-lived nitroso free radical. Because of this alteration of the metronidazole molecule, a concentration gradient is created and maintained which promotes the drug’s intracellular transport. The reduced form of metronidazole and free radicals can interact with DNA leading to inhibition of DNA synthesis and DNA degradation leading to death of bacteria. The precise mechanism of action of metronidazole is unclear.

DESCRIPTION Metronidazole Injection, USP is a sterile, parenteral dosage form of metronidazole in water. Each 100 mL of Metronidazole Injection, USP contains a sterile, nonpyrogenic, isotonic, buffered solution of Metronidazole, USP 500 mg, Sodium Chloride, USP 740 mg, Dibasic Sodium Phosphate Dihydrate, USP 75 mg and Citric Acid Anhydrous, USP 40 mg in Water for Injection, USP. Metronidazole Injection, USP has a calculated osmolality from 270 to 310 mOsmol/kg and a pH from 4.5 to 6.0. Sodium content: 13.5 mEq/container. Metronidazole is classified as a nitroimidazole antimicrobial and is administered by the intravenous route. Metronidazole, USP is chemically designated 2-methyl-5-nitroimidazole-1-ethanol (C 6 H 9 N 3 O 3 ): Not made with natural rubber latex. The flexible container is fabricated from a specially formulated non-plasticized, thermoplastic copolyolephine. The amount of water that can permeate from the container into the overwrap is insufficient to affect the solution significantly. Solutions in contact with the flexible container can leach out certain of the container's chemical components in very small amounts within the expiration period. The suitability of the container material has been confirmed by tests in animals according to USP biological tests for plastic containers. Structural Formula

OVERDOSAGE The use of dosages of metronidazole higher than those recommended has been reported. These include the use of 27 mg/kg three times a day for 20 days, and the use of 75 mg/kg as a single loading dose followed by 7.5 mg/kg maintenance doses. No adverse reactions were reported in either of the two cases. Single oral doses of metronidazole, up to 15 g, have been reported in suicide attempts and accidental overdoses. Symptoms reported include nausea, vomiting, and ataxia. Oral metronidazole has been studied as a radiation sensitizer in the treatment of malignant tumors. Neurotoxic effects, including seizures and peripheral neuropathy, have been reported after 5 to 7 days of doses of 6 to 10.4 g every other day. TREATMENT: There is no specific antidote for overdose; therefore, management of the patient should consist of symptomatic and supportive therapy.

HOW SUPPLIED Metronidazole Injection USP, 500 mg/100 mL (5 mg/mL) is a sterile clear, colorless to pale yellow color, nonpyrogenic, iso-osmotic, buffered solution supplied in 100 mL single-dose non-PVC plastic container. Each 100 mL contains 500 mg metronidazole, USP. It is available as follows: 500 mg/100 mL (5 mg/mL): 1 Single-dose Container in an Overwrap: NDC 80830-2465-1 Carton of 24: NDC 80830-2465-9 Store at 20° to 25°C (68° to 77° F); excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature] and protect from light during storage. Do not remove unit from overwrap until ready for use. The overwrap is a moisture barrier. The inner bag maintains the sterility of the product. After removing overwrap, check for minute leaks by squeezing inner bag firmly. If leaks are found, discard solution as sterility may be impaired. DIRECTIONS FOR USE OF PLASTIC CONTAINER Metronidazole injection is a ready-to-use iso-osmotic solution. No dilution or buffering is required. Do not refrigerate. Each container of metronidazole injection contains 14 mEq of sodium. Do not connect flexible plastic containers in series in order to avoid air embolism due to possible residual air contained in the primary container. Pressurizing intravenous solutions contained in flexible plastic containers to increase flow rates can result in air embolism if the residual air in the container is not fully evacuated prior to administration. Use of a vented intravenous administration set with the vent in the open position could result in air embolism. Vented intravenous administration sets with the vent in the open position should not be used with flexible plastic containers. Discard any unused portion. For single-dose only. To open Tear overwrap at notch and remove solution container. Visually inspect the container. If the twist-off port is damaged, detached, or not present, discard container as solution path sterility may be impaired. Some opacity of the plastic due to moisture absorption during the sterilization process may be observed. This is normal and does not affect the solution quality or safety. The opacity will diminish gradually. Check for leaks. Do not add supplementary medication . Preparation for Administration 1. Suspend container from eyelet support. 2. Remove twist-off port from bag. 3. Attach administration set. Refer to complete directions accompanying set. To report SUSPECTED ADVERSE REACTIONS, contact Amneal Pharmaceuticals LLC at 1-877-835-5472 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. Manufactured by: Amneal Pharmaceuticals Pvt. Ltd. Ahmedabad 382110, INDIA Distributed by: Amneal Pharmaceuticals LLC Bridgewater, NJ 08807 Rev. 07-2025-04