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CONTEPO (fosfomycin) for injection, for intravenous use, contains fosfomycin disodium, an epoxide antibacterial drug.
Fosfomycin disodium is a powder with the chemical name of disodium [(2R,3S)-3-methyloxiran-2-yl]-dioxidooxophosphorane, an empirical formula of C3H5Na2O4P and molecular weight of 182.
Figure 1 Chemical Structure of Fosfomycin Disodium
 |
Each CONTEPO for Injection single-dose vial contains white to almost white sterile powder with 6 grams of fosfomycin (equivalent to 7.9 grams fosfomycin disodium) and the inactive ingredient succinic acid (150 mg) for pH adjustment. It is intended for constitution and further dilution prior to intravenous infusion . Each gram of fosfomycin disodium contains 330 mg of sodium (i.e., each vial contains 1,980 mg of sodium).
The following adverse reactions are discussed in greater detail in the Warnings and Precautions section:
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.
CONTEPO was evaluated in a comparator-controlled clinical trial (Trial 1) in patients with cUTI, including acute pyelonephritis, which included 233 patients treated with CONTEPO and 231 treated with comparator (piperacillin/tazobactam 4.5 g every 8 hours) for 7 days, allowing bacteremic patients to receive up to 14 days. No switch to oral antibacterial drugs was allowed. The median age of treated patients was 54 years (range 18-89 years) and 64% were female. All patients were white (100%). Patients (99%) were predominantly enrolled in Eastern Europe. Concomitant bacteremia was identified in 9% of patients at baseline.
Serious adverse reactions occurred in 2.1% (5/233) CONTEPO and 2.6% (6/231) piperacillin/tazobactam-treated patients, respectively. Treatment was discontinued due to adverse reactions in 3% (7/233) of patients receiving CONTEPO and in 2.6% (7/231) of patients receiving piperacillin/tazobactam. The most common adverse reactions resulting in discontinuation of CONTEPO were gastrointestinal disorders (nausea, vomiting, and abdominal pain) in 1.3% (3/233) of patients. No deaths occurred in the clinical trial.
Table 3 lists adverse reactions occurring in 2% or greater of patients receiving CONTEPO in Trial 1. These adverse reactions were reversible upon completion of therapy.
Table 3 Adverse Reactions Occurring in 2% or Greater of Patients with cUTI Receiving CONTEPO in Trial 1
|
Adverse Reaction |
CONTEPO N=233 % |
Piperacillin/Tazobactam N=231 % |
|
Gastrointestinal Disorders |
||
|
Nausea |
4.3 |
1.3 |
|
Diarrhea |
3.9 |
4.8 |
|
Vomiting |
3.9 |
0.4 |
|
Laboratory Investigations |
||
|
Transaminase elevations a |
10.3 |
4.8 |
|
Hypokalemia |
9.9 |
1.7 |
|
Hypophosphatemia |
2.1 |
0.0 |
|
Hypocalcemia |
3.9 |
2.6 |
|
Hypernatremia |
3.4 |
0.9 |
|
Blood and Lymphatic System Disorders |
||
|
Neutropeniab |
6.4 |
3.9 |
|
Nervous System Disorders |
||
|
Headache |
2.6 |
2.2 |
| aTransaminase elevations include increased ALT and AST ≥3x ULN. bNeutropenia includes absolute neutrophil count <1500 cells/mm3 |
||
Blood and lymphatic system disorders: anemia, thrombocytopenia
Cardiac disorders: atrial fibrillation, palpitations, tachycardia, heart failure
Ear and labyrinth disorders: hearing loss
Gastrointestinal disorders: constipation
General disorders and administration site conditions: asthenia, infusion site reactions, peripheral edema
Hepatobiliary disorders: hepatic steatosis, hepatomegaly
Infections and infestations: vaginal infection, vaginitis
Investigations: increase creatinine kinase
Metabolism and nutritional disorders: hyperglycemia
Nervous system disorders: dysgeusia, syncope
Respiratory, thoracic, and mediastinal disorders: dyspnea
Skin and subcutaneous disorders: urticaria, rash, pruritis
The following additional adverse reactions were not reported with CONTEPO-treated patients in Trial 1 but have been identified with the use of oral fosfomycin tromethamine or during use of intravenous fosfomycin sodium outside of the United States for various indications and dosing regimens. 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:
Blood and lymphatic system disorders: aplastic anemia, eosinophilia, agranulocytosis, leukopenia, pancytopenia
Cardiac disorders: torsade de pointes
Ear and labyrinth disorders: vertigo
Eye disorders: visual impairment
Gastrointestinal disorders: dyspepsia, C. difficile-associated diarrhea and colitis, toxic megacolon
Hepatobiliary disorders: alkaline phosphatase increased, cholestatic hepatitis, icterus, hepatic necrosis
Immune system disorders: anaphylaxis
Metabolism and nutrition disorders: decreased appetite
Nervous system disorders: cerebral edema, dizziness, optic neuritis
Psychiatric disorders: confusion
Respiratory, thoracic, and mediastinal disorders: asthma attack, pulmonary edema
Skin and subcutaneous tissue disorders: angioedema, facial edema
Vascular disorders: hypertension
Co-administration of CONTEPO with other drugs known to prolong the QT interval may increase the risk for ventricular arrhythmia. Avoid co-administration of CONTEPO with drugs known to prolong the QT interval, such as class IA or class III antiarrhythmic medications, tricyclic antidepressants, macrolides, and antipsychotics [see Warnings and Precautions (5.2)].
Included as part of the PRECAUTIONS section.
CONTEPO contains 1,980 mg of sodium in each vial. The high sodium load associated with the use of CONTEPO may result in changes in serum electrolytes, such as increased levels of serum sodium and decreased levels of potassium, calcium, and phosphorous. Electrolyte disturbances, such as hypokalemia and hypocalcemia, may potentiate cardiac effects, including QT prolongation [see Warnings and Precautions (5.2) and Clinical Pharmacology (12.2)].
In Trial 1, a comparator-controlled clinical trial in patients with cUTI, hypokalemia, hypernatremia, hypophosphatemia, and hypocalcemia occurred more frequently in CONTEPO-treated patients compared with piperacillin/tazobactam-treated patients [see Adverse Reactions (6.1)]. Hypokalemia with serum potassium less than 3.0 mEq/L and/or requiring potassium supplementation occurred in 9.9% of patients receiving CONTEPO and 1.7% of patients receiving piperacillin/tazobactam. Hypophosphatemia with serum phosphate concentrations less than 1.0 mg/dL occurred in 2.1% of patients receiving CONTEPO and none of the patients receiving piperacillin/tazobactam. Hypernatremia with serum sodium greater than 150 mEq/L occurred in 3.4% of patients receiving CONTEPO and 0.9% of patients receiving piperacillin/tazobactam. Hypocalcemia with corrected serum calcium less than 8.0 mg/dL occurred in 3.9% of patients receiving CONTEPO and 2.6% of patients receiving piperacillin/tazobactam.
A low-sodium diet is recommended during CONTEPO treatment. Minimize administration of drugs containing sodium. Monitor serum electrolyte levels (sodium, potassium, calcium, magnesium, and phosphorus) and fluid status during treatment with CONTEPO. Electrolyte supplementation may be necessary in some cases. Monitor for signs of edema, particularly in patients who should restrict their sodium intake or are prone to fluid overload (e.g., cardiac insufficiency, renal impairment, cirrhosis, hypertension, hyperaldosteronism, hypernatremia or pulmonary edema) [see Adverse Reactions (6.1)].
CONTEPO has been shown to prolong the QT interval in some patients. QT prolongation can lead to development of torsade de pointes-type ventricular tachycardia with the risk increasing as the degree of prolongation increases. In Trial 1, 3.6% of patients treated with CONTEPO had > 60 msec increase in QTcF interval from baseline and 1% of patients had QTcF > 480 msec. Torsade de pointes has been reported during postmarketing experience with fosfomycin [see Adverse Reactions (6.2)]. The risk of QT prolongation may increase in patients with electrolyte abnormalities (such as hypokalemia and hypocalcemia), patients with conditions that have potential to cause electrolyte imbalance (such as renal impairment), or patients taking other drugs affecting electrolyte balance or QT prolongation. Avoid CONTEPO in patients with known QT prolongation or ventricular arrhythmias, including a history of torsade de pointes. Monitor electrolytes during treatment with CONTEPO [see Warnings and Precautions (5.1), Drug Interactions (7.1) and Clinical Pharmacology (12.2)].
In Trial 1, increases in transaminases occurred more frequently in CONTEPO-treated patients compared to piperacillin/tazobactam-treated patients. Transaminases (Alanine Aminotransferase (ALT) or Aspartate Aminotransferase (AST) were elevated > 3x upper limit of normal (ULN) in 10.3% of patients receiving CONTEPO and 4.8% of patients receiving piperacillin/tazobactam. Transaminase elevations were asymptomatic and reversible. No concurrent increases in serum bilirubin or alkaline phosphatase were observed. No patients met Hy’s Law criteria, and no patients discontinued CONTEPO therapy because of treatment-related transaminase elevation [see Adverse Reactions (6.1)]. Monitor hepatic enzymes during CONTEPO treatment.
CONTEPO is contraindicated in patients with known serious hypersensitivity to fosfomycin, or any of the excipients [see Contraindications (4)]. Hypersensitivity reactions, such as rash and urticaria, were reported in patients treated with CONTEPO in Trial 1. Anaphylaxis has been reported postmarketing [see Adverse Reactions (6.2)]. Before initiating therapy with CONTEPO, it is important to inquire about previous hypersensitivity reactions to oral or parenteral fosfomycin. If an allergic reaction to CONTEPO occurs, discontinue the drug immediately.
Neutropenia has been reported in patients receiving IV fosfomycin therapy. In Trial 1, 6.4% of patients in the CONTEPO arm developed neutropenia (absolute neutrophil count less than 1500 cells/mm3) as compared to 3.9% in the piperacillin/tazobactam comparator arm. In the post marketing setting, neutropenia cases progressing to agranulocytosis have been reported with IV fosfomycin therapy. Monitor complete blood counts during CONTEPO therapy particularly in patients with pre-existing conditions or patients receiving concomitant drugs that may predispose to bone marrow suppression. Discontinue CONTEPO if neutropenia occurs and consider alternative therapies.
Clostridioides difficile-associated diarrhea (CDAD) has been reported with use of nearly all systemic antibacterial agents, including CONTEPO, and may range in severity from mild to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon and may permit overgrowth of C. difficile.
C. difficile produces toxins A and B which contribute to the development of CDAD. CDAD must be considered in all patients who present with diarrhea following antibacterial use. Careful medical history is necessary because CDAD has been reported to occur more than 2 months after administration of antibacterial agents.
If CDAD is confirmed, discontinue antibacterials not directed against C. difficile, if possible. Manage fluid and electrolyte levels as appropriate, supplement protein intake, monitor antibacterial treatment of C. difficile, and institute surgical evaluation as clinically indicated.
Prescribing CONTEPO in the absence of a proven or strongly suspected bacterial infection indication is unlikely to provide benefit to the patient and increases the risk of the development of drug resistant bacteria [see Indications and Usage (1.2)].
Long-term carcinogenicity studies have not been conducted with fosfomycin.
Fosfomycin did not show evidence of mutagenic activity in standard tests that included bacterial reverse mutation assay, chromosomal aberration assay with Chinese hamster lung fibroblast cells and human peripheral blood lymphocytes, and the mouse bone marrow micronucleus assay.
In a fertility study, male and female rats were dosed intraperitoneally with fosfomycin disodium (for 7 or 14 days, respectively, before mating, for 14 days during cohabitation, and in mated females up to gestation day 7 at doses of 125, 250, 750 or 1500 mg/kg. Maternal toxicity (mortality) was observed at the 1500 mg/kg dose (about 0.8 times the clinical dose based on body surface area comparisons) along with increases in the number of dead or resorbed fetuses and a reduction in the number of live fetuses. There were no effects on fertility at 750 mg/kg (approximately 0.4 times the clinical dose).
To date, no cases of accidental overdose with clinically relevant intolerances have been reported. In the event of an overdose, the patient must be monitored and treated symptomatically. Fosfomycin is cleared from the body by hemodialysis, during which patients with end stage renal disease have an increased mean fosfomycin elimination half-life to approximately 4 hours.
CONTEPO is contraindicated in patients with known serious hypersensitivity to fosfomycin, or any of the excipients [see Warnings and Precautions (5.2)].
CONTEPO is an antibacterial drug [see Microbiology (12.4)].
The ratio of the unbound plasma fosfomycin AUC to MIC against the infecting organism has been shown to correlate with activity in animal models of infection.
The effect of CONTEPO on 12-lead electrocardiogram parameters was evaluated in a Phase 1 randomized, placebo and positive controlled, double-blind, single-dose crossover study in 36 healthy adult subjects. At single doses of 6 grams and 12 grams (2 times the maximum single recommended dosage), CONTEPO demonstrated a dose dependent increase in QTcF. Mean placebo-corrected QTcF change from baseline was 8.3 msec (90% CI: 5.39 to 11.30) and 17.0 msec (90% CI: 14.06 to 20.01) for single doses of 6 grams and 12 grams, respectively, compared to 13.4 msec (90% CI: 10.48 to 16.39) observed with the active control, oral moxifloxacin. There were no subjects receiving CONTEPO with QTcF change from baseline greater than 60 msec or a QTcF greater than 480 msec [see Warnings and Precautions (5.2)]. A 1-hour CONTEPO infusion of the studied doses did not have a clinically meaningful effect on heart rate or on cardiac conduction, i.e., the PR and QRS interval.
The mean pharmacokinetic parameters of fosfomycin in healthy adults with normal renal function after single doses of 6 grams administered as 1-hour IV infusion are summarized along with additional pharmacokinetic information in Table 4.
Table 4 Exposure Parameter Estimates (Mean ± SD)a Following Single Dose of 6 grams Fosfomycin Administered as 1-hour IV Infusion in Healthy Adults with Normal Renal Function
|
Cmax (mcg/mL) |
228 ± 43 |
|
AUC0-inf (mcg·hr/mL) |
734 ± 134 |
|
Dose Proportionality |
Fosfomycin Cmax and AUC0-inf increase proportionally with dose |
|
Distribution |
|
|
Volume of Distribution (L) |
27 ± 5.2 |
|
Protein Binding |
Fosfomycin is not bound to plasma proteins |
|
Elimination |
|
|
Half-Life (h) |
2.8 ± 0.6 |
|
Total Clearance (L/h) |
8.5 ± 1.7 |
|
Metabolism |
Fosfomycin is not metabolized. |
|
Excretion |
Urine: 70% of dose is excreted unchanged at 12 hours; 74-80% of dose is excreted unchanged at 48 hours |
| a Based on non-compartmental analysis of PK data | |
No clinically significant differences in the pharmacokinetics of fosfomycin based on sex, body weight/body surface area, race/ethnicity or age (18 to 89 years of age, when adjusted for renal function) were identified.
Patients with Renal Impairment
Dosage adjustment is required for patients whose creatinine clearance is 50 mL/min or less [see Dosage and Administration (2.2), Use in Specific Populations (8.6)]. When fosfomycin is administered prior to hemodialysis in patients on periodic or chronic hemodialysis, 61-79% of the fosfomycin dose is removed.
Patients with Hepatic Impairment
CONTEPO is not metabolized through the liver. The effect of hepatic impairment on the pharmacokinetics of CONTEPO is unknown. Monitoring fluid overload and electrolyte abnormalities is recommended for patients with severe hepatic impairment [see Warnings and Precautions (5.1), Use in Specific Populations (8.7)].
In Vitro Studies
Fosfomycin at clinically relevant concentrations does not inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5. Fosfomycin does not induce CYP1A2, CYP2B6, and CYP3A4. Fosfomycin is not a substrate for P-gp, BCRP, OATP1B1, OATP1B3, OAT1, OAT3, OCT2, MATE1 or MATE2-K. Fosfomycin inhibits MATE1 and MATE2-K with the observed IC50 values of 30.0 mM (4142 mcg/mL) and 56.4 mM (7787 mcg/mL), respectively. Fosfomycin does not inhibit P-gp, BCRP, OATP1B1, OATP1B3, OAT1, OAT3, OCT1, and OCT2.
Fosfomycin is an epoxide antibacterial drug that disrupts bacterial cell wall synthesis by covalently binding and inhibiting phosphoenolpyruvate transferase (MurA), thereby blocking the synthesis of peptidoglycan. Fosfomycin is bactericidal against Enterobacterales. Transport of fosfomycin into the bacterial cell occurs via two different transport systems, glycerol-3-phosphate (GlpT) and/or hexose-6-phosphate (UhpT).
Resistance to fosfomycin may occur by chromosomal mutations leading to alterations of bacterial transport systems and/or modification of the fosfomycin binding site in MurA (Cys115). Spontaneous mutations conferring various levels of fosfomycin resistance in E. coli and other Enterobacterales in vitro have been shown to occur in the structural transport genes (glpT and uhpT), transport regulatory genes (uhpA, uhpB, and uhpC) and genes involved in cAMP synthesis (cyaA, ptsI), all causing a decrease in fosfomycin uptake. Diminished activity of both transport systems is also evident when inactivation of cAMP-CRP occurs.
Plasmid-borne resistance mechanisms may result in enzymatic inactivation of fosfomycin by binding to glutathione, or by cleavage of the carbon-phosphorus-bond in the fosfomycin molecule. The enzymes responsible for this type of resistance are fosfomycin hydrolyzing enzymes (FosA, FosB, FosX) and fosfomycin kinases (FomA, FomB and FosC).
Resistance to fosfomycin due to spontaneous mutations occurs at frequencies between 10-7 to 10-9 for E. coli and 10-5 to 10-8 for K. pneumoniae at 4 times the fosfomycin Minimum Inhibitory Concentration (MIC).
There is no known cross-resistance to other antibacterial drug classes.
In vitro studies have not demonstrated antagonism between CONTEPO and the following antibacterial drugs: amikacin, gentamicin, aztreonam, ceftazidime, ceftriaxone, piperacillin/tazobactam, meropenem, levofloxacin, tigecycline, minocycline, linezolid, rifampin, trimethoprim-sulfamethoxazole, vancomycin, penicillin and colistin. The clinical significance of these findings is unknown.
Fosfomycin demonstrated activity in neutropenic thigh infection models caused by either E. coli (KPC and NDM producing) or K. pneumoniae (KPC and VIM producing) isolates.
CONTEPO has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections [see Indications and Usage (1.1)].
Aerobic bacteria
Gram-negative bacteria
Escherichia coli
Klebsiella pneumoniae
The following in vitro data are available, but their clinical significance is unknown. At least 90 percent of the following bacteria exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for CONTEPO against isolates of similar genus or organism group. However, the efficacy of CONTEPO in treating clinical infections caused by these bacteria has not been established in adequate and well-controlled clinical trials.
Aerobic bacteria
Gram-negative bacteria Citrobacter koseri
Enterobacter aerogenes
Klebsiella oxytoca
Proteus mirabilis
Serratia marcescens
For specific information regarding susceptibility test interpretive criteria, and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.
Advise patients that a low sodium diet is recommended during CONTEPO treatment because the high sodium load (each vial of CONTEPO contains 1,980 mg sodium) may cause changes in electrolytes or increased edema [see Warnings and Precautions (5.1)]. Blood tests to monitor electrolytes will be required. If peripheral edema develops, tell the patient to contact their health care provider.
Advise patients that allergic reactions, including serious allergic reactions, could occur and that serious reactions require immediate treatment. Ask patient about any previous hypersensitivity reactions to CONTEPO, fosfomycin or other allergens [see Warnings and Precautions (5.2)].
Advise patients that diarrhea is a common problem caused by antibacterial drugs, including CONTEPO. Sometimes, frequent watery or bloody diarrhea may occur and may be a sign of a more serious intestinal infection. If severe watery or bloody diarrhea develops, tell patient to contact his or her healthcare provider [see Warnings and Precautions (5.6)].
Patients should be counseled that antibacterial drugs including CONTEPO should only be used to treat bacterial infections. They do not treat viral infections (e.g. the common cold). When CONTEPO is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by CONTEPO or other antibacterial drugs in the future [see Warnings and Precautions (5.7)].
Advise females not to breastfeed during treatment with CONTEPO and for 24 hours after the final dose [see Use in Specific Populations (8.2)].
