Microbiology

The bactericidal action of cefotetan results from inhibition of cell wall synthesis.  Cefotetan has in vitro activity against a wide range of aerobic and anaerobic gram-positive and gram-negative organisms.  The methoxy group in the 7-alpha position provides cefotetan with a high degree of stability in the presence of beta-lactamases including both penicillinases and cephalosporinase of gram-negative bacteria. 

Cefotetan has been shown to be active against most strains of the following organisms both in vitro and in clinical infections (see INDICATIONS AND USAGE).

Gram-Negative Aerobes

Escherichia coli

Haemophilus influenzae (including ampicillin-resistant strains)

Klebsiella species (including K. pneumoniae)

Morganella morganii

Neisseria gonorrhoeae (nonpenicillinase-producing strains)

Proteus mirabilis

Proteus vulgaris

Providencia rettgeri

Serratia marcescens

NOTE: Approximately one-half of the usually clinically significant strains of Enterobacter species (e.g., E. aerogenes and E. cloacae) are resistant to cefotetan.  Most strains of Pseudomonas aeruginosa and Acinetobacter species are resistant to cefotetan.

Gram-Positive Aerobes

Staphylococcus aureus (including penicillinase- and nonpenicillinase-producing strains)

Staphylococcus epidermidis

Streptococcus agalactiae (group B beta-hemolytic streptococcus)

Streptococcus pneumoniae

Streptococcus pyogenes

NOTE: Methicillin-resistant staphylococci are resistant to cephalosporins.  Some strains of Staphylococcus epidermidis and most strains of enterococci, e.g., Enterococcus faecalis (formerly Streptococcus faecalis) are resistant to cefotetan. 

Anaerobes

Prevotella bivia (formerly Bacteroides bivius)

Prevotella disiens (formerly Bacteroides disiens)

Bacteroides fragilis

Prevotella melaninogenica (formerly Bacteroides melaninogenicus)

Bacteroides vulgatus

Fusobacterium species

Gram-positive bacilli (including Clostridium species; see WARNINGS)

NOTE: Most strains of C. difficile are resistant (see WARNINGS).

Peptococcus niger

Peptostreptococcus species

NOTE: Many strains of B. distasonis, B. ovatus and B. thetaiotaomicron are resistant to cefotetan in vitro.  However, the therapeutic utility of cefotetan against these organisms cannot be accurately predicted on the basis of in vitro susceptibility tests alone.

The following in vitro data are available but their clinical significance is unknown.  Cefotetan has been shown to be active in vitro against most strains of the following organisms:

Gram-Negative Aerobes

Citrobacter species (including C. diversus and C. freundii)

Klebsiella oxytoca

Moraxella (Branhamella) catarrhalis

Neisseria gonorrhoeae (penicillinase-producing strains)

Salmonella species

Serratia species

Shigella species

Yersinia enterocolitica

Anaerobes

Porphyromonas asaccharolytica (formerly Bacteroides asaccharolyticus)

Prevotella oralis (formerly Bacteroides oralis)

Bacteroides splanchnicus

Clostridium difficile (see WARNINGS)

Propionibacterium species

Veillonella species

Susceptibility Tests

Dilution Techniques

Quantitative methods are used to determine antimicrobial minimal inhibitory concentrations (MICs).  These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds.  The MICs should be determined using a standardized procedure.  Standardized procedures are based on a dilution method1 (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of cefotetan powder.  The MIC values should be interpreted according to the following criteria:

A report of 'Susceptible' indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentrations usually achievable.  A report of 'Intermediate' indicates that the result should be considered equivocal, and if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated.  This category implies possible clinical applicability in body sites where the drug is physiologically concentrated or in situations where high dosage of drug can be used.  This category also provides a buffer zone which prevents small uncontrolled technical factors from causing major discrepancies in interpretation.  A report of 'Resistant' indicates that the pathogen is not likely to be inhibited if the antimicrobial compound in the blood reaches the concentrations usually achievable; other therapy should be selected.

Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures.  Standard cefotetan powder should provide the following MIC values:

Diffusion Techniques

Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds.  One such standardized procedure2 requires the use of the standardized inoculum concentrations.  This procedure uses paper disks impregnated with 30 mcg cefotetan to test the susceptibility of microorganisms to cefotetan.

Reports from the laboratory providing results of the standard single-disk susceptibility test with a 30 mcg cefotetan disk should be interpreted according to the following criteria:

Interpretation should be as stated above for results using dilution techniques. Interpretation involves correlation of the diameter obtained in the disk test with the MIC for cefotetan.

As with standardized dilution techniques, diffusion methods require the use of laboratory control microorganisms that are used to control the technical aspects of the laboratory procedures.  For the diffusion technique, the 30 mcg cefotetan disk should provide the following zone diameters in these laboratory test quality control strains.

Anaerobic Techniques

For anaerobic bacteria, the susceptibility to cefotetan as MIC's can be determined by standardized test methods3.  The MIC values obtained should be interpreted according to the following criteria:

Interpretation is identical to that stated above for results using dilution techniques.

As with other susceptibility techniques, the use of laboratory control microorganisms is required to control the technical aspects of the laboratory standardized procedures.  Standardized cefotetan powder should provide the following MIC values:

Cefotetan for injection is indicated for the therapeutic treatment of the following infections when caused by susceptible strains of the designated organisms:

Urinary Tract Infections caused by E. coli, Klebsiella spp (including K. pneumoniae), Proteus mirabilis and Proteus spp (which may include the organisms now called Proteus vulgaris, Providencia rettgeri, and Morganella morganii).

Lower Respiratory Tract Infections caused by Streptococcus pneumoniae, Staphylococcus aureus (penicillinase- and nonpenicillinase-producing strains), Haemophilus influenzae (including ampicillin-resistant strains), Klebsiella species (including K. pneumoniae), E. coli, Proteus mirabilis, and Serratia marcescens.*

Skin and Skin Structure Infections due to Staphylococcus aureus (penicillinase- and nonpenicillinase-producing strains), Staphylococcus epidermidis, Streptococcus pyogenes, Streptococcus species (excluding enterococci), Escherichia coli, Klebsiella pneumoniae, Peptococcus niger*, Peptostreptococcus species.

Gynecologic Infections caused by Staphylococcus aureus, (including penicillinase- and nonpenicillinase-producing strains), Staphylococcus epidermidis, Streptococcus species (excluding enterococci), Streptococcus agalactiae, E. coli, Proteus mirabilis, Neisseria gonorrhoeae, Bacteroides species (excluding B. distasonis, B. ovatus, B. thetaiotaomicron), Fusobacterium species*, and gram-positive anaerobic cocci (including Peptococcus niger and Peptostreptococcus species).

Cefotetan, like other cephalosporins, has no activity against Chlamydia trachomatis.  Therefore, when cephalosporins are used in the treatment of pelvic inflammatory disease, and C. trachomatis is one of the suspected pathogens, appropriate antichlamydial coverage should be added.

Intra-abdominal lnfections caused by E. coli, Klebsiella species (including K. pneumoniae), Streptococcus species (excluding enterococci), Bacteroides species (excluding B. distasonis, B. ovatus, B. thetaiotaomicron) and Clostridium species*.

Bone and Joint Infections caused by Staphylococcus aureus*.

Efficacy for this organism in this organ system was studied in fewer than ten infections.

Specimens for bacteriological examination should be obtained in order to isolate and identify causative organisms and to determine their susceptibilities to cefotetan.  Therapy may be instituted before results of susceptibility studies are known; however, once these results become available, the antibiotic treatment should be adjusted accordingly.

In cases of confirmed or suspected gram-positive or gram-negative sepsis or in patients with other serious infections in which the causative organism has not been identified, it is possible to use cefotetan concomitantly with an aminoglycoside.  Cefotetan combinations with aminoglycosides have been shown to be synergistic in vitro against many Enterobacteriaceae and also some other gram-negative bacteria.  The dosage recommended in the labeling of both antibiotics may be given and depends on the severity of the infection and the patient's condition.

NOTE: Increases in serum creatinine have occurred when cefotetan was given alone.  If cefotetan and an aminoglycoside are used concomitantly, renal function should be carefully monitored, because nephrotoxicity may be potentiated.

Prophylaxis

The preoperative administration of cefotetan may reduce the incidence of certain post- operative infections in patients undergoing surgical procedures that are classified as clean contaminated or potentially contaminated (e.g., cesarean section, abdominal or vaginal hysterectomy, transurethral surgery, biliary tract surgery, and gastrointestinal surgery).

If there are signs and symptoms of infection, specimens for culture should be obtained for identification of the causative organism so that appropriate therapeutic measures may be initiated.

CONTRAINDICATIONS

Prescribing cefotetan in the absence of proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

As with other broad-spectrum antibiotics, prolonged use of cefotetan may result in overgrowth of nonsusceptible organisms.  Careful observation of the patient is essential.  If superinfection does occur during therapy, appropriate measures should be taken.

Cefotetan should be used with caution in individuals with a history of gastrointestinal disease, particularly colitis.

Information for Patients

Diarrhea is a common problem caused by antibiotics which usually ends when the antibiotic is discontinued.  Sometimes after starting treatment with antibiotics, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibiotic.  If this occurs, patients should contact their physician as soon as possible.

Patients should be counseled that antibacterial drugs, including cefotetan, should only be used to treat bacterial infections.  They do not treat viral infections (e.g., the common cold).  When cefotetan 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 cefotetan or other antibacterial drugs in the future.

As with some other cephalosporins, a disulfiram-like reaction characterized by flushing, sweating, headache, and tachycardia may occur when alcohol (beer, wine, etc.) is ingested within 72 hours after cefotetan administration.  Patients should be cautioned about the ingestion of alcoholic beverages following the administration of cefotetan.

Drug Interactions

Increases in serum creatinine have occurred when cefotetan was given alone.  If cefotetan and an aminoglycoside are used concomitantly, renal function should be carefully monitored, because nephrotoxicity may be potentiated.

Drug/Laboratory Test Interactions

The administration of cefotetan may result in a false positive reaction for glucose in the urine using Clinitest®‡, Benedict's solution, or Fehling's solution.  It is recommended that glucose tests based on enzymatic glucose oxidase be used. 

As with other cephalosporins, high concentrations of cefotetan may interfere with measurement of serum and urine creatinine levels by Jaffé reaction and produce false increases in the levels of creatinine reported.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Although long-term studies in animals have not been performed to evaluate carcinogenic potential, no mutagenic potential of cefotetan was found in standard laboratory tests.

Cefotetan has adverse affects on the testes of prepubertal rats.  Subcutaneous administration of 500 mg/kg/day (approximately 8-16 times the usual adult human dose) on days 6 to 35 of life (thought to be developmentally analogous to late childhood and prepuberty in humans) resulted in reduced testicular weight and seminiferous tubule degeneration in 10 of 10 animals.  Affected cells included spermatogonia and spermatocytes; Sertoli and Leydig cells were unaffected.  Incidence and severity of lesions were dose-dependant; at 120 mg/kg/day (approximately 2 to 4 times the usual human dose) only 1 of 10 treated animals was affected, and the degree of degeneration was mild.

Similar lesions have been observed in experiments of comparable design with other methylthiotetrazole-containing antibiotics and impaired fertility has been reported, particularly at high dose levels.  No testicular effects were observed in 7-week-old rats treated with up to 1000 mg/kg/day SC for 5 weeks, or in infant dogs (3 weeks old) that received up to 300 mg/kg/day IV for 5 weeks.  The relevance of these findings to humans is unknown.

Pregnancy

Teratogenic Effects. Pregnancy Category B

Reproduction studies have been performed in rats and monkeys at doses up to 20 times the human dose and have revealed no evidence of impaired fertility or harm to the fetus due to cefotetan.  There are, however, no adequate and well-controlled studies in pregnant women.  Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

Nursing Mothers

Cefotetan is excreted in human milk in very low concentrations.  Caution should be exercised when cefotetan is administered to a nursing woman.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

Geriatric Use

Of the 925 subjects who received cefotetan in clinical studies, 492 (53%) were 60 years and older, while 76 (8%) were 80 years and older.  No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and the other reported clinical experience has not identified differences in responses between elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.

This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function.  Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function (see DOSAGE AND ADMINISTRATION, Impaired Renal Function).

ADVERSE REACTIONS

The usual adult dosage is 1 or 2 grams of Cefotetan for Injection administered intravenously or intramuscularly.  Proper dosage and route of administration should be determined by the condition of the patient, severity of the infection, and susceptibility of the causative organism.

aKlebsiella pneumoniae skin and skin structure infections should be treated with 1 or 2 grams every 12 hours IV or IM.

b Maximum daily dosage should not exceed 6 grams.

If Chlamydia trachomatis is a suspected pathogen in gynecologic infections, appropriate antichlamydial coverage should be added, since cefotetan has no activity against this organism.

Prophylaxis

To prevent postoperative infection in clean contaminated or potentially contaminated surgery in adults, the recommended dosage is 1 or 2 g of cefotetan for injection administered once, intravenously, 30 to 60 minutes prior to surgery.  In patients undergoing cesarean section, the dose should be administered as soon as the umbilical cord is clamped.

Impaired Renal Function

When renal function is impaired, a reduced dosage schedule must be employed.  The following dosage guidelines may be used.

Dose determined by the type and severity of infection, and susceptibility of the causative organism.

Alternatively, the dosing interval may remain constant at 12 hour intervals, but the dose reduced to one-half the usual recommended dose for patients with a creatinine clearance of 10 to 30 mL/min, and one-quarter the usual recommended dose for patients with a creatinine clearance of less than 10 mL/min.

When only serum creatinine levels are available, creatinine clearance may be calculated from the following formula.  The serum creatinine level should represent a steady state of renal function.

Males:          Weight (kg) x (140 - age)                        

                      72 x serum creatinine (mg/100 mL)

Females:   0.85 x value for males

Cefotetan is dialyzable and it is recommended that for patients undergoing intermittent hemodialysis, one-quarter of the usual recommended dose be given every 24 hours on days between dialysis and one-half the usual recommended dose on the day of dialysis.

Preparation of Solution

For Intravenous Use

Reconstitute with Sterile Water for Injection.  Shake to dissolve and let stand until clear.

For Intramuscular Use

Reconstitute with Sterile Water for Injection; Bacteriostatic Water for Injection; Sodium Chloride Injection 0.9%, USP; 0.5% Lidocaine HCl; or 1% Lidocaine HCl.  Shake to dissolve and let stand until clear.

The intravenous route is preferable for patients with bacteremia, bacterial septicemia, or other severe or life-threatening infections, or for patients who may be poor risks because of lowered resistance resulting from such debilitating conditions as malnutrition, trauma, surgery, diabetes, heart failure, or malignancy, particularly if shock is present or impending.

For intermittent intravenous administration, a solution containing 1 gram or 2 grams of cefotetan for injection in Sterile Water for Injection can be injected over a period of three to five minutes.  Using an infusion system, the solution may also be given over a longer period of time through the tubing system by which the patient may be receiving other intravenous solutions.  Butterfly® or scalp vein-type needles are preferred for this type of infusion.  However, during infusion of the solution containing cefotetan for injection, it is advisable to discontinue temporarily the administration of other solutions at the same site.

NOTE: Solutions of cefotetan must not be admixed with solutions containing aminoglycosides.  If cefotetan and aminoglycosides are to be administered to the same patient, they must be administered separately and not as a mixed injection.

Intramuscular Administration

As with all intramuscular preparations, cefotetan for injection should be injected well within the body of a relatively large muscle such as the upper outer quadrant of the buttock (i.e., gluteus maximus); aspiration is necessary to avoid inadvertent injection into a blood vessel.

Compatibility and Stability

Frozen samples should be thawed at room temperature before use.  After the periods mentioned below, any unused solutions or frozen material should be discarded.  DO NOT REFREEZE.

NOTE:  Solutions of cefotetan for injection must not be admixed-with solutions containing aminoglycosides.  If cefotetan for injection and aminoglycosides are to be administered to the same patient, they must be administered separately and not as a mixed injection.  DO NOT ADD SUPPLEMENTARY MEDICATION.

Cefotetan for injection reconstituted as described above (see DOSAGE AND ADMINISTRATION, Preparation of Solution) maintains satisfactory potency for 24 hours at room temperature (25ºC/77ºF), for 96 hours under refrigeration (5ºC/41ºF), and for at least 1 week in the frozen state (-20ºC/-4ºF).  After reconstitution and subsequent storage in disposable glass or plastic syringes, cefotetan for injection is stable for 24 hours at room temperature and 96 hours under refrigeration.

NOTE: Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration whenever solution and container permit.

HOW SUPPLIED