Mefoxin Actions

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Actions of Mefoxin in details

The action of the drug on the human body is called Pharmacodynamics in Medical terminology. To produce its effect and to change the pathological process that is happening the body and to reduce the symptom or cure the disease, the medicine has to function in a specific way. The changes it does to the body at cellular level gives the desired result of treating a disease. Drugs act by stimulating or inhibiting a receptor or an enzyme or a protein most of the times. Medications are produced in such a way that the ingredients target the specific site and bring about chemical changes in the body that can stop or reverse the chemical reaction which is causing the disease.
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Pharmacology: Clinical

Pharmacology: Following an IV dose of 1 g, serum concentrations were 110 mcg/mL at 5 min, declining to <1 mcg/mL at 4 hrs. The t½ after an IV dose is 41-59 min. Approximately 85% of Mefoxin is excreted unchanged by the kidneys over a 6-hr period, resulting in high urinary concentrations. Probenecid slows tubular excretion and produces higher serum levels and increases the duration of measurable serum concentrations.

Mefoxin passes into pleural and joint fluids and is detectable in antibacterial concentrations in bile.

In a published study of geriatric patients ranging in age from 64-88 years with normal renal function for their age (creatinine clearance ranging from 31.5-174 mL/min), the t½ for Mefoxin ranged from 51-90 min, resulting in higher plasma concentrations than in younger adults. These changes were attributed to decreased renal function associated with the aging process.

Microbiology: The bactericidal action of Mefoxin results from inhibition of cell wall synthesis. Mefoxin has in vitro activity against a wide range of gram-positive and gram-negative organisms. The methoxy group in the 7α position provides Mefoxin with a high degree of stability in the presence of β-lactamases, both penicillinases and cephalosporinases, of gram-negative bacteria.

Mefoxin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in Indications.

Aerobic Gram-positive Microorganisms: Staphylococcus aureusa (including penicillinase-producing strains), Staphylococcus epidermidisa, Streptococcus agalactiae, Streptococcus pneumoniae, Streptococcus pyogenes.

aStaphylococci resistant to methicillin/oxacillin should be considered resistant to Mefoxin.

Most strains of enterococci eg, Enterococcus faecalis are resistant.

Aerobic Gram-negative Microorganisms: Escherichia coli, Haemophilus influenzae, Klebsiella spp (including K. pneumoniae), Morganella morganii, Neisseria gonorrhoeae (including penicillinase-producing strains), Proteus mirabilis, Proteus vulgaris, Providencia spp (including Providencia rettgeri).

Anaerobic Gram-positive Microorganisms: Clostridium spp, Peptococcus niger, Peptostreptococcus spp.

Anaerobic Gram-negative Microorganisms: Bacteroides distasonis, Bacteroides fragilis, Bacteroides ovatus, Bacteroides thetaiotaomicron, Bacteroides spp.

The following in vitro data are available, but their clinical significance is unknown.

Mefoxin exhibits in vitro minimum inhibitory concentrations (MICs) of ≤8 mcg/mL for aerobic microorganisms and ≤16 mcg/mL for anaerobic microorganisms against most (≥90%) strains of the following microorganisms; however, the safety and effectiveness of Mefoxin in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled clinical trials.

Aerobic Gram-negative Microorganisms: Eikenella corrodens (non-β-lactamase producers), Klebsiella oxytoca.

Anaerobic Gram-positive Microorganisms: Clostridium perfringens.

Anaerobic Gram-negative Microorganisms: Prevotella bivia (formerly Bacteroides bivius).

Mefoxin is inactive in vitro against most strains of Pseudomonas aeruginosa and enterococci and many strains of Enterobacter cloacae.

Susceptibility Testing: Dilution Techniques: Quantitative methods are used to determine antimicrobial 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 method (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of Mefoxin powder. The MIC values should be interpreted according to the following criteria:

For testing aerobic microorganismsa,b,c other than Neisseria gonorrhoeae :

aStaphylococci exhibiting resistance to methicillin/oxacillin should be reported as also resistant to Mefoxin despite apparent in vitro susceptibility.

bFor testing Haemophilus influenzae, these interpretative criteria applicable only to tests performed by broth microdilution method using Haemophilus Test Medium (HTM).

cFor testing streptococci, these interpretative criteria applicable only to tests performed by broth microdilution method using cation-adjusted Mueller-Hinton broth with 2-5% lysed horse blood.

For testing Neisseria gonorrhoeaed :

dInterpretative criteria applicable only to tests performed by agar dilution method using GC agar base with 1% defined growth supplement and incubated in 5% CO2. 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 Mefoxin 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 procedure requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with Mefoxin 30 mcg to test the susceptibility of microorganisms to Mefoxin.

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

For testing aerobic microorganismsa,b,c other than Neisseria gonorrhoeae :

aStaphylococci exhibiting resistance to methicillin/oxacillin should be reported as also resistant to Mefoxin despite apparent in vitro susceptibility.

bFor testing Haemophilus influenzae, these interpretative criteria applicable only to tests performed by disk diffusion method using HTM.

cFor testing streptococci, these interpretative criteria applicable only to tests performed by disk diffusion method using Mueller-Hinton agar with 5% defibrinated sheep blood and incubated in 5% CO2.

For testing Neisseria gonorrhoeaed :

dInterpretative criteria applicable only to tests performed by disk diffusion method using GC agar base with 1% defined growth supplement and incubated in 5% CO2.

Interpretation should be as stated previously for results using Dilution Techniques.

Interpretation involves correlation of the diameter obtained in the disk test with the MIC for Mefoxin.

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 Mefoxin disk should provide the following zone diameters in these laboratory test quality control strains :

Anaerobic Techniques: For anaerobic bacteria, the susceptibility to Mefoxin as MICs can be determined by standardized test methods. The MIC values obtained should be interpreted according to the following criteria :

Interpretation is identical to that stated previously 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. Standard Mefoxin powder should provide the following MIC values:

Using either an Agar Dilution Methoda or Using a Brothb Microdilution Method :

aRange applicable only to tests performed using either Brucella blood or Wilkins-Chalgren agar.

bRange applicable only to tests performed in the broth formulation of Wilkins-Chalgren agar.

Clinical Studies: A prospective, randomized, double-blind, placebo-controlled clinical trial was conducted to determine the efficacy of short-term prophylaxis with Mefoxin in patients undergoing cesarean section who were at high risk for subsequent endometritis because of ruptured membranes. Patients were randomized to receive either 3 doses of placebo (n=58), a single dose of Mefoxin (2 g) followed by 2 doses of placebo (n=64), or a 3-dose regimen of Mefoxin (each dose consisting of 2 g) (n=60), given IV, usually beginning at the time of clamping of the umbilical cord, with the 2nd and 3rd doses given 4 hrs and 8 hrs postoperatively. Endometritis occurred in 16/58 (27.6%) patients given placebo, 5/63 (7.9%) patients given a single dose of Mefoxin and 3/58 (5.2%) patients given 3 doses of Mefoxin. The differences between the 2 groups treated with Mefoxin and placebo with respect to endometritis were statistically significant (p<0.01) in favor of Mefoxin. The differences between the 1- and 3-dose regimens of Mefoxin were not statistically significant.

Two double-blind, randomized studies compared the efficacy of a single 2 g IV dose of Mefoxin to a single 2 g IV dose of cefotetan in the prevention of surgical site-related infection (major morbidity) and non-site related infections (minor morbidity) in patients following cesarean section. In the 1st study, 82/98 (83.7%) patients treated with Mefoxin and 71/95 (74.7%) patients treated with cefotetan experienced no major or minor morbidity. The difference in the outcomes in this study (95% CI: -0.03, +0.21) was not statistically significant. In the 2nd study, 65/75 (86.7%) patients treated with Mefoxin and 62/76 (81.6%) patients treated with cefotetan experienced no major or minor morbidity. The difference in the outcomes in this study (95% CI: -0.08, +0.18) was not statistically significant.

In clinical trials of patients with intra-abdominal infections due to Bacteroides fragilis group microorganisms, eradication rates at 1-2 weeks posttreatment for isolates were in the range of 70-80%. Eradication rates for individual species are listed as follows: Bacteroides distasonis 7/10 (70%), Bacteroides fragilis 26/33 (79%), Bacteroides ovatus 10/13 (77%), B. thetaiotaomicron 13/18 (72%).

How should I take Mefoxin?

Mefoxin is given as an injection through a needle placed into a vein. Your doctor, nurse, or other healthcare provider will give you this injection. You may be given instructions on how to inject your medicine at home. Do not use this medicine at home if you do not fully understand how to give the injection and properly dispose of needles and other items used in giving the medicine.

Use the medication exactly as it was prescribed for you. Do not use the medication in larger amounts, or use it for longer than recommended by your doctor. Follow the instructions on your prescription label.

Use this medication for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated. Mefoxin will not treat a viral infection such as the common cold or flu.

This medication can cause you to have unusual results with certain lab tests, including tests to check for glucose (sugar) in the urine. Tell any doctor who treats you that you are using Mefoxin.

To be sure this medication is helping your condition, your blood may need to be tested on a regular basis. Your kidney or liver function may also need to be tested. Do not miss any scheduled visits to your doctor.

If you keep this medicine at home, store it in a deep freezer at a temperature of 4 degrees below 0.

To use the medicine, thaw it in a refrigerator or at room temperature. Do not warm in a microwave or boiling water. Keep thawed medicine in the refrigerator and use it within 28 days after thawing it. Do not refreeze.

Do not use the medication if it looks cloudy or has any particles in it. Call your doctor for a new prescription.

Mefoxin administration

Administration of drug is important to know because the drug absorption and action varies depending on the route and time of administration of the drug. A medicine is prescribed before meals or after meals or along with meals. The specific timing of the drug intake about food is to increase its absorption and thus its efficacy. Few work well when taken in empty stomach and few medications need to be taken 1 or 2 hrs after the meal. A drug can be in the form of a tablet, a capsule which is the oral route of administration and the same can be in IV form which is used in specific cases. Other forms of drug administration can be a suppository in anal route or an inhalation route.
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Mefoxin is given as an injection through a needle placed into a vein. Your doctor, nurse, or other healthcare provider will give you this injection. You may be given instructions on how to inject your medicine at home. Do not use this medicine at home if you do not fully understand how to give the injection and properly dispose of needles and other items used in giving the medicine.

Use the medication exactly as it was prescribed for you. Do not use the medication in larger amounts, or use it for longer than recommended by your doctor. Follow the instructions on your prescription label.

Use this medication for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated. Mefoxin will not treat a viral infection such as the common cold or flu.

This medication can cause you to have unusual results with certain lab tests, including tests to check for glucose (sugar) in the urine. Tell any doctor who treats you that you are using Mefoxin.

To be sure this medication is helping your condition, your blood may need to be tested on a regular basis. Your kidney or liver function may also need to be tested. Do not miss any scheduled visits to your doctor.

If you keep this medicine at home, store it in a deep freezer at a temperature of 4 degrees below 0.

To use the medicine, thaw it in a refrigerator or at room temperature. Do not warm in a microwave or boiling water. Keep thawed medicine in the refrigerator and use it within 28 days after thawing it. Do not refreeze.

Do not use the medication if it looks cloudy or has any particles in it. Call your doctor for a new prescription.

Mefoxin pharmacology

Pharmacokinetics of a drug can be defined as what body does to the drug after it is taken. The therapeutic result of the medicine depends upon the Pharmacokinetics of the drug. It deals with the time taken for the drug to be absorbed, metabolized, the process and chemical reactions involved in metabolism and about the excretion of the drug. All these factors are essential to deciding on the efficacy of the drug. Based on these pharmacokinetic principles, the ingredients, the Pharmaceutical company decides dose and route of administration. The concentration of the drug at the site of action which is proportional to therapeutic result inside the body depends on various pharmacokinetic reactions that occur in the body.
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Following an intravenous dose of 1 gram, serum concentrations were 110 mcg/mL at 5 minutes, declining to less than 1 mcg/mL at 4 hours. The half-life after an intravenous dose is 41 to 59 minutes. Approximately 85 percent of Mefoxin is excreted unchanged by the kidneys over a 6-hour period, resulting in high urinary concentrations. Probenecid slows tubular excretion and produces higher serum levels and increases the duration of measurable serum concentrations.

Mefoxin passes into pleural and joint fluids and is detectable in antibacterial concentrations in bile. In a published study of geriatric patients ranging in age from 64 to 88 years with normal renal function for their age (creatinine clearance ranging from 31.5 to 174.0 mL/min), the half-life for Mefoxin ranged from 51 to 90 minutes, resulting in higher plasma concentrations than in younger adults. These changes were attributed to decreased renal function associated with the aging process.

Microbiology

Mechanism of Action

Mefoxin is a bactericidal agent that acts by inhibition of bacterial cell wall synthesis. Mefoxin has activity in the presence of some beta-lactamases, both penicillinases and cephalosporinases, of Gram-negative and Gram-positive bacteria.

Mechanism of Resistance

Resistance to Mefoxin is primarily through hydrolysis by beta-lactamase, alteration of penicillin-binding proteins (PBPs), and decreased permeability.

Mefoxin has been shown to be active against most isolates of the following bacteria, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section:

Gram-positive bacteria

Staphylococcus aureus (methicillin-susceptible isolates only)

Staphylococcus epidermidis (methicillin-susceptible isolates only)

Streptococcus agalactiae

Streptococcus pneumoniae

Streptococcus pyogenes

Gram-negative bacteria

Escherichia coli

Haemophilus influenzae

Klebsiella spp.

Morganella morganii

Neisseria gonorrhoeae

Proteus mirabilis

Proteus vulgaris

Providencia spp.

Anaerobic bacteria

Clostridium spp.

Peptococcus niger

Peptostreptococcus spp.

Bacteroides spp.

The following in vitro data are available, but their clinical significance is unknown. At least 90 percent of the following microorganisms exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for Mefoxin. However, the efficacy of Mefoxin in treating clinical infections due to these microorganisms has not been established in adequate and well-controlled clinical trials.

Gram-negative bacteria

Eikenella corrodens (non-β-lactamase producers)

Anaerobic bacteria

Clostridium perfringens

Prevotella bivia

Susceptibility Test Methods

When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antimicrobial drug products used in resident hospitals to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting an antibacterial drug product for treatment.

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 test method. Standard Mefoxin powder should provide the following range of MIC values noted in Table 2. For the diffusion technique using the 30 mcg disk, the criteria in Table 7 should be achieved.

Table 2: Acceptable Quality Control Ranges for Mefoxin

QC Strain Minimum Inhibitory Concentrations (mcg/mL) Disk Diffusion Zone Diameters (mm)
Escherichia coli ATCC 25922 2 - 8 23 - 29
Neisseria gonorrhoeae ATCC 49226 0.5 - 2 33 - 41
Staphylococcus aureus ATCC 25923 - 23 - 29
Staphylococcus aureus ATCC 29213 1 - 4 -
Bacteroides fragilis ATCC 25285 (Agar method) 4 - 6 -
Bacteroides fragilis ATCC 25285 (Broth method) 2 - 8 -
Bacteroides thetaiotaomicron ATCC 29741 (Agar method) 8 - 32 -
Bacteroides thetaiotaomicron ATCC 29741 (Broth method) 8 - 64 -
Eubacterium lentum ATCC 43055 (Agar method) 4 - 16 -
Eubacterium lentum ATCC 43055 (Broth method) 2 - 16 -

Clinical Studies

A prospective, randomized, double-blind, placebo-controlled clinical trial was conducted to determine the efficacy of short-term prophylaxis with MEFOXIN in patients undergoing cesarean section who were at high risk for subsequent endometritis because of ruptured membranes. Patients were randomized to receive either three doses of placebo (n=58), a single dose of MEFOXIN (2 g) followed by two doses of placebo (n=64), or a three-dose regimen of MEFOXIN (each dose consisting of 2 g) (n=60), given intravenously, usually beginning at the time of clamping of the umbilical cord, with the second and third doses given 4 and 8 hours post-operatively. Endometritis occurred in 16/58 (27.6%) patients given placebo, 5/63 (7.9%) patients given a single dose of MEFOXIN, and 3/58 (5.2%) patients given three doses of MEFOXIN. The differences between the two groups treated with MEFOXIN and placebo with respect to endometritis were statistically significant (p < 0.01) in favor of MEFOXIN. The differences between the one-dose and three-dose regimens of MEFOXIN were not statistically significant.

Two double-blind, randomized studies compared the efficacy of a single 2 gram intravenous dose of MEFOXIN to a single 2 gram intravenous dose of cefotetan in the prevention of surgical site-related infection (major morbidity) and non-site-related infections (minor morbidity) in patients following cesarean section. In the first study, 82/98 (83.7%) patients treated with MEFOXIN and 71/95 (74.7%) patients treated with cefotetan experienced no major or minor morbidity. The difference in the outcomes in this study (95% CI: –0.03, +0.21) was not statistically significant. In the second study, 65/75 (86.7%) patients treated with MEFOXIN and 62/76 (81.6%) patients treated with cefotetan experienced no major or minor morbidity. The difference in the outcomes in this study (95% CI: –0.08, +0.18) was not statistically significant.

In clinical trials of patients with intra-abdominal infections due to Bacteroides fragilis group microorganisms, eradication rates at 1 to 2 weeks posttreatment for isolates were in the range of 70% to 80%. Eradication rates for individual species are listed below:

Bacteroides distasonis 7/10 (70%)
Bacteroides fragilis 26/33 (79%)
Bacteroides ovatus 10/13 (77%)
B. thetaiotaomicron 13/18 (72%)

REFERENCES

1. Clinical and Laboratory Standards Institute (CLSI). Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically; Approved Standard - Ninth Edition, CLSI Document M07A9, Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2012.

2. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing; Twenty-third Informational Supplement, CLSI document M100-S23, Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2013.

3. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Disk Diffusion Susceptibility Tests; Approved Standard - Eleventh Edition, CLSI Document M02-A11, Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2012.

4. Clinical and Laboratory Standards Institute (CLSI). Methods for Anitmicrobial Susceptibility Testing of Anaerobic Bacteria; Approved Standard - Eight Edition, CLSI document M11-A8. Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2012.



References

  1. NCIt. "Cefuroxime: NCI Thesaurus (NCIt) provides reference terminology for many systems. It covers vocabulary for clinical care, translational and basic research, and public information and administrative activities.". https://ncit.nci.nih.gov/ncitbrowser... (accessed September 17, 2018).
  2. NCIt. "Cefoxitin: NCI Thesaurus (NCIt) provides reference terminology for many systems. It covers vocabulary for clinical care, translational and basic research, and public information and administrative activities.". https://ncit.nci.nih.gov/ncitbrowser... (accessed September 17, 2018).
  3. EPA DSStox. "Cefoxitin: DSSTox provides a high quality public chemistry resource for supporting improved predictive toxicology.". https://comptox.epa.gov/dashboard/ds... (accessed September 17, 2018).

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