Actions of Neofus in details
Pharmacology: Mechanism of Action: The main mechanism of action of Neofus is the inhibition of DNA gyrase. It is 2-fold stronger than that of ofloxacin. There is not much difference between the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The activity of Neofus is bactericidal. In the observation of bacterial morphology, bacteriolysis can be seen in the concentration around MIC.
Pharmacokinetics: Absorption:
Orally administered Neofus is rapidly and almost completely absorbed with peak plasma concentrations being obtained within 1 hr. The absolute bioavailability is approximately 100%. Food has little effect on the absorption of Neofus.
Distribution in Plasma: Approximately 30-40% of Neofus is bound to serum protein. Multiple dosing with Neofus 500 mg once daily showed neglible accumulation. There is modest but predictable accumulation of Neofus after doses of 500 mg twice daily. Steady state is achieved within 3 days.
Penetration into Tissues and Body Fluids: Penetration into Bronchial Mucosa, Epithelial Lining Fluid (ELF): Maximum Neofus concentrations in bronchial mucosa and ELF were 8.3 mcg/mL and 10.8 mcg/mL, respectively. These were reached approximately 1 hr after administration.
Penetration into Lung Tissue: Maximum Neofus concentrations in lung tissues were approximately 11.3 mcg/mL and were reached between 4-6 hrs after administration.
Metabolism: Neofus is metabolised to a very small extent, the metabolites being desmethyl-Neofus and Neofus N-oxide. These metabolites account for <5% of the dose excretion in urine. Neofus is stereochemically stable and does not undergo chiral inversion.
Elimination: Following oral and IV administration, Neofus is eliminated relatively slowly from the plasma (half-life: 6-8 hrs). Excretion is primarily by the renal route (>85% of the administered dose).
Microbiology: Neofus is a broad-spectrum antibacterial agent against gram-positive and gram-negative bacteria including anaerobes. Neofus has shown strong antibacterial activities against Staphylococcus spp, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus hemolyticus, Enterobacter spp, Escherichia coli, Klebsiella spp, Serratia spp, Enterococcus spp, Proteus spp and other glucose nonfermentative gram-negative rods, Pseudomonas aeruginosa, Haemophilus influenzae and Neisseria gonorrhoeae. Morever, Neofus has shown antibacterial activity against Chlamydia trachomatis. Neofus has an excellent protective and treatment effects in mice.
How should I take Neofus?
Follow all directions on your prescription label. Do not use this medicine in larger or smaller amounts or for longer than recommended.
Neofus is injected into a vein through an IV. You may be shown how to use an IV at home. Do not give yourself this medicine if you do not understand how to use the injection and properly dispose of needles, IV tubing, and other items used.
Neofus must be injected slowly, over at least 60 minutes.
For most infections, Neofus is given once or twice daily for 5 to 14 days. For prostate conditions or anthrax exposure, you may need to use Neofus for 1 to 2 months. Follow your doctor's dosing instructions very carefully.
Drink extra fluids to keep your kidneys working properly while using this medicine.
Use this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Skipping doses may also increase your risk of further infection that is resistant to antibiotics. Neofus will not treat a viral infection such as the flu or a common cold.
This medication can cause you to have a false positive drug screening test. If you provide a urine sample for drug screening, tell the laboratory staff that you are using Neofus.
Store at room temperature away from moisture, heat, and light. Do not freeze.
Neofus administration
Oral: Tablets may be administered without regard to meals.
Oral solution should be administered at least 1 hour before or 2 hours after meals. Maintain adequate hydration of patient to prevent crystalluria. Administer at least 2 hours before or 2 hours after antacids containing magnesium or aluminum, sucralfate, metal cations (eg, iron), multivitamin preparations with zinc, or didanosine chewable/buffered tablets or the pediatric powder for solution.
IV: Infuse 250 to 500 mg IV solution over 60 minutes; infuse 750 mg IV solution over 90 minutes. Too rapid of infusion can lead to hypotension. Avoid administration through an intravenous line with a solution containing multivalent cations (eg, magnesium, calcium). Maintain adequate hydration of patient to prevent crystalluria or cylindruria.
Neofus pharmacology
Mechanism of Action
Neofus is a member of the fluoroquinolone class of antibacterial agents.
Pharmacokinetics
The mean ± SD pharmacokinetic parameters of Neofus determined under single and steady-state conditions following oral tablet, oral solution, or intravenous (IV) doses of Neofus are summarized in Table 8.
ND = not determined
Absorption
Neofus is rapidly and essentially completely absorbed after oral administration. Peak plasma concentrations are usually attained one to two hours after oral dosing. The absolute bioavailability of Neofus from a 500 mg tablet and a 750 mg tablet of Neofus are both approximately 99%, demonstrating complete oral absorption of Neofus. Following a single intravenous dose of Neofus to healthy volunteers, the mean ± SD peak plasma concentration attained was 6.2 ± 1.0 mcg/mL after a 500 mg dose infused over 60 minutes and 11.5 ± 4.0 mcg/mL after a 750 mg dose infused over 90 minutes. Neofus
Oral Solution and Tablet formulations are bioequivalent.
Neofus pharmacokinetics are linear and predictable after single and multiple oral or IV dosing regimens. Steady-state conditions are reached within 48 hours following a 500 mg or 750 mg once-daily dosage regimen. The mean ± SD peak and trough plasma concentrations attained following multiple once-daily oral dosage regimens were approximately 5.7 ± 1.4 and 0.5 ± 0.2 mcg/mL after the 500 mg doses, and 8.6 ± 1.9 and 1.1 ± 0.4 mcg/mL after the 750 mg doses, respectively. The mean ± SD peak and trough plasma concentrations attained following multiple once-daily IV regimens were approximately 6.4 ± 0.8 and 0.6 ± 0.2 mcg/mL after the 500 mg doses, and 12.1 ± 4.1 and 1.3 ± 0.71 mcg/mL after the 750 mg doses, respectively.
Oral administration of a 500 mg dose of Neofus with food prolongs the time to peak concentration by approximately 1 hour and decreases the peak concentration by approximately 14% following tablet and approximately 25% following oral solution administration. Therefore, Neofus Tablets can be administered without regard to food. It is recommended that Neofus
Oral Solution be taken 1 hour before or 2 hours after eating.
The plasma concentration profile of Neofus after IV administration is similar and comparable in extent of exposure (AUC) to that observed for Neofus Tablets when equal doses (mg/mg) are administered. Therefore, the oral and IV routes of administration can be considered interchangeable.
Figure 2: Mean Neofus Plasma Concentration vs. Time Profile: 750 mg
Figure 3: Mean Neofus Plasma Concentration vs. Time Profile: 500 mg
Distribution
The mean volume of distribution of Neofus generally ranges from 74 to 112 L after single and multiple 500 mg or 750 mg doses, indicating widespread distribution into body tissues. Neofus reaches its peak levels in skin tissues and in blister fluid of healthy subjects at approximately 3 hours after dosing. The skin tissue biopsy to plasma AUC ratio is approximately 2 and the blister fluid to plasma AUC ratio is approximately 1 following multiple once-daily oral administration of 750 mg and 500 mg doses of Neofus respectively, to healthy subjects. Neofus also penetrates well into lung tissues. Lung tissue concentrations were generally 2- to 5-fold higher than plasma concentrations and ranged from approximately 2.4 to 11.3 mcg/g over a 24-hour period after a single 500 mg oral dose.
In vitro, over a clinically relevant range (1 to 10 mcg/mL) of serum/plasma Neofus concentrations, Neofus is approximately 24 to 38% bound to serum proteins across all species studied, as determined by the equilibrium dialysis method. Neofus is mainly bound to serum albumin in humans. Neofus binding to serum proteins is independent of the drug concentration.
Metabolism
Neofus is stereochemically stable in plasma and urine and does not invert metabolically to its enantiomer, D-ofloxacin. Neofus undergoes limited metabolism in humans and is primarily excreted as unchanged drug in the urine. Following oral administration, approximately 87% of an administered dose was recovered as unchanged drug in urine within 48 hours, whereas less than 4% of the dose was recovered in feces in 72 hours. Less than 5% of an administered dose was recovered in the urine as the desmethyl and N-oxide metabolites, the only metabolites identified in humans. These metabolites have little relevant pharmacological activity.
Excretion
Neofus is excreted largely as unchanged drug in the urine. The mean terminal plasma elimination half-life of Neofus ranges from approximately 6 to 8 hours following single or multiple doses of Neofus given orally or intravenously. The mean apparent total body clearance and renal clearance range from approximately 144 to 226 mL/min and 96 to 142 mL/min, respectively. Renal clearance in excess of the glomerular filtration rate suggests that tubular secretion of Neofus occurs in addition to its glomerular filtration. Concomitant administration of either cimetidine or probenecid results in approximately 24% and 35% reduction in the Neofus renal clearance, respectively, indicating that secretion of Neofus occurs in the renal proximal tubule. No Neofus crystals were found in any of the urine samples freshly collected from subjects receiving Neofus.
Geriatric
There are no significant differences in Neofus pharmacokinetics between young and elderly subjects when the subjects' differences in creatinine clearance are taken into consideration. Following a 500 mg oral dose of Neofus to healthy elderly subjects (66 – 80 years of age), the mean terminal plasma elimination half-life of Neofus was about 7.6 hours, as compared to approximately 6 hours in younger adults. The difference was attributable to the variation in renal function status of the subjects and was not believed to be clinically significant. Drug absorption appears to be unaffected by age. Neofus dose adjustment based on age alone is not necessary.
Pediatrics
The pharmacokinetics of Neofus following a single 7 mg/kg intravenous dose were investigated in pediatric patients ranging in age from 6 months to 16 years. Pediatric patients cleared Neofus faster than adult patients, resulting in lower plasma exposures than adults for a given mg/kg dose. Subsequent pharmacokinetic analyses predicted that a dosage regimen of 8 mg/kg every 12 hours (not to exceed 250 mg per dose) for pediatric patients 6 months to 17 years of age would achieve comparable steady state plasma exposures (AUC0-24 and Cmax) to those observed in adult patients administered 500 mg of Neofus once every 24 hours.
Gender
There are no significant differences in Neofus pharmacokinetics between male and female subjects when subjects' differences in creatinine clearance are taken into consideration. Following a 500 mg oral dose of Neofus to healthy male subjects, the mean terminal plasma elimination half-life of Neofus was about 7.5 hours, as compared to approximately 6.1 hours in female subjects. This difference was attributable to the variation in renal function status of the male and female subjects and was not believed to be clinically significant. Drug absorption appears to be unaffected by the gender of the subjects. Dose adjustment based on gender alone is not necessary.
Race
The effect of race on Neofus pharmacokinetics was examined through a covariate analysis performed on data from 72 subjects: 48 white and 24 non-white. The apparent total body clearance and apparent volume of distribution were not affected by the race of the subjects.
Renal Impairment
Clearance of Neofus is substantially reduced and plasma elimination half-life is substantially prolonged in adult patients with impaired renal function (creatinine clearance < 50 mL/min), requiring dosage adjustment in such patients to avoid accumulation. Neither hemodialysis nor continuous ambulatory peritoneal dialysis (CAPD) is effective in removal of Neofus from the body, indicating that supplemental doses of Neofus are not required following hemodialysis or CAPD.
Hepatic Impairment
Pharmacokinetic studies in hepatically impaired patients have not been conducted. Due to the limited extent of Neofus metabolism, the pharmacokinetics of Neofus are not expected to be affected by hepatic impairment.
Bacterial Infection
The pharmacokinetics of Neofus in patients with serious community-acquired bacterial infections are comparable to those observed in healthy subjects.
Drug-Drug Interactions
The potential for pharmacokinetic drug interactions between Neofus and antacids warfarin, theophylline, cyclosporine, digoxin, probenecid, and cimetidine has been evaluated.
Microbiology
Mechanism of Action
Neofus is the L-isomer of the racemate, ofloxacin, a quinolone antimicrobial agent. The antibacterial activity of ofloxacin resides primarily in the L-isomer. The mechanism of action of Neofus and other fluoroquinolone antimicrobials involves inhibition of bacterial topoisomerase IV and DNA gyrase (both of which are type II topoisomerases), enzymes required for DNA replication, transcription, repair and recombination.
Mechanism of Resistance
Fluoroquinolone resistance can arise through mutations in defined regions of DNA gyrase or topoisomerase IV, termed the Quinolone-Resistance Determining Regions (QRDRs), or through altered efflux.
Fluoroquinolones, including Neofus, differ in chemical structure and mode of action from aminoglycosides, macrolides and ß-lactam antibiotics, including penicillins. Fluoroquinolones may, therefore, be active against bacteria resistant to these antimicrobials.
Resistance to Neofus due to spontaneous mutation in vitro is a rare occurrence (range: 10-9 to 10-10). Cross-resistance has been observed between Neofus and some other fluoroquinolones, some microorganisms resistant to other fluoroquinolones may be susceptible to Neofus.
Activity in vitro and in vivo
Neofus has in vitro activity against Gram-negative and Gram-positive bacteria.
Neofus has been shown to be active against most isolates of the following bacteria both in vitro and in clinical infections as described in :
Gram-Positive Bacteria
Enterococcus faecalis
Staphylococcus aureus (methicillin-susceptible isolates)
Staphylococcus epidermidis (methicillin-susceptible isolates)
Staphylococcus saprophyticus
Streptococcus pneumoniae (including multi-drug resistant isolates [MDRSP])1
Streptococcus pyogenes
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1 MDRSP (Multi-drug resistant Streptococcus pneumoniae) isolates are isolates resistant to two or more of the following antibiotics: penicillin (MIC ≥ 2 mcg/mL), 2nd generation cephalosporins, e.g., cefuroxime; macrolides, tetracyclines and trimethoprim/sulfamethoxazole.
Gram-Negative Bacteria
Enterobacter cloacae
Escherichia coli
Haemophilus influenzae
Haemophilus parainfluenzae
Klebsiella pneumoniae
Legionella pneumophila
Moraxella catarrhalis
Proteus mirabilis
Pseudomonas aeruginosa
Serratia marcescens
Other Bacteria
Chlamydophila pneumoniae
Mycoplasma pneumoniae
The following in vitro data are available, but their clinical significance is unknown: Neofus exhibits in vitro minimum inhibitory concentrations (MIC values) of 2 mcg/mL or less against most (≥ 90%) isolates of the following microorganisms; however, the safety and effectiveness of Neofus in treating clinical infections due to these bacteria have not been established in adequate and well-controlled clinical trials.
Gram-Positive Bacteria
Staphylococcus haemolyticus
ß-hemolytic Streptococcus (Group C/F)
ß-hemolytic Streptococcus (Group G)
Streptococcus agalactiae
Streptococcus milleri
Viridans group streptococci
Bacillus anthracis
Gram-Negative Bacteria
Acinetobacter baumannii
Acinetobacter lwoffii
Bordetella pertussis
Citrobacter koseri
Citrobacter freundii
Enterobacter aerogenes
Enterobacter sakazakii
Klebsiella oxytoca
Morganella morganii
Pantoea agglomerans
Proteus vulgaris
Providencia rettgeri
Providencia stuartii
Pseudomonas fluorescens
Yersinia pestis
Anaerobic Gram-Positive Bacteria
Clostridium perfringens
Susceptibility Tests
When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antimicrobial drug products used in the 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 MIC values should be determined using a standardized procedure. Standardized procedures are based on a dilution method1, 2, 4 (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of Neofus powder. The MIC values should be interpreted according to the criteria outlined in Table 9.
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, 3 requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 5 mcg Neofus to test the susceptibility of bacteria to Neofus.
Reports from the laboratory providing results of the standard single-disk susceptibility test with a 5 mcg Neofus disk should be interpreted according to the criteria outlined in Table 9.
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 a 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.
Quality Control:
Standardized susceptibility test procedures require the use of laboratory controls to monitor and ensure the accuracy and precision of supplies and reagents used in the assay, and the techniques of the individuals performing the test.1,2,3,4 Standard Neofus powder should provide the range of MIC values noted in Table 10. For the diffusion technique using the 5 mcg disk, the criteria in Table 10 should be achieved.
References
- DailyMed. "LEVOFLOXACIN: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". https://dailymed.nlm.nih.gov/dailyme... (accessed September 17, 2018).
- NCIt. "Levofloxacin: 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).
- EPA DSStox. "Levofloxacin: 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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Information checked by Dr. Sachin Kumar, MD Pharmacology
