Gemifloxacin has in vitro activity against a wide range of Gram-negative and Gram-positive microorganisms. Gemifloxacin is bactericidal with minimum bactericidal concentrations (MBCs) generally within one dilution of the minimum inhibitory concentrations (MICs). Gemifloxacin acts by inhibiting DNA synthesis through the inhibition of both DNA gyrase and topoisomerase IV (TOPO IV), which are essential for bacterial growth. Streptococcus pneumoniae showing mutations in both DNA gyrase and TOPO IV (double mutants) are resistant to most fluoroquinolones. Gemifloxacin has the ability to inhibit both enzyme systems at therapeutically relevant drug levels in S. pneumoniae (dual targeting), and has MIC values that are still in the susceptible range for some of these double mutants. However, the presence of double mutants was not evaluated in clinical trials; therefore, the clinical significance of these in vitro data are unknown.
The mechanism of action of quinolones, including gemifloxacin, is different from that of macrolides, beta-lactams, aminoglycosides, or tetracyclines; therefore, microorganisms resistant to these classes of drugs may be susceptible to gemifloxacin and other quinolones. There is no known cross-resistance between gemifloxacin and the above mentioned classes of antimicrobials.
The main mechanism of fluoroquinolone resistance is due to mutations in DNA gyrase and/or TOPO IV. Resistance to gemifloxacin develops slowly via multistep mutations and efflux in a manner similar to other fluoroquinolones. The frequency of spontaneous mutation is low (10-7 to <10-10). Although cross-resistance has been observed between gemifloxacin and other fluoroquinolones, some microorganisms resistant to other fluoroquinolones may be susceptible to gemifloxacin.
Gemifloxacin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section.
Aerobic Gram-positive microorganisms
Streptococcus pneumoniae (including multi-drug resistant strains [MDRSP])*
* MDRSP: multi-drug resistant Streptococcus pneumoniae , includes isolates previously known as PRSP (penicillin-resistant Streptococcus pneumoniae), and are strains resistant to two or more of the following antibiotics: penicillin (MIC ≥2 μg/mL), 2nd generation cephalosporins (e.g., cefuroxime), macrolides, tetracyclines and trimethoprim/sulfamethoxazole.
Aerobic Gram-negative microorganisms
Klebsiella pneumoniae (many strains are only moderately susceptible)
The following data are available, but their clinical significance is unknown.
Gemifloxacin exhibits in vitro minimal inhibitory concentrations (MICs) of 0.25 μg/mL or less against most (≥90%) strains of the following microorganisms; however, the safety and effectiveness of gemifloxacin in treating clinical infections due to these microorganisms has not been established in adequate and well-controlled clinical trials:
Aerobic Gram-positive microorganisms
Staphylococcus aureus (methicillin-susceptible strains only)Streptococcus pyogenes
Aerobic Gram-negative microorganisms
Dilution techniques: Quantitative methods are used to determine antimicrobial minimum 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 gemifloxacin powder. The MICs should be interpreted according to the following criteria:
For testing Klebsiella pneumoniae:
For testing Haemophilus influenzae and Haemophilus parainfluenzae a:
a This interpretive standard is applicable only to broth microdilution susceptibility testing with Haemophilus influenzae and Haemophilus parainfluenzae using Haemophilus Test Medium (HTM)1.
The current absence of data on resistant strains precludes defining any results other than Susceptible. Strains yielding MIC results suggestive of a nonsusceptible category should be submitted to a reference laboratory for further testing.
For testing Streptococcus pneumoniae b:
b These interpretive standards are applicable only to broth microdilution susceptibility tests using cation-adjusted Mueller-Hinton broth with 2-5% lysed horse blood.
A report of Susceptible indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentration 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 concentration 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 gemifloxacin powder should provide the following MIC values:
|Microorganism||MIC Range (µg/mL)|
|Escherichia coli||ATCC 25922||0.004-0.016|
|Haemophilus influenzae||ATCC 49247||0.002-0.008c|
|Streptococcus pneumoniae||ATCC 49619||0.008-0.03d|
c This quality control range is applicable to only H. influenzae ATCC 49247 tested by a broth microdilution procedure using Haemophilus Test Medium (HTM)1.
d This quality control range is applicable to only S. pneumoniae ATCC 49619 tested by a broth microdilution procedure using cation-adjusted Mueller-Hinton broth with 2-5% lysed horse blood.
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 standardized inoculum concentrations. This procedure uses paper disks impregnated with 5 g gemifloxacin to test the susceptibility of microorganisms to gemifloxacin.
Reports from the laboratory providing results of the standard single-disk susceptibility test with a 5 g gemifloxacin disk should be interpreted according to the following criteria:
For testing Klebsiella pneumoniae:
|Zone Diameter (mm)||Interpretation|
For testing Haemophilus influenzae and Haemophilus parainfluenzae e:
|Zone Diameter (mm)||Interpretation|
e This interpretive standard is applicable only to disk diffusion susceptibility testing with Haemophilus influenzae and Haemophilus parainfluenzae using Haemophilus Test Medium (HTM).2
The current absence of data on resistant strains precludes defining any results other than Susceptible. Strains yielding zone diameter results suggestive of a nonsusceptible category should be submitted to a reference laboratory for further testing.
For testing Streptococcus pneumoniae f:
|Zone Diameter (mm)||Interpretation|
f These zone diameter standards apply only to tests performed using Mueller-Hinton agar supplemented with 5% defibrinated sheep blood incubated in 5% CO2 .
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 gemifloxacin.
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 5 g gemifloxacin disk should provide the following zone diameters in these laboratory quality control strains:
|Microorganism||Zone Diameter (mm)|
|Escherichia coli||ATCC 25922||29-36|
|Haemophilus influenzae||ATCC 49247||30-37g|
|Streptococcus pneumoniae||ATCC 49619||28-34h|
g This quality control range is applicable to only H. influenzae ATCC 49247 tested by a disk diffusion procedure using Haemophilus Test Medium (HTM)2.
h This quality control range is applicable to only S. pneumoniae ATCC 49619 tested by a disk diffusion procedure using Mueller-Hinton agar supplemented with 5% defibrinated sheep blood and incubated in 5% CO2 .
FACTIVE is indicated for the treatment of infections caused by susceptible strains of the designated microorganisms in the conditions listed below. (See DOSAGE AND ADMINISTRATION and CLINICAL STUDIES. )
Acute bacterial exacerbation of chronic bronchitis (ABECB) caused by Streptococcus pneumoniae, Haemophilus influenzae, Haemophilus parainfluenzae, or Moraxella catarrhalis.
Because fluoroquinolones, including FACTIVE, have been associated with serious adverse reactions (see WARNINGS) and for some patients ABECB is self-limiting, reserve FACTIVE for treatment of ABECB in patients who have no alternative treatment options.
Community-acquired pneumonia (of mild to moderate severity) caused by Streptococcus pneumoniae (including multi-drug resistant strains [MDRSP])*, Haemophilus influenzae, Moraxella catarrhalis, Mycoplasma pneumoniae, Chlamydia pneumoniae, or Klebsiella pneumoniae.
*MDRSP: multi-drug resistant Streptococcus pneumoniae , includes isolates previously known as PRSP (penicillin-resistant Streptococcus pneumoniae), and are strains resistant to two or more of the following antibiotics: penicillin (MIC ≥2 μg/mL), 2nd generation cephalosporins (e.g., cefuroxime), macrolides, tetracyclines and trimethoprim/sulfamethoxazole.
To reduce the development of drug-resistant bacteria and maintain the effectiveness of FACTIVE and other antibacterial drugs, FACTIVE should be used only to treat 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.
FACTIVE is contraindicated in patients with a history of hypersensitivity to gemifloxacin, fluoroquinolone antibiotic agents, or any of the product components.
Disabling and Potentially Irreversible Serious Adverse Reactions Including Tendinitis and Tendon Rupture, Peripheral Neuropathy, and Central Nervous System Effects:
Fluoroquinolones, including FACTIVE have been associated with disabling and potentially irreversible serious adverse reactions from different body systems that can occur together in the same patient. Commonly seen adverse reactions include tendinitis, tendon rupture, arthralgia, myalgia, peripheral neuropathy, and central nervous system effects (hallucinations, anxiety, depression, insomnia, severe headaches, and confusion). These reactions can occur within hours to weeks after starting FACTIVE. Patients of any age or without pre-existing risk factors have experienced these adverse reactions (See WARNINGS, Tendinitis and Tendon Rupture, Peripheral Neuropathy and Central Nervous System Effects ).
Discontinue FACTIVE immediately at the first signs or symptoms of any serious adverse reaction. In addition, avoid the use of fluoroquinolones, including FACTIVE, in patients who have experienced any of these serious adverse reactions associated with fluoroquinolones.
Tendinitis and Tendon Rupture: Fluoroquinolones, including FACTIVE, have been associated with an increased risk of tendinitis and tendon rupture in all ages. This adverse reaction most frequently involves the Achilles tendon, and has also been reported with the rotator cuff (the shoulder), the hand, the biceps, the thumb, and other tendons. Tendinitis or tendon rupture can occur within hours or days after starting FACTIVE, or as long as several months after completion of therapy. Tendinitis and tendon rupture can occur bilaterally.
The risk of developing fluoroquinolone-associated tendinitis and tendon rupture is increased in patients over 60 years of age, in patients taking corticosteroid drugs, and in patients with kidney, heart or lung transplants. Other factors, in addition to age and corticosteroid use, that may independently increase the risk of tendon rupture include strenuous physical activity, renal failure, and previous tendon disorders such as rheumatoid arthritis. Tendinitis and tendon rupture have also occurred in patients taking fluoroquinolones who do not have the above risk factors. Discontinue FACTIVE if the patient experiences pain, swelling, inflammation or rupture of a tendon. Avoid fluoroquinolones, including FACTIVE, in patients who have a history of tendon disorders or have experienced tendinitis or tendon rupture. Patients should be advised to rest at the first sign of tendinitis or tendon rupture, and to contact their healthcare provider regarding changing to a non-quinolone antimicrobial drug.
Peripheral Neuropathy: Fluoroquinolones, including FACTIVE, have been associated with an increased risk of peripheral neuropathy. Cases of sensory or sensorimotor axonal polyneuropathy affecting small and/or large axons resulting in paresthesias, hypoesthesias, dysesthesias and weakness have been reported in patients receiving fluoroquinolones, including FACTIVE. Symptoms may occur soon after initiation of FACTIVE and may be irreversible in some patients. Discontinue FACTIVE immediately if the patient experiences symptoms of peripheral neuropathy, including pain, burning, tingling, numbness, and/or weakness or other alterations in sensations including light touch, pain, temperature, position sense, and vibratory sensation.
CNS Effects: Fluoroquinolones, including FACTIVE, have been associated with an increased risk of central nervous system (CNS) effects, including convulsions, increased intracranial pressure (including pseudotumor cerebri), and toxic psychosis. In clinical studies with FACTIVE, central nervous system (CNS) effects have been reported infrequently. As with other fluoroquinolones, FACTIVE should be used with caution in patients with CNS diseases such as epilepsy or patients predisposed to convulsions. CNS stimulation which may lead to tremors, restlessness, anxiety, lightheadedness, confusion, hallucinations, paranoia, depression, insomnia, and rarely suicidal thoughts or acts may also be caused by other fluoroquinolones. If these reactions occur in patients receiving FACTIVE, discontinue FACTIVE immediately and institute appropriate measures.
Exacerbation of Myasthenia Gravis: Fluoroquinolones, including FACTIVE, have neuromuscular blocking activity and may exacerbate muscle weakness in patients with myasthenia gravis. Postmarketing serious adverse reactions, including deaths and requirement for ventilatory support, have been associated with fluoroquinolone use in patients with myasthenia gravis. Avoid FACTIVE in patients with known history of myasthenia gravis. (See PRECAUTIONS/Information for Patients and Adverse Reactions/Post-Marketing Adverse Reactions. )
THE SAFETY AND EFFECTIVENESS OF FACTIVE IN CHILDREN, ADOLESCENTS (LESS THAN 18 YEARS OF AGE), PREGNANT WOMEN, AND LACTATING WOMEN HAVE NOT BEEN ESTABLISHED. (See PRECAUTIONS: Pediatric Use, Pregnancy and Nursing Mothers subsections.)
QT Effects: Fluoroquinolones may prolong the QT interval in some patients. FACTIVE should be avoided in patients with a history of prolongation of the QTc interval, patients with uncorrected electrolyte disorders (hypokalemia or hypomagnesemia), and patients receiving Class IA (e.g., quinidine, procainamide) or Class III (e.g., amiodarone, sotalol) antiarrhythmic agents.
Pharmacokinetic studies between gemifloxacin and drugs that prolong the QTc interval such as erythromycin, antipsychotics, and tricyclic antidepressants have not been performed. FACTIVE should be used with caution when given concurrently with these drugs, as well as in patients with ongoing proarrhythmic conditions, such as clinically significant bradycardia or acute myocardial ischemia. No cardiovascular morbidity or mortality attributable to QTc prolongation occurred with FACTIVE treatment in over 8119 patients, including 707 patients concurrently receiving drugs known to prolong the QTc interval and 7 patients with hypokalemia.
The likelihood of QTc prolongation may increase with increasing dose of the drug; therefore, the recommended dose should not be exceeded especially in patients with renal or hepatic impairment where the Cmax and AUC are slightly higher. QTc prolongation may lead to an increased risk for ventricular arrhythmias including torsades de pointes. The maximal change in the QTc interval occurs approximately 5-10 hours following oral administration of gemifloxacin.
Hypersensitivity Reactions: Serious hypersensitivity and/or anaphylactic reactions have been reported in patients receiving fluoroquinolone therapy, including FACTIVE. Hypersensitivity reactions reported in patients receiving fluoroquinolone therapy have occasionally been fatal. These reactions may occur following the first dose. Some reactions have been accompanied by cardiovascular collapse, hypotension/shock, seizure, loss of consciousness, tingling, angioedema (including tongue, laryngeal, throat or facial edema/swelling), airway obstruction (including bronchospasm, shortness of breath and acute respiratory distress), dyspnea, urticaria, itching and other serious skin reactions.
FACTIVE should be discontinued immediately at the appearance of any sign of an immediate type I hypersensitivity skin rash or any other manifestation of a hypersensitivity reaction; the need for continued fluoroquinolone therapy should be evaluated. As with other drugs, serious acute hypersensitivity reactions may require treatment with epinephrine and other resuscitative measures, including oxygen, intravenous fluids, antihistamines, corticosteroids, pressor amines and airway management as clinically indicated. (See PRECAUTIONS and ADVERSE REACTIONS.)
Other serious and sometimes fatal reqactions, some due to hypersensitivity and some due to uncertain etiology, have been reported rarely in patients receiving therapy with quinolones, including FACTIVE. These events may be severe and generally occur following the administration of multiple doses. Clinical manifestations may include one or more of the following:
fever, rash or severe dermatologic reactions (e.g., toxic epidermal necrolysis, Stevens-Johnson Syndrome);
vasculitis; arthralgia; myalgia; serum sickness;
interstitial nephritis; acute renal insufficiency or failure;
hepatitis; jaundice; acute hepatic necrosis or failure;
anemia, including hemolytic and aplastic;
thrombocytopenia, including thrombotic thrombocytopenic purpura; leukopenia agranulocytosis; pancytopenia; and/or other hematologic abnormalities.
Discontinue FACTIVE immediately at the first appearance of a skin rash, jaundice, or any other sign of hypersensitivity and institute supportive measures instituted (See PRECAUTIONS: Information for Patients and ADVERSE REACTIONS ).
Clostridium difficile Associated Diarrhea: Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including FACTIVE, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.
C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.
If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile , and surgical evaluation should be instituted as clinically indicated.
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