ZYMAXID Ophthalmic solution Ref.[50660] Active ingredients: Gatifloxacin

Gatifloxacin ophthalmic solution 0.5% was administered to one eye of 6 healthy male subjects each in an escalated dosing regimen starting with a single 2 drop dose, then 2 drops 4 times daily for 7 days, and finally 2 drops 8 times daily for 3 days. At all time points, serum gatifloxacin levels were below the lower limit of quantification (5 ng/mL) in all subjects.

Gatifloxacin is an 8-methoxyfluoroquinolone with a 3-methylpiperazinyl substituent at C7. The antibacterial action of gatifloxacin results from inhibition of DNA gyrase and topoisomerase IV. DNA gyrase is an essential enzyme that is involved in the replication, transcription, and repair of bacterial DNA. Topoisomerase IV is an enzyme known to play a key role in the partitioning of the chromosomal DNA during bacterial cell division. The mechanism of action of fluoroquinolones including gatifloxacin is different from that of aminoglycoside, macrolide, and tetracycline antibiotics. Therefore, gatifloxacin may be active against pathogens that are resistant to these antibiotics and these antibiotics may be active against pathogens that are resistant to gatifloxacin. There is no cross-resistance between gatifloxacin and the aforementioned classes of antibiotics. Cross-resistance has been observed between systemic gatifloxacin and some other fluoroquinolones.

Resistance to gatifloxacin in vitro develops via multiple-step mutations. Resistance to gatifloxacin in vitro occurs at a general frequency of 1 × 10^-7 to 10^-10.

Gatifloxacin has been shown to be active against most isolates of the following organisms both microbiologically and clinically, in conjunctival infections:

Aerobic gram-positive bacteria:

Staphylococcus aureus
Staphylococcus epidermidis
Streptococcus mitis group*
Streptococcus oralis*
Streptococcus pneumoniae

Aerobic gram-negative bacteria:

Haemophilus influenzae

Efficacy for these organisms were studied in fewer than 10 infections.

Carcinogenesis

There was no increase in neoplasms among B6C3F1 mice given gatifloxacin in the diet for 18 months at doses averaging 81 mg/kg/day in males and 90 mg/kg/day in females. These doses are approximately 175-fold higher than the maximum recommended ophthalmic dose (MRHOD) of 0.04 mg/kg/day ZYMAXID in a 60 kg human (on a mg/m² basis).

A statistically significant increase in the incidence of large granular lymphocyte (LGL) leukemia was seen in male rats treated with 100 mg/kg/day (approximately 405-fold higher than the MRHOD, on a mg/m² basis). Fischer 344 rats have a high spontaneous background rate of LGL leukemia and the incidence in high-dose males only slightly exceeded the historical control range established for this strain. There was no increase in neoplasms among Fischer 344 rats given gatifloxacin in the diet for 2 years at doses averaging 47 mg/kg/day in males and 139 mg/kg/day in females (approximately 190- and 560-fold higher than the MRHOD, respectively), on a mg/m² basis.

Mutagenesis

In genetic toxicity tests, gatifloxacin was positive in 1 of 5 strains used in bacterial reverse mutation assays: Salmonella strain TA102. Gatifloxacin was positive in in vitro mammalian cell mutation and chromosome aberration assays. Gatifloxacin was positive in in vitro unscheduled DNA synthesis in rat hepatocytes but not human leukocytes. Gatifloxacin was negative in in vivo micronucleus tests in mice, cytogenetics test in rats, and DNA repair test in rats. The genotoxic findings are similar to findings obtained with other quinolones and may be due to the pharmacologic inhibitory effects of high concentrations of gatifloxacin on eukaryotic type II DNA topoisomerase.

Impairment of Fertility

Oral administration of gatifloxacin produced no adverse effects on fertility or reproduction in rats at doses up to 200 mg/kg/day (approximately 800-fold higher than the MRHOD, on a mg/m² basis).

In two randomized, double-masked, multicenter clinical trials, where patients 1-89 years of age were dosed for 5 days, ZYMAXID was clinically superior to its vehicle on day 6 in patients with conjunctivitis and positive conjunctival cultures. Clinical outcomes for the trials demonstrated clinical success (resolution of conjunctival hyperemia and conjunctival discharge) in 58% (193/333) of patients for the gatifloxacin-treated groups versus 45% (148/325) for the vehicle-treated groups. Microbiological outcomes for the same clinical trials demonstrated a statistically superior eradication rate for causative pathogens of 90% (301/333) for gatifloxacin vs. 70% (228/325) for vehicle. Please note that microbiological eradication does not always correlate with clinical outcome in anti-infective trials.