(orbifloxacin)

Brand

Orbax

Availability

• Tablets: 5.7 mg, 22.7 mg, 68 mg
• Suspension: can be made from tablets

Pharmacology

Orbifloxacin, a third-generation 4-fluoroquinolone, is a concentration dependent bactericidal drug. Its mechanism of action is to inhibit bacterial DNA gyrase, and prevent DNA supercoiling and synthesis.

It has activity against Gram-negative and Gram-positive bacilli and cocci such as: Klebsiella spp., enterobacter, shigella, Staphylococcus aureus, and E. coli, as well as other organisms such as mycoplasma, and chlamydia. Strains of pseudomonas and enterococcus are resistant to orbifloxacin.

Orbifloxacin is 95% absorbed, though eliminated by the kidneys 50% unchanged. This higher absorption rate, with urine levels remaining above minimum inhibitory concentration for susceptible organisms, may mean lower dosages in less of a frequency need be given.

It is known that the quinolone class of drugs have been shown to produce erosions of articular cartilage in weight bearing joints, as well as producing other signs of arthropathy in immature animals of various species, including juvenile rats (Kashida et al., 1997). However, evidence of cartilage abnormalities appear to be dose related (high dosages over extended period).

It is also important to note that although the use of fluoroquinolones have not been recommended for initial treatment in the pregnant and nursing doe or juvenile rats (under 4 months) due to the risks of cartilage abnormalities (Egerbacher et al., 2000), in cases where other antibiotics are not helping, or if the infection is deemed severe, the benefit of using fluoroquinolones (alone or in combination with other compatible antimicrobials) may, in fact, outweigh the risks.

Indications

Useful in respiratory infections, urinary tract infections, soft tissue infection and soft tissue injury.

Drug Interactions or Contraindications

• Concurrent administration of a quinolone, including orbifloxacin, with cation-containing GI products such as magnesium/aluminum antacids or sucralfate, or GI products containing calcium, iron, or zinc may reduce its absorption. It is suggested to separate dosing from any of these products by 2 hours.
• Theophylline blood levels may be increased when used with orbifloxacin.
• Probenecid blocks tubular secretion of orbifloxacin and may cause an increase in its blood level and half life.
• Synergism can occur when aminoglycosides, cephalosporins, and extended-spectrum penicillins are used with fluorinated quinolones such as orbifloxacin.
• Not recommended to be given to pregnant or very young rats due to the risk of causing cartilage abnormalities.

Adverse Reactions

CNS: restlessness, may lower seizure threshold (increasing likelihood of seizure activity)

GI: decreased appetite, diarrhea

GU: crystalluria

Other: itching

Dosage Recommendations

The dosages listed below are what some limited vets are using. There is no written documentation regarding dosages for rats. *Dosage is empirical.*

Dosing ranges that have been reported are 1 mg/lb to 5 mg/lb, PO, q24hr (5 mg/lb for MSU Veterinary Internal Medicine)

Dose reported being the most effective in rats is 5 mg/lb, this is also empiric. ¹²

*Note: toxicity less likely in once daily dosing therapy for aminoglycosides and the fluorinated quinolones.

Considerations

• Orbifloxacin can be used simultaneously with doxycycline in the treatment of Mycoplasma.
  Also, in treating suspected polymicrobial infections, where a broader coverage may be needed, synergistic or combination drugs may be used. The following drugs may be seen used simultaneously with orbifloxacin: aminoglycosides (e.g., amikacin or gentamicin), or aminopenicillins (e.g., amoxicillin or ampicillin), or third generation cephalosporins, or clindamycin, or metronidazole. ¹
• Please note that it is imperative to discuss the changing or adding of any medications during your rat’s treatment with your veterinarian to prevent future resistance of microbes to the drugs prescribed.
• Store tablets in tight moist free container.
• Be sure to keep animals well hydrated in order to prevent crystalluria (formation of crystals in urine).
• Reconstituted suspension from tablets should be kept refrigerated and has a 14 day expiration time.

Reference

1. Pallo-Zimmerman, L., Byron, J., & Graves, T. (July 2010). Fluoroquinolones: Then and Now. Vetlearn.com. Retrieved April 25, 2011, from www.vetlearn.com/Portals/0/PV0710_zimmerman_CE.pdf
2. Kashida Y, Kato M. Toxic effects of quinolone antibacterial agents on the musculoskeletal system in juvenile rats. Toxicol Pathol 1997;25:635-43. Retrieved 2011.