Enrofloxacin is widely used in veterinary medicine and is an important alternative to treating
bacterial infections, which play an important role as causes of disease and death in captive snakes. Its extralabel use in nontraditional species has been related to its excellent pharmacokinetic and antimicrobial characteristics. This can be demonstrated by its activity against gram-negative organisms implicated in serious
infectious diseases of reptile species with a rapid and concentration-dependent bactericidal effect and a large volume of distribution. Pharmacokinetic parameters for
enrofloxacin were investigated in seven urutu pit vipers (Bothrops alternatus), following
intramuscular injections of 10 mg/kg. The plasma concentrations of
enrofloxacin and its metabolite,
ciprofloxacin, were measured using high-performance liquid chromatography. Blood samples were collected from the ventral coccygeal veins at 0.5, 1, 2, 4, 8, 12, 24, 36, 48, 72, 96, 108, and 168 hr. The kinetic behavior was characterized by a relatively slow absorption (time of maximal plasma concentration = 4.50 +/- 3.45 hr) with peak plasma concentration of 4.81 +/- 1.12 microg/ml. The long half-life during the terminal elimination phase (t1/2 lambda = 27.91 +/- 7.55 hr) of
enrofloxacin after intramuscular administration, calculated in the present study, could suggest that the
antibiotic is eliminated relatively slowly and/or the presence of a slow absorption in urutu pit vipers.
Ciprofloxacin reached a peak plasma concentration of 0.35 microg/ml at 13.45 hr, and the fraction of
enrofloxacin metabolized to
ciprofloxacin was 13.06%. If
enrofloxacin's minimum inhibitory concentration (MIC90) values of 0.5 microg/ml were used, the ratios AUC(e+c): MIC90 (276 +/- 67 hr) and Cmax(e+c): MIC90 (10 +/- 2) reach the proposed threshold values (125 hr and 10, respectively) for optimized efficacy and minimized resistance development when treating
infections caused by Pseudomonas. The administration of 10 mg/kg of
enrofloxacin by the i.m. route should be considered to be a judicious choice in urutu pit vipers against
infections caused by microorganisms with MIC values < or = 0.5 microg/ml. For less susceptible bacteria, a dose increase and/or an interval reduction should be evaluated.