Effect of ofloxacin on theophylline pharmacokinetics at clinical dosage in dogs

Effects of TNFR1 gene silencing on early apoptosis of marbofloxacin-treated chondrocytes from juvenile dogs

Quinolones (QNs)-induced cartilaginous lesions in juvenile animals by chondrocyte apoptosis is an important toxic effect, which results in the restriction of their use in pediatrics. However, limited data about QNs chondrotoxicity are available for evaluation of the potential toxicity in both animals and human cartilage. To explore whether tumor necrosis factor/its receptor (TNF/TNFR1) signaling pathway is involved in the early apoptosis of marbofloxacin-induced chondrocytes, canine juvenile chondrocytes were treated with 0, 20, 50 and 100 μg/mL marbofloxacin. Results showed that the apoptosis rates of the chondrocytes at 2, 8 and 24 h were significantly increased in a concentration- and time-dependent manner (P <  0.05). The mRNA levels of apoptosis-related factors in TNF/TNFR1 signaling pathways and the protein levels of TNFα and TNFR1 were increased in canine chondrocytes treated with 20-100 μg/mL marbofloxacin (P <  0.05) while TNFR1 gene silencing significantly decreased the chondrocyte apoptosis and inhibited the mRNA expression of TNF/TNFR1 downstream signaling molecules after 100 μg/mL marbofloxacin treatment at 8 h (P <  0.01). It was confirmed that activated TNF/TNFR1 signaling pathway may play a leading role in the early apoptosis of marbofloxacin-induced canine juvenile chondrocytes, which is helpful for clinical estimation or prevention of the risk of QNs.

Possible drug-drug interaction in dogs and cats resulted from alteration in drug metabolism: A mini review

Pharmacokinetic drug-drug interactions (in particular at metabolism) may result in fatal adverse effects in some cases. This basic information, therefore, is needed for drug therapy even in veterinary medicine, as multidrug therapy is not rare in canines and felines. The aim of this review was focused on possible drug-drug interactions in dogs and cats. The interaction includes enzyme induction by phenobarbital, enzyme inhibition by ketoconazole and fluoroquinolones, and down-regulation of enzymes by dexamethasone. A final conclusion based upon the available literatures and author's experience is given at the end of the review.

Lack of inhibitory effects of several fluoroquinolones on cytochrome P-450 3A activities at clinical dosage in dogs

Inhibitory effects of several fluoroquinolones (FQs) on liver CYP3A activities were examined by in vitro and in vivo tests in dogs. Midazolam (MDZ) hydroxylation rate was used to determine the CYP3A activities in liver microsomes. Enrofloxacin (EFX), ofloxacin (OFX) orbifloxacin (OBFX) and ciprofloxacin (CFX) were tested. None of the FQs changed Vmax, Km or intrinsic clearance (Vmax/Km) of MDZ. For in vivo test, we examined the effects of oral administration of EFX and OFX on the pharmacokinetics of quinidine (QN), a CYP3A substrate. EFX or OFX (10 mg/kg) was administered once a day for 3 days. QN (2 mg/kg) was intravenously injected at 2 h after the final dose of FQs administration. The same dose of QN was intravenously injected 3 weeks before the start of FQs administration for control. Neither EFX nor OFX changed the pharmacokinetic parameters of QN. These in vitro and in vivo consisted results suggest that these FQs lack the inhibitory effects on CYP3A activities in dogs. Hence, given these results, the risk of drug-drug interaction is unlikely to occur between FQs and CYP3A substrates in clinical situation in dogs.