Lilia Gutiérrez Olvera

Comparative pharmacokinetics of a new oral long-acting formulation of doxycycline hyclate: A canine clinical trial.

Doxycicline is used in dogs as treatment of several bacterial infections, mycoplasma, chlamydia and rickettsial diseases. However, it requires long treatments and several doses to be effective. The aim of this study was to determine the pharmacokinetics of four formulations of doxycycline hyclate, administered orally, with different proportions of excipients, acrylic acid-polymethacrylate-based matrices, to obtain longer therapeutic levels than conventional formulation. Forty-eight dogs were randomly assigned in five groups to receive a single oral dose (20mg/kg) of doxycycline hyclate without excipients (control) or a long-acting formulation containing doxycycline, acrylic acid polymer, and polymethacrylate in one of the following four proportions: DOX1(1:0.25:0.0035), DOX2(1:0.5:0.0075), DOX3 (1:1:0.015), or DOX4(1:2:0.0225). Temporal profiles of serum concentrations were obtained at several intervals after each treatment. Therapeutic concentrations were observed for 60h for DOX1 and DOX4, 48h for DOX2 and DOX3 and only 24h for DOX-C. None of the pharmacokinetic parameter differed significantly between DOX1 and DOX2 or between DOX3 and DOX4; however, the findings for the control treatment were significantly different compared to all four long-acting formulations. Results indicated that DOX1 had the most adequate pharmacokinetic-pharmacodynamic relationships for a time-dependent drug and had longer release times than did doxycycline alone. However, all four formulations can be effective depend on the minimum effective serum doxycycline concentration of the microorganism being treated. These results suggest that the use of any of these formulations can reduce the frequency of administration, the patients stress, occurrence of adverse effects and the cost of treatment.

Pharmacokinetics of an oral extended-release formulation of doxycycline hyclate containing acrylic acid and polymethacrylate in dogs

OBJECTIVE To determine the pharmacokinetics of doxycycline hyclate administered orally in the form of experimental formulations with different proportions of acrylic acid-polymethacrylate-based matrices. ANIMALS 30 healthy adult dogs. PROCEDURES In a crossover study, dogs were randomly assigned (in groups of 10) to receive a single oral dose (20 mg/kg) of doxycycline hyclate without excipients (control) or extended-release formulations (ERFs) containing doxycycline, acrylic acid polymer, and polymethacrylate in the following proportions: 1:0.5:0.0075 (ERF1) or 1:1:0.015 (ERF2). Serum concentrations of doxycycline were determined for pharmacokinetic analysis before and at several intervals after each treatment. RESULTS Following oral administration to the study dogs, each ERF resulted in therapeutic serum doxycycline concentrations for 48 hours, whereas the control treatment resulted in therapeutic serum doxycycline concentrations for only 24 hours. All pharmacokinetic parameters for ERF1 and ERF2 were significantly different; however, findings for ERF1 did not differ significantly from those for the control treatment. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that both ERFs containing doxycycline, acrylic acid polymer, and polymethacrylate had an adequate pharmacokinetic-pharmacodynamic relationship for a time-dependent drug and a longer release time than doxycycline alone following oral administration in dogs. Given the minimum effective serum doxycycline concentration of 0.26 μg/mL, a dose interval of 48 hours can be achieved for each tested ERF. This minimum inhibitory concentration has the potential to be effective against several susceptible bacteria involved in important infections in dogs. Treatment of dogs with either ERF may have several benefits over treatment with doxycycline alone.