This canine study evaluated the pharmacokinetics of 4 oral long-acting formulations of doxycycline mixed with different proportions of acrylic acid and polymethacrylate-based matrix (DOX1, DOX2, DOX3, and DOX4). A control of 20 mg/kg of doxycycline with no excipients was included.
Therapeutic concentrations were observed for 60 hours after administration of DOX1 and DOX4, for 48 hours after DOX2 and DOX3, and for 24 hours after the control dose. Pharmacokinetic parameters between DOX1 and DOX2 and between DOX3 and DOX4 did not differ significantly; however, parameters for the control treatment differed significantly from all long-acting formulations. These doxycycline formulations may be useful in reducing dosing frequency and, in turn, may improve compliance and decrease costs and adverse effects. However, further safety studies are needed.