subject: Injectable ivermectin is insoluble in acqueous media [print this page] Injectable ivermectin is insoluble in acqueous media
Because injectable ivermectin is insoluble in acqueous media and because the solvent wherein the microspheres are suspended is saturated with dissolved ivermectin, there is only minimum diffusion of ivermectin from the microparticles containing the same towards the solvent and the microsphere content is released through erosion of the polymeric matrix once injected.
Such hardening processes are carried out by methods well known in the art, for example, by means of a solution of glutaraldehyde, solution of alum and other chemical agents or by heating the proteins up to coagulation temperature. For instance, the gelatin microspheres loaded with ivermectin may be subjected to treatment in an acqueous solution of glutaraldehyde at 25% during 24 hours and then suspended in any of the aforementioned solvents; the result is a system releasing ivermectin 40 to 60 days after the formulation is injected into the animal. A similar injectable formulation with a same ivermectin liberation profile is obtained by suspending ivermectin-loaded microspheres of DL-lactic-glycolic 1:1 copolymer. In this way, by suspending the ivermectin-loaded particles in a solution of ivermectin, a system is obtained wherein in a first phase ivermectin is released from the solvent for a period lasting between 20 and 40 days, depending on the selected solvent, followed by a second phase between days 40 and 60 after injection during which ivermectin is released from the gelatin microparticles or the lactic-glycolic copolymer. The second phase may last from 15 to 25 days such that the system achieves an overall ivermectin release period of 55 to 85 days.
The experts in the art may easily compute for themselves conditions and intensities of the microparticle hardening process required to obtain systems releasing ivermectin for periods in excess of 80 days, say after 100 or 120 days. Such hardening processes are known per se.
Thus, it is possible according to the present invention to obtain an injectable ivermectin solution containing microparticles which have undergone different hardening treatments or have been obtained with copolymers formed from different monomer ratios, in order to produce subsets of suspended microparticles such that each subset differs in the biodegradability resistance thereof. In this way, the resulting formulations generate three or more ivermectin release pulses, the starting point of each separated by programmable time intervals, for example from 10 to 30 days separation between pulses having a duration of 15 to 40 days of ivermectin bioavailability, such that the overall therapeutically efficient treatment period may be substantially longer than 100 days.
