Delivery of ivermectin by injectable microspheres

Area of Science:

• Veterinary Parasitology
• Drug Delivery Systems
• Biomaterials Science

Background:

• Livestock pest control is crucial for animal health and agricultural productivity.
• Existing treatments often require frequent administration, leading to compliance issues and potential resistance.
• There is a need for sustained-release formulations of antiparasitic drugs like ivermectin.

Purpose of the Study:

• To develop and characterize a bioabsorbable, injectable microsphere formulation of ivermectin.
• To evaluate the drug release profile and efficacy of the ivermectin microspheres in cattle.
• To assess the potential of this formulation for controlling ectoparasites in livestock and companion animals.

Main Methods:

• Ivermectin-loaded microspheres were prepared using a solvent-evaporation technique with poly-(lactide-co-glycolide) (PLA/PGA) copolymers.
• The microspheres were characterized for drug content (approx. 30% ivermectin) and size (25-250 microns).
• Pharmacokinetic studies in goats and efficacy trials in cattle against lone star ticks (Amblyomma americanum) and horn flies (Haematobia irritans) were conducted.

Main Results:

• The 50:50 PLA/PGA formulation in cattle showed two peaks of ivermectin serum concentration (45-50 ppb) at 1 week and 6-7 weeks post-injection.
• 100% inhibition of lone star tick larvae was observed for 8 weeks, with sustained efficacy up to 12 weeks.
• 98-100% control of larval horn flies in manure was achieved for 10 weeks.

Conclusions:

• The injectable ivermectin microsphere formulation provides sustained drug release and effective, long-lasting control of key livestock ectoparasites.
• This formulation demonstrates significant potential for managing tick and fly populations in cattle.
• The technology holds promise for broader applications, including tick control in specific regions and heartworm prevention in pets.