Development of an extemporaneous veterinary oral paste formulation with praziquantel and ivermectin for equine

The development of oral paste for horses through drug compounding represents a significant advancement in the veterinary medicine. In many countries limited availability of commercial anthelmintic medications has posed challenges. To address this issue, a compounded oral paste containing a combination of praziquantel and ivermectin has been developed. On the basis of authorized veterinary medicine products and a risk assessment, three different lipophilic bases for placebo oral pastes were selected: two contained mixtures of natural triglycerides and one had synthetic ones (shea butter, cacao butter and hard fats). Additionally, pharmaceutical formulations consisted of su- crose, hydroxypropyl methylcellulose and glycerol. The pharmaceutical-technological characterization, rheological assessments and microbiological evaluations of the compounded oral pastes were used as selection criteria for creat- ing an optimal formulation. All three placebo formulations were microbiologically stable for 45 days (<10 CFU/g), but the formulation with shea butter had the best spreadability and rheological characteristics. The final formulation consisted of 30% powdered particles with appropriate particle size distribution. The frequency sweep oscillatory rheological measurements (0.1-10 Hz) revealed a domination of storage modulus (G’) over loss modulus (G”) in all tested pharmaceutical formulations, suggesting solid-like viscoelastic behavior. Although the replacement of sucrose with praziquantel and ivermectin led to a slight decrease in spreadability, it was still superior to the other two placebo formulations. This newly developed extemporaneous preparation with a fixed combination of active pharmaceutical ingredients (praziquantel and ivermectin) offers the single application of two anthelmintic drugs. The compounded drugs ensure the fulfillment of the specific needs regarding accuracy of dosing, optimal therapeutic outcomes, and palatability.