Milbemycin A3

Moxidectin or F28249α is a potent endectocide and semisynthetic methoxime derivative of naturally occurring nemadectin. It is well known for the novel mode of action against a broad range of nematode and anthropod animal parasites. In this work, physicochemical and pharmaceutical aspects of moxidectin are described including stability, semisynthesis, purification processes, formulation compositions, impurities, and degradation pathways. Additional experiments such as DSC, XRD, and CHN analysis were carried out to complete the profile of moxidectin. The importance of safety and quality of drug substances was highlighted by chronological developments involving moxidectin and its analogues. The information gathered from the literature was used to trace the origins of moxidectin-related substances presented in the European Pharmacopeia (EP) compendial monograph. During the review, it was noticed that majority of impurities presented in the EP does not have any potential to increase with time in drug substance or formulated products; therefore, they do not require monitoring during stability studies. This also showed the requirement for further characterization of the impurities observed during long-term storage and development of stability indicating methods distinguishing between process impurities and the true degradation products. Furthermore, the stability of moxidectin in formulations is also reviewed in conjunction with known degradation routes and innovative ways to formulate products that are stable and effective at intended shelf life.

Diseases caused by helminth infections affect more than a quarter of the population of the world, but the therapeutic arsenal is limited. The approval of moxidectin in 2018 and triclabendazole in 2019 by the FDA marked an important moment in the fight against diseases of poverty, such as helminthiases.

Canine demodicosis, a disease caused by a proliferation of Demodex mites, typically leads to alopecia, comedones, follicular papules and pustules, scaling, and crusting. It may be treated with either amitraz rinses or macrocyclic lactones. Amitraz rinse is approved for application every 2 weeks at a concentration of 0.025%. Higher concentrations and more frequent applications increase the success rate but also increase the risk for adverse effects. Ivermectin is used at 0.3 to 0.6 mg/kg/d PO and moxidectin at 0.2 to 0.5 mg/kg/d PO. Both drugs may cause adverse neurologic effects in sensitive dogs. Milbemycin oxime at 1 to 2 mg/kg/d PO is a safer treatment option. A weekly spot-on combination of 2.5% moxidectin and 10% imidacloprid is recommended for milder forms of the disease.