The pharmacokinetics of moxidectin following intravenous and topical administration to swine

Pharmacokinetics of a topical application of moxidectin in bare-nosed wombats (Vombatus ursinus)

Sarcoptic mange is a debilitating disease that affects bare-nosed wombats (Vombatus ursinus). One of the drugs currently used for treatment is moxidectin, as it has a relatively high efficacy against endo and ectoparasites and side effects are uncommon in domestic species, thus it is considered a relatively safe drug to use at the recommended doses. Developing further understanding of the pharmacokinetics of moxidectin will aid in developing treatment regimens for sarcoptic mange in wombats. Here we analyzed the pharmacokinetic parameters of using 100 ml of moxidectin (5 g/l) applied topically. We found that mean peak plasma concentration was 0.50 ng/ml and half-life was 8 days. Moxidectin was excreted in scats with the mean peak concentration of 2461.43 ng/g (on a dry matter basis). Our study has provided the pharmacokinetic parameters of a commonly used treatment for sarcoptic mange in wombats. There were no adverse side effects recorded in the wombats after applying moxidectin topically. This study replicated real-world conditions using topical application on free-living wombats. The relatively low plasma concentration suggests the drug is not accumulating in the blood stream and is excreted via scats.

Free drug percentage of moxidectin declines with increasing concentrations in the serum of marsupials

Moxidectin (MOX) is a macrocyclic lactone used to eliminate endo and ectoparasites in many mammalian species. It is notably the active ingredient of the anti-parasitic drug Cydectin®, manufactured by Virbac, and is frequently used to treat sarcoptic mange in Australian wildlife. Protein binding plays a significant role in the efficacy of a drug, as the unbound/free drug in plasma ultimately reflects the pharmacologically relevant concentration. This study aimed to investigate the free drug percentage of Moxidectin after in vitro spiking into the sera of four sarcoptic mange-susceptible Australian wildlife species; the koala (Phascolarctos cinereus), the bare-nosed wombat (Vombatus ursinus), the eastern grey kangaroo (Macropus giganteus), and the mountain brushtail possum (Trichosurus cunninghami). Three concentration points of MOX were tested for each individual: 20 pg/μL, 100 pg/μL and 500 pg/μL. Serum from five individuals of each species underwent an equilibrium dialysis followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). The results showed an atypical concentration dependent binding across all species, where free drug percentage decreased as MOX concentration increased. In addition, wombats showed significantly lower free drug levels. These findings call for further research into the mechanisms of moxidectin protein binding to help understand MOX pharmacokinetics in marsupials.

Computational Approaches in Preclinical Studies on Drug Discovery and Development

Because undesirable pharmacokinetics and toxicity are significant reasons for the failure of drug development in the costly late stage, it has been widely recognized that drug ADMET properties should be considered as early as possible to reduce failure rates in the clinical phase of drug discovery. Concurrently, drug recalls have become increasingly common in recent years, prompting pharmaceutical companies to increase attention toward the safety evaluation of preclinical drugs. In vitro and in vivo drug evaluation techniques are currently more mature in preclinical applications, but these technologies are costly. In recent years, with the rapid development of computer science, in silico technology has been widely used to evaluate the relevant properties of drugs in the preclinical stage and has produced many software programs and in silico models, further promoting the study of ADMET in vitro. In this review, we first introduce the two ADMET prediction categories (molecular modeling and data modeling). Then, we perform a systematic classification and description of the databases and software commonly used for ADMET prediction. We focus on some widely studied ADMT properties as well as PBPK simulation, and we list some applications that are related to the prediction categories and web tools. Finally, we discuss challenges and limitations in the preclinical area and propose some suggestions and prospects for the future.