Pharmacodynamic properties
Moxidectin is an endectocide active against a wide range of internal and external parasites and is a second-generation macrocyclic lactone of the milbemycin family.

Moxidectin interacts with GABA and glutamate gated chloride channels. The net effect is to open the chloride channels on the postsynaptic junction to allow the inflow of chloride ions and induce an irreversible resting state. This results in flaccid paralysis and eventual death of parasites exposed to the drug.

The exact mechanisms of parasite resistance to moxidectin have not been elucidated. A resistance mechanism involving metabolism by p-glycoproteins and efflux from the cells by ABC transporters has been proposed for ivermectin and a similar mechanism is thought to play a role in moxidectin resistance. However, parasites resistant to ivermectin are known to show some degree but not complete cross-resistance to moxidectin. It has been proposed that the reason for the incomplete cross-resistance is that there are multiple avenues of moxidectin action in target parasites that may include receptors other than the Glutamate-gated chloride channels.

Pharmacokinetic particulars
Moxidectin is absorbed following subcutaneous injection with maximum blood concentrations being achieved 24 to 48 hours post injection. The drug is distributed throughout the body tissues but due to its lipophilicity it is concentrated mainly in the fat. The depletion half-life in fat is 26 – 32 days.

Moxidectin undergoes limited biotransformation by hydroxylation in the body. The only significant route of excretion is the faeces.

Environmental properties
Moxidectin fulfils the criteria for a (very) persistent, bioaccumulative and toxic (PBT) substance. In particular, in acute and chronic toxicity studies with algae, crustaceans and fish, moxidectin showed toxicity to these organisms, yielding the following endpoints:

Organism		EC50	NOEC
Algae	S. capricornutum	>86.9 µg/l	86.9 µg/l
Crustaceans (water fleas)	Daphnia magna (acute)	0.0302 µg/l	0.011 µg/l
	Daphnia magna (reproduction)	0.0031 µg/l	0.010 µg/l
Fish	O. mykiss	0.160 µg/l	Not determined
	L. macrochirus	0.620 µg/l	0.52 µg/l
	P. promelas (early life stages)	Not applicable	0.0032 µg/l
	Cyprinus carpio	0.11 µg/l	Not determined

EC50: the concentration which results in 50% of the test species individuals being adversely affected, i.e. both mortality and sub-lethal effects
NOEC: the concentration in the study at which no effects are observed.

This implies that when allowing moxidectin to enter water bodies, this may have a severe and lasting impact on aquatic life. To mitigate this risk, all precautions for use and disposal must be adhered to.