Abamectin B1b (Avermectin B1b) is a macrocyclic lactone containing an isopropyl reside in the 25-position broad anthelmintic activity. The oral administration of this formulation of avermectin B1 appeared to be highly efficacious against intestinal strongyles and Onchocera microfilaria. Avermectin B1b is a component of marketed and provided commercially Abamectin, which is used to control livestock parasitic nematodes. It is a broad-spectrum acaricide with additional insecticidal action on a limited number of insects. Abamectin acts on insects by increasing the membrane permeability to chloride ions, and it mainly stimulates the release of Ȗ-aminobutyric acid (GABA). The affected arthropod becomes paralysed, stops feeding, and dies after a few days. It exerts contact and stomach action, with limited plant systemic activity, but exhibits translaminar movement into treated leaves. Abamectin is also used as an anthelmintic drug in veterinary medicine.

Avermectin B1a (AVM B1a), a widely used insecticide and acaricide, is reported to both activate and inhibit gamma-aminobutyric acidA (GABA(A)) receptor function in mammalian brain. Avermectin B1a is an antiparasitic agent that paralyzes nematodes without causing hypercontraction or flaccid paralysis. AVM B1a binds to two different sites in the GABA-gated chloride channel with dual effects, i.e., activating the channel on binding to the high-affinity site and blocking it on further binding to the low-affinity site.

Ivermectin B1B (dihydroavermectin B1b) is the minor component (<10%) of the commercial anthelmintic, ivermectin. Members of the avermectin/milbemycin anthelmintic class exert their anthelmintic effects by binding to glutamate-gated chloride channels expressed on nematode neurons and pharyngeal muscle cells. The avermectin/milbemycins are also potent insecticides. In vitro, the B1b (25-isopropyl) analog is slightly more potent than the 25-sec-butyl (B1a) analog as an inhibitor of nematode larval development and paralysis, and also a more sensitive probe for ivermectin resistance.