Pharmacotherapeutic group: Milbemycin oxime Anthelmintic, Lufenuron Insect Growth Regulator
ATC Vet Code: QP54AB51
Milbemycin belongs to the group of macrocyclic lactones, isolated from the fermentation of Streptomyces hygroscopicus var. aureolacrimosus. Out of the selected analogues, the one currently used for medicinal purposes is Milbemycin A3/A4 oxime (ratio ≤20 : ≥80). As one of the active principles in Program Plus, it is effective against larval stages (L3, L4, and the microfilariae) of Dirofilaria immitis, and anthelmintic activity against the following nematodes: Toxocara canis, Trichuris vulpis, Ancylostoma caninum. The activity of milbemycin is correlated with its action on invertebrate neurotransmission: it potentiates GABA (gamma-amino-butyric acid), an inhibitor of neuromuscular transmission, leading to paralysis.
Lufenuron belongs to the chemical group of benzoylureas, and is considered an IGR (Insect Growth Regulator) or IDI (Insect Development Inhibitor). It inhibits the development of fleas by interfering with the normal synthesis, polymerisation and deposition of the chitin, the principal component of the
arthropod exoskeleton. The adult flea absorbs lufenuron via its bloodmeal. At therapeutic levels, lufenuron has no effect upon adult fleas, but passes transovarially to act upon certain stages of the development of the insect (egg and larva), thus interrupting the insect life cycle. Also, adult flea faeces containing lufenuron exert a larvicidal effect when ingested by the larvae directly.
Milbemycin oxime is characterised by gastro-enteric absorption. It reaches peak plasma concentrations of about 200 - 300 ng/mL within about 2 to 5 hours after oral administration at recommended dose. Thereafter, milbemycin oxime concentrations decrease in plasma with a half life of about 1 to 3 days.
Following oral administration, lufenuron is distributed via the blood to the adipose tissue, from which, metabolically unmodified, it is constantly released above the minimum effective concentration for at least one month.