Macrocyclic Lactones

MACROCYCLIC LACTONES

Avermectins / Milbemycins

  • Macrocyclic fermentation products of Streptomyces avermilitis(Avermectins) and Streptomyces cyanogriseus (Milbimycins)
  • Avermectins: Abamectin, Doramectin, eprinomectin, moxidectin and  milbemycin oxime, selamectin are available
  • Since these are active against nematodes and arthropods they are referred to as endectocides
  • Available as Oral / parentral/topical-spot.ons/pour - ons
  • Wide safety margin – but some breeds of dogs (collies) are sensitive to ivermectins
  • Both are lipophilic – stored in fat tissue and released slowly, metabolized and excreted. A temporary depot occurs in fat and liver and there is slow release.
  • Prolonged half life of these compounds also determines levels of residues in meat and milk .  Hence,  there is a compulsory withdrawal period following treatments in food producing animals
  • With exception of eprinomectin which has zeromilk withdrawal period, this class of compounds cannot be given to lactating cows (or) during the last 2 months of pregnancy

Mode of Action

  • Acts on γ amino butyric acid (GABA) neuro transmission at 2 or more sites blocking interneuronal stimulation of excitatory motor neurons – leading to flaccid paralysis – achieves this probably by stimulating the release of GABA from nerve endings & enhancing the binding of GABA to its receptor on the post synaptic membrane of an excitatory motor neuron
  • The enhanced GABA results in an increase flow of cl- ions into cell leading to hyperpolarization
Last modified: Monday, 9 May 2011, 9:47 AM