(monensin, salinomycin, lasalocid, narasin, maduramicin, and semduramicin) form complexes with various ions, principally sodium, potassium, and calcium, and transport these into and through biologic membranes. The ionophores affect both extra and intracellular stages of the parasite, especially during the early, asexual stages of parasite development. Drug tolerance was slow to emerge in chickens coccidia, probably because of the biochemically nonspecific way these fermentation products act on the parasite. Recent surveys suggest that drug tolerance is now widespread, but these products remain the most important class of anticoccidials.

 

Some ionophores may depress feed consumption when the dosage is above recommended levels. Primarily, this is the result of reduced feed consumption, but the reduced growth may be offset by improved feed conversion.