European Medicines Agency Veterinary Medicines and Inspections

1. Monensin (CAS 17090-79-8, CAS 22373-78-0 for sodium salt) is a polyether antibiotic from the group of carboxylic ionophores produced by Streptomyces cinnamonensis. Monensin is used as the sodium salt. It is composed of the analogues A, B, C and D with monensin A being the major component (equivalent to 98%). The intended use as a veterinary medicinal product in lactating dairy cattle is as an oral device (controlled release capsule) that will release monensin in the rumen at a maximum rate of 400 mg/day over about 100 days to control ketosis.