Estimating levamisole withdrawal period in Tilapia from the perspectives of food safety and responsible drug use

Parasitic disease outbreaks remain a major challenge in aquaculture, and approved veterinary drugs needed for controlling such diseases are limited. Levamisole has emerged as a promising alternative in fish farming because of its anthelmintic and immunostimulant properties, although it has not yet been approved for use. This study aimed to evaluate, for the first time, the residue depletion (non-radiolabelled) profile of levamisole and estimate its withdrawal period in Nile tilapia ( Oreochromis sp.) fish after oral administration under tropical conditions. Preliminary in vitro metabolism experiments supported the use of the parent compound as the marker residue. Levamisole was incorporated into medicated feed using an ethyl cellulose coating, resulting in uniform drug distribution (CV = 10%) and low leaching (