EUROPEAN JOURNAL OF PHARMACEUTICS AND BIOPHARMACEUTICS
Abstract
The aim of this work was to enhance the bioavailability of erythromycin base when administered orally
in rainbow trout (Oncorhynchus mykiss). Since erythromycin is normally given in the form of medicated
feed, in this study three new types of feed formulation were developed. A self-emulsifying system and
two types of double microemulsions (O/W/O) were prepared, characterized and adsorbed on a commercial
extruded diet for fish. The emulsified systems were based on saturated polyglycolized glycerides and
mono- and diglycerides of medium-chain fatty acids (as oily phase), Tween 80 (as surfactant) and, in the
case of double microemulsions, distilled water. The systems differed in percentage composition and for
the amount and position of erythromycin in different phases. The three medicated feed were then administered
orally by means of a gastric probe to rainbow trout and their relative bioavailability was estimated
in comparison with that obtained after oral administration of feed with erythromycin powder.
For each medicated feed, 80 fish were tested. Finally, plasma profiles of erythromycin after single administration
of medicated feeds were used to predict profiles obtainable by administering once-daily medicated
feeds for 7 consecutive days. The results proved that the feeds containing microemulsified
erythromycin provided largely superior oral bioavailability and the advantage of obtaining the same efficacy
against bacterial infections with a much lower dose of drug.
