European perspectives on the regulation of antimicrobial drugs.

EEC legislation has been drawn up over the past few years to harmonize requirements for authorizing and marketing veterinary medicines. These measures have taken into account not only antimicrobials used for treatment and prevention of disease but also those used for growth promotion. Existing Directives are in the process of amendment and in some instances the amended legislation has already been agreed upon. One of the issues dealt with in the original Directives was that of multiple antibiotic resistance, although only limited emphasis was placed on dealing with this aspect of microbiological concern. More recently, a Regulation has been issued which requires that an MRL (maximum residue level) should be set before Member States may grant marketing authorizations for any new product. A number of toxicological and pharmacological issues have to be addressed by the applicant in making up a dossier for determining the MRL, and the microbiological potential of residues is a subject which has to be considered. The applicant is given some degree of choice in determining precisely which studies to use to ascertain whether the induction or selection of resistant bacteria could alter the consumer's intestinal flora. This paper describes some of the background to the EC legislation on the studies required for residues and evaluates the need for such studies.