Since their discovery more than 70 years ago antibiotic drugs have been efficient tools for treating bacterial infections. However, the use of antibiotics may lead to resistance to the same or other substances. The risk of resistance appears to be larger in veterinary medicine, since antibiotics have been given as feed-additives in animal production, the amounts given are larger, and the risk of selecting the wrong substance is higher due to lack of diagnostic facilities. Historically, as resistance developed, new classes of antibiotics were developed. Today, however, this flow of new substances has declined considerably. This working paper contains a more technical exposition of the discussion in our paper Antimicrobial sensitivity – a natural resource to be protected by a Pigouvian tax? (Preventive Veterinary Medicine, 2010; 96: 9-18. Homepage: http://www.elsevier.com/locate/prevetmed) concerning how to minimize the problem of antibiotic resistance while, at the same time, increase incentives to develop new solutions regarding treatment of bacterial infections.