Prophylaxis of Recurrent Erythema Nodosum with Penicillin

363 face. This may result in poor penetration of ciclosporin into the nail structures and consequently inadequate topical treatment. So, patients who forget to homogenize the emulsion before application are at risk for treatment failure. Ciclosporin per se poorly penetrates into the skin and nail structures. Thus far, no biopharmaceutical data are available with regard to formulations that enhance penetration of ciclosporin into the skin and nail structures. On the other hand, chronic application of ciclosporin may result in unacceptable systemic exposure to ciclosporin. Therefore, biopharmaceutical investigations should focus on stability aspects, penetration into nail structures and systemic exposure to ciclosporin in the future. This case of a pharmaceutically instable ciclosporin emulsion illustrates the importance of good manufacturing practices (GMP) in the development process of new drug formulations. In a clinical setting, we advocate close cooperation between physicians and pharmacists to deal with pharmaceutical aspects of experimental drug formulations such as stability properties of topical emulsions in this particular case. In this regard GMP (GMP for experimental dosage forms, annex 13 of the European GMP) and thorough quality control of (experimental) dosage forms have to be taken into account [3–5] . GMP aspects and stability testing of new drug formulations are essential in preparing effective and safe drug formulations for our patients.