[Medical problems and risks of switching drugs according to legal requirements of drug discount contracts in Germany].
Since 2007 German health insurance funds may conclude discount contracts with pharmaceutical companies for individual drugs. According to German legislation pharmacies are liable to preferentially dispense these drugs to patients of the respective funds if the prescribed drug is identical regarding active ingredient, strength, package size, and route of administration, and is approved for the same indication. We aimed to assess the number and nature of clinically relevant differences between prescribed drug and its legal alternatives. Using databases and expert systems of the drug information system AiD KLINIK we evaluated all 258 412 exchangeable drug pairs of the German market currently regulated by discount contracts. 15,7 % of the drug pairs differed in dosage, in one quarter each colour or shape was significantly different, and in roughly 3 % the size of the substituted drug differed by more than 50 %. In 9,43 % splitting characteristics of solid oral doses differed and in 1,87 % the substituted drug contained additives with allergenic potential not present in the primarily selected drug. On average 0,44 clinically relevant differences could be calculated in each substitution. This study has revealed that current legal provision ignore important medical criteria of the substitution process including individual risks (e. g. allergies). Patients will have to change the drug application process and will therefore need appropriate information and training. All these differences between substitutional drug pairs should already be known when prescribing so as to maintain patient safety in the face of this merely cost-saving measure.