Drug-drug interactions in hospital.

Drug prescription charts of 200 randomly selected general medical patients in two Dublin hospitals were examined for potential drug-drug interactions. Using the Stockly Interaction alert, 37% of these patients had potential interactions but in only three was there clinical evidence that an interaction occurred. In an analysis of 150 spontaneous (yellow card) adverse drug reactions reports interactions contributed to only 8%. These results suggest that the importance of interactions as a cause of drug toxicity is commonly over-estimated.