Hospitals need to process large quantities of scattered information to properly screen medication orders. The data includes complex relationships involving drugs, diseases, and other drugs that determine whether a particular drug is contraindicated for a patient. Hospitals would therefore benefit from a flexible system for storing complex medical data relationships. We have used GPLAN, a CODASYL-like data management system, to construct a functioning model of a hospital pharmacy medication monitoring system. the patients' histories, drug-drug contraindications, disease-drug contraindications, and recommended dosages are stored in the data base in a network structure defined by the Data Description Language. Each drug order is checked for dose, allergies, current diseases, and current medications.