OBJECTIVE： To investigate drug combination in outpatient prescriptions of hypertension patients in our hospital， provide reference for rational drug use in clinic. METHODS： The outpatient prescriptions of patients diagnosed as hypertension during Jan. 1st to Feb. 1st in 2015 were collected from the hospital. The prescriptions of two or more than two drugs were screened， and the prescriptions of drug combination containing CYP enzyme substrate， inhibitor or inducer were recorded. Guided by metabolic enzymology theory， the potential metabolic drug interactions in prescriptions were evaluated on the basis of relevant literature and data reports. RESULTS： Totally 1 042 prescriptions were consulted. The prescriptions of the combined medication were 551， and the potential metabolic drug-drug interactions were detected at 249 prescriptions， accounting for 45.2％. Main CYP enzyme subtypes were CYP3A4， CYP2C9， CYP2C19 and CYP2D6. Totally 214 prescriptions were correlated with CYP3A4， accounting for 85.9％ of drug interaction prescriptions； CYP3A4 substrate combined with substrate in 199 prescriptions， with inhibitor in 27 prescriptions， and with inducer in 11 prescriptions. Totally 27 prescriptions were correlated with CYP2C9， accounting for 10.8％ of drug interaction prescriptions； CYP2C9 substrate combined with substrate in 8 prescriptions， and with inhibitor in 20 prescriptions. Totally 27 prescriptions were correlated with CYP2D6， accounting for 10.8％ of drug interaction prescriptions； CYP2D6 substrate combined with substrate in 15 prescriptions， and with inhibitor in 12 prescriptions. Totally 4 prescriptions were correlated with CYP2C19， accounting for 1.6％ of drug interaction prescriptions； CYP2C9 substrate combined with inhibitor in 2 prescriptions， and with inducer in 2 prescriptions. CONCLUSIONS： Many metabolic drug-drug interactions are detected in the outpatient prescriptions of hypertension patients in our hospital. In order to improve the rationality and safety of the prescription， clinicians and pharmacists should pay attention to the drug combinations with drug-drug interactions which have been reported in the existing literature， and choose similar drugs without or with little interactions.