We are interested in the association between a prescribing physician’s position in a physician shared-patient network and their patients’ receipt of risky drug combinations. An informal physician network (not restricted to a hospital or a health system) of physicians based in Ohio was constructed based on overlapping care of patients between physicians reflected in face-to-face visits in Fee-for-service Medicare claims for United States Ohio-residing beneficiaries. Separately, Medicare prescription drug events for beneficiaries receiving opioids, benzodiazepines, or non-benzodiazepine sedative hypnotics (sedative hypnotics) prescribe by these physicians in 2014 were used to map patients’ drug status with respect to these three classes. We assigned patient prescription receipt to time-varying drug states and linked each drug state transition to a ‘responsible’ prescribing physician. Outcomes of interest include transitions across drug states, particularly those resulting in combinations of increased risk (e.g., a benzodiazepine or sedative hypnotic with an opioid) while the key predictors of these transitions reflected characteristics of a prescriber’s physician network position. In models that adjusted for physician specialty and measures of physician prescribing volume, we found that among beneficiaries receiving none of the three risky drug groups, patients seeing physicians with higher closeness centrality (shorter average path lengths to other physicians through the network) were less likely to transition to two or three risky drugs; and they were more likely to discontinue overlapping prescriptions of an opioid, benzodiazepine, and sedative hypnotic. These findings suggest strategies for optimizing network-based interventions to improve prescribing quality.