Association between payments from manufacturers of pharmaceuticals to physicians and regional prescribing: cross sectional ecological study

Objective To examine the association between payments made by the manufacturers of pharmaceuticals to physicians and prescribing by physicians within hospital referral regions. Design Cross sectional analysis of 2013 and 2014 Open Payments and Medicare Part D prescribing data for two classes of commonly prescribed, commonly marketed drugs: oral anticoagulants and non-insulin diabetes drugs, overall and stratified by physician and payment type. Setting 306 hospital referral regions, United States. Participants 45 949 454 Medicare Part D prescriptions written by 623 886 physicians to 10 513 173 patients for two drug classes: oral anticoagulants and non-insulin diabetes drugs. Main outcome measures Proportion, or market share, of marketed oral anticoagulants and non-insulin diabetes drugs prescribed by physicians among all drugs in each class and within hospital referral regions. Results Among 306 hospital referral regions, there were 977 407 payments to physicians totaling $61 026 140 (£46 174 600; €54 632 500) related to oral anticoagulants, and 1 787 884 payments totaling $108 417 616 related to non-insulin diabetes drugs. The median market share of the hospital referral regions was 21.6% for marketed oral anticoagulants and 12.6% for marketed non-insulin diabetes drugs. Among hospital referral regions, one additional payment (median value $13, interquartile range, $10-$18) was associated with 94 (95% confidence interval 76 to 112) additional days filled of marketed oral anticoagulants and 107 (89 to 125) additional days filled of marketed non-insulin diabetes drugs (P<0.001). Payments to specialists were associated with greater prescribing of marketed drugs than payments to non-specialists (212 v 100 additional days filled per payment of marketed oral anticoagulants, 331 v 114 for marketed non-insulin diabetes drugs, P<0.001). Payments for speaker and consulting fees for non-insulin diabetes drugs were associated with greater prescribing of marketed drugs than payments for food and beverages or educational materials (484 v 110, P<0.001). Conclusions and study limitations Payments by the manufacturers of pharmaceuticals to physicians were associated with greater regional prescribing of marketed drugs among Medicare Part D beneficiaries. Payments to specialists and payments for speaker and consulting fees were predominantly associated with greater regional prescribing of marketed drugs than payments to non-specialists or payments for food and beverages, gifts, or educational materials. As a cross sectional, ecological study, we cannot prove causation between payments to physicians and increased prescribing. Furthermore, our findings should be interpreted only at the regional level. Our study is limited to prescribing by physicians and the two drug classes studied.