Evaluation of factors related to prescription drug expenditures, prescribing trends and physican visits: the role of direct-to-consumer advertising expenditures, demographics, and health insurance coverage
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This study evaluated the relationships of age, gender, health insurance coverage, and DTCA expenditures, with physician visits for symptoms and/or conditions treated with the five advertised drug classes (allergy medications, antilipemics, gastrointestinals, antidepressants, antihypertensives) selected, number of prescriptions written and expenditures for the selected advertised drugs from January 1994 to April 2001. The study also evaluated the relationships of physician visits with number of prescriptions written and expenditures for drugs from the five drug classes. All relationships were compared prior to and following the relaxation of the broadcast advertising guidelines: (a) January 1994 to August 1997; and (b) September 1997 to April 2001. The data for the study were obtained from the following: (a) CMR for DTCA expenditures; (b) NAMCS for age, gender, health insurance coverage, physician visits, and prescriptions written; and (c) AWP and Novartis Pharmacy Benefit reports to vii estimate prices of the drugs. Time series analysis was used to determine the relationships with the dependent variable physician visits. Mixed model analysis was used to evaluate the relationships with prescriptions written and expenditures. To compare the relationships, the datasets were split by time period and reanalyzed with time series or mixed model analysis as appropriate. Age had a negative relationship with the prescriptions written and expenditures for gastrointestinals while older individuals had a positive relationship with the prescriptions written and expenditures for antidepressants. Gender (women) was positively related to prescriptions written and expenditures for allergy medications and gastrointestinals. Health insurance coverage had a negative relationship with allergyrelated visits and prescriptions written and expenditures for antihypertensives. However, health insurance coverage was positively related to prescriptions written for antidepressants. DTCA expenditures were positively related to the number of patients diagnosed with hyperlipidemia and the prescriptions written and expenditures for allergy medications, antilipemics, and gastrointestinals. DTCA expenditures were negatively related to the prescriptions written and expenditures for antihypertensives. Only physician visits were consistently related to prescriptions written and expenditures for all drug classes for the entire time period and both time periods. The study results indicate that different factors are related to physician visits, prescriptions written and their expenditures for the different drug classes.