Physicians and patients should be aware that dispense as written designations not only increase costs to the patient but also adversely affect rates that patients purchase those prescriptions. Educational efforts to encourage generic acceptability should target those most likely to express concern about generics. Our findings indicate that specialists, older physicians, and patients aged 55 to 74 years are more likely to request dispense as written and may represent targets for educational outreach. These efforts should focus on initiation of chronic medications, because patients disproportionately fail to purchase these prescriptions when either physicians or patients request dispense as written.

Prescriptions for certain classes of medications were far more likely to be accompanied by a dispense as written request. In particular, classes with narrow therapeutic indices, such as thyroid medications, anticoagulants, and anticonvulsants, were commonly delivered with a dispense as written request. There has been substantial debate in the scientific literature as to the equivalency of these products; although the literature may not corroborate these clinical concerns, it is likely that patients and physicians have a clinical rationale for these requests. The high rates of dispense as written requests for migraine products, ulcer agents, and hypnotics are more surprising, and may be related to effective marketing campaigns to patients and physicians.

It is interesting to observe that physicians request dispense as written frequently for single-source branded products, medications for which no generics could be automatically substituted. Physicians with a strong preference for branded medications may not be aware of whether a generic is available and may request the branded agent as a preventive measure. Alternatively, physicians may request the branded medication to ensure that pharmacists do not substitute a different medication in the class for the prescribed medication (eg, substitution of simvastatin for atorvastatin [Lipitor, Pfizer Inc, New York, NY]); this so-called therapeutic substitution is generally not permitted without first contacting the physician. It is unclear whether these requests ultimately exert any influence on the medication that is delivered to the patient.

Substantial geographic variation in dispense as written requests was seen. This variation may reflect patterns of marketing or the culture of medical education and prescribing that pervade different regions. These also may reflect habit, reflex, or consequences of automatically checked boxes in electronic prescribing systems or on standardized prescription pads. In addition, these variations may be related to geographic differences in pharmacy practice that influence communication with patients and physicians.