The impact of wording in "Dear doctor" letters and in black box labels.

OBJECTIVES: The Food and Drug Administration and pharmaceutical manufacturers use "Dear doctor" letters to alert physicians about drug safety. To determine how such warnings may be improved, we retrospectively examined how variations in the wording of one series of "Dear doctor" letters affected their impact on concomitant dispensing of cisapride (Propulsid; Janssen Pharmaceutica, Titusville, NJ) and several medications contraindicated for concomitant use.
METHODS: Concomitant dispensing was defined as dispensing cisapride and a contraindicated medication on dates when the intended duration of the two dispensings overlapped on at least 1 day. Using outpatient pharmacy claims from a New England health insurer, we calculated a concomitant dispensing rate for each calendar month as the number of concomitant cisapride dispensings divided by the total number of cisapride dispensings. We grouped drugs contraindicated for concomitant use with cisapride as (1) explicitly named in the warnings, (2) only mentioned as examples of a drug class, or (3) only implied as drug class members. We used multivariate analysis to relate temporal changes in concomitant dispensing rates to type of warning (explicit, example, or implied), patient demographic characteristics, season, calendar year, and temporal relationship to the "Dear doctor" warnings.
RESULTS: A highly publicized letter sent in June 1998 was associated with a notable decline (58%) in the concomitant dispensing rate with explicitly contraindicated drugs but not in the concomitant dispensing of cisapride with the example or implied drugs. An earlier letter, which had been explicit but was accompanied by less publicity, had no measurable effect on this study's measure of coprescription, nor did a later letter that emphasized comorbidities.
CONCLUSIONS: Explicit, well-publicized drug warnings can change prescriber behavior.