Impact of interventions designed to increase market share and prescribing of fexofenadine at HMOs

The impact of interventions designed to shift prescribing from loratadine t o fexofenadine at HMOs was studied. Pharmacy claims data for a six-month preintervention period at four HMOs we re analyzed to identify all new and refill prescriptions For loratadine, fe xofenadine, astemizole, and cetirizine. The interventions consisted of a ma ndatory lockout of loratadine in favor of fexofenadine (at HMO A), a volunt ary switch to fexofenadine promoted through letters to both physicians and members (HMO B), and a voluntary switch promoted through letters to physici ans only (HMO C). There was no intervention at HMO D. Pharmacy claims data for the six months after each intervention program Was implemented were ana lyzed to determine changes in the market share and prescribing of the study drugs. After the intervention programs were implemented, the market share of fexof enadine increased from 18.9% to 65.2% at HMO A, from 14.8% to 21.0% at HMO B, and from 20.7% to 23.8% at HMO C. Loratadine's market share decreased fr om 62.3% to 8.7% at HMO A, from 67.5% to 58.6% at HMO B, and from 70.5% to 65.3%, at HMO C. HMOs A, B, and C each had greater shifts in market share f or fexofenadine and loratadine than the control HMO. Changes in prescribing followed a similar pattern for the 25 physicians at each HMO who had most frequently prescribed loratadine during the preintervention period. The ave rage cost per antihistamine prescription decreased 22.3% at HMO A. Prescrip tion costs continued to rise at HMOs B, C, and D. Mandating the use of fexofenadine produced a significant increase in its ma rket share, reduced the cost of nonsedating antihistamines, and successfull y influenced prescribing behavior. Voluntary programs had a more modest imp act on market share and did not stop increases in prescription costs.