Effect of Generic Competition on Atorvastatin Prescribing and Patients' Out-of-Pocket Spending

In November 2011, the cholesterol level-lowering medication atorvastatin calcium became available in the United States as a generic drug. However, only a single generic form (from a manufacturer that qualified for market exclusivity by challenging several of Pfizer's patents) and an authorized generic form (a brand-name drug sold as a generic) were available for the first 180 days.

To describe trends in the prescribing of generic atorvastatin after expiration of market exclusivity for the brand-name medication and the effect on patients' out-of-pocket spending.

A US population-based study used commercial claims data from the Optum Clinformatics research database (UnitedHealth Group) from December 1, 2010, to May 31, 2013. Participants were 1 968 709 adults with commercial insurance who had been prescribed 1 or more statins (13 285 223 statin prescriptions). An interrupted times series model was used to examine the effect of limited and full generic competition on brand-name and generic atorvastatin prescriptions. Data were analyzed from December 1, 2010, to May 31, 2013.

Prescription of brand-name atorvastatin, generic atorvastatin, and authorized generic atorvastatin were distinguished using National Drug Codes.

Total number of prescriptions dispensed per month and out-of-pocket expenditures for a typical 30-day supply of 20-mg atorvastatin during the periods of brand-name availability only, limited generic competition (lasting 180 days after market exclusivity ended), and full generic competition.

Of the 1 968 709 beneficiaries, 1 483 066 (58.8% male and 41.2% female; mean [SD] age, 55.6 [10.2] years) received a prescription for a single statin and were included in the analysis. The introduction of the first generic competitor was associated with a reduction in monthly brand-name atorvastatin fills by 20 896 prescriptions (level change, P = .001), an 18.1% change compared with the month preceding loss of exclusivity. Full generic competition reduced brand-name fills by 54 944 prescriptions (level change, P < .001), a 47.6% change relative to the month preceding loss of exclusivity. During the first 180 days of generic competition, no meaningful difference in monthly out-of-pocket spending was found between brand-name (median, $16.98; interquartile range [IQR], $8.76-$48.66) and generic (median, $19.98; IQR, $7.50-$54.90) atorvastatin. After full generic competition, estimated monthly out-of-pocket spending for generic atorvastatin (median $5.10; IQR, $3.36-$19.98) or authorized generic atorvastatin (median, $5.52; IQR, $3.48-$19.98) was substantially lower than that for brand-name atorvastatin (median, $30.00; IQR, $15.00-$91.38).

Among patients with commercial health insurance, delays in generic uptake and high levels of out-of-pocket spending during the first 180 days after atorvastatin lost market exclusivity slowed changes in drug prescribing and decreases in patients' out-of-pocket costs.