Background: Meta-analyses of oral hypoglycaemic agents (OHAs) revealed that rosiglitazone increased the risk of myocardial infarction (MI) and heart failure (HF) and that pioglitazone increased the risk of HF and decreased the risk of MI.

Objective: To characterise the change in the pattern of use of OHAs immediately after the publication of these meta-analyses on 21 May 2007.

Methods: Pharmacy and medical claims data for a managed care organisation in the USA were analysed for patients continuously enrolled from 1 Jan 2005 to 30 Nov 2007, with at least 1 pharmacy claim for OHA in the 13-month period between 1 Nov 2006 and 30 Nov 2007.  A 5-month pre-publication period (1 Nov 2006 to 31 Mar 2007) was compared with a 5-month post-publication period (1 Jul 2007 to 30 Nov 2007) using a differences-in-differences multinomial logistic regression.  This regression explored discontinuation; continuation with monotherapy or adding another drug; and switching to a drug different from the index monotherapy drug after adjusting for gender, age, type of insurance, past 1-year history of MI or HF, and risk factors for MI and HF in the past 1 year.

Results: The relative rate of switching to nonindex drug in the postpublication relative to prepublication was 2.64 (P = 0.046) for monotherapy rosiglitazone users and 0.72 (P = 0.583) for monotherapy pioglitazone users.  The differences-in-differences estimate of the rate of switching to nonindex drugs for monotherapy rosiglitazone users was 3.64 (P = 0.090) times higher relative to the estimate for monotherapy pioglitazone users.

Conclusions: The pattern of use differed fundamentally between monotherapy rosiglitazone users and users of all other monotherapy OHAs in the postperiod.  Not only were monotherapy rosiglitazone patients switching to non-rosiglitazone drugs at a higher rate, but the rate also was more than 3 times higher than similar switches among monotherapy pioglitazone users in the postperiod relative to the preperiod.  This shows that the market response as observed by patient/prescriber decisions to the adverse news was interpreted narrowly to monotherapy rosiglitazone, and there is little or no spillover to the other drugs.  Therefore, this study found that there was a differential effect of meta-analyses on the use of the 2 drugs.