Generic Substitution of Lamotrigine Among Medicaid Patients with Diverse Indications: A Cohort-Crossover Study
CNS Drugs, 07/18/2012
Hartung DM et al. – A statistically significant increase in emergency department visits, hospitalizations or condition–specific encounters was not observed following the switch from brand to generic lamotrigine, although a type II error cannot be ruled out.Methods
- This study was a retrospective cohort-crossover design using state Medicaid claims data from July 2006 through June 2009.
- Subjects were included in the cohort if they converted from brand to generic lamotrigine and had 2 years of lamotrigine use prior to conversion.
- The frequency of emergency department (ED) visits, hospitalizations and condition-specific ED visits or hospitalizations were recorded in the 60 days immediately following the conversion to generic lamotrigine, then compared with the incidence of the same events during a randomly selected time period indexed to one of the patient's past refills of branded lamotrigine.
- Multivariate conditional logistic regression was used to quantify the association between generic conversion and health services utilization while controlling for changes in lamotrigine dose and concurrent drug use.
- Of the 616 unique subjects included in this analysis, epilepsy was the most common diagnosis (41%), followed by bipolar disorder (32%), pain (30%) and migraine (18%).
- Conversion to generic lamotrigine was not associated with a statistically significant increase in the odds of an ED visit (adjusted odds ratio [AOR] = 1.35; 95% confidence interval [CI] 0.92, 1.97), hospitalization (AOR = 1.21; 95% CI 0.60, 2.50) or condition-specific encounter (AOR 1.75; 95 CI 0.87, 3.51).