PHILADELPHIA — Generic substitutions were linked with significantly increased medical care cost and total health care cost in a retrospective study of more than 600 epilepsy patients.
Even though a year's worth of treatment with the brand-name drug Lamictal costs an average of about $360 (Canadian dollars) more than a year's worth of generic lamotrigine, this excess was more than offset by an average 56% increased cost for in-patient hospitalization among those on the generic, as well as increased costs for drugs that were not antiepileptics.
Total health care costs averaged $1,482 (Canadian dollars)/patient-year higher in patients treated with generic lamotrigine, compared with those on Lamictal, a 23% relative increase that was statistically significant, Dr. Jacques LeLorier and his associates reported in a poster at the annual meeting of the American Epilepsy Society.
The study was sponsored by GlaxoSmithKline, which markets Lamictal. Dr. LeLorier has received consultation fees and research support from GlaxoSmithKline.
The study used data obtained by the medical and pharmacy health claims filed with the Quebec provincial health plan during April 1998-July 2006. Patients treated with any one of four different antiepileptic drugs switched from the generic to brand formulation at rates that ranged from 21% (for carbamazepine) to 44% (for clobazam). The switch rate for lamotrigine to Lamictal was 28%. In contrast, the switch rate for drugs for other disorders, such as the β-blocker carvedilol and the lipid drug simvastatin, ranged from 8% to 9%, reported Dr. LeLorier, a professor of medicine and pharmacology at the University of Montreal. Overall, patients treated with a generic antiepileptic drug were about 2.5-fold more likely to switch to a brand formulation than were patients who had other disorders.
A follow-up analysis in a second poster at the meeting attempted to convert the observed economic effects seen in Quebec into equivalent costs in the United States. Two different conversion formulas were used; each formula took into account economic factors that differed between the United States and Canada during the study period, including currency exchange rates, purchasing power, and medication and health care costs.
The extrapolation to U.S. costs showed a much larger cost difference between generic lamotrigine and Lamictal. In one cost-conversion model this difference meant that treatment with Lamictal cost an extra $1,175 (U.S. dollars) more than generic lamotrigine per patient-year. The second model calculated an excess cost for Lamictal of $1,926 (U.S. dollars) per patient-year, reported Mei Sheng Duh, Sc.D., an epidemiologist at the Analysis Group in Boston.
But despite the higher drug cost, patients treated with Lamictal could expect to save a net of $693 (U.S. dollars) per patient-year, based on one conversion formula used, or $787 (U.S. dollars) per patient-year according to the second formula.