Abstracts

Retention, a measure of antiepileptic drug (AED) [ldquo]effectiveness[rdquo], is the percentage of patients started on a drug who remain on it after a given period of time, and is a composite measure of efficacy & tolerability. Few studies have compared effectiveness of AEDs for use in this population.
We compared 12 month retention, seizure freedom & tolerability of newer & older AEDs in older adults with epilepsy., We reviewed patient background, medical history, AED use and 1-year retention, seizure-freedom, & side effects (& whether or not these led to a change in dose) for 413 patients [ge]55 years old, newly started on any AED at our center from 1/1/2000 - 12/31/2004. Results were calculated for the overall group & for subgroups with varying degrees of refractoriness, estimated by the number of prior AEDs tried: 0-1: non-refractory; 3-5: refractory; 5+: very refractory. In each comparison, the individual AED was compared to the average of all other AEDs. Those who were seizure-free but stopped an AED in [lt] 1 year due to side effects were excluded from the seizure-freedom analysis., Overall, 319/413 (77.2%) patients remained on at least 1 AED for at least 1 year. The following were 12-month retention rates for each AED (^*=p[lt]0.05 better, ^$=p[lt]0.05 worse, compared to average of other AEDs), listed from most to least effective: LTG^* (75.6%; 90/119), LEV^* (71.7%; 71/99), VPA (65.0%; 13/20), CLB (64.3%; 9/14), GBP (61.0%; 25/41), ZNS (58.8%; 10/17), TPM (52.4%; 11/21), PHT (50.0%; 7/14), CBZ (46.4%; 13/28), OXC^$ (24.2%; 8/33). Relative rates were similar in refractory patients, except VPA (improved to 90.0%; 9/10, p[lt]0.1) and CBZ^$ (dropped to 25%; 2/8).
12-month seizure-freedom rates were as follows (^*=p[lt]0.05 better, ^$=p[lt]0.05 worse, compared to average of other AEDs), listed from most to least efficacious: LTG^* (47.4%; 36/76), LEV (33.3%; 22/66), CBZ (23.1%; 6/26), VPA (20.0%; 3/15), GBP (17.9%; 5/28), TPM (17.6%; 3/17), PHT (16.7%; 2/12), OXC^$ (6.5%; 2/31) and ZNS (0.0%; 0/15). Relative rates were similar in refractory & very refractory patients. Tolerability data will be presented., In this study, LTG was the most effective AED as measured by 12 month retention and seizure-freedom, with LEV a close second; PHT, CBZ & OXC were consistently below average for effectiveness. For the 3 AEDs previously studied in the prospective, randomized, double-blinded VA cooperative trial of epilepsy in older adults (LTG, GBP and CBZ), our retention results are strikingly similar.
(Abbreviations: CBZ=carbamazepine, CLB=clobazam, GBP=gabapentin, LEV=levetiracetam, LTG=lamotrigine, OXC=oxcarbazepine, PHT=phenytoin, TPM=topiramate, VPA=valproic acid, ZNS=zonisamide)., (Supported by Elan, GlaxoSmithKline, Novartis, Ortho-McNeil, Pfizer and UCB Pharma.)