OK, found it -- can't post links, but the study is found in
Curr Neuropharmacol. 2009 June; 7(2): 77–82.
Title: Antiepileptic Drug Monotherapy: The Initial Approach in Epilepsy Management
Erik K St. Louis,1,* William E Rosenfeld,2 and Thomas Bramley3
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OK, research shows that 47% of patients with epilepsy become seizure free with the first AED tried, and another 13% become seizure free with the second AED given as monotherapy. (That leaves the other 40% that leaves the docs scratching their heads).
One question I have is how this study defines epilepsy. A single seizure?? That could happen from illness with high fever or any number of things without progressing to a seizure pattern. So...say...if a little kid gets an ear infection, runs a high fever, and has a seizure -- one seizure -- and then is given an AED -- does he count as an epileptic? Because, if so, that could be skewing the "success rate" of AEDs.
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Anyway, the article goes on to say: "Polytherapy may only minimally increase seizure control and can substantially increase AED toxicity, drug interactions, seizure aggravation, comorbid depression, risk of sudden unexplained death in epilepsy patients (SUDEP), [ noncompliance, [8] and cost [4]. Polytherapy and seizure burden were the two main causes of quality of life impairment in one recent survey of epilepsy patients"
And...the article says that research indicates that no AED has yet been developed that affects the pathophysiology of epilepsy itself, or favorably impact long-term outcome.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2730009/ (here's the link --Nak)