Levetiracetam (Keppra) Tolerability in Cocaine Abusing Methadone-maintained Patients.

The participants will start receiving Levetiracetam 500mg in the mornings of the first day on week 2. The dose will be titrated every third day, until the target dose of 3000mg/day is achieved by week 4. The study medication must be titrated to 3000 mg/day or to the subject's maximum tolerated dose (MTD). The physician overseeing this titration as well as all study staff will not be blind to the subject's medication administration. The medication will be discontinued over a two-week period