Levetiracetam, marketed under the trade name Keppra among others, is a medication used to treat epilepsy. It is used for partial onset, myoclonic, or tonic-clonic seizures. It is taken by mouth as an immediate or extended release formulation or by injection into a vein. Levetiracetam, marketed under the trade name Keppra among others, is a medication used to treat epilepsy. It is used for partial onset, myoclonic, or tonic-clonic seizures. It is taken by mouth as an immediate or extended release formulation or by injection into a vein. Common side effects include sleepiness, dizziness, feeling tired, and aggression. Severe side effects may include psychosis, suicide, and allergic reactions such as Stevens-Johnson syndrome and anaphylaxis. It is unclear if use is safe during pregnancy but it appear okay when breastfeeding. It is the S-enantiomer of etiracetam. How it works is not clear. Levetiracetam was approved for medical use in the United States in 1999. It is available as a generic medication. A month supply in the United Kingdom costs the NHS about £19.31 per month as of 2019. In the United States the wholesale cost of this amount is about US$4.50. In 2016 it was the 89th most prescribed medication in the United States with more than 8 million prescriptions. Levetiracetam is effective as single-drug treatment for newly-diagnosed focal epilepsy in adults. It reduces focal seizures by 50% or more as an add-on medication. Levetiracetam is effective as add-on treatment for partial (focal) epilepsy. Levetiracetam is effective for treatment of generalized tonic-clonic epilepsy. It has been approved in the United States as add-on treatment for myoclonic, and tonic-clonic seizures. Levetiracetam has been approved in the European Union as a monotherapy treatment for epilepsy in the case of partial seizures, or as an adjunctive therapy for partial, myoclonic, and tonic-clonic seizures. Levetiracetam is sometimes used off-label to treat status epilepticus Based on low-quality evidence, levetiracetam is about as effective as phenytoin for prevention of early seizures after traumatic brain injury. It may be effective for prevention of seizures associated with subarachnoid hemorrhages. Levetiracetam has not been found to be useful for treatment of neuropathic pain, nor for treatment of essential tremors. Levetiracetam has not been found to be useful for treating autism, but is an effective treatment for partial, myoclonic, or tonic-clonic seizures associated with autism spectrum disorder.