Epilepsy is a brain disorder in which nerves in the brain fire inappropriately. This rapid electrical activity causes a seizure. Seizures may or may not be accompanied by outward physical signs. Not all seizures result in convulsions, for example. Partial onset seizures are among the most common seizures, affecting about two-thirds of all epilepsy sufferers.
The brain is divided into two halves, called hemispheres. In a partial onset seizure, abnormal electrical activity begins in one portion of the brain. Partial onset seizures begin (and usually remain) in the cortical cells of just one hemisphere. The seizure may eventually spread throughout the brain. A person having a partial onset seizure may remain conscious and alert. This is called a simple partial seizure. In other instances, the person may lose consciousness or awareness, and may be unable to recall what happened. This is called a complex partial seizure.
There are many possible causes of seizures. But when seizures recur and there is no identifiable cause, a patient is usually diagnosed with epilepsy. Doctors most often treat epilepsy with prescription medications called anti-epileptic drugs (AEDs). They are also called anticonvulsants. AEDs work through a variety of mechanisms to control the brain’s electrical activity and prevent or reduce the intensity of future seizures.
Epilepsy has been familiar to mankind since the dawn of history. But scientists only discovered medications to treat the disease within the past two centuries, beginning with bromides. The first “modern” AED, phenobarbital, was introduced in 1912. There is, as yet, no cure for epilepsy. But about 70 percent of epilepsy patients are able to control their seizures with medications. Some patients will require more than one drug to achieve adequate control. This is called adjuvant or “add-on” therapy. About 30 to 40 percent of patients will require one or more additional drugs. The use of multiple drugs to treat a disease is known as combination therapy. In the past decade, the number of medications available to treat epilepsy has increased significantly.
Anti-epileptic drugs are classified according to their mechanism of action. Mechanism of action refers to the specific biochemical activity that enables a drug to produce its intended effect. It often involves binding to or blocking an enzyme, or affecting a receptor on the surface of a given type of cell. In the case of nerve cells, cellular structures and messenger chemicals that play a role in making electrical impulses are obvious drug targets.
One type of structure targeted by these is a sodium channel. Some drugs work by interfering with the activity of sodium channels. Others affect a brain messenger chemical called a neurotransmitter. Drugs that affect the neurotransmitter gamma-aminobutyric acid are in this class. More recently, scientists discovered a protein on the surface of nerve cells called synaptic vesicle protein 2. This protein helps regulate electrical activity among nerve cells. It is the target of some new drugs.
According to a recent study, epilepsy that is not controlled by one drug alone (monotherapy), may best be treated by combining drugs with different mechanisms of action. This approach was found to be more effective than combining drugs with a similar mechanism of action. This form of combination therapy provides better control of seizures, and better clinical outcomes in terms of hospitalizations and emergency department visits.
Effective treatment for partial onset seizures begins with a correct diagnosis of the specific type of epilepsy being treated. People with partial onset seizures will probably be prescribed one of several tried-and-true drugs initially. Sometimes, adjuvant drugs may also be prescribed. The goal is to achieve the best control of seizure activity, with the fewest possible side effects.
Below are several AEDs for partial onset seizures. The generic drug names are provided. Many options are available as either brand-name or generic drugs:
- carbamazepine: This is a first-line treatment.
- eslicarbazepine acetate: This is the latest new drug, approved in late 2013 for adjuvant use.
- felbamate: Due to rare but potentially serious side effects, this drug is not prescribed as often as others.
- gabapentin: It has fewer side effects than many other options.
- levetiracetam: This is an adjuvant therapy with other AEDs.
- lacosamide: This is another adjuvant therapy with other AEDs.
- lamotrigine: This has fewer side effects than many other options.
- oxcarbazepine: Recently found to reduce anxiety and combat depression better than other AEDs. It is a derivative of the older drug, carbamazepine.
- perampanel: This may be prescribed when other drugs have failed. It is the first entirely new class of treatment for partial onset seizures. It targets AMPA receptors and was approved for use in 2012.
- phenytoin: An old, reliable drug, but with numerous possible side effects.
- tiagabine: This is used as adjuvant therapy with other AEDs.
- topamax: An adjuvant therapy.
- valproic acid: This should not be prescribed to women of child-bearing age.
- vigabatrin: An adjuvant therapy.
- zonisamide: An adjuvant therapy.