Medical Health Encyclopedia

A rash occurs in 5% of patients; it may disappear in some patients who continue taking the drug, but in rare cases it can become very severe. The risk of the rash increases if the drug is started at too high a dose or if the patient is also taking valproic acid. (Serious rash is more common in young children who take the drug than it is in adults.) Other side effects may include nausea, dizziness, blurred vision, headache, and sleepiness. Some patients report severe insomnia. A rare but serious side effect is anticonvulsant hypersensitivity syndrome, which is characterized by fever, skin eruptions, abnormal lymph nodes, and liver damage.

Gabapentin. Gabapentin (Neurontin) is an effective add-on drug for controlling complex partial seizures and secondarily generalized partial seizures and is approved for adults and children with these seizures. In a 2002 analysis of current evidence, it achieved response rates in patients with resistant partial epilepsy that were as high as 28% at high doses. It is not at all useful for generalized petit mal seizures.

Its toxicity is low and side effects include sleepiness, headache, fatigue, and dizziness. Some weight gain has been reported. Gabapentin has no significant interactive effects when taken with other drugs. It has the added advantage of improving mood, which is independent from its effect on seizure control. Children may experience hyperactivity or aggressive behavior. Long-term adverse effects are still unknown.

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Pregabalin. Pregabalin (Lyrica) is similar to gabapentin. In 2005, it was approved as add-on therapy to treat partial-onset seizures in adults with epilepsy. In clinical trials, half of the patients who received pregabalin experienced a 50% reduction in seizure frequency. Side effects may include dizziness, sleepiness, dry mouth, swelling in hands and feet, blurred vision, weight gain, and trouble concentrating

Topiramate. Topiramate (Topamax) is similar to phenytoin and carbamazepine and is effective and safe for a wide variety of seizures in adults and children. It is approved as add-on therapy for patients 2 years and older with generalized tonic-clonic seizures, partial-onset seizures, or seizures associated with Lennox-Gastaut syndrome. It is also approved as single therapy for patients 10 years and older with tonic-clonic seizures or partial-onset seizures. Studies have shown a 34 - 87% reduction in seizure frequency with some patients becoming seizure-free. Topiramate may have fewer interactions with oral contraceptives than other AEDs.

Most side effects are mild to moderate and can be reduced or even prevented by beginning at low doses and increasing dosage gradually. Serious side effects may include glaucoma, decreased sweating, increased body temperature, kidney stones, sleepiness, dizziness, confusion, and trouble concentrating. Patients should immediately tell their doctor if they have blurred vision or eye pain.

Oxcarbazepine. Oxcarbazepine (Trileptal) is similar to phenytoin and carbamazepine but generally has fewer side effects. It is approved as single therapy or add-on therapy for partial seizures in adults and for children aged 4 to 16 years. Serious side effects, while rare, include Stevens-Johnson syndrome and toxic epidermal necrolysis. These skin reactions cause a severe rash that can be life-threatening. Rash and fever may also be a sign of multi-organ hypersensitivity, another serious side effect associated with this drug. Oxcarbazepine can also reduce sodium levels (hyponatremia). Your doctor may want to monitor the sodium level in your blood. This drug can also reduce the effectiveness of birth control pills. Women who take oxcarbazepine may need to use a different type of contraceptive.

Zonisamide. Zonisamide (Zonegran) is a unique drug that blocks sodium and calcium channels and may have nerve-protecting properties. It is approved as add-on therapy for adults with partial seizures and studies indicate it is often effective against infantile spasms (West's syndrome) and myoclonic seizures. Zonisamide increases the risk for kidney stones, which can be reduced with increased fluid intake and citrate. It has also been associated with reduced sweating and a sudden rise in body temperature, especially in hot weather. Children are especially at risk for this side effect, which can be serious. (The drug has not been approved for children.) Other side effects tend to decrease over time and include dizziness, forgetfulness, headache, weight loss, and nausea.

Levetiracetam. Levetiracetam (Keppra) is known as a nootropic drug and has been approved for partial onset seizures in adults and children aged 4 years and older. Some experts believe that levetiracetam represents a significant advance and will prove to be an important first-line drug. Some evidence suggests that it improves mental function and quality of life. Levitracetam has fewer drug interactions than other anti-epileptic agents and may be particularly useful for older patients.

Side effects occur mostly in the first month. They include: sleepiness and fatigue, muscle weakness and coordination difficulties, headache, flu symptoms, dizziness, behavioral abnormalities, and possible risk of a reduced white blood cell count and a higher rate of infections. Caution is advised for patients with kidney dysfunction. There have been some reports of adverse effects on mood (irritability, depression, anxiety) but recent studies have found fewer such effects than with other AEDs. Epilepsy, rather than the drug, is likely to be the cause of these mood changes. About 1% of patients report considerable weight loss.

Tiagabine. Tiagabine (Gabitril) has properties similar to phenytoin and carbamazepine, and is also showing promise. Evidence has reported some significant side effects with its use, including dizziness, fatigue, agitation, and tremor. At least one study suggested that it has more adverse effects than lamotrigine and is not as well tolerated. In February 2005, the FDA issued a warning advising that tiagabine may cause seizures in patients without epilepsy. Tiagabine is only approved for use with other anti-epilepsy medicines to treat partial seizures in adults and children 12 years and older.

Less Commonly Used AEDs

Felbamate. Felbamate (Felbatol) is an effective antiseizure drug. However, after reports of deaths from a serious blood condition known as aplastic anemia or from liver failure, felbamate is only recommended under certain circumstances. They include severe epilepsy, such as Lennox-Gastaut syndrome or as monotherapy for partial seizures in adults when other drugs fail.

Vigabatrin. Vigabatrin (Sabril) is a chemical called gamma-vinylGABA. It was designed to increase the brain levels of gamma aminobutyric acid (GABA), the enzyme that inhibits seizure activity. It has serious side effects, however, and is generally prescribed in the US in only certain cases, such as in low doses for patients with Lennox-Gastaut Syndrome. Overseas it is also used for partial seizures and as first line therapy in children with infantile spasms (West syndrome). Between 10% and 30% of people on long-term treatment have developed irreversible visual disturbances, including reductions in acuity and color vision. Men are at higher risk for this side effect than are women. Further studies are needed to determine the extent and severity of this complication, particularly in children. There is a slight risk for depression or psychosis when vigabatrin is used as add-on therapy, and particularly if the drug is administered too quickly. These risks are far lower if the drug is used as sole therapy.

Older Drugs. Some older but less effective drugs may still play a role against epilepsy:

• Acetazolamide (Diamox) is sometimes used against common types of seizures, but patients quickly develop a tolerance for it. Some experts suggest it still may be useful when drug interactions are a problem, when a rapid effect is required, or when an additional drug is needed for a short time.
• Trimethadione (Tridione) is effective for petit mal seizures, but has very serious side effects, and its use is severely limited.

Investigative Drugs

GABA Enhancers.Retigabine is an investigative GABA enhancer that may prove to be more effective than current AEDs with similar actions (vigabatrin, tiagabine, gabapentin and topiramate). It is currently in phase III trials for treatment of partial-onset seizures.

Other Investigative Anti-Epilepsy Drugs.Losigamone is a unique AED whose exact mechanism is unclear. In a well-conducted 2003 study, the drug appeared to be effective and safe for adults with partial epilepsy. Most side effects occurred within the first month and then subsided.

Drugs known as AMPA receptor antagonists, for example, have anti-seizure properties and are under investigation. Talampanel is one such potentially effective AED and is currently in early trials.

Other anti-seizure drugs being investigated include fluorofelbamate, safinamide, brivaracetam, and seletracetam.

Cannabinoids. Cannabinoids are compounds in marijuana (cannabis), which may have properties that protect nerve cells. In one 2003 report, people with epilepsy were twice as likely to use marijuana as the general public, with two thirds of them taking it because they believed it reduced their seizures. Other active users of marijuana reported no effect on seizures. No one has reported worse seizures from the drug. Animal studies further support some protection from cannabinoids against seizures. Clinical studies using humans have not been conducted.

Melatonin. Melatonin is a hormone found in the brain that is best known for its role in sleep. Some researchers believe that it might have properties that could benefit patients with epilepsy. Melatonin is a powerful hormone that can have major effects on all parts of the body. No one with epilepsy should experiment with this supplement except as part of a clinical trial. Of note, in some studies, melatonin has been found to cause seizures in children who have existing neurologic problems.