Anti-seizure medications: Relief from nerve pain

(MayoClinic.com) Anti-seizure medications were originally designed to help people who have epilepsy. But the nerve-calming qualities of many of these drugs can also help quiet the burning, stabbing or shooting pain often caused by nerve damage.

Nerves can be damaged by many things, including injury, surgery, disease or exposure to toxins. The damaged nerves fire inappropriately and send pain signals that don't serve a useful purpose. This type of pain can be debilitating and difficult to control.

Nerve damage can be caused by many conditions, including:

• Diabetes. High blood sugar levels, common in diabetes, can damage nerves throughout the body, but the first symptom typically is numbness and pain in the hands and feet.
• Shingles. Anyone who has had chickenpox is at risk of shingles, a rash of blisters that can be painful or itchy. A condition called postherpetic neuralgia occurs if shingles pain persists after the rash disappears.
• Chemotherapy. Some chemotherapy drugs can damage nerves, causing pain and numbness that typically begins in the tips of your toes and fingers.
• Herniated disk. Nerve damage can occur if a herniated disk in your spine squeezes a nerve passing through your vertebrae too tightly.

The exact mechanism of action isn't fully understood, but anti-seizure medications appear to interfere with the overactive transmission of pain signals sent from damaged nerves.

Some anti-seizure drugs work particularly well for certain conditions. Carbamazepine (Carbatrol, Tegretol) is widely prescribed for trigeminal neuralgia, a condition that causes searing facial pain that feels like an electric shock. A newer form of this drug, called oxcarbazepine (Trileptal), has fewer side effects.

Anti-seizure drugs have been used to treat nerve pain for more than 50 years, but their use was limited by the severity of side effects they produce.

Older anti-seizure drugs include:

• Carbamazepine (Carbatrol, Tegretol)
• Phenytoin (Dilantin)
• Valproic acid (Depakene)

Side effects may include:

• Liver damage
• Nausea
• Vomiting
• Double vision
• Loss of coordination
• Drowsiness
• Headache

Because these older drugs generally have more side effects than do the newer anticonvulsants, they often are used only when the newer medications prove ineffective.

Many new anti-seizure drugs have been developed in the past 15 years. Some help relieve pain caused by damaged nerves.

• Gabapentin (Neurontin)
• Oxcarbazepine (Trileptal)
• Pregabalin (Lyrica)
• Tiagabine (Gabitril)
• Topiramate (Topamax)

Gabapentin has the fewest side effects, so it typically is the first anti-seizure drug tried in people experiencing nerve pain. Gabapentin and pregabalin, which is similar to gabapentin, are particularly effective in the treatment of postherpetic neuralgia, diabetic neuropathy and migraines.

As scientists learn more about the way anti-seizure drugs work, this information will be useful in determining which drugs may work best for different types of nerve pain. Pain caused by nerve damage can be disabling, but anti-seizure drugs sometimes provide relief.

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