Anti-seizure drugs often are used to help control the type of pain caused by damaged nerves. By Mayo Clinic Staff

Anti-seizure medications were originally designed to treat people with epilepsy. But the nerve-calming qualities of some of these medications 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 are activated 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 (neuropathy) can be caused by many conditions, including:

  • Diabetes. High blood sugar levels, common in diabetes, can damage nerves throughout your body. The first symptom generally is numbness and pain in your hands and feet (diabetic neuropathy).
  • 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.

    Because the risk of shingles increases with age, everyone age 50 and older should receive the varicella-zoster virus vaccine (Zostavax), which can help prevent this painful condition.

  • Chemotherapy. Some chemotherapy drugs can damage nerves, causing pain and numbness that generally begin in the tips of your toes and fingers (neuropathy).
  • Herniated disk. Nerve damage can occur if a herniated disk in your spine squeezes a nerve passing through your vertebrae too tightly.
  • Fibromyalgia. Fibromyalgia is a chronic condition that causes pain and tenderness throughout your body.

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.

It's important to note that the Food and Drug Administration has issued a warning that all anti-seizure medications are associated with a slightly increased risk of suicidal thoughts or actions. Talk to a doctor or counselor promptly if you feel depressed or suicidal.

More recent research supports the use of the anticonvulsants gabapentin (Neurontin) or pregabalin (Lyrica) to help relieve pain caused by damaged nerves.

Both gabapentin and pregabalin are particularly effective in the treatment of postherpetic neuralgia, diabetic neuropathy and pain caused by a spinal cord injury. Pregabalin also may be used to treat fibromyalgia.

Because these drugs have few side effects and are usually well tolerated, they are often the first medications to try for neuropathic pain. You may experience side effects, such as drowsiness, dizziness, confusion or swelling in the feet and legs. These side effects are limited by starting with a low dosage and slowly increasing it.

Medications from other drug classes with distinct mechanisms of pain relief (such as antidepressants) may be used in combination with anti-seizure class medications if anti-seizure medications fail to control your pain.

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

Older anti-seizure drugs include:

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

Side effects may include:

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

If you take an older anticonvulsant, you generally need regular follow-up visits so that your doctor can monitor for side effects. These older drugs often have more side effects than do the newer anticonvulsants, and the evidence supporting use of the older anticonvulsants for neuropathic pain is sparse at times. As a result, older drugs may be recommended only when the newer medications prove ineffective.

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.

Aug. 22, 2013