Anti-seizure medications (anticonvulsants) 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 zoster virus vaccine (Shingrix), which can help prevent this painful condition. Anyone over age 60 should get the herpes zoster vaccine (Zostavax).

• 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.

Anti-seizure medications may also help with fibromyalgia, a chronic condition that causes muscular pain and tenderness throughout your body.

Anti-seizure medications appear to interfere with the overactive transmission of pain signals sent from damaged nerves (neuropathy) or overly sensitized nerves, as in fibromyalgia.

Some anti-seizure drugs work particularly well for certain conditions. Carbamazepine (Carbatrol, Tegretol, others) is widely prescribed for trigeminal neuralgia, a condition that can cause searing facial pain that feels like an electric shock.

Research supports the use of the anticonvulsants gabapentin (Gralise, Neurontin, Horizant) and 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 may also 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. Most doctors will prescribe gabapentin first; if that doesn't work, they will try pregabalin. 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 dose and slowly increasing it.

These medications are removed from the body by the kidneys, so if your kidney function is impaired, the dose may need to be adjusted. Having impaired kidney function also increases your risk of side effects. Lower doses of these medications are safe to use if you have kidney disease.

It's important to note that 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.

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

Anti-seizure drugs have been used to treat nerve pain for many years, but if you use them, you may have to be monitored regularly by your doctor. Depending on your type of pain, your doctor may prescribe these other types of anticonvulsants.

Other anti-seizure drugs include:

• Carbamazepine
• Oxcarbazepine (Trileptal, Oxtellar XR)
• Lamotrigine (Lamictal)
• Phenytoin (Dilantin)
• Valproic acid (Depakene)

Side effects may include:

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

If you take some of these other anticonvulsants, you may need regular follow-up visits so that your doctor can monitor for side effects.

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 may provide moderate pain relief.

Sept. 12, 2019

Original article: https://www.mayoclinic.org/diseases-conditions/peripheral-neuropathy/in-depth/pain-medications/art-20045004