gabapentin enacarbil (Horizant, Gralise, Neurontin)

Gabapentin enacarbil is used for treating restless leg syndrome (RLS) and postherpetic neuralgia. It is a prodrug of the anticonvulsant gabapentin, which means it is first converted to gabapentin in the body before it can have its effects.

The mechanism of action of gabapentin in treating restless leg syndrome (RLS) or postherpatic neuralgia is not known. Gabapentin structurally resembles the neurotransmitter, gamma aminobutyric acid (GABA). (A neurotransmitter is a chemical that nerves use to communicate with one another.) It is possible that this similarity is related to gabapentin's mechanism of action. In animal models used for testing the anti-seizure and anti-pain (analgesic) activities of drugs, gabapentin prevents seizures and reduces pain-related responses. The FDA approved gabapentin enacarbil in April 2011.

What brand names are available for gabapentin enacarbil?

Horizant, Gralise, Neurontin

Is gabapentin enacarbil available as a generic drug?

No

Do I need a prescription for gabapentin enacarbil?

Yes

The most common side effects of gabapentin enacarbil are:

• dizziness,
• somnolence,
• ataxia,
• fatigue, and
• drowsiness.

Gabapentin enacarbil may cause significant driving impairment. Fluid retention, hostility, nausea and vomiting also occur. Other adverse events associated with gabapentin enacarbil include:

• weight gain,
• joint pain,
• motion sickness,
• blurred vision, and
• viral infections.

Gabapentin enacarbil is converted to gabapentin, which is an anti-seizure medication. Anti-seizure medications have been associated with an increased risk of suicidal thinking and behavior. Anyone considering the use of anti-seizure drugs must balance this risk of suicide with the clinical need. Patients who are started on therapy should be closely observed for clinical worsening, suicidal thoughts, or unusual changes in behavior.

Gabapentin enacarbil should be taken with food. The recommended dose for postherpetic neuralgia is 1200 mg daily. The initial dose of 600 mg daily is increased after three days to the recommended daily dose. Gabapentin enacarbil is not interchangeable with other gabapentin products. Restless leg syndrome is treated with 600 mg once daily.

Alcohol increases the amount of gabapentin enacarbil released into the body. Alcohol should not be used with gabapentin enacarbil. Combining gabapentin enacarbil with morphine significantly increases the occurrence of sedation and dizziness over either drug alone.

Safety in pregnancy has not been established.

Gabapentin is secreted in human breast milk. Nursing mothers should only use gabapentin enacarbil if it is necessary.

What preparations of gabapentin enacarbil are available?

Tablets (extended release): 300, 600 mg

How should I keep gabapentin enacarbil stored?

Gabapentin enacarbil should be store between 15 C to 30 C (59 F to 86 F).