Pharmacy Author: Omudhome Ogbru, Pharm.D.
Medical Editor: Jay W. Marks, M.D.

GENERIC NAME: gabapentin

BRAND NAME: Neurontin, Gabarone

DRUG CLASS AND MECHANISM: Gabapentin is an anticonvulsant that is used for preventing seizures and for treating postherpetic neuralgia. The mechanism of action of gabapentin is not known. Gabapentin structurally resembles the neurotransmitter gamma aminobutyric acid (GABA). It is possible that this similarity is related to gabapentin's mechanism of action. In animal models used for testing the anticonvulsant and analgesic activity of drugs, gabapentin prevents seizures and reduces pain-related responses. The FDA approved gabapentin in December 1993.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS:

• Capsules: 100, 300, and 400 mg.
• Tablets: 100, 300, 400, 600, and 800 mg.
• Solution: 250 mg/5 ml

STORAGE: Tablets and capsules should be stored between 15-30 C (59-86 F). Gabapentin solution should be refrigerated between 2-8 C (36-46 F).

PRESCRIBED FOR: Gabapentin is approved for treating seizure disorders and nerve damage from herpes zoster (shingles, postherpetic neuralgia). There are many non-approved uses for gabapentin. These include alcohol withdrawal, cocaine withdrawal, hiccups, restless leg syndrome, hyperhidrosis, headaches, diabetic neuropathy, hot flashes, and fibromyalgia.

DOSING: Gabapentin may be taken with or without food. The recommended dose for postherpetic neuralgia is 1800 mg daily in 3 divided doses. The initial dose of 300 mg daily is increased over several days to the recommended daily dose. Seizures are treated with 900-1800 mg/daily in 3 divided doses. Withdrawal of treatment should occur slowly over a week.

DRUG INTERACTIONS: Antacids reduce the concentration of gabapentin in blood. Therefore, gabapentin should be administered 2 hours or more after taking antacids. Morphine significantly increases blood concentrations of gabapentin and may increase central nervous system-related adverse events associated with gabapentin.

PREGNANCY: Safety in pregnancy has not been established.

NURSING MOTHERS: Gabapentin is secreted in human breast milk. Nursing mothers should only use gabapentin if the benefits outweigh the unknown risk to the fetus.

SIDE EFFECTS: Common side effects of gabapentin are dizziness, somnolence, ataxia, fatigue, fluid retention, hostility, nausea and vomiting. Other adverse events associated with gabapentin include hypertension, anorexia, bruising, joint pain, motion sickness, and pneumonia.

Antiepileptic medications have been associated with increased risk of suicidal thinking and behavior. Anyone considering the use of antiepileptic 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.

Reference: FDA Prescribing Information