Gabapentin is a 1-aminomethyl-cyclohexane acetic acid and is a structural analogue of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). It was originally approved by the Food and Drug Administration (FDA) in 1993.

While it is not a controlled substance under the federal Controlled Substances Act (CSA), its misuse and association with overdose deaths have led several states to classify it as a Schedule V controlled substance.

Licit Uses

Gabapentin has several FDA-approved medical uses in the United States:

  • Seizures: It is used as an adjunctive therapy for partial-onset seizures.
  • Postherpetic Neuralgia: It treats the pain following a shingles outbreak.
  • Restless Legs Syndrome (RLS): Certain formulations are approved for moderate-to-severe primary RLS.

Clinicians also prescribe it “off-label” for conditions such as neuropathy, various pain syndromes, and anxiety. Common brand names include Neurontin®, Gralise®, and Horizant®.

Chemistry and Pharmacology

Chemical Structure

Gabapentin consists of a GABA molecule bound to a lipophilic cyclohexane ring.

Mechanism of Action

  • GABA Interaction: Although it is an analogue of GABA, it does not bind to GABA receptors, nor does it affect the synthesis or uptake of GABA.
  • Binding Site: Its primary action is binding with high affinity to the $\alpha_2\delta$ subunit of voltage-gated calcium channels in the central nervous system.
  • Pharmacokinetics: The drug is absorbed from the gastrointestinal tract and eliminated unchanged through renal excretion.

Depressant Effects

Gabapentin acts as a central nervous system (CNS) depressant.

  • Common Side Effects: Dizziness, somnolence (drowsiness), ataxia (lack of muscle coordination), and fatigue.
  • Serious Risks: It can cause respiratory depression, especially when combined with other CNS depressants like opioids.

Illicit Uses and Abuse

Gabapentin is increasingly used for its psychoactive effects, often in combination with other substances.

  • Reasons for Abuse: Individuals use it to experience euphoria, “highs” similar to cannabis, relaxation, or to manage withdrawal symptoms from other drugs.
  • Co-Ingestion: It is frequently abused alongside opioids, benzodiazepines, or alcohol to enhance their effects.
  • Prevalence: Reports indicate that gabapentin is present in a significant percentage of overdose deaths involving opioids (approximately 10% in some studies).

Illicit Distribution

  • Source: The illicit market is primarily supplied through the diversion of legitimate prescriptions.
  • Street Names: It is known by various slang terms, including “Gabbies,” “Johnnies,” “Morontin,” and “Neuro”.

Control Status

  • Federal: Gabapentin is not a controlled substance under the federal Controlled Substances Act.
  • State Level: Due to rising abuse, several states (including Kentucky, Michigan, Tennessee, West Virginia, and Alabama) have classified it as a Schedule V controlled substance. Other states have implemented mandatory reporting through Prescription Monitoring Programs (PMPs).

Contact Information:

Comments or additional information are welcome by the Drug and Chemical Evaluation Section:

  • Fax: 571-362-4250
  • Telephone: 571-362-3249
  • Email: DPE@dea.gov