What is Gabapentin?
Gabapentin is an anticonvulsant medication that is available only by prescription [1.2.1, 1.4.4]. It was first approved by the U.S. Food and Drug Administration (FDA) in 1993 [1.2.2]. Structurally similar to the neurotransmitter gamma-aminobutyric acid (GABA), gabapentin works by altering electrical activity in the brain and influencing how the body senses pain [1.4.2, 1.6.2]. It is available in various forms, including capsules, tablets, and oral solutions, under brand names like Neurontin, Gralise, and Horizant, as well as in generic versions [1.8.1, 1.8.2].
FDA-Approved and Off-Label Uses
The FDA has approved gabapentin for specific conditions:
- Postherpetic Neuralgia: This is nerve pain that can persist after a shingles infection [1.4.2, 1.2.1].
- Partial Onset Seizures: It is used as an adjunctive therapy for adults and children aged 3 and older with epilepsy [1.2.1, 1.4.3].
- Restless Legs Syndrome (RLS): An extended-release formulation of gabapentin (Horizant) is approved for moderate to severe RLS [1.4.2, 1.8.2].
Despite its limited approved uses, up to 95% of gabapentin prescriptions are for "off-label" conditions [1.5.1]. This means doctors prescribe it for conditions it wasn't officially approved to treat, based on medical evidence and clinical judgment. Common off-label uses include:
- Diabetic neuropathy [1.4.2]
- Fibromyalgia [1.4.1]
- Anxiety disorders [1.2.3]
- Alcohol withdrawal and dependence [1.2.3, 1.5.3]
- Insomnia, particularly when related to other conditions like hot flashes [1.4.1]
How Gabapentin Works
Although it was designed to mimic GABA, gabapentin does not bind to GABA receptors [1.6.1]. Instead, its primary mechanism of action is binding to a specific subunit (alpha-2-delta) of voltage-gated calcium channels in the central nervous system [1.6.1, 1.6.3]. This action is thought to inhibit the release of excitatory neurotransmitters, thereby calming nerve activity, which helps control seizures and reduce neuropathic pain [1.6.1, 1.4.2].
The Controlled Substance Question
Federally, gabapentin is not classified as a controlled substance by the Drug Enforcement Administration (DEA) [1.2.4, 1.2.3]. However, due to growing concerns about its potential for misuse, abuse, and diversion, a number of states have taken legislative action to regulate it more strictly [1.3.1].
As of recent data, several states classify gabapentin as a Schedule V controlled substance. This is the least restrictive category for controlled substances but means prescriptions are tracked more closely [1.2.3]. States that have scheduled gabapentin include:
- Alabama [1.2.3]
- Kentucky [1.2.3]
- Michigan [1.2.3]
- North Dakota [1.2.3]
- Tennessee [1.2.3]
- Virginia [1.2.3]
- West Virginia [1.2.3]
Other states and Washington D.C. have not scheduled the drug but mandate that its prescriptions be reported to the state's Prescription Drug Monitoring Program (PDMP) [1.2.3]. These programs are databases that help prescribers and pharmacists identify patients who may be misusing controlled medications [1.2.3]. This increased monitoring reflects a broader recognition of gabapentin's risks, especially when used in combination with other central nervous system depressants like opioids [1.10.4].
Potential for Misuse and Associated Risks
Initially marketed as having a low abuse potential, emerging evidence paints a more complex picture [1.11.3]. Gabapentin can produce feelings of euphoria or relaxation, particularly at high doses, which contributes to its misuse [1.2.3]. Studies show that between 40% and 65% of people with a gabapentin prescription may misuse it [1.11.3].
The greatest danger arises when gabapentin is combined with other substances. In 2019, the FDA issued a warning about serious breathing difficulties when gabapentinoids are taken with CNS depressants like opioids, benzodiazepines, or alcohol [1.8.1]. This combination significantly increases the risk of respiratory depression and fatal overdose [1.10.4, 1.11.3].
Common and Serious Side Effects
Like all medications, gabapentin has potential side effects.
Common side effects include:
- Drowsiness and dizziness [1.7.1]
- Clumsiness or unsteadiness [1.7.2]
- Swelling of hands, feet, or ankles [1.7.4]
- Nausea and vomiting [1.7.1]
- Weight gain [1.7.1]
Serious side effects requiring immediate medical attention include:
- Severe allergic reactions (swelling of the face, lips, or throat; difficulty breathing) [1.7.1]
- Thoughts of suicide or self-harm [1.7.1]
- Severe breathing problems, especially when taken with other CNS depressants [1.7.3]
- Yellowing of the skin or eyes (jaundice) or long-lasting stomach pain, which could indicate pancreas or liver problems [1.7.1, 1.7.3]
It is critical to never stop taking gabapentin abruptly, as this can cause withdrawal symptoms like anxiety, insomnia, pain, and seizures [1.13.1]. A doctor will typically recommend a gradual tapering of the dose [1.13.1].
Gabapentin vs. Pregabalin (Lyrica)
Gabapentin is often compared to pregabalin (Lyrica), another gabapentinoid. While they have similar mechanisms, there are key differences.
| Feature | Gabapentin | Pregabalin (Lyrica) |
|---|---|---|
| Federal Status | Not a controlled substance [1.2.4] | Schedule V controlled substance [1.9.1] |
| Bioavailability | Variable and decreases with higher doses (saturable absorption) [1.9.1, 1.9.4] | High and consistent (linear absorption) [1.9.1, 1.9.4] |
| Dosing Frequency | Typically 3 times per day [1.13.3] | Typically 2 to 3 times per day [1.9.3] |
| FDA-Approved Uses | Seizures, postherpetic neuralgia, RLS (Horizant) [1.4.2, 1.2.1] | Seizures, postherpetic neuralgia, diabetic peripheral neuropathy, fibromyalgia, neuropathic pain from spinal cord injury [1.9.1] |
| Potency | Less potent [1.9.4] | Estimated to be 2.4 to 2.8 times more potent than gabapentin [1.9.4] |
Conclusion
To be clear, gabapentin is a prescription medication in the United States [1.2.1]. It is a widely used drug with legitimate, FDA-approved applications for controlling seizures and treating nerve pain, but its off-label use is far more common [1.5.1]. While it is not federally scheduled as a controlled substance, a growing number of states are implementing stricter regulations due to its recognized potential for misuse, dependence, and the significant dangers of combining it with other depressants [1.3.1, 1.2.3]. Patients should only use gabapentin as prescribed by their healthcare provider and be fully aware of its risks and side effects.
For a comprehensive understanding of drug safety, consult an authoritative source such as the FDA's Drug Safety Communications.
