Gabapentin

Gabapentin

Chemical structure of gabapentin

Gabapentin is a medication used primarily to treat epilepsy and neuropathic pain. It is also prescribed for various off-label uses, such as the treatment of anxiety disorders, restless leg syndrome, and alcohol withdrawal. Gabapentin, a gamma-aminobutyric acid (GABA) analog, was originally developed as an anticonvulsant and is chemically related to the neurotransmitter GABA, although its exact mechanism of action is not fully understood.

Medical uses

Gabapentin is prescribed for several medical conditions, including:

• Epilepsy: As an adjunctive therapy for partial seizures, gabapentin is used in combination with other anticonvulsant medications to control seizures.
• Neuropathic pain: Gabapentin is effective in the treatment of neuropathic pain, particularly in conditions such as diabetic neuropathy, postherpetic neuralgia, and central neuropathic pain.
• Off-label uses: Physicians may prescribe gabapentin for various off-label purposes, including anxiety disorders, bipolar disorder, restless leg syndrome, and alcohol withdrawal.

Mechanism of action

Gabapentin is structurally similar to the neurotransmitter GABA, but it does not bind to GABA receptors or influence GABA uptake. Its exact mechanism of action remains unclear, but it is believed to involve binding to the α2δ subunit of voltage-gated calcium channels, which leads to a reduction in the release of excitatory neurotransmitters.

Side effects

Common side effects of gabapentin include:

• Dizziness
• Drowsiness
• Fatigue
• Weight gain
• Peripheral edema
• Ataxia
• Nausea and vomiting
• Headache

In rare cases, gabapentin may cause more serious side effects, such as an increased risk of suicidal thoughts and behaviors, hypersensitivity reactions, or respiratory depression.

Contraindications and precautions

Patients with a known hypersensitivity to gabapentin should not take the medication. Additionally, gabapentin should be used with caution in patients with renal impairment, as dose adjustments may be necessary. It is also important for patients to avoid abruptly discontinuing gabapentin, as this may increase the risk of seizures.

Drug interactions

Gabapentin may interact with several other medications, including:

• Antacids: Concurrent use of antacids may reduce the bioavailability of gabapentin.
• CNS depressants: Gabapentin may have additive effects when used in combination with other central nervous system (CNS) depressants, such as opioids or benzodiazepines.
• Other anticonvulsant medications: Combining gabapentin with other anticonvulsants may increase the risk of side effects or alter the efficacy of the medications.

Liver safety of Gabapentin

Therapy with gabapentin is not associated with serum aminotransferase elevations, but several cases of clinically apparent liver injury from gabapentin have been reported. 

Dosage and administration

Gabapentin is available in various formulations, including capsules, tablets, and oral solutions. The dosage and administration of gabapentin depend on the specific condition being treated and the patient's individual needs. Some general guidelines include:

• Epilepsy: For adult patients, the initial dose is typically 300 mg, taken orally three times a day. The dose can be gradually increased to a maximum of 3600 mg per day, depending on the patient's response and tolerance.
• Neuropathic pain: For adult patients with postherpetic neuralgia, the initial dose is usually 300 mg, taken orally on the first day, followed by 600 mg on the second day, and 900 mg on the third day. The dose can be further adjusted to a maximum of 1800 mg per day, based on the patient's response and tolerance.
• Renal impairment: Patients with renal impairment may require dose adjustments, as gabapentin is primarily eliminated through the kidneys.
• Healthcare professionals should individualize the dosing regimen for each patient, taking into account factors such as age, weight, and the presence of other medical conditions.

Abuse potential

Gabapentin has been associated with a potential for abuse, particularly in patients with a history of substance use disorders. Some individuals may misuse gabapentin to achieve euphoria or other psychoactive effects. In response to this potential for abuse, several states in the United States have classified gabapentin as a Schedule V controlled substance, which places restrictions on its prescription and dispensing.

Pregnancy and breastfeeding

The safety of gabapentin during pregnancy and breastfeeding has not been fully established. Studies in animals have shown potential risks, but there are limited data on the use of gabapentin in pregnant women. Gabapentin should only be used during pregnancy if the potential benefits outweigh the risks. Additionally, gabapentin is excreted in breast milk and may have adverse effects on a nursing infant. Therefore, healthcare professionals should carefully consider the benefits and risks of using gabapentin during breastfeeding.

Storage and disposal

Gabapentin should be stored at room temperature, away from light and moisture. It is important to keep the medication out of the reach of children and pets to prevent accidental ingestion.

When disposing of gabapentin, patients should follow local regulations and guidelines for the disposal of medications. Many communities have designated drug take-back programs, which provide a safe and environmentally responsible way to dispose of unused or expired medications. Patients should not flush gabapentin down the toilet or pour it down the drain unless specifically instructed to do so.

Monitoring and follow-up

Patients taking gabapentin should be regularly monitored by their healthcare providers to evaluate the medication's effectiveness and to detect any potential side effects. This may include periodic assessments of seizure frequency, pain levels, and the occurrence of any adverse effects. Additionally, patients with renal impairment may require regular monitoring of kidney function while on gabapentin therapy.

Overdose

Symptoms of a gabapentin overdose may include drowsiness, dizziness, double vision, slurred speech, and difficulty breathing. In severe cases, an overdose may result in coma or death. If an overdose is suspected, patients or caregivers should seek immediate medical attention.

Treatment of a gabapentin overdose typically involves supportive care and may include measures such as airway management, intravenous fluids, and monitoring of vital signs. There is no specific antidote for gabapentin overdose, and the drug is not effectively removed by hemodialysis.

External links

• Drugs.com: Gabapentin
• MedlinePlus: Gabapentin

See also

• Pregabalin
• Anticonvulsant
• Neuropathic pain
• Epilepsy

• Dailymed label info on Gabapentin
• FDA Gabapentin

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