What are the side effects of Gabapentin (Neurontin)?

From the Guidelines

Gabapentin commonly causes side effects that patients should be aware of before starting treatment, including dizziness, drowsiness, fatigue, and unsteadiness, which affect about 20-30% of patients, as reported in a study published in the journal Ophthalmology 1. The most frequent side effects of gabapentin include:

• Dizziness
• Drowsiness
• Fatigue
• Unsteadiness Other common side effects include:
• Peripheral edema (swelling in extremities)
• Blurred vision
• Dry mouth
• Weight gain
• Cognitive issues like difficulty concentrating or memory problems Gastrointestinal effects such as nausea, vomiting, and constipation may also occur. These side effects typically appear within the first few weeks of treatment and often diminish over time as the body adjusts to the medication. Starting at a low dose (such as 100-300mg daily) and gradually increasing can help minimize these effects, as suggested in a study published in the Mayo Clinic Proceedings 1. More serious but rare side effects include mood changes, suicidal thoughts, severe allergic reactions, and respiratory depression, particularly when combined with opioids or other central nervous system depressants. Gabapentin works by modulating calcium channels in the nervous system, which explains its calming effects but also accounts for many of its side effects. Patients should never stop gabapentin suddenly as this can trigger withdrawal symptoms; instead, the medication should be tapered gradually under medical supervision, as recommended in a study published in the Annals of emergency medicine 1. It is essential to discuss the potential side effects and the risk-benefit profile with patients before using gabapentin, and to reassess the risk-benefit profile at 6 months before continuing the drug, as suggested in a guideline published in the journal Chest 1. The dosing information for gabapentin should be based on the results of randomized controlled trials, such as the one conducted by Ryan et al, which found that gabapentin was effective in reducing cough-specific quality of life and cough severity, with a dose escalation schedule starting at 300 mg once a day and increasing as tolerated up to a maximum tolerable daily dose of 1,800 mg a day in two divided doses 1.

From the FDA Drug Label

The most common adverse reactions associated with the use of gabapentin in adults, not seen at an equivalent frequency among placebo-treated patients, were dizziness, somnolence, and peripheral edema The most common adverse reactions with gabapentin in combination with other antiepileptic drugs in patients >12 years of age, not seen at an equivalent frequency among placebo-treated patients, were somnolence, dizziness, ataxia, fatigue, and nystagmus The most common adverse reactions with gabapentin in combination with other antiepileptic drugs in pediatric patients 3 to 12 years of age, not seen at an equal frequency among placebo-treated patients, were viral infection, fever, nausea and/or vomiting, somnolence, and hostility Gabapentin may cause serious side effects including: suicidal thoughts or actions, changes in behavior and thinking, and serious or life-threatening allergic reactions The most common side effects of gabapentin tablets include: lack of coordination, viral infection, feeling drowsy, nausea and vomiting, difficulty with speaking, tremor, swelling, usually of legs and feet, feeling tired, fever, jerky movements, difficulty with coordination, double vision, unusual eye movement

Common side effects of gabapentin include:

• Dizziness
• Somnolence
• Peripheral edema
• Ataxia
• Fatigue
• Nystagmus
• Viral infection
• Fever
• Nausea and/or vomiting
• Hostility
• Lack of coordination
• Tremor
• Swelling
• Feeling tired
• Jerky movements
• Difficulty with coordination
• Double vision
• Unusual eye movement

Serious side effects of gabapentin include:

• Suicidal thoughts or actions
• Changes in behavior and thinking
• Serious or life-threatening allergic reactions 2 2 2

From the Research

Gabapentin Side Effects

• Gabapentin is associated with a high risk of adverse events and withdrawal because of adverse events, but serious adverse events are not significantly raised 3
• The most common side effects of gabapentin include dizziness, fatigue, and nausea 4
• Gabapentin can cause cognitive impairment, including memory loss and confusion, especially in elderly patients 4
• Gabapentin can also cause mood changes, including depression, anxiety, and irritability 5
• High daily doses of gabapentin can lead to misuse, with factors associated with misuse including age, multiple prescribers, cancer, multiple sclerosis, neuropathy, depression, and methadone use 5

Comparison with Other Antiepileptic Drugs

• Gabapentin and pregabalin have similar efficacy in the treatment of neuropathic pain, but gabapentin has a higher risk of adverse events 3
• Gabapentin and pregabalin are more effective than other antiepileptic drugs, such as carbamazepine and lamotrigine, in the treatment of central poststroke pain 6
• Gabapentin and pregabalin have different side effect profiles, with gabapentin causing more dizziness and fatigue, and pregabalin causing more weight gain and edema 4

Drug Interactions

• Gabapentin does not affect the exposure of factor Xa inhibitors, such as edoxaban, apixaban, and rivaroxaban 7
• Carbamazepine, another antiepileptic drug, can decrease the exposure of factor Xa inhibitors, and dose adjustment may be required to maintain an adequate anticoagulant effect 7