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 when walking, which occur in about 20-30% of patients, as reported in a recent study 1. The most frequent side effects of gabapentin include:

• Dizziness
• Drowsiness
• Fatigue
• Unsteadiness when walking Other common side effects include:
• Peripheral edema (swelling in extremities)
• Blurred vision
• Dry mouth
• Weight gain
• Difficulty concentrating Some patients experience mood changes including depression, anxiety, or in rare cases, suicidal thoughts. Gastrointestinal effects like 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 with a low dose (typically 300mg daily) and gradually increasing can help minimize these effects, as recommended in a study on the treatment of neuropathic pain 1. Gabapentin works by modulating calcium channels in the nervous system, which explains its calming effect on nerve signals but also accounts for many of its side effects, as described in a review of medical management options for erythromelalgia 1. Patients should never stop gabapentin suddenly as this can cause withdrawal symptoms including anxiety, insomnia, nausea, pain, and in rare cases, seizures. Always consult with a healthcare provider before adjusting gabapentin dosage, as advised in a consensus recommendation on the diagnosis, assessment, and management of painful diabetic peripheral neuropathy 1.

From the FDA Drug Label

Gabapentin tablets can cause serious side effects including:

1. Suicidal Thoughts. Like other antiepileptic drugs, gabapentin tablets may cause suicidal thoughts or actions in a very small number of people, about 1 in 500
2. Changes in behavior and thinking - Using gabapentin tablets in children 3 to 12 years of age can cause emotional changes, aggressive behavior, problems with concentration, restlessness, changes in school performance, and hyperactivity.
3. Gabapentin tablets may cause serious or life-threatening allergic reactions that may affect your skin or other parts of your body such as your liver or blood cells. 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

The possible side effects of gabapentin tablets include:

• Serious side effects: suicidal thoughts, changes in behavior and thinking, and serious or life-threatening allergic reactions
• Common side effects: lack of coordination, viral infection, feeling drowsy, nausea and vomiting, difficulty with speaking, tremor, swelling, feeling tired, fever, jerky movements, difficulty with coordination, double vision, and unusual eye movement
• Other side effects: problems driving while using gabapentin tablets, sleepiness and dizziness, which could increase the occurrence of accidental injury, including falls 2 2
• Postmarketing experience: jaundice, elevated creatine kinase, elevated liver function tests, hyponatremia, rhabdomyolysis, movement disorder, breast enlargement, changes in libido, ejaculation disorders, anorgasmia, angioedema 2

From the Research

Gabapentin Side Effects

• The side effects of gabapentin tend to be mild to moderate in intensity, most frequently affect the central nervous system, and resolve with time in many individuals 3.
• Common side effects associated with gabapentin include dizziness and somnolence, with a frequency of 21%-26% 4.
• Other side effects caused by gabapentin are teratogenicity, hypoventilation, respiratory failure, and myopathy 5.
• Gabapentin has been labeled category C on the basis of effects on rodent fetuses, and experience with use in pregnant women is limited 3.
• The medication is well tolerated, in general, but dose reductions due to adverse effects were statistically significantly higher in the gabapentin group than the pregabalin group 6.

Comparison with Pregabalin

• Pregabalin showed superior results compared to gabapentin in the Visual Analog Scale (VAS) at various time intervals up to 12-14 weeks 7.
• Pregabalin resulted in lower opioid consumption and led to fewer adverse events, including nausea and vomiting, compared to gabapentin 7.
• Gabapentin had a higher incidence of nausea and vomiting compared to pregabalin 7.
• Pregabalin may afford better tolerability and lower pill burden compared to gabapentin 6.

Interactions and Contraindications

• Some of the main substances that interact with gabapentin are morphine, caffeine, losartan, ethacrynic acid, phenytoin, mefloquine, and magnesium oxide 5.
• Gabapentin is contraindicated in conditions such as myasthenia gravis and myoclonus 5.
• The risks of gabapentin misuse are based on the increased level of prescriptions, related fatalities, recreational misuse, and higher doses of self-administration 5.