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, somnolence, dry mouth, and constipation, as reported in a study published in Ophthalmology in 2017 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 effects like difficulty concentrating or memory problems Gastrointestinal issues such as nausea, vomiting, constipation, or diarrhea may also occur. Some patients experience mood changes including depression, anxiety, or irritability. These side effects often appear when starting gabapentin or increasing the dose, and many diminish over time as the body adjusts to the medication. More serious but rare side effects include severe allergic reactions, suicidal thoughts, unusual bruising or bleeding, and severe skin reactions. Patients should start at a low dose (typically 300mg) and gradually increase to minimize side effects, as recommended in a study published in Chest in 2016 1. Gabapentin should not be stopped abruptly as this can cause withdrawal symptoms; instead, the dose should be tapered gradually under medical supervision. These side effects occur because gabapentin affects neurotransmitters in the brain, particularly GABA, which influences nerve activity throughout the body. A study published in Mayo Clinic Proceedings in 2023 found that gabapentin is relatively safe, with the most common adverse effect being sedation, and edema of the lower extremities is also frequently reported 1. Another study published in Mayo Clinic Proceedings in 2010 reported that gabapentin and pregabalin have few drug interactions, but both can produce dose-dependent dizziness and sedation, which can be reduced by starting with lower dosages and titrating cautiously 1. Overall, the side effects of gabapentin should be carefully monitored and managed to minimize their impact on the patient's quality of life.

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 side effects of gabapentin include suicidal thoughts, changes in behavior and thinking, and allergic reactions. Common side effects are 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 2.

In clinical trials, the most common adverse reactions associated with the use of gabapentin in adults were dizziness, somnolence, and peripheral edema 2.

In pediatric patients 3 to 12 years of age, the most common adverse reactions were viral infection, fever, nausea and/or vomiting, somnolence, and hostility 2.

Gabapentin may also cause movement disorder, elevation of creatine kinase, elevated liver function tests, hyponatremia, rhabdomyolysis, breast enlargement, changes in libido, ejaculation disorders, anorgasmia, and angioedema 2.

From the Research

Side Effects of Gabapentin

• The side effects of gabapentin have been studied in various clinical trials, with some studies reporting higher risks of dizziness and somnolence in patients taking gabapentin compared to placebo 3.
• Gabapentin has been found to have a synergistic effect when used in combination with pregabalin for pain control, but this combination may also increase the risk of adverse reactions 4.
• The benefits and harms of gabapentin and pregabalin have been evaluated, with evidence suggesting that patients may not benefit from these medications but remain at risk of adverse drug reactions 5.
• Gabapentin and pregabalin have been found to be effective in treating neuropathic pain and pruritus in maintenance haemodialysis patients, but may cause adverse effects such as dizziness and somnolence 6.
• Common adverse effects of gabapentin include dizziness, somnolence, and ataxia, while pregabalin has been found to have similar side effects 7, 3, 4, 5, 6.

Specific Side Effects

• Dizziness: Gabapentin has been found to increase the risk of dizziness, with a risk ratio of 4.45 compared to placebo 3.
• Somnolence: Gabapentin has also been found to increase the risk of somnolence, with a risk ratio of 3.29 compared to placebo 3.
• Ataxia: Gabapentin and pregabalin have been found to cause ataxia, although the exact risk ratio is not specified in the studies 7, 4, 5, 6.