What are the side effects of Gabapentin (Neurontin)?

From the Guidelines

Gabapentin commonly causes side effects including dizziness, drowsiness, fatigue, and unsteadiness which affect about 10-20% of patients. Other frequent side effects include peripheral edema (swelling in extremities), blurred vision, weight gain, and cognitive effects like difficulty concentrating or memory problems. Some patients experience mood changes, including depression or, paradoxically, euphoria. Gastrointestinal side effects such as nausea, vomiting, constipation, or dry mouth may occur. Less common but serious side effects include allergic reactions, suicidal thoughts, and severe skin reactions. When stopping gabapentin, it should be tapered gradually over at least one week to avoid withdrawal symptoms like anxiety, insomnia, nausea, pain, and sweating. These side effects occur because gabapentin affects calcium channels and GABA neurotransmission in the brain. Side effects are typically more pronounced when starting treatment or increasing dosage, and many diminish over time as the body adjusts to the medication. Patients should report persistent or severe side effects to their healthcare provider immediately.

Key Side Effects

• Dizziness
• Drowsiness
• Fatigue
• Unsteadiness
• Peripheral edema
• Blurred vision
• Weight gain
• Cognitive effects (difficulty concentrating or memory problems)
• Mood changes (depression or euphoria)
• Gastrointestinal side effects (nausea, vomiting, constipation, or dry mouth)

Management of Side Effects

According to the most recent study 1, gabapentinoids, such as gabapentin, can cause sedation and require careful titration, especially in patients with renal impairments. The study also highlights the importance of monitoring for signs of dependence and withdrawal symptoms when using gabapentinoids. Another study 1 notes that gabapentinoids can cause reinforcing euphoria, sedation, and dissociation, and that evidence now shows that when gabapentinoids are taken with opioids, a dangerous respiratory depression can occur.

Recommendations

Patients taking gabapentin should be closely monitored for signs of side effects and dependence. The medication should be tapered gradually when stopping treatment to avoid withdrawal symptoms. Patients should also be advised to report any persistent or severe side effects to their healthcare provider immediately. Additionally, healthcare providers should be cautious when prescribing gabapentinoids, especially in patients with a history of substance use disorder or those taking opioids, due to the risk of respiratory depression 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.