What to monitor with Gabapentin (Anticonvulsant) therapy?

From the Guidelines

When taking gabapentin, it is crucial to monitor for side effects such as dizziness, drowsiness, and unsteadiness, as well as changes in mood, kidney function, and potential drug interactions, as these can significantly impact morbidity, mortality, and quality of life 1. To ensure safe and effective use of gabapentin, several key aspects of health should be monitored:

• Side effects: Watch for dizziness, drowsiness, and unsteadiness, especially when starting the medication or increasing the dose, as these can increase the risk of falls and accidents.
• Mood changes: Monitor for depression, anxiety, or unusual thoughts, as gabapentin can affect mental health, and changes in mood can impact quality of life and increase the risk of suicidal thoughts or behaviors.
• Kidney function: Track kidney function through regular blood tests, as gabapentin is eliminated through the kidneys and may need dose adjustments if kidney function changes, to prevent toxicity and minimize the risk of adverse effects.
• Drug interactions: Be aware of potential drug interactions if taking other medications, particularly opioids or other central nervous system depressants, as these can increase the risk of adverse effects such as respiratory depression.
• Allergic reactions: Pay attention to any allergic reactions such as rash, itching, or swelling, and seek medical attention immediately if these occur. For patients with epilepsy, keeping a seizure diary to track effectiveness is essential, and elderly patients should be particularly vigilant about fall risk due to the medication's sedating effects. Regular follow-ups with a healthcare provider are essential to assess the medication's effectiveness and any necessary adjustments, and to minimize the risk of adverse effects and maximize quality of life. Gabapentin works by affecting neurotransmitters in the brain, particularly GABA, which explains many of its effects and the need for careful monitoring, and its use should be guided by the most recent and highest quality evidence, such as the recommendations for the pharmacological management of neuropathic pain 1.

From the FDA Drug Label

Patients should be carefully observed for signs of central nervous system (CNS) depression, such as somnolence and sedation, when gabapentin is used with other drugs with sedative properties because of potential synergy Patients treated with any AED for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior The increased risk of suicidal thoughts or behavior with AEDs was observed as early as one week after starting drug treatment with AEDs and persisted for the duration of treatment assessed.

Key parameters to monitor with gabapentin:

• Somnolence and sedation: due to potential synergy with other sedative drugs 2
• Suicidal thoughts or behavior: emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior 2
• Central nervous system (CNS) depression: signs of CNS depression, such as somnolence and sedation, when gabapentin is used with other drugs with sedative properties 2
• Seizure frequency: in patients with epilepsy, to avoid increasing seizure frequency when discontinuing gabapentin 2
• Renal function: in patients with compromised renal function, to adjust the dose accordingly 2
• Mood or behavior changes: any unusual changes in mood or behavior, or the emergence of suicidal thoughts, behavior, or thoughts about self-harm 2

From the Research

Monitoring Parameters for Gabapentin

When monitoring patients taking gabapentin, several parameters should be considered:

• Seizure frequency: Gabapentin has been shown to reduce seizure frequency by > or = 50% in 18 to 28% of patients with refractory partial seizures 3.
• Adverse events: Common adverse events include somnolence, fatigue, ataxia, and dizziness, which have been reported in about 75% of gabapentin recipients 3.
• Drug interactions: Gabapentin is not protein-bound, not metabolized, and does not induce liver enzymes, which diminishes the likelihood of drug interactions with other antiepileptic agents and drugs such as oral contraceptives 3.
• Renal function: Gabapentin is primarily excreted by the kidneys, so monitoring renal function is essential, especially in patients with pre-existing renal impairment.
• Mental status: Patients with a history of substance abuse should be monitored for signs of addiction and dependence, as gabapentin has been reported to be misused in these populations 4, 5.

Laboratory Tests

Laboratory tests that may be useful in monitoring patients taking gabapentin include:

• Serum gabapentin levels: Therapeutic drug monitoring (TDM) can be useful in patients taking gabapentin, especially in those with renal impairment or those who are elderly 6.
• Liver function tests: Although gabapentin is not metabolized by the liver, monitoring liver function tests may be useful in patients with pre-existing liver disease.
• Renal function tests: Monitoring renal function tests, such as serum creatinine and urine output, is essential in patients taking gabapentin, especially in those with pre-existing renal impairment.

Special Considerations

Special considerations when monitoring patients taking gabapentin include:

• Elderly patients: Gabapentin may be more likely to cause adverse events in elderly patients, such as somnolence and dizziness 3, 6.
• Patients with a history of substance abuse: These patients should be monitored closely for signs of addiction and dependence, as gabapentin has been reported to be misused in these populations 4, 5.
• Patients with renal impairment: Gabapentin should be used with caution in patients with renal impairment, as it is primarily excreted by the kidneys.