Gabapentin (Neurontin, Gralise, Horizant) is an anticonvulsant commonly prescribed to manage partial seizures and nerve pain, such as postherpetic neuralgia. Although the drug has a wide therapeutic range and is relatively non-lethal when taken alone, taking it in excess can lead to a serious medical emergency. An overdose is possible through misuse, accidental ingestion, or exceeding the prescribed limit, causing significant toxicity. Life-threatening overdoses, however, almost always involve the co-ingestion of other substances.
Recognizing the Signs of Gabapentin Overdose
A gabapentin overdose occurs when the amount of the drug in the body exceeds a toxic threshold, amplifying its effects on the central nervous system (CNS). The symptoms can range from moderate signs of over-sedation to severe, life-threatening complications. Identifying these signs quickly is crucial for obtaining timely medical help.
Moderate signs of toxicity often present as an extreme version of the medication’s common side effects, such as profound drowsiness or sedation that makes the person difficult to wake. A common physical manifestation is ataxia, which is a loss of control over bodily movements leading to severe dizziness, unsteadiness, and difficulty walking. Other observable neurological signs include slurred speech, double vision, or unusual, uncontrolled muscle movements.
In severe cases, the signs indicate a dangerous suppression of the body’s vital functions, particularly the respiratory system. This manifests as labored breathing, slow or shallow respirations, and a decrease in oxygen saturation. Cardiovascular changes may also occur, including low blood pressure (hypotension) or a rapid heart rate. Without immediate intervention, severe CNS depression can progress to a coma.
Factors Increasing Overdose Risk
The most significant factor increasing the risk and severity of a gabapentin overdose is the simultaneous use of other central nervous system (CNS) depressants. This combination, known as polypharmacy, creates a synergistic effect where the combined impact is much greater than the sum of the individual drugs. Combining gabapentin with opioids, benzodiazepines, or alcohol is especially dangerous because these substances slow down the brain activity that controls breathing.
This concurrent use greatly increases the risk of life-threatening respiratory depression, the primary cause of death in gabapentin-related overdoses. Combining gabapentin with opioids is associated with a substantially increased risk of opioid-related death, as gabapentin may increase the opioid’s absorption and effects. The combination results in breathing becoming too shallow and slow to provide enough oxygen, potentially leading to respiratory arrest.
Renal Impairment
Another major risk factor relates to how the body processes the medication, specifically the health of the kidneys. Gabapentin is not metabolized by the liver but is almost entirely eliminated unchanged by the kidneys. For individuals with diminished kidney function (renal impairment), the drug is cleared much more slowly, causing it to build up to toxic levels in the bloodstream even if the prescribed dose is followed.
This accumulation significantly prolongs the drug’s half-life, which can extend from the normal 5 to 7 hours to over 100 hours in patients with severe renal failure. Patients with chronic kidney disease are at a much higher risk of toxicity, and their gabapentin dosage must be carefully adjusted based on their current kidney function. Taking doses far beyond the therapeutic range or using the drug recreationally also constitutes a risk.
Emergency Response and Medical Treatment
If a gabapentin overdose is suspected, immediate action is required to prevent serious complications, especially if other CNS depressants were involved. The first step is to call for emergency medical help immediately, such as by dialing 911 or contacting Poison Control. Provide emergency responders with information about what was taken, including the amount and any other drugs or alcohol involved.
While awaiting medical assistance, the person should be kept awake, monitored closely for signs of slow or stopped breathing, and should not be left alone. Unlike opioid overdose, there is no specific antidote for gabapentin. Treatment in a hospital setting is primarily supportive care, focusing on stabilizing the patient’s vital signs and managing symptoms until the drug is naturally eliminated.
Medical staff prioritize maintaining a clear airway and ensuring adequate breathing, which may involve supplemental oxygen or, in severe respiratory depression or coma, intubation and mechanical ventilation. The patient’s heart rate, blood pressure, and oxygen levels are continuously monitored. For recent, large ingestions, activated charcoal may be administered to reduce further absorption from the gastrointestinal tract. In severe cases, particularly for patients with impaired kidney function, hemodialysis can manually filter and remove gabapentin from the bloodstream, significantly speeding up its elimination.
Severity and Long-Term Outcomes
When gabapentin is taken by itself, an overdose is rarely fatal, and most patients recover fully within 24 to 48 hours with supportive medical care. The drug has a relatively short half-life and is eliminated efficiently in individuals with normal kidney function. The prognosis is generally good, and significant long-term complications are uncommon.
However, the severity changes dramatically when gabapentin is combined with other CNS depressants, such as alcohol or opioids. This polypharmacy drastically increases the risk of death, primarily due to profound respiratory depression. If oxygen deprivation (hypoxia) is severe or prolonged during the overdose, it can lead to permanent neurological injury, such as anoxic brain damage. While rare, severe overdose can also lead to complications like rhabdomyolysis or acute kidney injury.