Abstracts

RATIONALE: Gabapentin is an anti-epileptic drug, now used for many conditions other than epilepsy. It has stable pharmacokinetics, relatively few side effects and drug interactions. We report a case of an elderly lady on gabapentin who had markedly elevated gabapentin levels, developed status epilepticus and died subsequently.
METHODS: A 72 year old lady was found unresponsive and comatose at home, last seen by relatives about 24 hours prior. At the local ER, she was found to have agonal breathing and facial twitching. She was intubated and given IV lorazepam (2+3mg). An EEG done at that time reportedly showed evidence of status epilepticus, and then was given IV Phenobarbital. She was transferred by helicopter to UW Hospital for further management.
Her past medical history was significant for congestive heart failure, polyneuropathy, polyradiculopathy, monoclonal gammopathy, chronic atrial fibrillation and depression. She had undergone cholecystectomy, appendectomy and hysterectomy in the past. Her medications included gabapentin 900 mg tid (recently increased from 300 tid) for polyneuropathy, furosemide 80 mg qd, levothyroxine 125 mcg qd, lisinopril 10 mg qd, fluoxetine 20 mg qd and premarin 300 mcg qd.
On examination, she was intubated and was on a ventilator. She was comatose and unresponsive. Fundi were normal. Pupils were 3 mm and non-reactive. Corneal reflexes were absent. All four limbs were flaccid and areflexic. Plantars were mute.
Lab findings: CBC was normal. Sodium 140 meq/l Potassium 5.2 meq/l Chloride 99 meq/l Glucose 139 mg% BUN 67 Creatinine 4.2 (4.8)
CK 6252 Gabapentin levels: 84 (day 1) 62.7 (day2) 17.7 (day3)
EEG: Phase reversing sharp waves in R parasagital + diffuse slowing
The patient did not recover and died one week after admission. Autopsy of the brain was essentially unremarkable.
RESULTS: Gabapentin was introduced as an adjunctive therapy for treatment of seizures. However, after gaining experience with its safety profile and lack of drug interactions, it was used extensively for conditions other than epilepsy, most commonly for chronic pain, depression and headache. There have been anecdotal reports noting its lack of toxicity despite large doses and elevated levels. Our case report illustrates a patient who developed status epilepticus and had markedly elevated gabapentin levels. Her laboratory work also demonstrates signs of acute renal failure, which is probably due to the status, as indicated by elevated CK levels. Although there was no clinical improvement with lowered gabapentin levels seen serially, it is likely that elevated gabapentin levels lead to the development of status, as she died from complications of status epilepticus.
CONCLUSIONS: High doses of gabapentin or rapid increase in dosage can lead to elevated gabapentin levels and result in serious consequences such as status epilepticus. It should be used carefully in the elderly, especially with co-morbid conditions. The prolific use of gabapentin in many neurological and non-neurological conditions should be tempered with caution, until we completely understand the mechanisms of action and toxicity.
(Disclosure: Grant - UCB Pharma, Glaxo Smith Kline (Gidal), Consulting - UCB Pharma, Glaxo Smith Kline, Ivax (Gidal), Honoraria - UCB Pharma, Pfizer, Glaxo Smith Kline, Elan Pharma (Gidal, Dixit))