A case of sustained massive gabapentin overdose without serious side effects

Concurrent Gabapentin and Opioid Use and Risk of Mortality in Medicare Recipients with Non-Cancer Pain

Gabapentin is prescribed for pain and is perceived as safe generally. However, gabapentin can cause respiratory depression, exacerbated by concomitant central nervous system depressants (e.g., opioids), a concern for vulnerable populations. We compared mortality rates among new users of either gabapentin or duloxetine with or without concurrent opioids in the 20% Medicare sample. We conducted a new-user design retrospective cohort study, in Medicare enrollees ages 65-89 years with noncancer chronic pain and no severe illness who filled prescriptions between 2015 and 2018 for gabapentin (n = 233,060) or duloxetine (n = 34,009). Daily opioid doses, estimated in morphine milligram equivalents (MMEs), were classified into none, low (0 < MME < 50), and high (≥ 50 MME), based on Centers for Disease Control and Prevention (CDC) recommendations. The outcomes were all-cause mortality (primary) and out-of-hospital mortality (secondary). We used inverse probability of treatment weighting to adjust for differences between gabapentin and duloxetine users. During 116,707 person-years of follow-up, 1,379 patients died. All-cause mortality rate in gabapentin users was 12.16 per 1,000 person-years vs. 9.94 per 1,000 in duloxetine users. Risks were similar for users with no concurrent opioids (adjusted hazard ratio (aHR) = 1.03, 95% confidence interval (CI): 0.80-1.31) or low-dose daily opioids (aHR = 1.06, 95% CI: 0.63-1.76). However, gabapentin users receiving concurrent high-dose daily opioids had an increased rate of all-cause mortality compared with duloxetine users on high-dose opioids (aHR = 2.03, 95% CI: 1.19-3.46). Out-of-hospital mortality yielded similar results. In this retrospective cohort study of Medicare beneficiaries, concurrent use of high-dose opioids and gabapentin was associated with a higher all-cause mortality risk than that for concurrent use of high-dose opioids and duloxetine.

Extracorporeal Treatment for Gabapentin and Pregabalin Poisoning: Systematic Review and Recommendations From the EXTRIP Workgroup

Toxicity from gabapentin and pregabalin overdose is commonly encountered. Treatment is supportive, and the use of extracorporeal treatments (ECTRs) is controversial. The EXTRIP workgroup conducted systematic reviews of the literature and summarized findings following published methods. Thirty-three articles (30 patient reports and 3 pharmacokinetic studies) met the inclusion criteria. High gabapentinoid extracorporeal clearance (>150mL/min) and short elimination half-life (<5 hours) were reported with hemodialysis. The workgroup assessed gabapentin and pregabalin as "dialyzable" for patients with decreased kidney function (quality of the evidence grade as A and B, respectively). Limited clinical data were available (24 patients with gabapentin toxicity and 7 with pregabalin toxicity received ECTR). Severe toxicity, mortality, and sequelae were rare in cases receiving ECTR and in historical controls receiving standard care alone. No clear clinical benefit from ECTR could be identified although major knowledge gaps were acknowledged, as well as costs and harms of ECTR. The EXTRIP workgroup suggests against performing ECTR in addition to standard care rather than standard care alone (weak recommendation, very low quality of evidence) for gabapentinoid poisoning in patients with normal kidney function. If decreased kidney function and coma requiring mechanical ventilation are present, the workgroup suggests performing ECTR in addition to standard care (weak recommendation, very low quality of evidence).

Gabapentin in Infants: Critical Evaluation of a Novel Sedative/Analgesic Medication

Chronic pain and agitation can complicate the clinical course of critically ill infants. Randomized controlled trials of analgesia and sedation in neonatal intensive care have focused on relatively short durations of exposure. To date, clinicians have few options to treat chronic visceral pain and hyperalgesia. Gabapentin has emerged as a common therapy for a diverse group of pain syndromes and neurologic conditions in adults. In neonates, case reports and series describe the successful treatment of visceral hyperalgesia arising from gastrointestinal insults with or without concomitant neurologic morbidities. Additionally, a case report and series describe the utility of gabapentin for neonatal abstinence syndrome refractory to standard pharmacotherapy. The adverse effect profile of gabapentin, most notably bradycardia and sedation, compares favorably to alternative analgesics and sedatives. However, the long-term impacts of prolonged gabapentin therapy have not been studied. Therefore, candidates for therapy must be selected carefully, and response must be assessed objectively. Future studies must assess the short-term and long-term benefits and risks of gabapentin compared to standard therapies for chronic pain and agitation in infants and refractory neonatal abstinence syndrome.

Multimorbidity and Critical Care Neurosurgery: Minimizing Major Perioperative Cardiopulmonary Complications

With increasing prevalence of chronic diseases, multimorbid patients have become commonplace in the neurosurgical intensive care unit (neuro-ICU), offering unique management challenges. By reducing physiological reserve and interacting with one another, chronic comorbidities pose a greatly enhanced risk of major postoperative medical complications, especially cardiopulmonary complications, which ultimately exert a negative impact on neurosurgical outcomes. These premises underscore the importance of perioperative optimization, in turn requiring a thorough preoperative risk stratification, a basic understanding of a multimorbid patient’s deranged physiology and a proper appreciation of the potential of surgery, anesthesia and neurocritical care interventions to exacerbate comorbid pathophysiologies. This knowledge enables neurosurgeons, neuroanesthesiologists and neurointensivists to function with a heightened level of vigilance in the care of these high-risk patients and can inform the perioperative neuro-ICU management with individualized strategies able to minimize the risk of untoward outcomes. This review highlights potential pitfalls in the intra- and postoperative neuro-ICU period, describes common preoperative risk stratification tools and discusses tailored perioperative ICU management strategies in multimorbid neurosurgical patients, with a special focus on approaches geared toward the minimization of postoperative cardiopulmonary complications and unplanned reintubation.

A case of gabapentin overdose induced rhabdomyolysis requiring renal replacement therapy

We report a rare case with gabapentin overdose that caused severe rhabdomyolysis and acute tubular necrosis which required renal replacement therapy. A better awareness of its adverse effect and a close follow-up of laboratory tests are recommended. Prescribers should also be aware of high-risk population and monitor for signs of abuse.

Efficacy and Safety of Gabapentin in the Treatment of Chronic Cough: A Systematic Review

Despite recent clinical guidelines, the optimal therapeutic strategy for the management of refractory chronic cough is still a challenge. The present systematic review was designed to assess the evidence for efficacy and safety of gabapentin in the treatment of chronic cough. A systematic search of PubMed, Embase, Cochrane Library databases, and publications cited in bibliographies was performed. Articles were searched by two reviewers with a priori criteria for study selection. Seven relevant articles were identified, including two randomized controlled trials, one prospective case-series designed with consecutive patients, one retrospective case series of consecutive patients, one retrospective case series with unknown consecutive status, and two case reports comprising six and two patients, respectively. Improvements were detected in cough-specific quality of life (Leicester Cough Questionnaire score) and cough severity (visual analogue scale score) following gabapentin treatment in randomized controlled trials. The results of prospective case-series showed that the rate of overall improvement of cough and sensory neuropathy with gabapentin was 68%. Gabapentin treatment of patients with chronic cough showed superior efficacy and a good safety record compared with placebo or standard medications. Additional randomized and controlled trials are needed.

How addictive are gabapentin and pregabalin? A systematic review

In the last ten years, gabapentin and pregabalin have been becoming dispensed broadly and sold on black markets, thereby, exposing millions to potential side-effects. Meanwhile, several pharmacovigilance-databases have warned for potential abuse liabilities and overdose fatalities in association with both gabapentinoids. To evaluate their addiction risk in more detail, we conducted a systematic review on PubMed/Scopus and included 106 studies. We did not find convincing evidence of a vigorous addictive power of gabapentinoids which is primarily suggested from their limited rewarding properties, marginal notes on relapses, and the very few cases with gabapentinoid-related behavioral dependence symptoms (ICD-10) in patients without a prior abuse history (N=4). In support, there was no publication about people who sought treatment for the use of gabapentinoids. Pregabalin appeared to be somewhat more addictive than gabapentin regarding the magnitude of behavioral dependence symptoms, transitions from prescription to self-administration, and the durability of the self-administrations. The principal population at risk for addiction of gabapentinoids consists of patients with other current or past substance use disorders (SUD), mostly opioid and multi-drug users, who preferred pregabalin. Pure overdoses of gabapentinoids appeared to be relative safe but can become lethal (pregabalin > gabapentin) in mixture with other psychoactive drugs, especially opioids again and sedatives. Based upon these results, we compared the addiction risks of gabapentin and pregabalin with those of traditional psychoactive substances and recommend that in patients with a history of SUD, gabapentinoids should be avoided or if indispensable, administered with caution by using a strict therapeutic and prescription monitoring.

Clinical outcomes in newer anticonvulsant overdose: a poison center observational study

Clinicians have limited experience with assessment and treatment of overdose from newer anticonvulsant medications. The aim of this investigation was to evaluate clinical effects of newer anticonvulsant overdose, determine if a relationship exists between dose and clinical effect, and if a particular agent appears more toxic in overdose. This was a retrospective study using electronic poison center data, evaluating clinical outcomes from newer anticonvulsant overdose. The Toxicall™ database from January 1, 2002 to December 31, 2011 was queried using key words: "gabapentin," "lamotrigine," "levetiracetam," "tiagabine," "topiramate," "zonisamide," "pregabalin," and "oxcarbazine." Polypharmacy overdose and children less than 15 years of age were excluded. Charts were reviewed by two abstractors for pharmaceutical, self-reported dose, clinical effect score, and clinical signs, symptoms, and vital signs recorded in the chart. Ordinal logistic regression was used to evaluate the relationship between drug type, dose, age, and sex to clinical effect score. Out of 501 cases identified, 347 met the final inclusion criteria. There were 116 gabapentin, 67 lamotrigine, 15 levetiracetam, 15 tiagabine, 56 topiramate, 23 pregabalin, and 55 oxcarbazepine cases. Overdose of newer anticonvulsants frequently results in altered mental status. Seizures may be more common with tiagabine, lamotrigine, and oxcarbazepine. There was one death reported from intentional overdose of topiramate. An information index was created to rank drug toxicity based on reported signs and symptoms for each overdose. There was no significant effect of dose on severity of outcome (β = 0.12, p = 0.23). However, the risk of a more severe outcome score was significantly increased with tiagabine relative to other drugs (β = 2.8, p = 0.001). Lamotrigine ranked highest in terms of toxicity (HT = 1.66) and number of interventions performed (HI = 1.17), and levetiracetam the lowest (HT = 0.98; HI = 0.88). We could not identify a dose-effect in these data which likely reflects the limitations of self-reported doses. Despite limitations of these data, the risk of more severe outcome scores appear to be higher with tiagabine overdose while lamotrigine overdose appears to result in more reported signs, symptoms, and interventions.

An acute gabapentin fatality: a case report with postmortem concentrations

Gabapentin (GBP) (Neurontin®, Horizant®, Gralise®) is a widely prescribed medication used primarily for the treatment of epilepsy and neuropathic pain. GBP has a favorable adverse effect profile in therapeutic dosing with the most common reported effects being dizziness, fatigue, drowsiness, weight gain, and peripheral edema. Even with intentional GBP self-poisonings, serious effects are rare. A 47-year-old female was found dead at work with her daughter's bottle of GBP 600 mg. There were 26 tablets missing and the decedent's only known medication was hydrocodone/acetaminophen. Following initial detection by an alkaline drug screen (GC-MS), analysis utilizing specific liquid chromatography-mass spectrometry revealed an elevated postmortem GBP peripheral blood concentration of 37 mg/L, central blood 32 mg/L, liver 26 mg/kg, vitreous 32 mg/L, and gastric contents 6 mg. Screening for volatiles, drugs of abuse, alkaline compounds, and acid/neutral compounds was negative with the exception of ibuprofen (<2 mg/L) detected in peripheral blood. This report presents a fatality that appears to be associated with an isolated and acute GBP ingestion.

A review on the efficacy and safety of gabapentin in the treatment of chronic cough

INTRODUCTION

Effective antitussives available to control cough are limited. Consolidation among different afferent branches of the vagus nerve is needed to bring about cough. A general, widely accepted view is that the chronic increase in the sensitivity of the cough reflex is associated with inflammatory hypersensitivity such as from gastro-esophageal reflux disease. There is increasing evidence that an important mechanism is a sensory disorder of the laryngeal branches of the vagus nerve. Neuromodulating drugs are effectively used in the treatment of chronic pain and neuropathic disorders and may have a role in the treatment of refractory chronic cough (CC).

AREAS COVERED

Current evidence on the efficacy and safety of gabapentin in the treatment of CC is reviewed. Relevant randomized controlled trials, case reports and reviews were identified through a PubMed search of English-language literature referring to cough, sensory neuropathy and gabapentin over the last 10 years.

EXPERT OPINION

Gabapentin appears to be effective and well tolerated in the treatment of CC and in other sensory neuropathic disorders. Relevant clinical trials investigating its efficacy and safety profile in the treatment of cough are limited and further studies are needed. Gabapentin has been shown to cause minimal to no toxicity in overdose.

Gabapentin for Pruritus in Palliative care

Itch/pruritus can be very distressing in palliative care population and often is difficult to treat. Conventional antihistamines lack efficacy. Cutaneous and central pathogenesis of itch is extremely complex and unclear, making its treatment challenging. Neuronal mechanisms have been identified in the pathophysiology of itch hence providing a myriad of therapeutic options. It has been established that pruritus and pain neuronal pathway interact with each other, hence neuropathic analgesics like gabapentin has shown to be efficacious antipruritic therapeutic option. Gabapentin impedes transmitting nociceptive sensations to brain, thus also suppressing pruritus. Gabapentin is safe and found to be effective in uremic pruritus, cancer/hematologic causes, opiod-induced itch, brachioradial pruritis, burns pruritus, and pruritus of unknown origin. Further research is required in this area to establish whether gabapentin is consistently effective.

Suicide by gabapentin overdose

Gabapentin is an antiepileptic drug that is prescribed for both FDA-approved and multiple off-label conditions, and has a relatively safe side-effect profile. Rare cases of overdose-related adverse effects have been reported in the literature. Described herein are the circumstances and autopsy findings of a 62-year-old woman with a history of depression, whose death was caused by intentional ingestion of excess gabapentin. The postmortem peripheral blood gabapentin concentration as determined by high-performance liquid chromatography/tandem mass spectroscopy was 88 μg/mL. Previously reported cases of individuals surviving gabapentin overdoses are discussed and compared with this case. Based on a review of the available literature, this appears to be the first published report of a death due solely to gabapentin toxicity.

[Therapeutic drug monitoring of gabapentin]

Gabapentin is a structural analogue of GABA used in the treatment of the partial epilepsies of adult and child of more than 12 years, in monotherapy or in association with other anticonvulsant drugs. In association, gabapentin presents the advantage of not interfering with the other anticonvulsant drugs. The interindividual pharmacokinetic variability and the saturable absorption are, with the adaptation in case of renal insufficiency, the only arguments in favor of TDM. During clinical studies, the plasma concentrations of gabapentin were generally included between 2 and 20 mg/L. For this molecule, the level of proof of the interest of therapeutic drug monitoring was estimated in: possibly useful.

A probable case of gabapentin-related reversible hearing loss in a patient with acute renal failure

BACKGROUND

As described in the literature, gabapentin toxicity in patients with impaired renal function can manifest as coma, myoclonus, tremulousness, or altered mental status. Gabapentin is an antiepileptic agent indicated for use as an adjunct therapy in partial seizures and postherpetic neuralgia but is also prescribed for the treatment of diabetic peripheral neuropathy.

CASE SUMMARY

A 46-year-old white woman (height, 167 cm; weight, 177 kg; body mass index, 62.8 kg/m2) with a 6-year history of diabetes mellitus and previously normal renal function, presented to the emergency department of Wake Forest University Baptist Medical Center with anuria (a serum creatinine level of 7.4 mg/dL), hearing loss, myoclonus, and confusion with hallucinations lasting for 3 days. Her blood pressure was 110/74 mm Hg. The patient's preadmit medication list included: lisinopril (40 mg QD), hydrochlorothiazide (25 mg QD), and furosemide (80 mg QD) for hypertension; atorvastatin (10 mg QD) for hyperlipidemia; omeprazole (20 mg QD) for gastroesophageal reflux disease; salmeterol/fluticasone inhaler (100/50 microg; 1 puff BID) and albuterol metered-dose inhaler (90 microg as needed) for asthma; metformin (500 mg BID) and insulin lispro per sliding scale for type 2 diabetes mellitus; oxycodone controlled release (60 mg TID) for chronic osteoarthritis and low back pain; alprazolam (0.5 mg every 8 hours as needed) for generalized anxiety disorder; venlafaxine (150 mg BID) for depression; and gabapentin (300 mg TID) for diabetic peripheral neuropathy. The patient's symptoms (hearing loss, myoclonus, and confusion) improved after 1 session of hemodialysis (approximately 10 hours following admission) and had resolved at the time of discharge (4 days later). On admission, the gabapentin concentration was 17.6 microg/mL, and following hemodialysis, the gabapentin concentration was undetectable (by discharge/day 4). The timing of the patient's last dose of gabapentin is unknown. Normal doses for the treatment of diabetic peripheral neuropathy range from 900 to 3600 mg/d divided 3 times daily.

CONCLUSIONS

We report a patient with acute renal failure who developed hearing loss, myoclonus, and confusion with hallucinations in the presence of elevated gabapentin concentrations. Due to rapid improvement after hemodialysis and discontinuation of gabapentin, we believe that these symptoms were probably due to gabapentin toxicity.

Gabapentin toxicity in renal failure: the importance of dose adjustment

OBJECTIVE

This case report outlines a significant type of morbidity due to continued use of gabapentin during an episode of acute renal failure. Setting. University teaching hospital.

DISCUSSION

Gabapentin is widely used in the management of pain. It is entirely excreted through the renal system so this needs to be considered in any patient becoming acutely ill and developing renal failure. We describe a patient who developed significant deterioration in her conscious level due to iatrogenic gabapentin overdose.

CONCLUSION

All doctors need to be aware of the need to review the indications for gabapentin use during periods of acute illness, especially with regard to renal impairment. Off-label use should be discouraged.

Should Gabapentin Be Dose Adjusted: What are the Clinical Consequences?

Objective:

To review the clinical necessity of renal dose adjustment of gabapentin.

Data Sources:

Medical literature (1966–February 2006, week 2) was accessed through MEDLINE, EMBASE, Pre-MEDLINE, International Pharmaceutical Abstracts, and the manufacturer's package insert. Search terms included gabapentin, side effects/adverse effects, overdose, toxicity, and renal impairment. Literature references were consulted for relevant information.

Study Selection and Data Extraction:

All studies from the data sources that were published in English were evaluated. Case reports, case series, and clinical trials with primarily adult populations were included in the review to determine the clinical necessity of dosage adjustment, including morbidity and mortality associated with dose adjustment failure. Case reports of gabapentin overdose were evaluated for clinically significant outcomes. All reports were examined for clinical relevance and adequate information to address the issue of major clinical consequences of failure to dose adjust gabapentin in specific patient populations, including renally impaired and elderly patients.

Data Synthesis:

The package insert suggests dose adjustment of gabapentin in patients with decreased renal function, yet published information regarding clinical consequences of gabapentin in patients is limited. Although gabapentin possesses a favorable safety profile and is generally well tolerated, there have been cases reporting serious adverse effects. While clinical studies and the majority of case reports demonstrate minimal adverse effects, there is some concern that select patients may experience serious outcomes if the drug is not dose adjusted.

Conclusions:

The recommendation for dosage adjustment is suitably based upon the pharmacokinetic properties of gabapentin, yet healthcare practitioners should determine the need for gabapentin dosage adjustment in specific patients. There should be continued emphasis on recommending renal dose adjustments, with the most concern applied to the elderly and patients with significant renal impairment/end-stage renal disease.

Gabapentin-induced coma in a patient with renal failure

We describe a 60-year-old woman who became comatose after a single dose of gabapentin for right-sided sciatalgia. The patient was improved by hemodialysis. Gabapentin toxicity should be considered when mental status changes develop in patients with renal failure after even a single dose.

Gabapentin-Induced Neurologic Toxicities

Gabapentin is an antiepileptic drug approved for the treatment of postherpetic neuralgia and as adjunctive therapy for partial seizures. The drug has been shown to be safe and nontoxic. The current literature has limited reports of neurologic toxicity associated with gabapentin therapy in patients with or without renal dysfunction. We describe the case of a 75-year-old man with renal dysfunction who developed neurologic toxicity due to gabapentin accumulation. Future studies are warranted to confirm the neurologic adverse effects of gabapentin, including any additional risks in patients with renal dysfunction.

Attenuation of morphine tolerance by intrathecal gabapentin is associated with suppression of morphine-evoked excitatory amino acid release in the rat spinal cord

This study was designed to investigate the effect of acute and chronic intrathecal (i.t.) injection of gabapentin (GBP) on the antinociceptive effect of morphine and tolerance development using a tail-flick latency test. Levels of excitatory amino acids (EAA) in i.t. CSF dialysates were also measured by high performance liquid chromatography. Male Wistar rats were implanted with either one or two i.t. catheters for drug injection or pump infusion and with a microdialysis probe for CSF dialysate collection. The effect of acute GBP (10 microg i.t.) injection on the morphine dose response was examined in both naïve rats and rats made tolerant by continuous infusion of morphine (15 microg/h i.t.) for 5 days. At such a low dose (10 microg i.t.), GBP did not enhance morphine's antinociception in naïve rats. In morphine-tolerant rats, however, acute GBP (10 microg i.t.) injection potentiated morphine's antinociception and yielded a 14.6-fold shift in morphine's dose-response curve. When GBP (10 microg/h i.t.) was co-infused with morphine (15 microg/h i.t.) to examine its effect on the development of morphine tolerance, GBP attenuated the development of morphine tolerance. The effect of GBP and morphine on CSF glutamate and aspartate levels was examined in naïve rats, and the effect of morphine challenge on CSF glutamate and aspartate levels was examined in rats previously infused for 5 days with morphine alone or morphine plus GBP. Acute injection of GBP (10 microg i.t.), morphine (50 microg i.t.), or GBP (10 microg i.t.) followed by morphine (50 microg i.t.) 30 min later had no significant effect on CSF EAA concentration in naïve rats; however, in tolerant rats, morphine challenge (50 microg i.t.) increased aspartate and glutamate levels to 221 +/- 22% and 296 +/- 43%, respectively, of those before morphine challenge, and this phenomenon was inhibited by GBP co-infusion. Our results show that GBP, at a dose without enhanced effect on morphine's antinociception in naïve rats, not only potentiates morphine's antinociceptive effect in morphine-tolerant rats but also attenuates the development of morphine tolerance. The mechanism of the effect of GBP on morphine tolerance might be via suppression of the EAA concentration in spinal CSF dialysate.

Managing Bipolar Disorder in the Elderly

Clinical research in geriatric psychopharmacology has been a relatively neglected focus compared with the wealth of information on younger populations, and there is a dearth of published, controlled trials. Similarly, these are limited data in the area of geriatric bipolar disorder. Although there is an absence of rigorous, evidence-based information, preliminary data on older adults with bipolar disorder suggest some promising treatment options and important differences in older versus younger patients with bipolar illness. Lithium, while widely utilised in younger populations, is often poorly tolerated in the elderly. Clinical evidence regarding use of antiepileptic compounds in late-life bipolar disorder is generally compiled from bipolar disorder studies in mixed populations, studies in older adults with seizure disorders, and studies on dementia and psychotic conditions other than bipolar disorder. Valproate semisodium and carbamazepine are widely prescribed compounds in older adults with bipolar disorder. However, the popularity of these compounds has occurred in context of an absence of evidence-based data. The atypical antipsychotics have expanded the treatment armamentarium for bipolar disorder in mixed populations and may offer particular promise in management of bipolar illness in older populations as well. Olanzapine, risperidone, quetiapine, ziprasidone and aripiprazole are atypical antipsychotics that have been approved by the US FDA for the treatment of bipolar disorder; however, there are no published, controlled trials with atypical antipsychotics specific to mania in geriatric patients. Preliminary reports on the use of clozapine, risperidone, olanzapine and quetiapine suggest a role for the use of these agents in late-life bipolar disorder. Information with ziprasidone and aripiprazole specific to geriatric bipolar disorder is still lacking.

The role of gabapentin in treating diseases with cutaneous manifestations and pain

BACKGROUND

Gabapentin was first approved by the FDA in 1993 as an add-on treatment for partial epileptic seizures. In May of 2002, it was approved as treatment for post-herpetic neuralgia by the Food and Drug Administration. It appears to be a promising agent in the treatment of pain, alterations of sensation and pruritus associated with dermatological disease, but no review of these uses exists.

METHODS

Medline and Google searches were performed for the words "Gabapentin" and "Neurontin." The articles found were reviewed. Article identified that contained references to the treatment of skin disease and neuropathic pain were examined and their contents surveyed.

RESULTS

Approximately 1200 articles were located in Medline that referred to Garbapentin or Neurontin. Over 150 articles reviewed its use for neuropathic pain, neuritis or neuralgia of various sorts. Approximately 20 articles reviewed its use for a variety of dermatological conditions or diseases with dermatological manifestations that included: pain control associated with wound dressing changes, erythromelagia, piloleiomyoma related pain, brachioradial pruritus, Glossodynia, vulvodynia, and reflex sympathetic dystrophy. Over 100 articles that related to Gabapentin side effects were reviewed.

CONCLUSIONS

Gabapentin is a very promising medication in the treatment of post-herpetic neuralgia and pain. Because dermatological patients suffer pain from painful tumors, after surgery, in conjunction with neuropathic ulcers, during dressing changes involving serious medical conditions, its applications seem manifold. Future studies must assess its role in the treatment of pruritus and other dermatological conditions involving pain or alteration of sensation.

Gabapentin dosing in the treatment of epilepsy

BACKGROUND

Gabapentin is considered a safe and well-tolerated antipileptic drug (AED) with a favorable pharmacokinetic profile and a broad therapeutic index. However, recent studies have used higher doses and faster titration schedules than those used in the pivotal trials that established the efficacy of gabapentin in the treatment of partial seizures.

OBJECTIVE

The purposes of this review were to assess the gabapentin titration and dosing regimens that have been published in peer-reviewed journals, to develop dosing recommendations to maximize antiseizure efficacy without compromising tolerability, and to formulate guidelines for an adequate therapeutic assessment of gabapentin dosage efficacy.

METHODS

In the absence of sufficient placebo-controlled, double-blind studies, a formal evidence-based assessment could not be performed. However, a MEDLINE search using the search terms gabapentin and epilepsy, spanning back to the year 1986, produced numerous published reports from randomized, placebo-controlled and open-label trials, as well as case reports. These were reviewed to assess the range of dosing and titration schedules reported. Reports that employed gabapentin doses and titration schedules were selected for review.

RESULTS

Our review of this literature suggests improved seizure control at higher gabapentin maintenance dosages (< or =3600 mg/d) than are used today in clinical practice (1800 mg/d) without an increase in the incidence of adverse reactions. Most of the patients who received high dosages (eg, 3600 mg/d) or experienced fast titration rates tolerated gabapentin well. Side effects occurred around the onset of dosing and were reported in some studies to be transient.

CONCLUSIONS

Based in the literature here, in most adult patients, gabapentin may be initiated at a dosage of 900 mg/d and titrated to maintenance dosages > or = 3600 mg/d. Children may be treated with gabapentin 23 to 78 mg/kg per day. Based on controlled and open trials, the majority of patients will tolerate gabapentin well enough for an adequate therapeutic assessment. Titration to effect can be accomplished rapidly, if necessary; however, as with other AEDs, optimal seizure control may take months to achieve.

Characterization of gabapentin overdose using a poison center case series

BACKGROUND

Gabapentin is an anticonvulsant that is being used for an increasing number of off-label indications. The purpose of this study is to document the clinical manifestations and outcomes of gabapentin exposures reported to poison centers.

METHODS

A multicenter prospective observational study of all gabapentin exposures reported to three poisoncenters was conducted between 4/1/98 and 4/1/2000. Cases involving gabapentin only were evaluated.

RESULTS

There were 20 cases with gabapentin as the sole substance in doses ranging from 50 mg to 35 g. Ten of the 20 cases involved children and adolescents. Clinical effects developed early and resolved within 10 hours in most patients. Seven cases were managed in the home with only observation. Four of these patients remained asymptomatic. Effects reported in the three symptomatic patients were drowsiness (3) and ataxia (1). Thirteen patients were managed in a health care facility. Nine were symptomatic with reported effects of drowsiness (6), dizziness (3), nausea/vomiting (2), tachycardia (2), and hypotension (2). None of the patients were admitted for medical care.

CONCLUSION

In this cases series, gabapentin exposures caused no or minimal toxicity.

Flumazenil and dialysis for gabapentin-induced coma

OBJECTIVE

To describe a case of gabapentin-induced coma that was reversed with flumazenil and hemodialysis.

CASE SUMMARY

We describe an 83-year-old dialysis-dependent white man who became comatose after a single dose of gabapentin for phantom limb pain. The patient was successfully revived from the coma with administration of flumazenil, which was then followed by hemodialysis. Serum concentration data before and 4 hours after dialysis document the effectiveness of hemodialysis for gabapentin toxicity.

DISCUSSION

An objective causality assessment revealed that this adverse event was probably related to the gabapentin that the patient received. To our knowledge, this is the first documented case of not only gabapentin-induced coma, but also the effectiveness of flumazenil for treatment of this type of coma. Although therapeutic hemodialysis has been previously described, our case report is strengthened by the serum concentration monitoring accompanying it.

CONCLUSIONS

This report underscores the importance of initiating gabapentin therapy at low doses in dialysis-dependent patients and introduces a novel treatment for those who experience toxicity.

Gabapentin: pharmacology and its use in pain management

Although its exact mode of action is not known, gabapentin appears to have a unique effect on voltage-dependent calcium ion channels at the postsynaptic dorsal horns and may, therefore, interrupt the series of events that possibly leads to the experience of a neuropathic pain sensation. Gabapentin is especially effective at relieving allodynia and hyperalgesia in animal models. It has been shown to be efficacious in numerous small clinical studies and case reports in a wide variety of pain syndromes. Gabapentin has been clearly demonstrated to be effective for the treatment of neuropathic pain in diabetic neuropathy and postherpetic neuralgia. This evidence, combined with its favourable side-effect profile in various patient groups (including the elderly) and lack of drug interactions, makes it an attractive agent. Therefore, gabapentin should be considered an important drug in the management of neuropathic pain syndromes.

Long-term use of gabapentin for treatment of pain after traumatic spinal cord injury

OBJECTIVE

To determine the long-term efficacy of gabapentin as a treatment of pain after spinal cord injury.

DESIGN

All patients with traumatic-onset spinal cord injury treated with gabapentin were identified and followed up using a longitudinal observational design with two contact points (6 and 36 months after the trial) using a semi-structured interview. The first follow-up interview attempted to capture all 31 patients placed on therapeutic trial. The second follow-up interview attempted to capture those reporting a favorable response (n = 14) to the therapeutic trial at the first follow-up.

RESULTS

Of the 27 patients contacted at the first follow-up (87% response rate), 6 (22%) discontinued the trial secondary to intolerable side effects; therefore, the pain analgesic effects of gabapentin in these patients could not be determined. Of the remaining 21 patients, 14 (67%) reported a favorable response (i.e., a 2 or greater point reduction on a 0-10 pain-rating scale). The second follow-up interview captured 11 (79% response rate) of the 14 patients reporting a favorable response at the first interview, and 91% (10 of 11 patients) continued to report that gabapentin was an effective analgesic. There was no evidence to suggest dosing difficulties due to tolerance over the 3-year period. Sedation, dizziness, and forgetfulness were the most common side effects.

CONCLUSIONS

Gabapentin may be an effective treatment of pain after spinal cord injury among those able to tolerate initial and long-term side effects.