Renal impairment as a possible side effect of gabapentin. A single case report

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).

Vitamin E protects against gabapentin-induced chronic hepatic and renal damage associated with the inhibition of apoptosis and tissue injury in rats

AIMS

This study aimed to investigate the potential protective effects of vitamin E against gabapentin-induced chronic liver and kidney injury associated with the inhibition of biomarkers of apoptosis and tissue injury.

MATERIALS AND METHODS

Four groups of adult male rats were included; control, gabapentin (100 mg/kg/day), Vitamin E (80 mg/kg/day), and a combination of gabapentin and Vitamin E for 90 days. Serum levels of AST, ALT, LDH, ALP, urea, and creatinine were measured in addition to malondialdehyde (MDA), and reduced glutathione (GSH) tissue levels. P53 gene expression, histological, and immunohistochemical examinations were performed in liver and kidney tissue samples.

KEY FINDINGS

Gabapentin increased AST, ALT, LDH, ALP, urea, creatinine, MDA, and p53 gene expression and it reduced GSH. Moreover, gabapentin administration caused structural changes in the hepatic and renal architecture with a weak Periodic acid-Schiff (PAS) reaction that reflects glycogen deposition in the liver and kidney and a positive immunoreaction for BCL2-associated X protein (BAX) that reflects activated apoptosis. Vitamin E significantly (p<0.05) reversed the biochemical alterations associated with chronic gabapentin administration and improved the histopathological picture of hepatic and renal tissue with a partial inhibition of BAX.

SIGNIFICANCE

Chronic administration of gabapentin causes hepatic and renal impairments, which is ameliorated by Vitamin E; possibly due to the inhibition of biomarkers of apoptosis and tissue injury.

Gabapentin in the treatment of mental illness: the echo chamber of the case series

BACKGROUND

Bipolar disorder is a common and debilitating psychiatric illness. Several antiepileptic drugs (AEDs) have been approved for the treatment of bipolar disorder. Gabapentin gained a large market share of AED use in the late 1990s in spite of a lack of randomized clinical trial (RCT) evidence and no labeled indication from the U.S. Food and Drug Administration for its use in psychiatric illness. This article describes the results of a literature review, the purpose of which was to examine the characteristics of studies conducted in humans concerning the efficacy of gabapentin in bipolar disorder.

METHODS

Publications relevant to this topic were identified based on a PUBMED search as well as an examination of references from a published systematic review and citations from relevant review articles.

RESULTS

The search located 29 studies published between 1997 and 2007, with the greatest number of articles published in 1998 and 1999. Of these 29 publications, 15 involved uncontrolled case series, while 6 were single case reports. The sample size in the studies was generally small, and often we could not identify the funding source. Despite the generally weak study design in the identified publications, the authors of the articles often commented on the promising nature of gabapentin therapy for bipolar disorder. However, 4 small, randomized trials in heterogeneous populations demonstrated little if any evidence of such efficacy. Nine letters to the editor demonstrated a similar pattern.

CONCLUSIONS

The large number of case series concerning gabapentin is striking. The number of reports and their distribution in many different journals created a type of "echo chamber" effect, through which the sheer number of publications and citations may give legitimacy to the practice of using gabapentin for bipolar disorder. Although the case series were generally of poor quality, their publication in peer-reviewed journals may have been partially responsible for the widespread use of an ineffective medication.

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.

Pancreatitis associated with atypical antipsychotics: from the Food and Drug Administration's MedWatch surveillance system and published reports

STUDY OBJECTIVE

To investigate the relative numbers and clinical characteristics of pancreatitis in patients treated with the atypical antipsychotic agents, clozapine, olanzapine, and risperidone, versus the conventional neuroleptic, haloperidol.

DESIGN

Pharmacovigilance study of pooled, spontaneously reported adverse events.

SETTING

Government-affiliated drug evaluation center.

PATIENTS

One hundred ninety-two patients who developed pancreatitis during treatment with one or more antipsychotic agents.

INTERVENTION

Patients were identified with the Food and Drug Administration's MedWatch surveillance program and a MEDLINE search.

MEASUREMENTS AND MAIN RESULTS

Most cases of pancreatitis occurred within 6 months after the start of therapy with one or more antipsychotic agents. Of the reports of pancreatitis occurring in conjunction with these drugs, 40%, 33%, 16%, and 12% were in patients receiving treatment with clozapine, olanzapine, risperidone, and haloperidol, respectively. In 50% of the patients receiving haloperidol, an atypical antipsychotic was listed as a concomitant drug. Valproate was administered concomitantly in 23% of patients. Hyperglycemia and acidosis, although uncommon, developed with all the drugs except haloperidol. Twenty-two patients died. In contrast to patients who developed pancreatitis while receiving an atypical antipsychotic, those who developed the disease while receiving haloperidol were women and tended to be older.

CONCLUSION

The number of reports involving the three atypical antipsychotic agents and the relative paucity of reports involving haloperidol, despite its more extensive patient exposure, suggest that atypical antipsychotics may precipitate pancreatitis. However, the risk may not be the same with all agents; pancreatitis was reported most frequently with clozapine, followed by olanzapine, and then risperidone. The temporal relationship of the onset of pancreatitis with the start of drug therapy further supports a cause-and-effect relationship.

Treatment of Anxiety and Depression in Transplant Patients

Depressive and anxiety disorders appear during the transplant process due to psychological stressors, medications and physiological disturbances. Treatment is necessary to prevent impact on patient compliance, morbidity and mortality. Psychotropic medications provide an effective option, although most are only available as oral formulations. Because of this, they are more susceptible to alterations in pharmacokinetic behaviour arising from organ dysfunction in the pretransplant period. Kinetics are also an issue when considering potential drug-drug interactions before and after transplantation. Prior to transplant, organ dysfunction can change the pharmacokinetic behaviour of some psychotropic agents, requiring adjustment of dosage and schedules. Thoracic or abdominal organ failure may reduce drug absorption through disturbances in intestinal motility, perfusion and function. Cirrhotic patients experience increased drug bioavailability due to portosystemic shunting, and thus dosage is adjusted downward. In contrast, dosage needs to be raised when peripheral oedema expands the drug distribution volume for hydrophilic and protein-bound agents. Drug clearance for most psychotropic medications is dependent upon hepatic metabolism, which is often disrupted by endstage organ disease. Selection of drugs or their dosage may need to be adjusted to lower the risk of drug accumulation. Further adjustments in dosage may be called for when renal failure accompanies thoracic or abdominal organ failure, resulting in further impairment of clearance. Studies regarding the treatment of anxiety and depressive disorders in the medically ill are limited in number, but recommendations are possible by review of clinical and pharmacokinetic data. Selective serotonin reuptake inhibitors are well tolerated and efficacious for depression, panic disorder and post-traumatic stress disorder. Adjustments in dosage are required when renal or hepatic impairment is present. Among them, citalopram and escitalopram appear to have the least risk of drug-drug interactions. Paroxetine has demonstrated evidence supporting its use with generalised anxiety disorder. Venlafaxine is an alternative option, beneficial in depression, post-traumatic stress and generalised anxiety disorders. Nefazodone may also be considered, but there is some risk of hepatotoxicity and interactions with immunosuppressant drugs. Mirtazapine still needs to be studied further in anxiety disorders, but can be helpful for depression accompanied by anorexia and insomnia. Bupropion is effective in the treatment of depression, but data are sparse about its use in anxiety disorders. Psychostimulants are a unique approach if rapid onset of antidepressant action is desired. Acute or short-term anxiolysis is obtained with benzodiazepines, and selection of particular agents entails consideration of distribution rate, half-life and metabolic route.

Newer antiepileptic drugs in bipolar disorder: rationale for use and role in therapy

Antiepileptic drugs (AEDS) are used regularly in the treatment of patients with bipolar disorders. Carbamazepine and valproic acid (sodium valproate) are effective as antimanic treatments, and the success of these medications has prompted investigation of other AEDs as possible treatments in patients with mood disorders. Lamotrigine appears to be the most promising of the newer AEDs with respect to effects in mood disorders. Current evidence suggests efficacy of this drug both as monotherapy and as an adjunctive agent in bipolar depression, and studies are underway to clarify its efficacy in mood stabilisation and rapid cycling, as currently available data are equivocal. Use of gabapentin is not as well supported in the literature, although data from open trials using it as an adjunctive agent suggest that it may be helpful in patients with bipolar depression. There have been some open trials and case reports supporting the use of topiramate as an adjunctive agent for the treatment of mania; however, data from controlled trials are not yet available. Further controlled trials of lamotrigine, gabapentin or topiramate as monotherapy and adjunctive treatment are needed to clarify their potential roles in the treatment of patients with mood disorders.