Efficacy of gabapentin as adjunctive therapy in a large, multicenter study. The Steps Study Group

Can gabapentinoids decrease perioperative opioid requirements in orthopaedic trauma patients? A single-centre retrospective analysis

INTRODUCTION

Perioperative pain control in patients with orthopaedic trauma/extremity fractures has gained a lot of attraction from the scientific community in the last two decades. In addition to multimodal analgesia, the use of non-opioid drugs like gabapentinoids for pain relief is gradually finding its place in several orthopaedic subspecialties like spinal surgery, arthroplasty, and arthroscopic procedures. We envisage investigating the effectiveness of gabapentin in perioperative pain control in patients with extremity fractures undergoing surgical fixation.

METHODOLOGY

This was a retrospective comparative study conducted between January 2020 and January 2022. Patients with isolated fractures of the extremity involving long bones who were treated at our trauma centre, during the study period were divided into two groups based on the analgesics they received. Patients who received gabapentin and paracetamol were placed in group GP and those who received only paracetamol were assigned group NGP. Gabapentin was given in a single dose of 300 mg 4 h before surgery. Postoperatively, they were given 300 mg 12 hourly for 2 days. All patients in our trauma centre are usually managed with parenteral paracetamol administration pre and postoperatively. VAS score was calculated postoperatively at 2, 6, 12, 24 and 48 h. Patients requiring additional analgesics for pain relief were administered intravenous tramadol or a buprenorphine patch was applied. Patients in both groups were compared in terms of pain control, the additional requirement of opioid analgesics, and any adverse event related to medications.

RESULTS

One hundred and nineteen patients were enrolled in the study. Out of 65 patients in the NGP group (non-gabapentin group), 74% of patients received additional opioid analgesics apart from paracetamol. Out of the 54 patients in the GP group (gabapentin group), only 41% required additional opioid analgesia for pain control. There was a significant difference in opioid consumption between the two groups (p < 0.01). VAS scores were not significantly different between the two groups at 2, 4, 6, 12, 24 and 48 h. Gender and fracture morphology did not affect opioid intake in the GP group. However, in the non-gabapentin group, there was a significant difference in opioid requirement in patients with intraarticular fractures (p < 0.01).

CONCLUSION

Analgesic requirements vary from patient to patient depending on the injury's severity and surgery duration. However, there are no strict guidelines for pain relief in limb trauma surgeries which often leads to overuse and opioid-related complications or underuse and chronic pain. Gabapentinoids can supplement the analgesic effect of paracetamol in trauma patients during the perioperative period, decreasing the need for opioids.

Safety, Tolerability, and Efficacy of Pain Reduction by Gabapentin for Acute Headache and Meningismus After Aneurysmal Subarachnoid Hemorrhage: A Pilot Study

Introduction: Severe, often sudden-onset headache is the principal presenting symptoms of aneurysmal subarachnoid hemorrhage (aSAH). We hypothesized that gabapentin would be safe and tolerable for aSAH-induced headaches and would reduce concurrent opioid use.

Methods: We performed a single-center, double-blind, randomized, placebo-controlled trial (registered at ClinicalTrials.gov; NCT02330094) from November 24, 2014, to June 24, 2017, where aSAH patients received either dose-escalating gabapentin or oral placebo, both alongside a standard of care pain regimen. After 7 days, patients had the option to continue in an open-label period until 14 days after enrollment or until discharge from the intensive care unit. Our primary endpoint was the efficacy of gabapentin in reducing headache numeric pain scores and opioid usage in patients with aSAH compared to the placebo group. We identified 63 potential patients with aSAH for the study. After applying stringent exclusion criteria, 16 eligible patients were enrolled into one of two arms.

Results: The study ended prematurely after reaching a pre-specified funding period and an unexpected drop in aSAH cases. There was a trend toward lower headache numeric pain scores and opioid use in the gabapentin treated arm; however this was not significantly different. Gabapentin was well tolerated by participants and no adverse effects were reported.

Conclusions: While there was a trend toward lower pain scores and opioid requirement in the gabapentin group, the study was underpowered to detect a difference. Larger multicenter trials are required to evaluate the efficacy of gabapentin to reduce opioid requirements after aSAH.

Repurposed molecules for antiepileptogenesis: Missing an opportunity to prevent epilepsy?

Prevention of epilepsy is a great unmet need. Acute central nervous system (CNS) insults such as traumatic brain injury (TBI), cerebrovascular accidents (CVA), and CNS infections account for 15%-20% of all epilepsy. Following TBI and CVA, there is a latency of days to years before epilepsy develops. This allows treatment to prevent or modify postinjury epilepsy. No such treatment exists. In animal models of acquired epilepsy, a number of medications in clinical use for diverse indications have been shown to have antiepileptogenic or disease-modifying effects, including medications with excellent side effect profiles. These include atorvastatin, ceftriaxone, losartan, isoflurane, N-acetylcysteine, and the antiseizure medications levetiracetam, brivaracetam, topiramate, gabapentin, pregabalin, vigabatrin, and eslicarbazepine acetate. In addition, there are preclinical antiepileptogenic data for anakinra, rapamycin, fingolimod, and erythropoietin, although these medications have potential for more serious side effects. However, except for vigabatrin, there have been almost no translation studies to prevent or modify epilepsy using these potentially "repurposable" medications. We may be missing an opportunity to develop preventive treatment for epilepsy by not evaluating these medications clinically. One reason for the lack of translation studies is that the preclinical data for most of these medications are disparate in terms of types of injury, models within different injury type, dosing, injury-treatment initiation latencies, treatment duration, and epilepsy outcome evaluation mode and duration. This makes it difficult to compare the relative strength of antiepileptogenic evidence across the molecules, and difficult to determine which drug(s) would be the best to evaluate clinically. Furthermore, most preclinical antiepileptogenic studies lack information needed for translation, such as dose-blood level relationship, brain target engagement, and dose-response, and many use treatment parameters that cannot be applied clinically, for example, treatment initiation before or at the time of injury and dosing higher than tolerated human equivalent dosing. Here, we review animal and human antiepileptogenic evidence for these medications. We highlight the gaps in our knowledge for each molecule that need to be filled in order to consider clinical translation, and we suggest a platform of preclinical antiepileptogenesis evaluation of potentially repurposable molecules or their combinations going forward.

Combination therapy of levetiracetam and gabapentin against nonconvulsive seizures induced by penetrating traumatic brain injury

BACKGROUND

Posttraumatic seizures are a medical problem affecting patients with traumatic brain injury. Yet effective treatment is lacking owing to the limitations of antiepileptic drugs (AEDs) applicable to these patients.

METHODS

In this study, we evaluated the dose-response efficacy of levetiracetam (12.5-100.0 mg/kg) and gabapentin (1.25-25.0 mg/kg) administered either individually or in pairs at fixed-dose ratios as a combination in mitigating posttraumatic nonconvulsive seizures induced by severe penetrating ballistic-like brain injury (PBBI) in rats. Seizures were detected by continuous electroencephalogram (EEG) monitoring for 72 hours postinjury. Animals were treated twice per day for 3 days by intravenous injections.

RESULTS

Both levetiracetam (25-100 mg/kg) and gabapentin (6.25-25 mg/kg) significantly reduced PBBI-induced seizure frequency by 44% to 73% and 61% to 69%, and seizure duration by 45% to 64% and 70% to 78%, respectively. However, the two drugs manifested different dose-response profiles. Levetiracetam attenuated seizure activity in a dose-dependent fashion, whereas the beneficial effects of gabapentin plateaued across the three highest doses tested. Combined administration of levetiracetam and gabapentin mirrored the more classic dose-response profile of levetiracetam monotherapy. However, no additional benefit was derived from the addition of gabapentin. Furthermore, isobolographic analysis of the combination dose-response profile of levetiracetam and gabapentin failed to reach the expected level of additivity, suggesting an unlikelihood of favorable interactions between these two drugs against spontaneously occurring posttraumatic seizure activities at the particular set of dose ratios tested.

CONCLUSION

This study was the first attempt to apply isobolographic approach to studying AED combination therapy in the context of spontaneously occurring posttraumatic seizures. Despite the failure to achieve additivity from levetiracetam and gabapentin combination, it is important to recognize the objectivity of the isobolographic approach in the evaluation of AED combination therapy against seizures directly associated with brain injuries.

Administration of four different doses of gabapentin reduces awakening from breakthrough pain and adverse effects in outpatients with neuropathic pain during the initial titration

Background

Gabapentin is a safe and well-tolerated anticonvulsant with a wide therapeutic index, and it is used for neuropathic pain. The aim of this study was to compare previous dosing methods with the administration of four different doses of gabapentin while maintaining the same maximum daily dose for the safe administration of high doses of the medication.

Methods

The subjects were outpatients with various neuropathic pain syndromes, with at least two of the following symptoms: allodynia, burning pain, shooting pain, or hyperalgesia. The TID group received equal doses of gabapentin 3 times per day, while the QID group received 4 different doses of gabapentin per day. The pain score, frequency of breakthrough pain (BTP), severity and the duration of pain, sleep disturbance due to nocturnal pain, and adverse effects were recorded each day.

Results

The average daily pain score and sleep disturbance were significantly reduced in the QID group between days 3 and 10 of the experiment. The adverse effects of the medication were also reduced in the QID group. However, the frequency of BTP and severity and duration of pain were not significantly different between two groups.

Conclusions

Administration of 4 different doses of gabapentin during the initial titration in outpatients with neuropathic pain resulted in a significant reduction in awakening from breakthrough pain and a reduction in the adverse effects of the medication.

Study of neurontin: titrate to effect, profile of safety (STEPS) trial: a narrative account of a gabapentin seeding trial

BACKGROUND

Seeding trials, clinical studies conducted by pharmaceutical companies for marketing purposes, have rarely been described in detail.

METHODS

We examined all documents relating to the clinical trial Study of Neurontin: Titrate to Effect, Profile of Safety (STEPS) produced during the Neurontin marketing, sales practices, and product liability litigation, including company internal and external correspondence, reports, and presentations, as well as depositions elicited in legal proceedings of Harden Manufacturing vs Pfizer and Franklin vs Warner-Lambert, most which were created between 1990 and 2009. Using a systematic search strategy, we identified and reviewed all documents related to the STEPS trial in order to identify key themes related to the trial's conduct and determine the extent of marketing involvement in its planning and implementation.

RESULTS

Documents demonstrated that STEPS was a seeding trial posing as a legitimate scientific study. Documents consistently described the trial itself, not trial results, to be a marketing tactic in the company's marketing plans. Documents demonstrated that at least 2 external sources questioned the validity of the study before execution, and that data quality during the study was often compromised. Furthermore, documents described company analyses examining the impact of participating as a STEPS investigator on rates and dosages of gabapentin prescribing, finding a positive association. None of these findings were reported in 2 published articles.

CONCLUSION

The STEPS trial was a seeding trial, used to promote gabapentin and increase prescribing among investigators, and marketing was extensively involved in its planning and implementation.

[Development or worsening of myoclonus associated with gabapentin therapy]

PURPOSE

To evaluate the development or worsening of myoclonus in patients receiving gabapentin (GBP).

METHODS

Clinical charts of 162 patients treated with GBP were reviewed concerning development or worsening of myoclonus.

RESULTS

We found 3 cases (1.9%) of myoclonus. Two patients had preexisting myoclonus and generalized tonic-clonic seizures, while the other one had generalized tonic-clonic seizures only. All patients experienced development or worsening of myoclonus within 2 weeks after starting GBP. Dose at the onset of development or worsening of myoclonus varied from 600 mg to 1,800 mg. Two patients developed multifocal myoclonus. Discontinuation of GBP or clonazepam add-on resulted in cessation of myoclonus with no serious sequela.

CONCLUSION

GBP may increase the risk of development of de novo myoclonus or worsening of myoclonus in patients with preexistent myoclonus. According to the result of this study and the treatment guidelines, GBP should be avoided when a patient has preexistent myoclonus.

[Specificity of epileptic seizures in the elderly: A proposed electro-clinical scale]

Diagnosis of epileptic seizure may be difficult in older patients because seizure manifestations are often unusual: confusion, paresis... and because there are multiple differential diagnoses (syncope, transient ischemic attack, transient global amnesia...). To promote and facilitate the diagnosis of seizures in the elderly, neurologists and gerontologists must work together and focus their strategy on two points: firstly, the knowledge of the specific presentation of seizures in elderly patients, and secondly, the adoption of a reasoning based on seizures and not epileptic syndromes. A multidisciplinary group worked on epilepsy of the elderly to elaborate an electro-clinical score which aims to help establish the diagnosis of epilepsy in elderly patients in different clinical settings. This electro-clinical score is based on a systematic review of scientific literature and the recommendations are explicitly linked to supporting evidence. Further, clinical validation of the electro-clinical score is required.

Adjunctive therapy of uncontrolled partial seizures with levetiracetam in Australian patients

OBJECTIVE

The goal of the work described here was to explore the efficacy, safety, and tolerability of adjunctive therapy with levetiracetam and associated changes in health-related quality of life in Australian patients with uncontrolled partial seizures.

METHODS

A phase IV open-label 16-week clinical trial was undertaken. Patients received adjunctive levetiracetam, adjusted according to clinical response to a final daily dose of 1000-3000 mg. Seizure frequency and adverse events were recorded. A quality-of-life questionnaire (QOLIE-10-P) was administered at the start and end of therapy.

RESULTS

The intention-to-treat population (N=152) experienced a median reduction in total seizure frequency of 57.7%. The 50% responder rate was 56.6%, and 12.5% of patients were free of seizures throughout the trial. Adverse events were mostly mild or moderate, leading to discontinuation in 9.9%. The most common adverse events were somnolence, fatigue, headache, and dizziness. Behavioral adverse events occurred in approximately one-quarter of patients, including two-thirds of those who withdrew because of adverse events. There was an improvement in the QOLIE-10-P score.

CONCLUSION

Levetiracetam is effective and well tolerated when added to existing therapy in patients with uncontrolled partial seizures.

Comparison of the efficacy and tolerability of new antiepileptic drugs: what can we learn from long-term studies?

OBJECTIVE

A review of long-term open-label studies was performed with the aim of detecting differences in efficacy and/or tolerability of new antiepileptic drugs (AEDs).

METHODS

From more than 500 open studies conducted to evaluate the efficacy and tolerability of gabapentin (GBP), lamotrigine (LTG), levetiracetam (LEV), oxcarbazepine (OXC), pregabalin (PGB), tiagabine (TGB), topiramate (TPM) or zonisamide (ZNS), we selected all studies that reported or allowed us to calculate the number of patients who achieved seizure freedom for 6 months and/or the number of patients withdrawing for adverse effects and/or the number or percentage of patients continuing treatment after 1 year.

RESULTS

No studies were found in which this information was available for OXC, PGB, TGB or ZNS. The number of patients who achieved seizure freedom for 6 months was reported in four studies each for GBP and TPM, five studies for LTG, and eight studies for LEV. The best efficacy profile using this end point was found for LEV, followed by TPM, LTG, and GBP. Twenty-two studies reported the number of patients withdrawing due to adverse effects. LEV was the best-tolerated AED, a little ahead of LTG, and significantly better than GBP or TPM . TPM was by far the least well-tolerated drug. Information concerning patients continuing treatment after 1 year was reported in two GBP studies, two TPM studies, six LEV studies and five LTG studies. GBP had a very low retention rate (between 20% and 25% of patients continued the drug), while TPM and LTG had a retention rate of 40-60% and LEV had a retention rate of 60-75%.

CONCLUSION

One limitation of these rankings is that their statistical value is limited because of the indirect nature of the comparisons. Anyhow, this review covers the main studies published thus far on this subject and provides full updated information on the current literature about these drugs.

Lamotrigine therapy in patients requiring a change in antiepileptic drug regimen

INTRODUCTION

The tolerability of lamotrigine as adjunctive and monotherapy in patients requiring a change in antiepileptic drug (AED) therapy was assessed in this multicenter, open-label study. Open-label studies conducted in the clinic setting may provide additional drug tolerability and effectiveness information that may not be evident in pre-approval clinical trials.

METHODS

Adult patients with partial seizures received adjunctive lamotrigine for 16 weeks. Patients taking a single enzyme-inducing AED could convert to lamotrigine monotherapy for an additional 12 weeks. Patients were assessed at baseline, end of adjunctive therapy, and end of monotherapy using the Liverpool Adverse Experience Profile (AEP), Quality of Life in Epilepsy-31, a patient satisfaction rating, and a subjective investigator global assessment.

RESULTS

Of the 547 patients enrolled (mean age 42.7 years, 58% female), 421 (77%) completed adjunctive therapy. Upon completion of the adjunctive phase, mean improvement from baseline was 4.3 points on the AEP, and investigators rated 71% of patients as improved in global status. Overall score on the QOLIE 31 improved by 10 points from baseline. One hundred and seventy-eight patients entered and 143 (80%) patients completed the monotherapy phase. In patients completing lamotrigine monotherapy, mean improvement from baseline was 5.9 points on the AEP, and investigators rated 92% as improved in global status. Overall score on the QOLIE 31 score improved by 15 points from baseline.

CONCLUSION

Lamotrigine as adjunctive treatment and monotherapy may improve side effect burden and quality of life in patients requiring a change in AED therapy.

Sustained efficacy and long-term safety of oxcarbazepine: one-year open-label extension of a study in refractory partial epilepsy

PURPOSE

To evaluate the long-term efficacy, tolerability, and safety of oxcarbazepine (OXC) in medically refractory partial epilepsy.

METHODS

This study is the open-label extension phase that followed a multicenter, randomized, double-blind, dose-response clinical study of OXC monotherapy in patients with medically refractory partial epilepsy. We analyzed the efficacy, tolerability, and safety of OXC during the first 48 weeks of open-label therapy. To evaluate efficacy, we compared the change in seizure frequency throughout the 48 weeks of treatment with OXC with the baseline seizure frequency that preceded the double-blind phase of the core study by an intent-to-treat and completer analysis. Safety and tolerability were evaluated by using an intent-to-treat analysis.

RESULTS

Of the 87 patients enrolled in the double-blind study, 76 patients participated in the open-label extension phase. Fifty-five (72%) patients completed 48 weeks of open-label treatment on a median OXC dose of 2,400 mg/day. Based on an intent-to-treat analysis, the median reduction in seizure frequency was 47%(p = 0.0054); the 50 and 75% responder rates were 46.1 and 25.0%, respectively, with 6.6% of patients remaining seizure free. The completer analysis yielded comparable efficacy results. OXC was well tolerated, with 13% of patients exiting because of adverse events. The six most common adverse events, irrespective of their causal relation to OXC, were dizziness, headache, fatigue, diplopia, nausea, and rash. For the most part, these adverse events tended to be transient.

CONCLUSIONS

The efficacy of OXC is sustained with good safety and tolerability profiles during long-term treatment of patients with medically refractory partial epilepsy.

Selection criteria for the clinical use of the newer antiepileptic drugs

In recent years, several new antiepileptic drugs (AEDs) have been licensed: felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, vigabatrin and zonisamide. These drugs have proven efficacy as add-on therapy in patients with difficult-to-treat partial epilepsy, as 20-50% of patients treated in add-on trials experienced a seizure reduction of >or=50%. Relatively few trials have been conducted to evaluate these drugs as monotherapy for patients with newly diagnosed epilepsy. In the monotherapy trials that have been conducted, the newer drugs were often as efficacious as conventional drugs, and their tolerability was often better. However, the methodology of these trials can be criticised. Because of the relative lack of robust data for the newer agents, the conventional drugs have thus far maintained their status as first-line monotherapy. However, when first-line monotherapy fails, an alternative drug has to be chosen from the available conventional and newer drugs. This article aims to give detailed background information on the newer AEDs in order to enable physicians to make a rational choice from the available drugs for individual patients. Data are provided for the different newer AEDs on mechanisms of action; efficacy in refractory partial epilepsy, newly diagnosed epilepsy in adults and generalised seizure types; adverse effects; pharmacokinetics; and use in special patient categories.

Overtreatment in adults with epilepsy

Overtreatment of epilepsy patients is traditionally associated with the use of polytherapy, i.e. use of more than one antiepileptic drug (AED). Although monotherapy is now being used in 70% of patients with epilepsy, these patients are also at risk at being overtreated. Ten to 20% of patients withdraw from their first drug because of adverse effects. This is partly related to high starting dosages and fast titration rates. The conventional AEDs are still first choice monotherapy drugs, although they potentially have more adverse effects, especially in the elderly. Other problems are the random selection of second or third choice drugs and the uncertainty about when to switch to polytherapy. Several authors have suggested that patients with progressive forms of epilepsy, such as patients with mesiotemporal sclerosis, should be treated adequately as soon as possible and that epilepsy surgery should be considered for them in a much earlier stage. Overtreatment in polytherapy is still a large threat, due to several reasons: drug loads are much higher, and thus more adverse effects are likely to develop; drug combinations are selected randomly, as evidence about effective combinations has been scarce; the constant choice between continuing the existing treatment (which is suboptimal) and trying new drugs (which may disturb a patient's equilibrium); the long-term use of benzodiazepines.

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.

Gabapentin in postherpetic neuralgia: a randomised, double blind, placebo controlled study

A multicentre double blind, randomised, placebo controlled 7-week study evaluated the efficacy and safety of gabapentin 1800 or 2400 mg/day in treating postherpetic neuralgia. Three hundred and thirty-four men and women aged at least 18 years (mean 73) received gabapentin 1800 or 2400 mg daily or placebo in three divided doses with a forced titration schedule. The primary outcome measure was change in average daily pain diary score (baseline week v final week). Secondary outcomes included mean weekly sleep interference score; Short Form-McGill Pain Questionnaire (SF-MPQ); Clinician and Patient Global Impression of Change (CGIC/PGIC); Short Form-36 Health Survey (SF-36). From week 1, pain scores showed a significantly greater improvement with gabapentin: the final difference v baseline was -34.5% for the 1800 mg dose, -34.4% for the 2400 mg dose compared with -15.7% for the placebo group. The difference vs. placebo was 18.8% for the 1800 mg dose (95% confidence interval 10.9-26.8%; P<0.01) and 18.7% for the 2400 mg dose (10.7-26.7%; P<0.01). Sleep interference diaries showed a similar pattern. There were significant differences in favour of gabapentin for number of patients reporting >50% reduction in their pain intensity, in the CGIC and PGIC, in the sensory and total scores of the SF-MPQ (both doses), in the visual analogue scale of pain of the SF-MPQ (2400 mg only) and in the vitality, bodily pain and mental health domains of the SF-36. Overall gabapentin was well tolerated. The most common adverse events were dizziness and somnolence, particularly during the titration phase. Thus, this study confirms the role of gabapentin as an efficacious and well-tolerated treatment for postherpetic neuralgia.