Efficacy and safety of pregabalin in patients with spinal cord injury: a pooled analysis

OBJECTIVE

To summarize the efficacy and examine the safety and tolerability of pregabalin in patients with central neuropathic pain due to spinal cord injury (SCI).

RESEARCH DESIGN AND METHODS

Data were pooled from two 12 to 16 week, placebo-controlled trials of pregabalin in patients with neuropathic pain due to SCI. Pain diaries were used to rate pain from 0 = no pain to 10 = worst possible pain. Efficacy measures included: mean change in pain from baseline to endpoint; duration adjusted average change (DAAC) in pain; the percentage of patients with ≥30% or ≥50% reductions in pain score from baseline to endpoint; and Patient Global Impression of Change (PGIC) score at endpoint. Adverse events (AEs) were also compared between treatment groups.

RESULTS

In total 174 patients received placebo and 182 received pregabalin. Mean change in pain from baseline to endpoint was improved in the pregabalin group compared with placebo (placebo-adjusted difference = -0.79; 95% CI = -1.15, -0.43; p < 0.001; baseline-observation-carried-forward). DAAC in pain was improved in patients receiving pregabalin compared with placebo (p < 0.001). The percentage of patients achieving ≥30% and ≥50% reductions in pain from baseline to endpoint was greater in the pregabalin arm compared with placebo (placebo: 30% = 22.5%, 50% = 11.6: pregabalin 30% = 35.6%, 50% = 22.4%) (all p < 0.01). PGIC scores at endpoint were significantly better in the pregabalin arm compared with placebo (p < 0.05). Treatment-related AEs, most commonly somnolence, dizziness, dry mouth, fatigue, edema, blurred vision, and constipation occurred more frequently in patients treated with pregabalin than placebo. The majority of AEs were mild to moderate in severity.

CONCLUSIONS

Pregabalin reduced neuropathic pain due to SCI over a 12 to 16 week treatment period. Treatment-related AEs were mostly mild to moderate in severity and are consistent with the known safety profile of pregabalin. These findings should not be extrapolated to longer durations of treatment or other patient populations.

[Incomplete atrioventricular block in a patient on pregabalin therapy]

The authors report on a case of incomplete atrio-ventricular block in a patient on pregabalin therapy. Pregabalin was not overdosed; renal function of the patient was normal. The effect reverted after pregabalin discontinuation.

Pharmacological treatment for pain in Guillain-Barré syndrome

BACKGROUND

Pain in Guillain-Barré syndrome (GBS) is common, yet it is often under recognised and poorly managed. In recent years, a variety of pharmacological treatment options have been investigated in clinical trials for people with GBS-associated pain.

OBJECTIVES

To assess the efficacy and safety of pharmacological treatments for various pain symptoms associated with GBS, during both the acute and convalescent (three months or more after onset) phases of GBS.

SEARCH METHODS

On 27 August 2012, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL (2012, Issue 8) in The Cochrane Library, MEDLINE (January 1966 to August 2012) and EMBASE (January 1980 to August 2012). In addition, we searched ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs in participants with confirmed GBS, with pain assessment as either the primary or secondary outcome. For cross-over trials, an adequate washout period between phases was required for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy and assessed the risk of bias of each study.

MAIN RESULTS

Three short-term RCTs, which enrolled 277 randomised participants with acute phase GBS, were included. Risk of bias in the included studies was generally unclear due to insufficient information. None of the included studies reported the primary outcome selected for this review, which was number of patients with self reported pain relief of 50% or greater. One small study investigated seven-day regimens of gabapentin versus placebo. Pain was rated on a scale from 0 (no pain) to 10 (maximum pain). Amongst the 18 participants, significantly lower mean pain scores were found at the endpoint (day 7) in the gabapentin phase compared to the endpoint of the placebo phase (mean difference -3.61, 95% CI -4.12 to -3.10) (very low quality evidence). For adverse events, no significant differences were found in the incidence of nausea (risk ratio (RR) 0.50, 95% CI 0.05 to 5.04) or constipation (RR 0.14, 95% CI 0.01 to 2.54). A second study enrolling 36 participants compared gabapentin, carbamazepine and placebo, all administered over seven days. Participants in the gabapentin group had significantly lower median pain scores on all treatment days in comparison to the placebo and carbamazepine groups (P < 0.05). There were no statistically significant differences in the median pain scores between the carbamazepine and placebo groups from day 1 to day 3, but from day 4 until the end of the study significantly lower median pain scores were noted in the carbamazepine group (P < 0.05) (very low quality evidence). There were no adverse effects of gabapentin or carbamazepine reported other than sedation. One large RCT (223 participants, all also treated with intravenous immunoglobulin), compared a five-day course of methylprednisolone with placebo and found no statistically significant differences in number of participants developing pain (RR 0.89, 95% CI 0.68 to 1.16), number of participants with decreased pain (RR 0.95, 95% CI 0.63 to 1.42) or number of participants with increased pain (RR 0.85, 95% CI 0.52 to 1.41) (low quality evidence). The study did not report whether there were any adverse events.

AUTHORS' CONCLUSIONS

While management of pain in GBS is essential and pharmacotherapy is widely accepted as being an important component of treatment, this review does not provide sufficient evidence to support the use of any pharmacological intervention in people with pain in GBS. Although reductions in pain severity were found when comparing gabapentin and carbamazepine with placebo, the evidence was limited and its quality very low. Larger, well-designed RCTs are required to further investigate the efficacy and safety of potential interventions for patients with pain in GBS. Additionally, interventions for pain in the convalescent phase of GBS should be investigated.

Long-term treatment of anxiety disorders with pregabalin: a 1 year open-label study of safety and tolerability

OBJECTIVE

Short-term clinical trials have demonstrated the efficacy and safety of pregabalin in the treatment of generalized anxiety disorder (GAD). This study examined long-term safety and tolerability of pregabalin in patients with GAD, social anxiety disorder (SAD), or panic disorder (PD).

RESEARCH DESIGN AND METHODS

Patients (n = 528) completing one of four randomized, double-blind, placebo-controlled trials of pregabalin for GAD, SAD, or PD were treated, open label, with flexible-dose pregabalin (150-600 mg/day) for 1 year.

CLINICAL TRIAL REGISTRATION

NCT00150449.

MAIN OUTCOME MEASURES

The primary outcomes were safety and tolerability. Illness severity was assessed at baseline and Weeks 27/52 using the Clinical Global Impression of Severity (CGI-S) scale. Patients were characterized as 'responders' or 'non-responders' based on CGI-S scores ≤2 and >2, respectively. Analyses were performed on the total anxiety (GAD, SAD and PD) and GAD groups.

RESULTS

During 1 year of treatment with pregabalin, dizziness (12.5%) was the only treatment-related adverse event (AE) occurring ≥10%. Somnolence, weight gain, headache and insomnia occurred at 7.6%, 5.5%, 5.3% and 4.7%, respectively. Few treatment-related AEs were rated as severe in the total anxiety (5.1%) or GAD (3.6%) groups. Discontinuation rates due to AEs were similar (9.7% and 10.6%, respectively). No clinically significant laboratory, electrocardiogram, or other treatment-related safety findings were noted, except for treatment-related weight gain, which occurred in both the total (24.4%) and GAD (19.4%) groups. Mean CGI-S scores were similar at baseline in the total (n = 528; score, 3.4) and GAD groups (n = 330; score, 3.6), and CGI-S responder rates were similar at last-observation-carried-forward endpoint (51.3% and 48.1%, respectively).

CONCLUSIONS

Pregabalin was generally well tolerated in the long-term treatment of anxiety disorders. Improvement in illness severity was maintained over time. The key limitations of this study were that it was not randomized and neither placebo- nor active-comparator-controlled.

Successful management of postoperative pain with pregabalin after thoracotomy

PURPOSE

There is no established treatment for intercostal neuralgia associated with thoracotomy. We investigated the administration of pregabalin as a new perioperative treatment, assessing its safety and efficacy for intercostal neuralgia after thoracotomy.

METHODS

Thirty patients suffering pain after thoracotomy severe enough to cause insomnia were prospectively enrolled and treated with 150 mg of pregabalin. We evaluated pain scores (Numeric Rating Scale, NRS), severity of nocturnal insomnia, and adverse effects before and after pregabalin administration.

RESULTS

We noted significant decreases in pain scores, before vs. after pregabalin administration, from 8.2 ± 1.3 to 3.4 ± 1.3 (p < 0.0001), with improvement in nocturnal insomnia in 29 out of 30 patients. Eight patients reported adverse effects, including dizziness and daytime drowsiness; however, by reducing the dose of pregabalin, these effects were minimized while pain was controlled well.

CONCLUSION

Pregabalin was highly effective for neuralgia associated with intercostal damage after thoracotomy.

[Efficacy and safety of pregabalin for oxaliplatin- and paclitaxel-induced peripheral neuropathy]

This study included patients who were prescribed pregabalin, vitamin B12, amitriptyline, clonazepam, or carbamazepine to improve oxaliplatin(L-OHP)- or paclitaxel(PTX)-induced peripheral neuropathy at Iwate Medical University Hospital between April 2011 and July 2012. The efficacy and safety of pregabalin was evaluated by comparing 27 patients with L-OHP-induced peripheral neuropathy and 28 with PTX-induced peripheral neuropathy prescribed pregabalin(pregabalin group) with 20 patients with L-OHP-induced peripheral neuropathy and 25 with PTX-induced peripheral neuropathy prescribed other drugs(non-pregabalin group). Response was defined as a decrease in neuropathy of at least 1 grade from baseline. The response rates were 40.7% and 10.0% for L-OHP-induced peripheral neuropathy patients and 28.6% and 12.0% for PTX-induced peripheral neuropathy patients in the pregabalin and non-pregabalin groups, respectively. The severity of peripheral neuropathy before and after the administration of pregabalin differed significantly[L-OHP, 1.33±0.48(mean±SD) vs. 1.00±0.78 and PTX, 1.46±0.69 vs. 1.21±0.88]. In 28-37% of patients, pregabalin was associated with adverse events, with drowsiness and dizziness being frequently observed. In conclusion, pregabalin was efficacious in reducing the severity of L-OHP- and PTX-induced peripheral neuropathy.

Efficacy of combination of meloxicam and pregabalin for pain in knee osteoarthritis

PURPOSE

Osteoarthritic pain is largely considered to be inflammatory pain. Sensory nerve fibers innervating the knee have been shown to be significantly damaged in rat models of knee osteoarthritis (OA) in which the subchondral bone junction is destroyed, and this induces neuropathic pain (NP). Pregabalin was developed as a pain killer for NP; however, there are no reports on pregabalin use in OA patients. The purpose of this study was to investigate the efficacy of pregabalin for pain in OA patients.

MATERIALS AND METHODS

Eighty-nine knee OA patients were evaluated in this randomized prospective study. Patients were divided into meloxicam, pregabalin, and meloxicam+pregabalin groups. Pain scores were evaluated before and 4 weeks after drug application using a visual analogue scale (VAS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Pain scales among groups were compared using a Kruskal-Wallis test.

RESULTS

Before drug application, there was no significant difference in VAS and WOMAC scores among the three groups (p>0.05). Significant pain relief was seen in the meloxicam+pregabalin group in VAS at 1, 2, and 4 weeks, and WOMAC score at 4 weeks, compared with the other groups (p<0.05). No significant pain relief was seen in the meloxicam only group in VAS during 4 weeks and WOMAC score at 4 weeks compared with the pregabalin only group (p>0.05).

CONCLUSION

Meloxicam+pregabalin was effective for pain in OA patients. This finding suggests that OA pain is a combination of inflammatory and NP.

[Promising effects of pregabalin in the treatment of oxaliplatin-induced sensory neuropathy in patients with colorectal carcinoma]

Thirteen patients with metastatic colorectal cancer who suffered from oxaliplatin-induced sensory neuropathy were evaluated to determine the neuropathy Grade before and after the administration of pregabalin. All patients received oxaliplatin as adjuvant or first-line chemotherapy. The mFOLFOX6 and CapeOX groups included 3 and 10 cases, respectively, and the average treatment regimens were 8 and 5 doses, respectively. Before receiving pregabalin, sensory neuropathy was classified as Grade 3 in 2 patients, as Grade 2 in 8 patients, and as Grade 1 in 3 patient. The average amount of pregabalin administered to patients was 237 (range: 150-450) mg. After administering pregabalin, we observed improvements in 8 neuropathy cases (61. 5%)within approximately 2 weeks. All side effects were mild. In this study, pregabalin was shown to positively impact sensory neuropathy resulting from oxaliplatin treatment and to enable the long-term use of oxaliplatin-based chemotherapy.

Randomized, placebo-controlled pilot trial of gabapentin during an outpatient, buprenorphine-assisted detoxification procedure

This pilot study examined the efficacy of the N-type calcium channel blocker gabapentin to improve outcomes during a brief detoxification protocol with buprenorphine. Treatment-seeking opioid-dependent individuals were enrolled in a 5-week, double-blind, placebo-controlled trial examining the effects of gabapentin during a 10-day outpatient detoxification from buprenorphine. Participants were inducted onto buprenorphine sublingual tablets during Week 1, were randomized and inducted onto gabapentin or placebo during Week 2, underwent a 10-day buprenorphine taper during Weeks 3 and 4, and then were tapered off gabapentin/placebo during Week 5. Assessments included thrice-weekly opioid withdrawal scales, vitals, and urine drug screens. Twenty-four individuals (13 male; 17 Caucasian, 3 African American, 4 Latino; mean age 29.7 years) participated in the detoxification portion of the study (gabapentin, n = 11; placebo, n = 13). Baseline characteristics did not differ significantly between groups. Self-reported and observer-rated opioid withdrawal ratings were relatively low and did not differ between groups during the buprenorphine taper. Urine results showed a Drug × Time interaction, such that the probability of opioid-positive urines significantly decreased over time in the gabapentin versus placebo groups during Weeks 3 and 4 (OR = 0.73, p = .004). These results suggest that gabapentin reduces opioid use during a 10-day buprenorphine detoxification procedure.

Risk of heart failure and edema associated with the use of pregabalin: a systematic review

BACKGROUND

Pregabalin is used in the treatment of postherpetic neuralgia, diabetic neuropathic pain, partial seizures, anxiety disorders and fibromyalgia. Recognized adverse effects associated with its use include cognitive impairment, somnolence and dizziness. Heart failure associated with pregabalin has been described, however the strength of this association has not been well characterized. To examine this further, we will conduct a systematic review of the risk of heart failure and edema associated with use of pregabalin.

METHODS/DESIGN

We will include all studies (experimental, quasi-experimental, observational, case series/reports, drug regulatory reports) that examine the use of pregabalin compared to placebo, gabapentin or conventional care. Our primary outcome is heart failure and the secondary outcomes include edema and weight gain. We will search electronic databases (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials), and grey literature sources (trial registries, conference abstracts) to identify relevant studies. To ensure literature saturation, we will contact drug manufacturers, conduct forward citation searching, and scan the reference lists of key articles and included studies. We will not restrict inclusion by language or publication status.Two reviewers will screen citations (titles and abstracts) and full-text articles, conduct data abstraction, and appraise risk of bias. Random-effects meta-analysis will be conducted if the studies are deemed heterogeneous in terms of clinical, statistical and methodological factors but still suitable for meta-analysis.

CONCLUSIONS

The results of this review will assist physicians to better appreciate pregabalin's risk for edema or congestive heart failure and will be pertinent to the thousands of patients worldwide who are administered this medication.Our protocol was registered in the PROSPERO database (CRD42012002948).

Randomised phase II trial (NCT00637975) evaluating activity and toxicity of two different escalating strategies for pregabalin and oxycodone combination therapy for neuropathic pain in cancer patients

Purpose

Neuropathic pain is commonly associated with cancer. Current treatments include combination opioid and adjuvant therapies, but no guidelines are available for dose escalation strategies. This phase II study compared the efficacy and tolerability of two dose escalation strategies for oxycodone and pregabalin combination therapy.

Methods

Patients (N = 75) with oncological neuropathic pain, previously untreated with pregabalin, were recruited in 5 Italian institutions between 2007 and 2010. Patients were randomised to two different dose escalation strategies (arm A; N = 38) oxycodone at a fixed dose with increasing pregabalin doses; (arm B; N = 37) pregabalin at a fixed dose with increasing oxycodone doses. Patients were evaluated from daily diaries and follow-ups at 3, 7, 10, and 14 days after beginning treatment with a numerical rating scale (NRS), neuropathic pain scale (SDN), and well-being scale (ESAS). The primary endpoint was a ≥1/3 reduction in pain (NRS); secondary endpoints included the time to analgesia and adverse effects. The study had a 90% probability of detecting the best strategy for a true difference of at least 15%.

Results

More patients in arm A (76%) than arm B (64%) achieved ≥1/3 overall pain reduction even after controlling for baseline factors (gender, baseline pain). Group A reported fewer side effects than group B; constipation 52.8% vs. 66.7%; nausea: 27.8% vs. 44.4%; drowsiness: 44.4% vs. 55.6%; confusion: 16.7% vs. 27.8%; itching: 8.3% vs. 19.4%.

Conclusions

Both strategies effectively controlled neuropathic pain, but according to the adopted selection design arm A is preferable to arm B for pain control.

Trial Registration

ClinicalTrials.gov NCT00637975

The intestinal absorption mechanism of gabapentin makes it appropriate for gastroretentive delivery

Gabapentin is approved for the treatment of postherpetic neuralgia (PHN) and epilepsy. The pharmacokinetic (PK) properties of gabapentin, including absorption, distribution, metabolism, and excretion (ADME), were investigated during the development of Neurontin®, an immediate-release (IR) formulation of gabapentin that is orally administered three-times daily. Recently, a gastroretentive (GR) once-daily formulation of gabapentin (Gralise®) has been developed and marketed for the treatment of PHN. This review focuses on the ADME properties of gabapentin and illustrates how GR delivery enhances its absorption compared with IR formulations and allows once-daily dosing with the evening meal for the treatment of PHN. It includes the following aspects: 1) the mechanism of gastroretention of gabapentin GR tablets, 2) in vitro dissolution profiles of the GR and IR formulations, 3) site of absorption of gabapentin in the human intestine, 4) studies of the mechanism of gabapentin absorption using intestinal tissue preparations, 5) human PK studies to examine the effects of dose and formulations on PK profiles and the bioavailability of gabapentin at therapeutically relevant doses, and 6) efficacy and safety of gastroretentive gabapentin in patients with PHN. The data reviewed support that GR delivery of gabapentin optimizes its absorption via a saturable uptake mechanism. The prolonged residence of the GR tablets in the stomach coupled with the gradual release of gabapentin attenuates saturation of the transporter, thus enhancing absorption and increasing bioavailability, especially at therapeutically relevant doses. The net result is a once-daily formulation of gabapentin that is well tolerated and efficacious for the treatment of PHN.

[Management of cognitive impairment in children and adolescents with cerebral palsy treated with pantocalcin]

A randomized study on the efficacy and safety of the hopantenic acid preparation (pantocalcin) and its effect on cognitive functions in children with cerebral palsy (CCP) has been carried out. The positive effect of pantocalcin on the visual memory and attention concentration, activity and fatigability has been shown. At the same time, there was a decrease of anxiety in children and adolescents with CCP. No evidence for the effect of the drug on visual-motor skills has been found. The results of the study have demonstrated the high safety profile of pantocalcin when used in pediatric practice.

Gabapentin enacarbil in Japanese patients with restless legs syndrome: a 12-week, randomized, double-blind, placebo-controlled, parallel-group study

OBJECTIVE

Gabapentin enacarbil (GEn) was effective and well-tolerated for the treatment of restless legs syndrome (RLS) in North American studies. However, no placebo-controlled studies of GEn have been performed in Asian patients with RLS. Therefore, we investigated the efficacy and safety of GEn in Japanese patients with RLS to determine the optimal dosage.

RESEARCH DESIGN AND METHODS

Outpatients with RLS (International Restless Legs Syndrome Rating Scale (IRLS) scores ≥15) were randomized (n = 474) and treated (n = 469) in a double-blind manner with once-daily placebo (n = 116), 600 (n = 120), 900 (n = 119) or 1200 (n = 114) mg GEn for 12 weeks.

CLINICAL TRIAL REGISTRATION

NCT00530530 (ClinicalTrials.gov)

MAIN OUTCOME MEASURE

The primary outcome was the change in IRLS score. Secondary outcomes included Investigator (ICGI)- and Patient (PCGI)-rated Clinical Global Impression and adverse events.

RESULTS

The mean change in IRLS score from baseline to the final observation was -8.96 for placebo versus -11.10, -10.28 and -11.38 for 600, 900 and 1200 mg GEn. Williams' multiple comparison test showed that only 1200 mg GEn was superior to placebo (p = 0.011). However, in post hoc mixed-effects models with repeated measures, which accounted for the time-course of changes in IRLS, the placebo-adjusted changes were -2.31, -1.92 and -2.31 for 600, 900 and 1200 mg GEn. ICGI and PCGI response rates were significantly greater for all three GEn doses versus placebo (all p ≤ 0.014). Adverse events, including somnolence, dizziness and nasopharyngitis, were frequent but of mild-to-moderate severity. However, there was a tendency toward a dose-dependent increase in the incidence of adverse events.

CONCLUSIONS

GEn is effective and well-tolerated for the treatment of RLS in Japanese patients. All three doses produced improvements in IRLS compared with placebo; 600 mg GEn is a suitable target dose. However, our analysis possibly introduced positive bias by assuming that symptoms improve after discontinuation.

New generation nonhormonal management for hot flashes

Hot flashes are very common in women in menopause and can have a detrimental effect on quality of life. Hormone therapy (estrogen with or without progestin) remains the gold standard treatment for hot flashes, but concerns for the risk of hormone therapy have resulted in its decline and a demand for nonhormonal treatments with demonstrated efficacy for hot flashes. Several nonhormonal therapies have been tested in randomized placebo-controlled trials including nonpharmacologic approaches and pharmacologic nonhormonal agents. Among them, two classes of nonhormonal medications have been demonstrated to effectively alleviate hot flashes: γ-aminobutyric acid (GABA) analogs and selective serotonin reuptake inhibitors (SSRIs). This article discusses the superior efficacy of the newer nonhormonal prescriptions for the treatment of hot flashes when compared with estrogen replacement therapy, and provides some recommendations regarding use of them in peri- and postmenopausal women.

Real-world treatment of post-herpetic neuralgia with gabapentin or pregabalin

BACKGROUND AND OBJECTIVES

There are limited data examining the real-world use of gabapentin and pregabalin for the treatment of post-herpetic neuralgia (PHN). This study examines dosing patterns, therapy outcomes, healthcare utilization and costs of patients with PHN who initiate treatment with gabapentin or pregabalin.

METHODS

This was a retrospective administrative claims data analysis from July 2005 to February 2010. Patients with PHN initiating gabapentin or pregabalin (index therapy) from January 2006 to February 2009 were identified and were observed for 12 months after index therapy initiation. Outcomes were mean daily dosages of the index therapy, attainment of minimally effective dosages of gabapentin (≥ 1,800 mg/day) or pregabalin (≥ 150 and ≥ 300 mg/day) persistence, discontinuation, index therapy switching, addition of neuropathic pain medications to index therapy, and healthcare resource use and costs.

RESULTS

1,645 patients were identified. The mean daily dosage was 826 mg for gabapentin and 187 mg for pregabalin. Only 52.6 % of patients initiating gabapentin and 56.9 % initiating pregabalin obtained a refill during the post-index period. Approximately 14 % of patients treated with gabapentin reached the target dosage (1,800 mg/day). For pregabalin, 87 % reached ≥ 150 mg/day and 27 % reached ≥ 300 mg/day. On average, patients took 10 weeks to reach 1,800 mg/day gabapentin, and 5.0 and 9.2 weeks to reach ≥ 150 mg/day and ≥ 300 mg/day pregabalin, respectively. Approximately one-third of patients in both index therapy cohorts added a pain medication; more than half added opioids. The percentage of patients switching from either drug (57 %) or adding a therapy (34 %) were similar between index therapy cohorts; opioids were the most common therapy patients switched to or added.

CONCLUSION

It appears that gabapentin and pregabalin are not used effectively to treat PHN. Suboptimal dosing and discontinuation may be associated with supplementary use of other analgesics, especially opioids.

Differences in reporting of analyses in internal company documents versus published trial reports: comparisons in industry-sponsored trials in off-label uses of gabapentin

BACKGROUND

Details about the type of analysis (e.g., intent to treat [ITT]) and definitions (i.e., criteria for including participants in the analysis) are necessary for interpreting a clinical trial's findings. Our objective was to compare the description of types of analyses and criteria for including participants in the publication (i.e., what was reported) with descriptions in the corresponding internal company documents (i.e., what was planned and what was done). Trials were for off-label uses of gabapentin sponsored by Pfizer and Parke-Davis, and documents were obtained through litigation.

METHODS AND FINDINGS

For each trial, we compared internal company documents (protocols, statistical analysis plans, and research reports, all unpublished), with publications. One author extracted data and another verified, with a third person verifying discordant items and a sample of the rest. Extracted data included the number of participants randomized and analyzed for efficacy, and types of analyses for efficacy and safety and their definitions (i.e., criteria for including participants in each type of analysis). We identified 21 trials, 11 of which were published randomized controlled trials, and that provided the documents needed for planned comparisons. For three trials, there was disagreement on the number of randomized participants between the research report and publication. Seven types of efficacy analyses were described in the protocols, statistical analysis plans, and publications, including ITT and six others. The protocol or publication described ITT using six different definitions, resulting in frequent disagreements between the two documents (i.e., different numbers of participants were included in the analyses).

CONCLUSIONS

Descriptions of analyses conducted did not agree between internal company documents and what was publicly reported. Internal company documents provide extensive documentation of methods planned and used, and trial findings, and should be publicly accessible. Reporting standards for randomized controlled trials should recommend transparent descriptions and definitions of analyses performed and which study participants are excluded.

Clinical Inquiry: Do venlafaxine and gabapentin control hot flashes in women with a history of breast cancer?

Venlafaxine reduces hot flashes more than placebo in women with a history of breast cancer; adverse effects include dry mouth and constipation.

Pregabalin monotherapy for epilepsy

BACKGROUND

Many people with epilepsy suffer from poorly controlled seizures, despite current antiepileptic treatments. Due to high rates of treatment resistance, there is interest in new pharmacological treatment options such as pregabalin. However, it remains unclear whether existing evidence of pregabalin is rigorous enough to support its monotherapy.

OBJECTIVES

To determine the efficacy and tolerability of pregabalin in people with epilepsy.

SEARCH METHODS

We searched the Cochrane Epilepsy Group's Specialized Register (August 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 7 ), MEDLINE (1946 to August week 1, 2012), EMBASE (1974 to August 2012) and the Chinese Biomedical Literature Database (CBM) (1978 to August 2012). No language restrictions were imposed.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing pregabalin with placebo or another antiepileptic drug monotherapy for epilepsy.

DATA COLLECTION AND ANALYSIS

Two review authors (QZ and LY) independently extracted trial data and assessed trial quality. We assessed the following outcomes: (1) time to withdrawal after randomisation; (2) time to achieve six-, 12- or 24-month remission; (3) the proportion of participants who remained seizure-free for six or more continuous months; (4) time to first seizure after randomisation; (5) validated quality of life measures; (6) health economic outcomes; (7) adverse effects. We expressed time-to-event outcomes as hazard ratios (HRs) with 95% confidence interval (CI), where an HR > 1 indicates an event is more likely to occur earlier on pregabalin than the comparator.

MAIN RESULTS

Two short-term studies involving 753 participants met the inclusion criteria. Only one study investigated the effects of pregabalin compared with lamotrigine in patients with newly diagnosed partial seizures, and the other study investigated the effects of pregabalin compared with gabapentin in hospitalised patients with refractory partial epilepsy. There were no studies on generalised-onset tonic-clonic seizures (with or without other generalised seizure types).We found that pregabalin was inferior in comparison to lamotrigine when measuring time to withdrawal due to inadequate seizure control after dose stabilisation from randomisation: hazard ratio (HR) 4.52; 95% confidence interval (CI) 1.93 to 10.60; time to achieve six-month remission after dose stabilisation from randomisation: HR 0.56; 95% CI 0.41 to 0.76; the proportion of participants who remained seizure-free for six or more continuous months: RR 0.76, 95% CI 0.67 to 0.87 (Europe: 0.83, 95% CI 0.69 to 0.99; Asia: RR 0.70, 95% CI 0.57 to 0.86; the Americas: RR 0.62, 95% CI 0.33 to 1.19); and time to first seizure after dose stabilisation from randomisation: HR 1.74; 95% CI 1.26 to 2.39. There was no significant difference in safety-related outcomes between pregabalin and lamotrigine, but more participants in the pregabalin group developed somnolence, weight increase and convulsion. Pregabalin was better than gabapentin when measuring time to withdrawal due to all reasons after randomisation: HR 0.25; 95% CI 0.11 to 0.57; and time to withdrawal due to inadequate seizure control after randomisation: HR 0.41; 95% CI 0.18 to 0.92. No significant difference was found in safety-related outcomes between pregabalin and gabapentin. But we found some limitations in the study design which may have had an influence on the results.

AUTHORS' CONCLUSIONS

Pregabalin seems to have similar tolerability but inferior efficacy in comparison to lamotrigine for newly diagnosed partial seizures. However, considering the limitations in the study design (such as the short-term follow-up and the low initial target dose selection), the results should be interpreted with caution. The available data were too limited to draw any conclusions between pregabalin and gabapentin. The result indicated that the treatment effects were influenced by the study regions. The clinical disadvantage of pregabalin was more prominent in Asia when compared with lamotrigine. We should determine whether pregabalin has ethnic differences in the treatment of epilepsy in the future. This review does not inform any treatment policy for patients with generalized onset tonic-clonic seizures. Further long-term trials are needed to investigate the genuine effectiveness of pregabalin as monotherapy.