Morphine, gabapentin, or their combination for neuropathic pain

BACKGROUND

The available drugs to treat neuropathic pain have incomplete efficacy and dose-limiting adverse effects. We compared the efficacy of a combination of gabapentin and morphine with that of each as a single agent in patients with painful diabetic neuropathy or postherpetic neuralgia.

METHODS

In this randomized, double-blind, active placebo-controlled, four-period crossover trial, patients received daily active placebo (lorazepam), sustained-release morphine, gabapentin, and a combination of gabapentin and morphine--each given orally for five weeks. The primary outcome measure was mean daily pain intensity in patients receiving a maximal tolerated dose; secondary outcomes included pain (rated according to the Short-Form McGill Pain Questionnaire), adverse effects, maximal tolerated doses, mood, and quality of life.

RESULTS

Of 57 patients who underwent randomization (35 with diabetic neuropathy and 22 with postherpetic neuralgia), 41 completed the trial. Mean daily pain (on a scale from 0 to 10, with higher numbers indicating more severe pain) at a maximal tolerated dose of the study drug was as follows: 5.72 at baseline, 4.49 with placebo, 4.15 with gabapentin, 3.70 with morphine, and 3.06 with the gabapentin-morphine combination (P<0.05 for the combination vs. placebo, gabapentin, and morphine). Total scores on the Short-Form McGill Pain Questionnaire (on a scale from 0 to 45, with higher numbers indicating more severe pain) at a maximal tolerated dose were 14.4 with placebo, 10.7 with gabapentin, 10.7 with morphine, and 7.5 with the gabapentin-morphine combination (P<0.05 for the combination vs. placebo, gabapentin, and morphine). The maximal tolerated doses of morphine and gabapentin were lower (P<0.05) with the combination than for each drug as single agent. At the maximal tolerated dose, the gabapentin-morphine combination resulted in a higher frequency of constipation than gabapentin alone (P<0.05) and a higher frequency of dry mouth than morphine alone (P<0.05).

CONCLUSIONS

Gabapentin and morphine combined achieved better analgesia at lower doses of each drug than either as a single agent, with constipation, sedation, and dry mouth as the most frequent adverse effects.

Pregabalin for the treatment of postherpetic neuralgia: a randomized, placebo-controlled trial

OBJECTIVE

To evaluate the efficacy and safety of pregabalin in the treatment of postherpetic neuralgia (PHN).

METHODS

The authors conducted a multicenter, parallel-group, double-blind, placebo-controlled, 8-week, randomized clinical trial in PHN, defined as pain for 3 or more months following herpes zoster rash healing. Patients (n = 173) were randomized to treatment with pregabalin or placebo. Patients randomized to pregabalin received either 600 mg/day (creatinine clearance > 60 mL/min) or 300 mg/day (creatinine clearance 30 to 60 mL/min). The primary efficacy measure was the mean of the last seven daily pain ratings. Secondary endpoints included additional pain ratings, sleep interference, quality of life, mood, and patient and clinician ratings of global improvement.

RESULTS

Pregabalin-treated patients had greater decreases in pain than patients treated with placebo (endpoint mean scores 3.60 vs 5.29, p = 0.0001). Pain was significantly reduced in the pregabalin-treated patients after the first full day of treatment and throughout the study, and significant improvement on the McGill Pain Questionnaire total, sensory, and affective pain scores was also found. The proportions of patients with >or=30% and >or=50% decreases in mean pain scores were greater in the pregabalin than in the placebo group (63% vs 25% and 50% vs 20%, p = 0.001). Sleep also improved in patients treated with pregabalin compared to placebo (p = 0.0001). Both patients and clinicians were more likely to report global improvement with pregabalin than placebo (p = 0.001). Given the maximal dosage studied, pregabalin had acceptable tolerability compared to placebo despite a greater incidence of side effects, which were generally mild to moderate in intensity.

CONCLUSIONS

Treatment of PHN with pregabalin is safe, efficacious in relieving pain and sleep interference, and associated with greater global improvement than treatment with placebo.

Pregabalin relieves symptoms of painful diabetic neuropathy: a randomized controlled trial

OBJECTIVE

Pregabalin, an alpha2-delta ligand with analgesic, anxiolytic, and anticonvulsant activity, has been evaluated for treatment of neuropathic pain. The authors assessed the efficacy and tolerability of pregabalin (75, 300, 600 mg/day) vs placebo in patients with diabetic peripheral neuropathy (DPN).

METHODS

Patients with a 1- to 5-year history of DPN and average weekly pain score of > or =4 on an 11-point numeric pain-rating scale were enrolled in a 5-week, double-blind, multicenter, placebo-controlled study. Patients (n = 338) were randomized to receive one of three doses of pregabalin or placebo TID. Pregabalin 600 mg/day was titrated over 6 days; lower doses were initiated on day 1.

RESULTS

Patients in the 300- and 600-mg/day pregabalin groups showed improvements in endpoint mean pain score (primary efficacy measure) vs placebo (p = 0.0001). Improvements were also seen in weekly pain score, sleep interference score, patient global impression of change, clinical global impression of change, SF-McGill Pain Questionnaire, and multiple domains of the SF-36 Health Survey. Improvements in pain and sleep were seen as early as week 1 and were sustained throughout the 5 weeks. Responders (patients with > or =50% reduction in pain compared to baseline) were 46% (300 mg/day), 48% (600 mg/day), and 18% (placebo). Pregabalin was well tolerated with a low discontinuation rate. The most common adverse events were dizziness and somnolence.

CONCLUSIONS

In patients with diabetic peripheral neuropathy, pregabalin demonstrated early and sustained improvement in pain and a beneficial effect on sleep, which were confirmed by positive patient global impression. Pregabalin was well tolerated at all doses.

Efficacy of pregabalin in neuropathic pain evaluated in a 12-week, randomised, double-blind, multicentre, placebo-controlled trial of flexible- and fixed-dose regimens

Pregabalin binds with high affinity to the alpha2-delta subunit protein of voltage-gated calcium channels and, thereby, reduces release of excitatory neurotransmitters. This 12-week randomised, double-blind, multicentre, placebo-controlled, parallel-group study evaluated the efficacy and safety of pregabalin in patients with chronic postherpetic neuralgia (PHN) or painful diabetic peripheral neuropathy (DPN). Patients were randomised to placebo (n=65) or to one of two pregabalin regimens: a flexible schedule of 150, 300, 450, and 600 mg/day with weekly dose escalation based on patients' individual responses and tolerability (n=141) or a fixed schedule of 300 mg/day for 1 week followed by 600 mg/day for 11 weeks (n=132). Both flexible- and fixed-dose pregabalin significantly reduced endpoint mean pain score (primary outcome) versus placebo (P=0.002, P<0.001) and were significantly superior to placebo in improving pain-related sleep interference (P<0.001). The most common adverse events (AEs) for pregabalin-treated patients were dizziness, peripheral oedema, weight gain (not affecting diabetes control), and somnolence. These results are consistent with previous studies' demonstrating pregabalin's efficacy, tolerability, and safety for treatment of chronic neuropathic pain associated with DPN or PHN. Pregabalin dosing aimed at optimal balance of efficacy and tolerability provides significant pain relief and may reduce risks for AEs and therapy discontinuation.

Do Surgical Patients Benefit from Perioperative Gabapentin/Pregabalin? A Systematic Review of Efficacy and Safety

BACKGROUND

Gabapentin and pregabalin have antiallodynic and antihyperalgesic properties useful for treating neuropathic pain. These properties may also be beneficial in acute postoperative pain. In this study we evaluated randomized, controlled trials examining the analgesic efficacy, adverse effects, and clinical value of gabapentinoids in postoperative pain.

METHODS

A systematic search of Medline, PubMed, and Cochrane Central Register of Controlled Trials (CENTRAL) databases yielded 22 randomized, controlled trials on perioperative administration of gabapentinoids for postoperative pain relief.

RESULTS

Pain relief was better in the gabapentin groups compared with the control groups. The opioid-sparing effect during the first 24 h after a single dose of gabapentin 300-1200 mg, administered 1-2 h preoperatively, ranged from 20% to 62%. The combined effect of a single dose of gabapentin was a reduction of opioid consumption equivalent to 30 +/- 4 mg of morphine (mean +/- 95% CI) during the first 24 h after surgery. Metaregression analysis suggested that the gabapentin-induced reduction in the 24-h opioid consumption was not significantly dependent on the gabapentin dose. Gabapentin reduced opioid-related adverse effects, such as nausea, vomiting, and urinary retention (number-needed-to-treat 25, 6, and 7, respectively). The most common adverse effects of the gabapentinoids were sedation and dizziness (number-needed-to-harm 35 and 12, respectively).

CONCLUSIONS

Gabapentinoids effectively reduce postoperative pain, opioid consumption, and opioid-related adverse effects after surgery. Conclusions about the optimal dose and duration of the treatment cannot be made because of the heterogeneity of the trials. Studies are needed to determine the long-term benefits, if any, of perioperative gabapentinoids.

Gabapentin and postoperative pain – a systematic review of randomized controlled trials

The objective of this systematic review was to evaluate the efficacy and tolerability of perioperative gabapentin administration for the control of acute postoperative pain. We searched Medline (1966-2006), the Cochrane Library (2006), Scopus, CINAHL and bibliographies from clinical trials and review articles. We included randomized controlled trials (RCTs) comparing gabapentin with inactive controls in surgical patients. Sixteen valid RCTs were included. Weighted mean difference (WMD) for postoperative pain intensity (0-100 mm visual analogue scale) was -16.55 mm at 6 h and -10.87 mm at 24 h for treatment with a single preoperative dose of gabapentin 1200 mg. Cumulative opioid consumption at 24 h was also significantly decreased with gabapentin (WMD, -27.90 mg). When gabapentin was administered at doses less than 1200 mg, pain intensity was also lower at 6 h (WMD, -22.43 mm) and 24 h (WMD, -13.18 mm). Cumulative 24 h opioid consumption was also lower (WMD, -7.25 mg). Gabapentin was associated with an increased risk of sedation (Peto OR 3.86; 95% CI 2.50-5.94) but less opioid-related side effects such as vomiting (Peto OR 0.58; 95% CI 0.39-0.86) and pruritus (Peto OR 0.27; 95% CI 0.10-0.74). In conclusion, gabapentin has an analgesic and opioid-sparing effect in acute postoperative pain management when used in conjunction with opioids.

New onset geriatric epilepsy: a randomized study of gabapentin, lamotrigine, and carbamazepine

OBJECTIVE

To determine the relative tolerability and efficacy of two newer antiepileptic drugs, lamotrigine (LTG) and gabapentin (GBP), as compared to carbamazepine (CBZ) in older patients with epilepsy.

METHODS

This was an 18-center, randomized, double-blind, double dummy, parallel study of 593 elderly subjects with newly diagnosed seizures. Patients were randomly assigned to one of three treatment groups: GBP 1,500 mg/day, LTG 150 mg/day, CBZ 600 mg/day. The primary outcome measure was retention in trial for 12 months.

RESULTS

Mean age was 72 years. The most common etiology was cerebral infarction. Patients had multiple medical conditions and took an average of seven comedications. Mean plasma levels at 6 weeks were as follows: GBP 8.67 +/- 4.83 microg/mL, LTG 2.87 +/- 1.60 microg/mL, CBZ 6.79 +/- 2.92 microg/mL. They remained stable throughout the trial. Early terminations: LTG 44.2%, GBP 51%, CBZ 64.5% (p = 0.0002). Significant paired comparisons: LTG vs CBZ: p < 0.0001; GBP vs CBZ: p = 0.008. Terminations for adverse events: LTG 12.1%, GBP 21.6%, CBZ 31% (p = 0.001). Significant paired comparisons: LTG vs CBZ: p < 0.0001; LTG vs GBP: p = 0.015. There were no significant differences in seizure free rate at 12 months.

CONCLUSIONS

The main limiting factor in patient retention was adverse drug reactions. Patients taking lamotrigine (LTG) or gabapentin (GBP) did better than those taking carbamazepine. Seizure control was similar among groups. LTG and GBP should be considered as initial therapy for older patients with newly diagnosed seizures.

Relief of painful diabetic peripheral neuropathy with pregabalin: a randomized, placebo-controlled trial

This was a 6-week, randomized, double-blind, multicenter study evaluating the efficacy of pregabalin in the treatment of painful diabetic neuropathy. Two hundred forty-six men and women with painful diabetic neuropathy received pregabalin (150 or 600 mg/day by mouth) or placebo. The primary efficacy variable was mean pain score at the end of treatment. Efficacy results indicate that pregabalin 600 mg/day significantly decreased mean pain score to 4.3 (vs 5.6 for placebo, P = .0002) and increased the proportion of patients who had a > or =50% decrease from baseline pain (39% vs 15% for placebo, P = .002). Pregabalin also significantly reduced sleep interference, past week and present pain intensity, sensory and affective pain scores, and bodily pain and decreased by > or =50% the number of patients describing their pain as gnawing, sickening, fearful, and punishing-cruel. More patients receiving pregabalin 600 mg/day than placebo showed improvement, as rated on the Clinical and Patient Global Impression of Change scales, 73% vs 45% and 85% vs 47%, respectively. Pregabalin 150 mg/day was essentially no different from placebo. Dizziness was the most common side effect. These study results show pregabalin 600 mg/day to be safe and effective in reducing the pain and other associated symptoms of painful diabetic neuropathy.

PERSPECTIVE

Painful diabetic peripheral neuropathy is a challenging neuropathic pain syndrome. This randomized controlled trial demonstrates that pregabalin, a new drug that interacts with the alpha2-delta protein subunit of the voltage-gated calcium channel, is an efficacious and safe treatment for the pain of this condition.

Pregabalin in central neuropathic pain associated with spinal cord injury: A placebo-controlled trial

OBJECTIVE

To evaluate pregabalin in central neuropathic pain associated with spinal cord injury.

METHODS

A 12-week, multicenter study of patients randomized to either flexible-dose pregabalin 150 to 600 mg/day (n = 70) or placebo (n = 67), administered BID. Patients were allowed to remain on existing, stable pain therapy. The primary efficacy variable was the endpoint mean pain score, derived from patients' last 7 days daily pain diary entries. Key secondary endpoints included pain responder rates, the SF-MPQ, sleep interference, mood, and the patient global measure of change.

RESULTS

The mean baseline pain score was 6.54 in the pregabalin group and 6.73 in the placebo group. The mean endpoint pain score was lower in the pregabalin group (4.62) than the placebo group (6.27; p < 0.001), with efficacy observed as early as week 1 and maintained for the duration of the study. The average pregabalin dose after the 3-week stabilization phase was 460 mg/day. Pregabalin was significantly superior to placebo in endpoint assessments on the SF-MPQ. The > or =30% and > or =50% pain responder rates were higher with pregabalin than placebo (p < 0.05). Pregabalin was associated with improvements in disturbed sleep (p < 0.001) and anxiety (p < 0.05), and more patients reported global improvement at endpoint in the pregabalin group (p < 0.001). Mild or moderate, typically transient, somnolence and dizziness were the most common adverse events.

CONCLUSIONS

Pregabalin 150 to 600 mg/day was effective in relieving central neuropathic pain, improving sleep, anxiety, and overall patient status in patients with spinal cord injury.

Gabapentin for hot flashes in 420 women with breast cancer: a randomised double-blind placebo-controlled trial

BACKGROUND

Most women receiving systemic therapy for breast cancer experience hot flashes. We undertook a randomised, double-blind, placebo-controlled, multi-institutional trial to assess the efficacy of gabapentin in controlling hot flashes in women with breast cancer.

METHODS

420 women with breast cancer who were having two or more hot flashes per day were randomly assigned placebo, gabapentin 300 mg/day, or gabapentin 900 mg/day by mouth in three divided doses for 8 weeks. Each patient kept a 1-week, self-report diary on the frequency, severity, and duration of hot flashes before the start of the study and during weeks 4 and 8 of treatment. Analyses were by intention to treat.

FINDINGS

Evaluable data were available on 371 participants at 4 weeks (119 placebo, 123 gabapentin 300 mg, and 129 gabapentin 900 mg) and 347 at 8 weeks (113 placebo, 114 gabapentin 300 mg, and 120 gabapentin 900 mg). The percentage decreases in hot-flash severity score between baseline and weeks 4 and 8, respectively were: 21% (95% CI 12 to 30) and 15% (1 to 29) in the placebo group; 33% (23 to 43) and 31% (16 to 46) in the group assigned gabapentin 300 mg; and 49% (42 to 56) and 46% (34 to 58) in the group assigned gabapentin 900 mg. The differences between the groups were significant (p=0.0001 at 4 weeks and p=0.007 at 8 weeks by ANCOVA for overall treatment effect, adjusted for baseline values); only the higher dose of gabapentin was associated with significant decreases in hot-flash frequency and severity.

INTERPRETATION

Gabapentin is effective in the control of hot flashes at a dose of 900 mg/day, but not at a dose of 300 mg/day. This drug should be considered for treatment of hot flashes in women with breast cancer.

Efficacy and tolerability of twice-daily pregabalin for treating pain and related sleep interference in postherpetic neuralgia: a 13-week, randomized trial

OBJECTIVE

This trial evaluated the efficacy and safety of pregabalin dosed twice daily (BID) for relief of neuro-pathic pain associated with postherpetic neuralgia (PHN).

RESEARCH DESIGN AND METHODS

The 13-week, double-blind, placebo-controlled study randomized 370 patients with PHN to pregabalin (150, 300, or 600 mg/day BID) or placebo.

MAIN OUTCOME MEASURES

Primary efficacy measure was endpoint mean pain score from daily pain diaries. Secondary efficacy measures included endpoint mean sleep-interference score from daily sleep diaries and Patient Global Impression of Change (PGIC). Safety evaluations included adverse events (AEs), physical and neurologic examinations, 12-lead ECG, vital signs, and laboratory testing.

RESULTS

Pregabalin provided significant, dose-proportional pain relief at endpoint: difference from placebo in mean pain score, 150 mg/day, -0.88, p = 0.0077; 300 mg/day, -1.07, p = 0.0016; 600 mg/day, -1.79, p = 0.0003. Weekly mean pain scores significantly improved as early as week 1. Sleep interference in all pregabalin groups was also significantly improved at endpoint, compared with placebo (p < 0.001), beginning at week 1 (p < 0.01). At study termination, patients in the 150 (p = 0.02) and 600 mg/day (p = 0.003) groups were more likely to report global improvement than were those in the placebo group. Most AEs were mild or moderate. Among pregabalin-treated patients, 13.5% withdrew due to AEs, most commonly for dizziness (16 patients, 5.8%), somnolence (8, 2.9%), or ataxia (7, 2.5%).

CONCLUSIONS

Pregabalin, dosed BID, reduced neuropathic pain associated with PHN and was well tolerated. It also reduced the extent to which pain interfered with sleep. Pregabalin's effects were seen as early as week 1 and were sustained throughout the 13-week study.

Multimodal analgesia with gabapentin and local anesthetics prevents acute and chronic pain after breast surgery for cancer

We evaluated the effect of multimodal analgesia on acute and chronic pain after breast surgery for cancer. Fifty patients scheduled for breast cancer surgery were blindly randomized to receive gabapentin, eutectic mixture of local anesthetics cream, and ropivacaine in the wound or three placebos. Pain (visual analog scale) and analgesics were recorded in the postanesthesia care unit (PACU) 3, 6, and 9 h and 8 days after surgery. Three and 6 mo later, patients were assessed for chronic pain. The treatment group consumed less paracetamol in the PACU (469 versus 991 mg; P < 0.002) and less Lonalgal (1.0 versus 4.4 tablets; P = 0.003) than the controls, exhibited lower visual analog scale scores at rest in the PACU (P = 0.001) and on postoperative Days 1, 3, and 5 (P = 0.040, P = 0.015, and P = 0.045, respectively), and after movement in the PACU (P = 0.001) and on postoperative Days 2, 4, and 8 (P = 0.028, P = 0.007, and P = 0.032, respectively). Three and 6 mo after surgery, 18 of 22 (82%) and 12 of 21 (57%) of the controls reported chronic pain versus 10 of 22 (45%) and 6 of 20 (30%) in the treatment group (P = 0.028 and P = 0.424, respectively); 5 of 22 and 4 of 21 of the controls required analgesics versus 0 of 22 and 0 of 20 of those treated (P = 0.048 and P = 0.107, respectively). Multimodal analgesia reduced acute and chronic pain after breast surgery for cancer.

Vigabatrin-associated retinal cone system dysfunction: electroretinogram and ophthalmologic findings

OBJECTIVE

To determine the sources of vigabatrin-associated visual disturbances in patients treated for epilepsy.

BACKGROUND

Vigabatrin is an extremely effective antiepileptic drug that selectively increases brain gamma-aminobutyric acid (GABA). Several patients recently developed constricted visual fields during vigabatrin treatment in the United Kingdom, indicating the possibility of GABA-associated retinal dysfunction.

METHODS

Patients with visual symptoms treated chronically with vigabatrin at our center underwent visual evoked potentials (VEP), electroretinograms (ERG), and visual field and ophthalmologic examinations.

RESULTS

Four of 38 patients treated with vigabatrin developed visual symptoms 2 to 40 months after starting the drug. Two patients complained of constricted visual fields and two had blurred vision. ERG demonstrated evidence of bilateral retinal dysfunction consistent with reduced inner retinal cone response in all four patients. Oscillatory potential responses were lost, suggesting impairment of the highly GABAergic amacrine cells. Two of the patients had normal VEPs and minimal findings on clinical ophthalmology examinations despite abnormal ERGs. Abnormal examination findings were narrowed retinal arteries, surface wrinkling retinopathy, and abnormal macular reflexes. One patient also had reduced rod photoreceptor function in the more symptomatic left eye.

CONCLUSIONS

Visual field constriction and blurring during vigabatrin therapy is associated with retinal cone system dysfunction. Visual symptoms may represent selective vulnerability of retinas of affected patients to GABAergic effects of vigabatrin. The prevalence and course of retinal changes associated with vigabatrin therapy are important to determine in a larger group of patients.

Pregabalin in generalized anxiety disorder: a placebo-controlled trial

OBJECTIVE

Current drug therapies for generalized anxiety disorder have limitations. In a controlled trial, the novel agent pregabalin was studied for the treatment of patients with generalized anxiety disorder.

METHOD

In this double-blind study, patients with DSM-IV generalized anxiety disorder were randomly assigned to receive pregabalin (150 mg/day or 600 mg/day), lorazepam (6 mg/day), or placebo. A 1-week placebo lead-in was followed by 4 weeks of treatment and then a 1-week dose taper. The primary efficacy measure was the Hamilton Anxiety Rating Scale score at endpoint.

RESULTS

A total of 276 patients were randomly assigned to a treatment group and received at least one dose of their assigned medication. Fewer patients given lorazepam (59%, N=40 of 68) completed the trial than did those given placebo (73%, N=50 of 69), 600 mg/day of pregabalin (71%, N=50 of 70), or 150 mg/day or pregabalin (90%, N=62 of 69). The mean baseline-to-endpoint decreases in total Hamilton anxiety scale score in the patients given 150 mg/day of pregabalin (-9.2), 600 mg/day of pregabalin (-10.3), and lorazepam (-12.0) were significantly greater than the decrease in those given placebo (-6.8). As early as the week 1 observation, pregabalin significantly reduced the total Hamilton anxiety scale score compared with placebo. The most frequent adverse events reported for pregabalin and lorazepam were somnolence and dizziness. There were no serious adverse events reported by patients given pregabalin, and no withdrawal syndrome was associated with pregabalin treatment.

CONCLUSIONS

These results indicate that pregabalin is an effective, rapidly acting, and safe treatment for generalized anxiety disorder. In short-term treatment, pregabalin does not appear to have the withdrawal symptoms associated with the benzodiazepines.

Practice parameter: treatment of postherpetic neuralgia: an evidence-based report of the Quality Standards Subcommittee of the American Academy of Neurology

A systematic review of the literature on postherpetic neuralgia was performed. The authors identified studies using the National Library of Medicine's Medline database and Cochrane Library database. The authors determined absolute reduction rate, number needed to treat (NNT), 95% CI for NNT, and number needed to harm (NNH) for successful therapies of postherpetic neuralgia. Tricyclic antidepressants, gabapentin, pregabalin, opioids, and lidocaine patch were found to be effective in reducing the pain of postherpetic neuralgia.

Pregabalin for treatment of generalized anxiety disorder: a 4-week, multicenter, double-blind, placebo-controlled trial of pregabalin and alprazolam

BACKGROUND

Pregabalin inhibits release of excess excitatory neurotransmitters, presumably by binding to the alpha2-delta subunit protein of widely distributed voltage-dependent calcium channels in the brain and spinal cord.

OBJECTIVE

To assess the anxiolytic efficacy of pregabalin in patients with generalized anxiety disorder.

DESIGN

Double-blind, placebo-controlled, active-comparator trial. Patients were randomized to 4 weeks of treatment with pregabalin, 300 mg/d (n = 91), 450 mg/d (n = 90), or 600 mg/d (n = 89); alprazolam, 1.5 mg/d (n = 93); or placebo (n = 91).

SETTING

Psychiatry research and clinic settings.

PATIENTS

Outpatients meeting the DSM-IV criteria for generalized anxiety disorder, with a baseline Hamilton Anxiety Rating Scale (HAM-A) total score of 20 or greater.

MAIN OUTCOME MEASURES

Change from baseline to end point in total HAM-A score in the pregabalin and alprazolam groups compared with the placebo group. The end point response criterion was 50% or greater reduction in the HAM-A total score.

RESULTS

Pregabalin and alprazolam produced a significantly greater reduction in mean +/- SE HAM-A total score at last-observation-carried-forward end point compared with placebo (-8.4 +/- 0.8): pregabalin, 300 mg (-12.2 +/- 0.8, P<.001), 450 mg (-11.0 +/- 0.8, P = .02), and 600 mg (-11.8 +/- 0.8, P = .002), and alprazolam (-10.9 +/- 0.8, P = .02). By week 1 and at last-observation-carried-forward end point, the 3 pregabalin groups and the alprazolam group had significantly (P<.01) improved HAM-A psychic anxiety symptoms compared with the placebo group. Compared with the placebo group, HAM-A somatic anxiety symptoms were also significantly (P<.02) improved by the 300- and 600-mg pregabalin groups, but not by the 450-mg pregabalin (week 1, P = .06; week 4, P = .32) and the alprazolam groups (week 1, P = .21; week 4, P = .15). Of the 5 treatment groups, the 300-mg pregabalin group was the only medication group that differed statistically in global improvement at treatment end point not only from the placebo group but also from the alprazolam group.

CONCLUSION

Pregabalin was significantly more efficacious than placebo for the treatment of psychic and somatic symptoms of generalized anxiety disorder and was well tolerated by most study patients.

Gabapentin for chronic neuropathic pain in adults

BACKGROUND

Gabapentin is commonly used to treat neuropathic pain (pain due to nerve damage). This review updates a review published in 2014, and previous reviews published in 2011, 2005 and 2000.

OBJECTIVES

To assess the analgesic efficacy and adverse effects of gabapentin in chronic neuropathic pain in adults.

SEARCH METHODS

For this update we searched CENTRAL), MEDLINE, and Embase for randomised controlled trials from January 2014 to January 2017. We also searched the reference lists of retrieved studies and reviews, and online clinical trials registries.

SELECTION CRITERIA

We included randomised, double-blind trials of two weeks' duration or longer, comparing gabapentin (any route of administration) with placebo or another active treatment for neuropathic pain, with participant-reported pain assessment.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality and potential bias. Primary outcomes were participants with substantial pain relief (at least 50% pain relief over baseline or very much improved on Patient Global Impression of Change scale (PGIC)), or moderate pain relief (at least 30% pain relief over baseline or much or very much improved on PGIC). We performed a pooled analysis for any substantial or moderate benefit. Where pooled analysis was possible, we used dichotomous data to calculate risk ratio (RR) and number needed to treat for an additional beneficial outcome (NNT) or harmful outcome (NNH). We assessed the quality of the evidence using GRADE and created 'Summary of findings' tables.

MAIN RESULTS

We included four new studies (530 participants), and excluded three previously included studies (126 participants). In all, 37 studies provided information on 5914 participants. Most studies used oral gabapentin or gabapentin encarbil at doses of 1200 mg or more daily in different neuropathic pain conditions, predominantly postherpetic neuralgia and painful diabetic neuropathy. Study duration was typically four to 12 weeks. Not all studies reported important outcomes of interest. High risk of bias occurred mainly due to small size (especially in cross-over studies), and handling of data after study withdrawal.In postherpetic neuralgia, more participants (32%) had substantial benefit (at least 50% pain relief or PGIC very much improved) with gabapentin at 1200 mg daily or greater than with placebo (17%) (RR 1.8 (95% CI 1.5 to 2.1); NNT 6.7 (5.4 to 8.7); 8 studies, 2260 participants, moderate-quality evidence). More participants (46%) had moderate benefit (at least 30% pain relief or PGIC much or very much improved) with gabapentin at 1200 mg daily or greater than with placebo (25%) (RR 1.8 (95% CI 1.6 to 2.0); NNT 4.8 (4.1 to 6.0); 8 studies, 2260 participants, moderate-quality evidence).In painful diabetic neuropathy, more participants (38%) had substantial benefit (at least 50% pain relief or PGIC very much improved) with gabapentin at 1200 mg daily or greater than with placebo (21%) (RR 1.9 (95% CI 1.5 to 2.3); NNT 5.9 (4.6 to 8.3); 6 studies, 1277 participants, moderate-quality evidence). More participants (52%) had moderate benefit (at least 30% pain relief or PGIC much or very much improved) with gabapentin at 1200 mg daily or greater than with placebo (37%) (RR 1.4 (95% CI 1.3 to 1.6); NNT 6.6 (4.9 to 9.9); 7 studies, 1439 participants, moderate-quality evidence).For all conditions combined, adverse event withdrawals were more common with gabapentin (11%) than with placebo (8.2%) (RR 1.4 (95% CI 1.1 to 1.7); NNH 30 (20 to 65); 22 studies, 4346 participants, high-quality evidence). Serious adverse events were no more common with gabapentin (3.2%) than with placebo (2.8%) (RR 1.2 (95% CI 0.8 to 1.7); 19 studies, 3948 participants, moderate-quality evidence); there were eight deaths (very low-quality evidence). Participants experiencing at least one adverse event were more common with gabapentin (63%) than with placebo (49%) (RR 1.3 (95% CI 1.2 to 1.4); NNH 7.5 (6.1 to 9.6); 18 studies, 4279 participants, moderate-quality evidence). Individual adverse events occurred significantly more often with gabapentin. Participants taking gabapentin experienced dizziness (19%), somnolence (14%), peripheral oedema (7%), and gait disturbance (14%).

AUTHORS' CONCLUSIONS

Gabapentin at doses of 1800 mg to 3600 mg daily (1200 mg to 3600 mg gabapentin encarbil) can provide good levels of pain relief to some people with postherpetic neuralgia and peripheral diabetic neuropathy. Evidence for other types of neuropathic pain is very limited. The outcome of at least 50% pain intensity reduction is regarded as a useful outcome of treatment by patients, and the achievement of this degree of pain relief is associated with important beneficial effects on sleep interference, fatigue, and depression, as well as quality of life, function, and work. Around 3 or 4 out of 10 participants achieved this degree of pain relief with gabapentin, compared with 1 or 2 out of 10 for placebo. Over half of those treated with gabapentin will not have worthwhile pain relief but may experience adverse events. Conclusions have not changed since the previous update of this review.

Dose-response trial of pregabalin adjunctive therapy in patients with partial seizures

BACKGROUND

Pregabalin is an alpha(2)-delta ligand that has anxiolytic, analgesic, and anticonvulsant properties.

OBJECTIVE

To establish the efficacy, safety, and tolerability of pregabalin administered twice-daily (BID) without dose titration as adjunctive treatment in patients with partial seizures and to confirm the dose-response relationship.

METHODS

This 76-center, double-blind, randomized, placebo-controlled, parallel-group study consisted of an 8-week baseline and a 12-week double-blind phase. Patients with refractory partial seizures on one to three antiepileptic drugs were randomly assigned to one of five treatment groups (placebo or 50, 150, 300, and 600 mg/d pregabalin, all administered BID). Efficacy was assessed using seizure frequency reduction and responder rate (> or =50% seizure reduction from baseline). Pharmacokinetic parameters were estimated.

RESULTS

A total of 453 patients were included in the intent-to-treat analysis. The median baseline seizure rate was 10 per month. Seizure frequency reductions from baseline were 7% (placebo; n = 100), 12% (50 mg/d; n = 88), 34% (150 mg/d; n = 86), 44% (300 mg/d; n = 90), and 54% (600 mg/d; n = 89). Responder rates (> or =50% seizure reduction) were 14% (placebo), 15% (50 mg/d), 31% (150 mg/d), 40% (300 mg/d), and 51% (600 mg/d). Discontinuation rates due to adverse events were 5% (placebo), 7% (50 mg/d), 1% (150 mg/d), 14% (300 mg/d), and 24% (600 mg/d). The 150-, 300-, and 600-mg/d pregabalin groups were associated with greater reductions in seizures (p < or = 0.0001) and greater responder rates compared with the placebo group (p < or = 0.006). There was a favorable dose-response trend for both seizure reductions (p < or = 0.0001) and responder rate (p < or = 0.001).

CONCLUSION

Adjunctive therapy with pregabalin 150, 300, and 600 mg/d, given in twice-daily doses without titration, is significantly effective and well tolerated in the treatment of patients with partial seizures as demonstrated in patients with refractory partial seizures.

Pregabalin: A novel γ-aminobutyric acid analogue in the treatment of neuropathic pain, partial-onset seizures, and anxiety disorders

BACKGROUND

The US Food and Drug Administration (FDA) approved pregabalin in December 2004 for the treatment of neuropathic pain associated with diabetic peripheral neuropathy and postherpetic neuralgia. Pregabalin is the first drug approved in the United States and in Europe for both conditions. In June 2005, pregabalin was approved as an adjunctive treatment in adults with partial-onset seizures. The FDA currently is considering the approval of pregabalin as adjunctive therapy in adults with generalized anxiety disorder (GAD) or social anxiety disorder (SAD).

OBJECTIVES

The goals of this review were to summarize the pharmacology, pharmacokinetics, efficacy, and tolerability of pregabalin; review its approved uses in the management of neuropathic pain and refractory partial-onset seizures; and investigate its potential use in patients with GAD or SAD.

METHODS

Relevant English-language literature was identified through a search of MEDLINE (1993-June 2006) and International Pharmaceutical Abstracts (2000-June 2006). The search terms included pregabalin, Lyrica, S-(+)-3 isobutyl-gaba, PN, DPN, diabetic peripheral neuropathy, PHN, postherpetic neuralgia, partial seizures, epilepsy, generalized anxiety disorder, and CI-1008.

RESULTS

In 4 clinical trials in a total of 1068 patients with diabetic peripheral neuropathy, the patients receiving pregabalin 300 to 600 mg/d had significantly greater improvement in mean pain scores than placebo recipients (P < or = 0.01). Patients with postherpetic neuralgia receiving pregabalin 450 to 600 mg/d had significantly greater improvement in relief of pain and pain-related sleep interference than placebo recipients (P < or = 0.002). Patients with refractory partial-onset seizures who received pregabalin 150 to 600 mg/d (divided into 2 or 3 doses) concomitantly with antiepileptic drugs had significantly fewer seizures than placebo recipients (P < or = 0.001). In the 3 studies that evaluated the efficacy of pregabalin in patients with GAD or SAD, the patients receiving pregabalin 200 to 600 mg/d (divided into 2 or 3 daily doses) had a significantly greater reduction in mean pain scores on the Hamilton Anxiety Scale than placebo recipients (P < or = 0.01). Across all the reviewed clinical trials, the most commonly reported adverse effects (AEs) were those affecting the central nervous system, including somnolence (< or =50%), dizziness (< or =49%), and headache (< or =29%). AEs resulted in withdrawal from the study in < or =32% of patients.

CONCLUSIONS

Pregabalin appears to be an effective therapy in patients with diabetic peripheral neuropathy, postherpetic neuralgia, and adults with refractory partial-onset seizures. The available data suggest that pregabalin may be beneficial as an adjunctive therapy in adult patients with GAD or SAD.

Pregabalin for relief of neuropathic pain associated with diabetic neuropathy: a randomized, double-blind study

Seven published, randomized, placebo-controlled clinical trials with pregabalin have shown robust efficacy for relief of neuropathic pain from DPN and PHN. An investigation of the efficacy and safety of twice daily pregabalin enrolled 395 adults with painful DPN for > or = 1 year in a 12-week, double-blind, placebo-controlled trial. Patients were randomized to placebo, 150, 300, or 600 mg/day pregabalin (n = 96, 99, 99, and 101). Primary efficacy measure was change from baseline in endpoint mean pain score from patients' daily pain diaries. Secondary efficacy measures included pain-related sleep-interference scores, Patient and Clinical Global Impressions of Change (PGIC, CGIC), and the EuroQOL Health Utilities Index (EQ-5D). Statistically significant reduction in pain was observed in patients receiving pregabalin 600 mg/day, and 46% of patients treated with 600 mg/day pregabalin reported > or = 50% improvement in mean pain scores from baseline (vs 30% of placebo patients, p = 0.036). Number needed to treat to achieve such response was 6.3. Pregabalin 600 mg/day was significantly superior to placebo in improving pain-related sleep-interference scores (p = 0.003), PGIC (p = 0.021), and CGIC (p = 0.009). (Neither pregabalin 150 nor 300 mg/day separated from placebo on these measures, largely because of an atypically large placebo response in one country representing 42% of patients.) All pregabalin dosages were superior to placebo in improving EQ-5D utility scores (all p > or = 0.0263 vs placebo). Pregabalin was well tolerated at all dosages; adverse events were generally mild to moderate. Number needed to harm (discontinuation because of adverse events) was 10.3 for pregabalin 600 mg/day.

Preoperative gabapentin for postoperative analgesia: a meta-analysis

PURPOSE

Gabapentin's role in the treatment of chronic neuropathic pain is well known. What is less well established is its role for managing postoperative pain. In order to clarify whether gabapentin's utility in acute pain control is more than just theoretical, we conducted a meta-analysis of all randomized trials that addressed gabapentin's role in acute postoperative pain control. We specifically addressed whether gabapentin reduces pain scores, analgesia consumption, and/or analgesia-related side effects in the first 24 hr following surgery.

SOURCE

We identified eight placebo-controlled, randomized controlled trials and conducted a meta-analysis using the primary outcomes of pain scores, total analgesia consumption, and side effects over a 24-hr period.

PRINCIPLE FINDINGS

Patients who received gabapentin preoperatively reported significantly lower pain scores (-11.9 at rest and -11.0 with movement on a 100-point visual analogue scale) and opioid consumption (-14.7 mg of morphine in 24 hr) with no difference in the incidence of side effects.

CONCLUSION

Although gabapentin given preoperatively decreases pain scores and analgesic consumption in the first 24 hr after surgery, the clinical significance of this finding has yet to be determined. This meta-analysis could not demonstrate a significant reduction in the incidence of side effects. Due to the small numbers enrolled in the studies, larger randomized control trials are warranted.

Prolonged-release oxycodone enhances the effects of existing gabapentin therapy in painful diabetic neuropathy patients

BACKGROUND

Neuropathic pain remains one of the most challenging pain syndromes; under-diagnosed, poorly managed and associated with significant co-morbidity. With standard therapeutic treatments, responders rarely exceed 50% pain relief and the majority suffer from residual pain. Titration to optimum dose is often limited by dose-related adverse events.

AIMS

This randomized, double-blind, placebo-controlled study assessed the potential benefit of adding oxycodone (OxyContin tablets) to gabapentin. The primary endpoint was to evaluate the analgesic efficacy of co-administration of gabapentin and prolonged-release oxycodone, whilst also evaluating the use of escape medication, sleep quality and global assessment of pain.

METHODS

Three hundred and thirty eight patients with moderate to severe painful diabetic neuropathy despite receiving their maximum tolerated dose of gabapentin, had oral prolonged-release oxycodone or placebo tablets added to their therapy for up to 12 weeks.

RESULTS

Oxycodone-gabapentin reduced pain score by 33% from baseline to end of treatment. The overall treatment effect was greater with oxycodone-gabapentin than with placebo-gabapentin (P = 0.007). Oxycodone-gabapentin also significantly improved pain relief vs gabapentin alone (P = 0.003). Oxycodone-gabapentin co-administration was associated with less escape medication use (P = 0.03) and fewer nights of disturbed sleep (P < 0.05). Discontinuations due to lack of therapeutic effect were much lower (14% vs 54%) with oxycodone-gabapentin. The commonly seen opiate-induced adverse events were not exacerbated by the combination of oxycodone and gabapentin.

CONCLUSIONS

This study provides the first evidence that co-administration of prolonged-release oxycodone and existing gabapentin therapy has a clinically meaningful effect in painful diabetic neuropathy.

Safety and efficacy of two pregabalin regimens for add-on treatment of partial epilepsy

OBJECTIVE

To evaluate the efficacy, tolerability, and safety of two pregabalin regimens administered as adjunctive therapy to that of placebo in patients with medically refractory partial epilepsy.

METHODS

A multicenter, double-blind, randomized, parallel-group, placebo-controlled trial was performed. Following a prospective 8-week baseline phase, patients were randomized to 12 weeks of double-blind treatment with placebo or pregabalin 600 mg/day administered twice daily (BID) or three times daily (TID). Primary efficacy was measured as change in seizure frequency from baseline of either pregabalin regimen compared with placebo. Secondary efficacy comparisons included the proportion of patients experiencing > or =50% reduction in seizure frequency (responder rate) and median percentage change from baseline in seizure frequency. Safety/tolerability assessments included adverse events (AEs), physical and neurologic examinations, and clinical laboratory evaluation. Efficacy and safety analyses were performed on the intent-to-treat (ITT) population.

RESULTS

Pregabalin treatment resulted in seizure frequency reductions: 53% for pregabalin TID (p < or = 0.0001) and 44% for pregabalin BID (p < or = 0.0001) compared with a 1% increase for placebo. Responder rates were 49% for pregabalin TID and 43% for pregabalin BID compared with 9% for placebo (p < or = 0.001). Both pregabalin regimens were similar in efficacy and tolerability. The most common AEs were dizziness, somnolence, and ataxia.

CONCLUSIONS

Pregabalin administered at 600 mg/day is safe, generally well tolerated, and efficacious as adjunctive therapy for the treatment of patients with partial seizures, with or without secondary generalizations. This dose can be administered on a twice daily or three times daily schedule with similar efficacy and tolerability results.

Effect of a second-generation alpha2delta ligand (pregabalin) on visceral sensation in hypersensitive patients with irritable bowel syndrome

BACKGROUND

Visceral hypersensitivity is an important pathophysiological factor in irritable bowel syndrome (IBS). Pre-clinical studies suggest that the alpha(2)delta ligand pregabalin reduces both visceral allodynia and hyperalgesia, but is inactive on basal sensitivity.

AIM

To assess the effect of pregabalin on the perception of rectal distension in hypersensitive IBS patients.

METHODS

Twenty-six patients with Rome-II-defined IBS (aged 18-46 years, 7 male) were included in a randomized, double-blind, placebo-controlled, parallel-group study in which they received either 3 weeks oral pregabalin (titrated: 50 mg tid days 1-3, 100 mg tid days 4-7, 150 mg tid days 8-11; fixed 200 mg tid days 12-21 +/-4) or placebo control. Rectal sensitivity was assessed using a barostat technique, in which sensory thresholds were determined using the ascending method of limits, followed by tracking both before and after treatment. Only patients with a pain threshold of

RESULTS

Pregabalin significantly increased the sensory thresholds from baseline for first sensation (p = 0.045), desire to defecate (p = 0.008) and pain (p = 0.048) compared with placebo control. In addition, pregabalin significantly increased rectal compliance (p<0.0001), although this appeared to be unrelated to the changes in sensitivity. Despite the occurrence of mild dizziness and somnolence, pregabalin was generally well tolerated.

CONCLUSIONS

Pregabalin increased distension sensory thresholds to normal levels in IBS patients with rectal hypersensitivity. A concomitant increase in rectal compliance appeared to be unrelated to the reduction in sensitivity. These data suggest that alpha(2)delta ligands are worthy of further investigation in the treatment of visceral pain disorders, including IBS.

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Key Words

• pregabalin
• α2δ ligands
• visceral sensitivity
• irritable bowel syndrome

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MESH Headings

• Administration, Oral
• Adolescent
• Adult
• Analgesics/administration & dosage
• Analgesics/adverse effects
• Analgesics/blood
• Double-Blind Method
• Female
• Humans
• Irritable Bowel Syndrome/physiopathology
• Male
• Middle Aged
• Pain/physiopathology
• Pain Measurement
• Pain Threshold/physiology
• Pregabalin
• Pressure
• Rectum/physiopathology
• Sensation/physiology
• Sensory Thresholds/physiology
• gamma-Aminobutyric Acid/administration & dosage
• gamma-Aminobutyric Acid/adverse effects
• gamma-Aminobutyric Acid/analogs & derivatives
• gamma-Aminobutyric Acid/blood

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