Gabapentin vs amitriptyline for the treatment of peripheral neuropathy

WITHDRAWN: Gabapentin for acute and chronic pain

BACKGROUND

February 2009: The authors are aware of unpublished trial data for Gabapentin which could affect the results of this review. This information together with that from trials published since 2005, will be considered when this review is updated in 2009.Anticonvulsant drugs have been used in the management of pain since the 1960s. The clinical impression is that they are useful for chronic neuropathic pain, especially when the pain is lancinating or burning.

OBJECTIVES

To evaluate the analgesic effectiveness and adverse effects of gabapentin for pain management in clinical practice.

SEARCH STRATEGY

Randomised trials of gabapentin in acute, chronic or cancer pain were identified by MEDLINE (1966 to Nov 2004), EMBASE (1994 to Nov 2004), SIGLE (1980 to Jan 2004) and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2004). Additional studies were identified from the reference list of the retrieved papers, and by contacting investigators. Date of most recent search: January 2004.

SELECTION CRITERIA

Randomised trials reporting the analgesic effects of gabapentin in participants with subjective pain assessment as either the primary or a secondary outcome.

DATA COLLECTION AND ANALYSIS

Data were extracted by two independent review authors, and trials were quality scored. Numbers-needed-to-treat-to-benefit (NNTs) were calculated, where possible, from dichotomous data for effectiveness, adverse effects and drug-related study withdrawal.

MAIN RESULTS

Fourteen reports describing 15 studies of gabapentin were considered eligible (1468 participants). One was a study of acute pain. The remainder included the following conditions: post-herpetic neuralgia (two studies), diabetic neuropathy (seven studies), a cancer related neuropathic pain (one study) phantom limb pain (one study), Guillain Barré syndrome (one study), spinal chord injury pain (one study) and various neuropathic pains (one study).The study in acute post-operative pain (70 participants) showed no benefit for gabapentin compared to placebo for pain at rest.In chronic pain, the NNT for improvement in all trials with evaluable data is 4.3 (95% CI 3.5 to 5.7). Forty two percent of participants improved on gabapentin compared to 19% on placebo. The number needed to harm (NNH) for adverse events leading to withdrawal from a trial was not significant. Fourteen percent of participants withdrew from active arms compared to 10% in placebo arms. The NNH for minor harm was 3.7 (95% CI 2.4 to 5.4). The NNT for effective pain relief in diabetic neuropathy was 2.9 (95% CI 2.2 to 4.3) and for post herpetic neuralgia 3.9 (95% CI 3 to 5.7).

AUTHORS' CONCLUSIONS

There is evidence to show that gabapentin is effective in neuropathic pain. There is limited evidence to show that gabapentin is ineffective in acute pain.

A qualitative systematic review of head-to-head randomized controlled trials of oral analgesics in neuropathic pain

BACKGROUND

Neuropathic pain (NP) encompasses many difficult-to-treat disorders. There are few head-to-head, comparative, randomized controlled trials (RCTs) of drugs for NP in different analgesic categories, or of different drugs within a category, despite many placebo-controlled RCTs for individual agents. Well-designed head-to-head comparative trials are an effective way to determine the relative efficacy and safety of a new drug.

OBJECTIVE

To perform a systematic review of head-to-head RCTs of oral analgesics in NP.

METHODS

A systematic review of RCTs involving NP patients was performed, of which head-to-head comparative trials were selected. Reference lists from published systematic reviews were searched. These studies were rated according to the Jadad scale for quality.

RESULTS AND CONCLUSIONS

Twenty-seven such trials were identified. Seventeen were comparisons of different analgesics, and 10 were of different drugs within an analgesic class. Important information was obtained about the relative efficacy and safety of drugs in different categories and within a category. Some significant differences between active treatments were reported. Trial inadequacies were identified. More and improved head-to-head RCTs are needed to inform clinical choices.

Antidepressants in the treatment of neuropathic pain

Neuropathic pain is due to lesion or dysfunction of the peripheral or central nervous system. Tricyclic antidepressants and anticonvulsants have long been the mainstay of treatment of this type of pain. Tricyclic antidepressants may relieve neuropathic pain by their unique ability to inhibit presynaptic reuptake of the biogenic amines serotonin and noradrenaline, but other mechanisms such as N-methyl-D-aspartate receptor and ion channel blockade probably also play a role in their pain-relieving effect. The effect of tricyclic antidepressants in neuropathic pain in man has been demonstrated in numerous randomised, controlled trials, and a few trials have shown that serotonin noradrenaline and selective serotonin reuptake inhibitor antidepressants also relieve neuropathic pain although with lower efficacy. Tricyclic antidepressants will relieve one in every 2-3 patients with peripheral neuropathic pain, serotonin noradrenaline reuptake inhibitors one in every 4-5 and selective serotonin reuptake inhibitors one in every 7 patients. Thus, based on efficacy measures such as numbers needed to treat, tricyclic antidepressants tend to work better than the anticonvulsant gabapentin and treatment options such as tramadol and oxycodone, whereas the serotonin noradrenaline reuptake inhibitor venlafaxine appears to be equally effective with these drugs and selective serotonin reuptake inhibitors apparently have lower efficacy. Head-to-head comparisons between antidepressants and the other analgesics are lacking. Contraindications towards the use of tricyclic antidepressants and low tolerability in general of this drug class--may among the antidepressants--favour the use of the serotonin noradrenaline reuptake inhibitors. A recent study on bupropion, which is a noradrenaline and dopamine uptake inhibitor, indicated a surprisingly high efficacy of this drug in peripheral neuropathic pain. In conclusion, antidepressants represent useful tools in neuropathic pain treatment and must still be considered as first line treatments of neuropathic pain. However, without head-to-head comparisons between antidepressants and other analgesics, it is not possible to provide real evidence-based treatment algorithms for neuropathic pain.

Gabapentin for acute and chronic pain

BACKGROUND

Anticonvulsant drugs have been used in the management of pain since the 1960s. The clinical impression is that they are useful for chronic neuropathic pain, especially when the pain is lancinating or burning.

OBJECTIVES

To evaluate the analgesic effectiveness and adverse effects of gabapentin for pain management in clinical practice.

SEARCH STRATEGY

Randomised trials of gabapentin in acute, chronic or cancer pain were identified by MEDLINE (1966-Nov 2004), EMBASE (1994-Nov 2004), SIGLE (1980-Jan 2004) and the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library Issue 4, 2004). Additional reports were identified from the reference list of the retrieved papers, and by contacting investigators. Date of most recent search: January 2004.

SELECTION CRITERIA

Randomised trials reporting the analgesic effects of gabapentin in patients, with subjective pain assessment as either the primary or a secondary outcome.

DATA COLLECTION AND ANALYSIS

Data were extracted by two independent reviewers, and trials were quality scored. Numbers-needed-to-treat (NNTs) were calculated, where possible, from dichotomous data for effectiveness, adverse effects and drug-related study withdrawal.

MAIN RESULTS

Fourteen reports describing 15 studies of gabapentin were considered eligible (1468 participants). One was a study of acute pain. The remainder included the following conditions: post-herpetic neuralgia (two studies), diabetic neuropathy (seven studies), a cancer related neuropathic pain (one study) phantom limb pain (one study), Guillain Barré syndrome (one study) , spinal chord injury pain (one study) and various neuropathic pains (one study). The study in acute post-operative pain (70 participants) showed no benefit for gabapentin compared to placebo for pain at rest. In chronic pain, the NNT for improvement in all trials with evaluable data is 4.3 (95%CI 3.5-5.7). Forty two percent of participants improved on gabapentin compared to 19% on placebo. The number needed to harm(NNH) for adverse events leading to withdrawal from a trial was not significant. Fourteen percent of participants withdrew from active arms compared to 10% in placebo arms. The NNH for minor harm was 3.7 (95% CI 2.4 to 5.4). The NNT for effective pain relief in diabetic neuropathy was 2.9 (95% CI 2.2 to 4.3) and for post herpetic neuralgia 3.9 (95% CI 3 to 5.7).

AUTHORS' CONCLUSIONS

There is evidence to show that gabapentin is effective in neuropathic pain. There is limited evidence to show that gabapentin is ineffective in acute pain.

Gabapentin for neuropathic pain: systematic review of controlled and uncontrolled literature

OBJECTIVE

To assess the efficacy/effectiveness and side effects of gabapentin for the treatment of neuropathic pain.

DESIGN

Systematic review of the literature.

METHODS

Extensive search of several electronic databases located both controlled and uncontrolled studies. Efficacy was assessed through meta-analysis of randomized controlled trials (RCTs), whereas the effectiveness of gabapentin in uncontrolled studies was assessed via a novel system of dichotomous classification of "bad" versus "good" results.

FINDINGS

Thirty-five papers involving 727 patients with multiple neuropathic pain conditions met the inclusion criteria. The meta-analysis of the 2 high-quality, placebo-controlled RCTs showed positive effect of gabapentin in diabetic neuropathy and post-herpetic neuralgia. The addition of 2 low-quality, placebo-controlled RCTs did not alter the magnitude or direction of observed effect. The uncontrolled studies demonstrated positive effect on pain in different neuropathic syndromes, as well as benefit on different types of neuropathic pain; highest dose administered and rate-of-dose escalation showed wide variability between prescribers. Fewer and less severe side effects were reported in the uncontrolled studies.

CONCLUSIONS

Gabapentin seems to be effective in multiple painful neuropathic conditions. The variable prescribing patterns of the uncontrolled studies raise the suspicion that effectiveness may be reduced if one limits administration of the drug to very low doses, whereas rapid dose escalation may be associated with increased central nervous system side effects. Well-designed controlled trials may provide insight into differential symptom sensitivity to the drug.

Cancer Pain: Progress Since the WHO Guidelines

In has been 15 years since the WHO Guidelines for the management of cancer pain were developed. This article reviews the guideline development and its effectiveness. Current trends in cancer care utilizing aggressive chemotherapeutic and surgical protocols lead to many patients living longer with advanced cancer and an attendant increase in pain. Future trends in cancer pain care are outlined.