A double‐blind, placebo‐controlled, parallel group multicentre study of 165 diabetic patients with a 1–5‐year history of painful peripheral diabetic neuropathy reported a beneficial effect with gabapentin .
A post-marketing surveillance study of gabapentin usage in Filipino patients with neuropathic pain wasconducted. Safety, tolerability and analgesic efficacy were assessed after a minimum of two weeks ofgabapentin treatment, with starting and final doses determined by the prescribing physician.
Of the1,214 patients who entered the study, 95.7% completed the minimum two weeks duration of therapy.The mean age was 54 years, and the most common neuropathic pain diagnoses were painful diabeticneuropathy (30.4%), nonspecific neuropathies (20.2%), trigeminal neuralgia (12.8%), central pain afterstroke (8.8%), and post-herpetic neuralgia (8.4%). Ninety-two percent of patients were maintainedwithin a dose range of 300mg/day to 1200mg/day.
The incidence of adverse events was 6%, andconsisted mostly of somnolence and dizziness, with 76% of patients reporting “very good” to“excellent” tolerability. There were 34 documented dropouts (2.9%), of which only seven (0.6%) werethought to be related to an adverse event from gabapentin.
Visual analog scale pain scores declinedsignificantly from a mean of mm at baseline, to mm after treatment (p< 0.05). Inconclusion, gabapentin at 300mg/d to 1200mg/d is well tolerated and efficacious among Filipinopatients with various neuropathic pain syndromes.Gabapentin showed significant reduction in pain and other related symptoms in all types of neuropathic painNeurol J Southeast Asia 2002; 7 : 25 – 34
Eighty‐four patients were allocated to the␣gabapentin group and 81 to the placebo group.
Gabapentin was titrated to a maximum of 3600 mg daily.
Gabapentin was generally well tolerated and 67% of the gabapentin group reached 3600 mg.day−1. A statistically significant (p < 0.0001) reduction in mean daily pain score (using an 11‐point Likert scale) in the gabapentin group (baseline 6.4, endpoint 3.9), compared with placebo (baseline 6.5, endpoint 5.1), was achieved.
The number‐needed‐to‐treat (NNT, defined as the number of patients needed to be treated for one patient to receive at least 50% pain relief) for the analgesic effects in neuropathic pain with gabapentin in this study was 3.8 . This compares with a NNT of 2.3 for carbemazepine and 2.1 for phenytoin in other randomised controlled trials . Another double‐blind, placebo‐controlled trial of gabapentin in 32 diabetic patients with neuropathic pain showed a statistically significant analgesic effect during the first month of treatment.
Morello et al. conducted a randomised, double‐blind cross‐over study comparing the efficacy of gabapentin with that of amitriptyline in diabetic peripheral neuropathy and found both drugs provided equal pain relief.
Gabapentin in neuropathic pain syndromes: a randomised, double-blind, placebo-controlled trial.
In an open‐label pilot study over 12 weeks involving 25 randomised patients (13 received gabapentin, 12 received amitriptyline), gabapentin significantly reduced pain scores (p = 0.026) and paraesthesia (p = 0.004) compared with amitriptyline . Adverse effects were also less frequent in the gabapentin group (p = 0.003). Further trials are required to confirm these preliminary results indicating that gabapentin is more efficacious than amitriptyline in diabetic peripheral neuropathy.
A double-blind, randomised, placebo-controlled 8-week study was conducted to evaluate the efficacy and safety of gabapentin in the treatment of neuropathic pain, using doses up to 2400 mg/day.
The study used a novel design that was symptom- rather than syndrome-based; an approach that aimed to reflect the realities of clinical practice. Participants had a wide range of neuropathic pain syndromes, with at least two of the following symptoms: allodynia, burning pain, shooting pain, or hyperalgesia.
Patients were randomised to gabapentin (n=153) or placebo (n=152). Gabapentin was given in three divided doses, initially titrated to 900 mg/day over 3 days, followed by two further increases, to a maximum of 2400 mg/day if required by the end of week 5.
The primary outcome measure was changed in average daily pain diary score (baseline versus final week). Over the 8 week study, this score decreased (i.e. improved) by 1.5 (21%) in gabapentin treated patients and by 1.0 (14%) in placebo treated patients (P=0.048, rank-based analysis of covariance).
Significant differences were shown in favour of gabapentin (P<0.05) for the Clinician and Patient Global Impression of Change, and some domains of the Short Form-McGill Pain Questionnaire. Improvements were also shown in patient-reported outcomes in quality of life, as seen by significant differences in favour of gabapentin in several domains of the Short-Form-36 Health Survey.
Gabapentin was well tolerated and the majority of patients completed the study (79 versus 73% for placebo). The most common adverse events were mild to moderate dizziness and somnolence, most of which were transient and occurred during the titration phase.
This study shows that gabapentin reduces pain and improves some quality-of-life measures in patients with a wide range of neuropathic pain syndromes.