Review finds no evidence for topiramate in treating neuropathic pain

Unhappy woman

Diabetic neuropathy is a common complication of diabetes.  This condition is very painful and substantially compromises quality of life.  Its progressive nature places a further burden on patients and their carers.

Current guidance recommends a range of possible drug treatments, including the antidepressant drugs amitriptyline or duloxetine and the anti-convulsant pregabalin.  A recent Cochrane review looked at whether the anti-epileptic drug topiramate could be added to this armoury of possible treatments.

Clinical question

  • In adults with chronic neuropathic pain, does topiramate improve pain symptoms?

Methods

Lots of different pills

There are many different treatments and possible combinations (don’t try this at home…)

The reviewers searched Medline, EMBASE and clinical trials registries for randomised trials of at least two weeks’ duration.  Studies were assessed by two independent reviewers.

Their primary outcome was the proportion of participants reporting a reduction in pain of at least 50%.

Results

Four clinical trials were found, of which three looked at diabetic neuropathy.  There reviewers reported that there was no high quality evidence that topiramate reduced painful symptoms in any of the trials or in the meta-analysis.

However, only one study reported the outcome the reviewers were most interested in.  This trial was flawed by a high rate of withdrawal from the topirimate group (25% compared with 8% from the placebo group), which were compensated for by imputing outcomes data from the last recorded entry.

Substantial numbers of patients reported one or more adverse effects of the drug.

Comments

  • Pain scale

    The studies were very different in how they measured pain outcomes.

    The reviewers commented that the trials were of sub-optimal methodological quality.  No studies met all of their “tier one” criteria for unbiased evidence.

  • The review was also limited because of the different ways in which the studies measured pain reduction.
  • Further research is needed with standardised, patient-important outcomes measures.
  • Such studies need to take into account combination therapies, and fair comparison with alternative treatments.

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