Endometriosis.org announced the commencement of the GaPP2 clinical trial in the U.K. to determine whether the anti-seizure drug gabapentin reduces pelvic pain in women for whom no disease cause has been found. The investigators are also interested to learn whether gabapentin could improve these patients’ quality of life.
Gabapentin (technically a lipophilic structural analogue of the inhibitory neurotransmitter aminobutyric acid or GABA) is an anticonvulsant drug originally approved by the U.S. Food and Drug Administration (FDA) in December 1993 as a treatment for epilepsy. The drug has been marketed under the trade name Neurontin and has a well-established track record. According to the National Institute’s of Health Medline Plus, besides treating epilepsy, gabapentin has been found effective as a painkiller for neuropathic pain (pain that affects the nerves), hot flashes (in women being treated for breast cancer or who have experienced menopause), and restless leg syndrome (RLS; a condition that causes discomfort in the legs and a strong urge to move the legs, especially at night and when sitting or lying down). It is also recommended as a first-line agent for treating neuropathic pain arising from diabetic neuropathy (numbness or tingling due to nerve damage in people who have diabetes), post-herpetic neuralgia (PHN; the burning, stabbing pain or aches that may last for months or years after an attack of shingles), and central neuropathic pain. Gabapentin has been available in the U.S. for some time as a generic, and is relatively inexpensive, with a cost per daily dose typically under $1.00. The researchers speculate that gabapentin may also help with chronic pelvic pain, but that theory is unproven.
Half of the women in the GaPP2 trial (a multicenter, randomized and controlled efficacy and mechanism study) will be given gabapentin and the other half a placebo, with results compared at the study’s end. The study is also double-blinded, meaning participants and researchers won’t know which subjects received which treatment until end results are revealed. The primary outcome is dual measures of worst and average pelvic pain scores assessed by a numerical rating scale (NRS) during the final four weeks of treatment (weeks 13-16 post-randomization).
It is hoped that 300 women with a history of pelvic pain in whom a laparoscopy reveals no obvious pelvic pathology will be recruited for the trial. Women eligible to take part in the GaPP2 trial will be age 18 to 50, have suffered from chronic pelvic pain for more than three months, and have had a laparoscopy in the past three years (>2 weeks).
The investigators will collect information on participants’ pain, and physical and emotional well-being, at the beginning of the study and again after 12 weeks of taking the drugs via questionnaires. They will also ask 50 women (recruited in Edinburgh, Scotland) to undergo a brain scan to help them further understand how gabapentin works.
Funded by the National Institute for Health Research (NIHR) Efficacy and Mechanism Evaluation (EME) program, the trial is being run by Andrew Horne, chief investigator, University of Edinburgh Professor of Gynaecology and Reproductive Sciences, with the The University of Birmingham Clinical Trials Unit (BCTU) overseeing the administrative side.
Hospitals are taking part in the GaPP2 trial are:
Aberdeen Royal Infirmary
Birmingham Womens NHS Foundation Trust
Edinburgh Royal Infirmary
University Hospitals of Leicester NHS Trust
University College London
James Cook University Hospital, Middlesborough
John Radcliffe Hospital, Oxford
Southampton General Hospital
More information on the study and the hospitals recruiting participants can be found at the trial website:
U.S. Food and Drug Administration (FDA)
National Institutes of Health
University of Edinburgh
University of Birmingham Clinical Trials Unit (BCTU)