About The GaPP2 Trial

GaPP2 is a double-blind multi-centre randomised controlled trial of the efficacy and mechanism of action of gabapentin for the management of chronic pelvic pain in women


Chronic pelvic pain (CPP) affects >1 million UK women. It accounts for 20% of gynaecological consultations and was highlighted in the Chief Medical Officer’s Annual Report in 2009 as a key area of unmet need. Evidence-based treatments for CPP are limited, and management is often unsatisfactory. If no pathology is identified, the pain is much more difficult to treat and a drug called gabapentin, which has been used safely and successfully to treat other chronic pain conditions is being increasingly prescribed. There is currently no evidence to show whether it is effective or not for CPP.

We will investigate the effectiveness of gabapentin in women with CPP. In addition, we want to understand whether changes in the central nervous system of women with CPP are responsible for their symptoms and whether these can predict response to gabapentin. The main aim of the study is to demonstrate whether a reduction in daily pain can be achieved with the treatment of gabapentin.

We will invite 300 women with CPP where no cause has been found, to participate in a clinical trial where they are allocated at random to gabapentin or placebo (dummycapsules). We will collect information on pain, physical and emotional wellbeing at the beginning of the study and after 12 weeks of optimal treatment. We will ask a subset of 50 women (from Scottish sites) to undergo a functional magnetic resonance imaging (fMRI) scan to look at brain activity before and during treatment.

How does the Trial work?

Women will be identified by their clinician and asked if they will talk to a member of the clinical research team. If they agree, they will then be given a patient information sheet and will be asked if they are happy to be contacted to get their decision on whether they wish to participate. This will give them ample time to read the patient information sheet, ask any questions and make an informed choice of whether to participate or not.

For the fMRI substudy, participating women in Scotland will be asked if they are willing to undergo two fMRI scans and two blood tests. A separate patient information sheet and consent form will be given. The scans will take place in Edinburgh.

Who can enter?

Women who are admitted to a gynaecology clinic who fulfil all the following criteria will be eligible to be randomised into the trial:


  • Women aged between 18-50 years
  • Chronic pelvic pain (non-cyclical with or without dysmenorrhoea or dyspareunia) of >3 months duration
  • Pain located within the true pelvis or between and below anterior iliac crests
  • Associated functional disability
  • No obvious pelvic pathology at laparoscopy (laparoscopy must have taken place at least 2 weeks ago, but no more than 36 months prior to screening)
  • Using or willing to use effective contraception if necessary to avoid pregnancy
  • Able to give informed consent


  • Known pelvic pathology: Endometriosis (macroscopic lesions)  (patients can still be recruited if they have had endometriosis in the past but have had a negative laparoscopy in the last 3 years)
  • complex or >5cm ovarian cyst, fibroid >3cm, dense adhesions
  • Worst pain score <4 out of 10 on Numerical Rating Scale (NRS) at baseline (of the four measurements taken)
  • Current malignancy under treatment
  • Past history of gabapentin/pregabalin use for the management of CPP
  • Taking morphine and unable/unwilling to stop
  • Taking GnRH agonists and unable/unwilling to stop
  • Surgery of planned in next 6 months
  • History of significant renal impairment
  • Previous reaction to gabapentin
  • Breast feeding
  • Pregnant
  • Planned pregnancy in next 6 months
  • Pain suspected to be of gastrointestinal origin (positive Rome III Diagnostic Criteria)
  • Prohibited medications (see 6.6.3)
  • Metal implant/pacemaker/claustrophobia (fMRI subgroup only).
  • Co-enrolment in another CTIMP