Condition category
Signs and Symptoms
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Background and study aims
Chronic pelvic pain (CPP) in women is where pain is felt in the pelvic region (the area below the belly button and between the hips) for at least 6 months. It affects more than 1 million women in the UK every year, accounting for about 20% of all gynaecologist appointments. Despite this, there are a limited amount of effective treatments available, especially when the cause of the pain cannot be identified. In recent years, a drug called gabapentin is being prescribed more and more to treat people with CPP. It was belongs to a group of medications used to treat epilepsy, but it is also now used to treat a range of long-term pain conditions. Although gabapentin is being increasingly prescribed to people with CPP, there is not enough evidence to say whether it is an effective treatment. The aim of this study is to find out whether treatment with gabapentin an effective way of treating CPP in women.

Who can participate?
Women who are suffering from CPP with on obvious cause.

What does the study involve?
Participants are randomly allocated to one of two groups. Those in the first group are given 300mg gabapentin to take orally (by mouth). Participants start by taking one 300mg capsule a day, and increase this dose by one 300mg capsule every three days (up to a maximum dose of nine 300mg capsules a day) until they are getting enough pain relief or start to experience side-effects. Those in the second group are given identical-looking placebo (dummy) capsules to take in the same way. At the start of the study and then after 16 weeks, participants complete a number of questionnaires in order to measure their pain levels and how well they have been coping with daily life physically and emotionally.

What are the possible benefits and risks of participating?
Not provided at time of registration.

Where is the study run from?
Birmingham Clinical Trials Unit (UK)

When is the study starting and how long is it expected to run for?
November 2015 to August 2017

Who is funding the study?
National Institute for Health Research (UK)

Who is the main contact?
Miss Afia Sajid

Trial website

Contact information



Primary contact

Miss Afia Sajid


Contact details

Birmingham Clinical Trials Unit
School of Health & Population Sciences
College of Medical and Dental Sciences
Public Health Building
University of Birmingham
B15 2TT
United Kingdom

Additional identifiers

EudraCT number

2014-005035-13 number

Protocol/serial number


Study information

Scientific title

GaPP 2: A multicentre randomised controlled trial of the efficacy and mechanism of action of gabapentin for the management of chronic pelvic pain in women


Study hypothesis

The aim of this study is to find out whether gabapentin is a safe and effective treatment for chronic pelvic pain (CPP) in women.

Ethics approval

West Midlands - Coventry & Warwickshire Research Ethics Committee, 03/02/2015, ref: 15/WM/0036

Study design

Double-blind multi-centre randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details to request a patient information sheet


Topic: Reproductive health and childbirth; Subtopic: Reproductive Health and Childb (all Subtopics); Disease: General Gynaecology


Participants will be randomised in an equal (1:1) ratio to take either gabapentin or placebo.

Group 1: Participants are given gabapentin to take orally for the study period. Participants will start on 1 capsule (300 mg) daily and will increase by 1 capsule (300 mg) increments every three days until they perceive that they are gaining adequate pain relief, or report side effects (e.g. dizziness, somnolence, mood changes, appetite and poor concentration), precludes them from further increases, up to a maximum dose of 9 capsules (2700 mg). The titration phase will last a maximum of 4 weeks. If necessary they will be titrated down to the last tolerated dose with minimal side effects and asked to maintain this dose for the next 12 weeks.

Group 2: Participants are given placebo capsules to take orally for the study period.

Participants complete questionnaires at baseline and 16 weeks to assess pain levels and physical/emotional functioning.

Intervention type



Not Applicable

Drug names


Primary outcome measure

Pelvic pain is measured using a numerical rating scale (NRS) at baseline and 13-16 weeks post-randomisation

Secondary outcome measures

Physical/emotional functioning is assessed using questionnaires at baseline and week 16

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Women aged between 18-50 years
2. Chronic pelvic pain (non-cyclical with or without dysmenorrhoea or dyspareunia) of >3 months duration
3. Pain located within the true pelvis or between and below anterior iliac crests
4. 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)
5. Using or willing to use effective contraception if necessary to avoid pregnancy
6. Able to give informed consent
7. For both the worst and average pre-randomisation Numerical Rating Scale (NRS) questions, at least three of the four weekly scores returned to the trials office. At least two of the worst pain scores should be ≥4

Participant type


Age group




Target number of participants

Planned Sample Size: 300; UK Sample Size: 300

Total final enrolment


Participant exclusion criteria

1. Known pelvic pathology: o Endometriosis (macroscopic lesions) o complex or >5cm ovarian cyst o fibroid >3cm o dense adhesions
2. Current malignancy under treatment
3. Current use of gabapentin/pregabalin
4. Taking GnRH agonists and unable/unwilling to stop
5. Surgery planned in the next 6 months
6. History of significant renal impairment
7. Previous reaction to gabapentin
8. Breast feeding
9. Pregnancy
10. Planned pregnancy in next 6 months
11. Pain suspected to be of gastrointestinal origin (positive Rome III Diagnostic Criteria)
12. Prohibited medications (see SmPC – Appendix 2))
13. Metal implant/pacemaker/claustrophobia (fMRI subgroup only)
14. Co-enrolment in another CTIMP

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Birmingham Clinical Trials Unit
School of Health & Population Sciences College of Medical and Dental Sciences Public Health Building University of Birmingham
B15 2TT
United Kingdom

Sponsor information


University of Edinburgh

Sponsor details

The Queen’s Medical Research Institute
Royal Infirmary of Edinburgh
51 Little France Crescent
Old Dalkeith Road
EH16 4SA
United Kingdom

Sponsor type




Funder type


Funder name

National Institute for Health Research

Alternative name(s)


Funding Body Type

government organisation

Funding Body Subtype

National government


United Kingdom

Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Available on request

Basic results (scientific)

Publication list

2018 protocol in
2020 results in (added 30/09/2020)

Publication citations

Additional files

Editorial Notes

30/09/2020: The following changes were made to the trial record: 1. Publication reference added. 2. The total final enrolment was added. 15/11/2018: The recruitment end date was changed from 01/10/2018 to 31/01/2019. 22/06/2018: The following changes were made to the trial record: 1. The recruitment end date was changed from 01/08/2017 to 01/10/2018. 2. The overall trial end date was changed from 01/08/2017 to 01/02/2019. 14/02/2018: Publication reference added. 07/11/2016: Changed recruitment start date from 11/11/2015 to 30/11/2015