Implications for practice
The key findings of the GaPP2 trial are clear and sufficiently generalisable to inform clinical practice. Women with CPP and no obvious pelvic pathology should be advised that gabapentin may not alleviate their pain and may give them unpleasant side effects.
Recommendations for future research
In our opinion, no further research is required to evaluate the role of gabapentin in the management of women with CPP and no obvious pelvic pathology. Questions that remain unaddressed relate to the use of other pharmacological interventions (monotherapy vs. combination therapy), physiotherapy and cognitive–behavioural therapy for treating women with CPP. These are outlined below.
Research question
What is the clinical effectiveness, cost-effectiveness and tolerability of pharmacological monotherapy compared with other pharmacological interventions (monotherapy vs. combination therapy), physiotherapy and cognitive–behavioural therapy for treating women with CPP?
Population
Women with a diagnosis of CPP with and without demonstrable pathology. Demonstrable pathology could include endometriosis, adenomyosis, adhesions, pelvic inflammatory disease, irritable bowel syndrome, bladder pain syndrome, nerve entrapment and musculoskeletal pain.
Intervention(s)
Any pharmacological agent as monotherapy or combination therapy, physiotherapy and cognitive–behavioural therapy. The pharmacological agents include:
- neuromodulators (e.g. amitriptyline, imipramine, nortriptyline, duloxetine, gabapentin and pregabalin)
- opiates (e.g. co-codamol, co-dydramol, dihydrocodeine, fentanyl, morphine, oxycodone, tapentadol and tramadol)
- ovarian suppressive drugs (e.g. combined oral contraceptive pill, progestogens and gonadotrophin-releasing hormone agonist)
- others (e.g. cannabis sativa extract).
Comparator(s)
Any of the pharmacological agents listed above as monotherapy compared with any combinations of the pharmacological agents listed above as combination therapy compared with physiotherapy and cognitive–behavioural therapy. Compare the treatment response across different groups of participants with different underlying aetiology.
Outcome(s)
- Patient-reported global improvement (on a 7-point scale).
- Patient-reported improvement in daily physical and emotional functioning, including sleep (on a 9-point scale).
- At least 30% and 50% pain reduction (on a 0–10-point NRS).
- Mean change from baseline pain scores (on a 11-point NRS).
- Withdrawal owing to adverse effects of the pharmacological agents.
- Adverse effects of the pharmacological agents.
- Health-related quality of life (e.g. EuroQol-5 Dimensions questionnaire).
Study design
- Randomised controlled trial.
- All participants should have a ‘washout’ period before assessment for inclusion in the study.
- Concomitant medications should not be allowed or should be restricted and maintained at a stable dose during the study. Differences in concomitant pain medication usage at baseline should be clearly described in each trial group, including details of the number of patients on different drugs.
- Rescue pain medications should either not be allowed or be accurately documented if they are used.