Comparing Adjuvant Treatments for High Tone Pelvic Floor Dysfunction

Inclusion Criteria:

* Self-reported moderate to severe chronic pelvic pain for \>6 months duration at time of screening visit. Moderate to severe chronic pain is defined as \>4 on 0-10 (worst daily pain) for \>14 days per month. Pelvic pain is defined as pain perceived to be located in the anatomic pelvis.
* Diagnosis of high tone pelvic floor dysfunction (HTPFD), defined as \>12/60 summative pelvic floor tenderness score on standardized pelvic examination by chronic pelvic pain specialist (MD or NP) within the past year
* Referred to pelvic floor physical therapy (PFPT) by their chronic pelvic pain specialist for management of HTPFD
* Willing to undergo a 12-session course of PFPT for HTPFD, including internal/vaginal tissue manipulation per standardized protocol
* Willing to delay start of PFPT until Phase 2 of the trial
* Willing to be randomized to either daily use of cyclobenzaprine or use of vibrating pelvic floor muscle massage wand for total of 18 weeks
* Willing to undergo standardized pelvic floor myofascial exam three times over the study period (baseline, end of Phase 1, end of Phase 2)
* Willing to undergo quantitative sensory testing (QST) two times over the study period (baseline, end of Phase 1)
* Willing to undergo blood draw two times over the study period (baseline, end of Phase 1)
* Ability to read and speak English to allow for written informed consent, phenotyping, and patient-reported outcome measures
* No plans for pregnancy within the next 12 months

Exclusion Criteria:

* Hypersensitivity or allergy to cyclobenzaprine or any component of cyclobenzaprine
* Underwent PFPT within 6 months of screening date
* Pregnancy at any point during study period (self-reported home urine pregnancy test or serum b-Hcg test, positive urine pregnancy test at baseline, post-Phase 1, or post-Phase 2 study visits).
* Currently breastfeeding at time of screening visit
* Scheduled for or are planning moderate/major gynecologic surgery (including hysterectomy, excision of endometriosis, ovarian cystectomy/oopherectomy, myomectomy) within the following 6 months of screening date
* Current (at time of screening visit) diagnosis of postural orthostatic tachycardia syndrome
* Current significant neurologic or musculoskeletal conditions that would preclude participation in PFPT (cerebral palsy, severe hip/back osteoarthritis that would prevent lithotomy position during sessions)
* Unwilling to avoid or stop baseline use of cyclobenzaprine and other muscle relaxants (including methocarbamol, tizanidine, baclofen, carisoprodol, metaxalone)
* Current use of tricyclic antidepressants
* Current use of monoamine oxidase inhibitor
* Current use of vaginally delivered benzodiazepine such as diazepam (more than once per month) and unwilling to stop use of vaginally delivered benzodiazepine for the duration of this study
* Current diagnosis of hyperthyroidism
* Current diagnosis of moderate or severe hepatic impairment
* Myocardial infarction within prior 12 months
* Current diagnosis of congestive heart failure
* Current cardiac pacemaker in place
* Current diagnosis of closed angle glaucoma
* Current major psychiatric condition (including psychosis or suicidal ideation within past year)