Pilot Study of Cyclobenzaprine for Treatment of Sleep Disturbance in Aromatase Inhibitor-treated Breast Cancer Patients

Inclusion Criteria: * Female gender, age ≥ 18, postmenopausal. * Histologically proven stage 0-III invasive carcinoma of the breast * Initiating or have been receiving a standard dose of aromatase inhibitor therapy (letrozole 2.5mg once daily or exemestane 25mg once daily or anastrozole 1mg once daily) for up to a total of 48 months of AI therapy. * Trouble sleeping during the past week. (After signing the informed consent document, subjects must also have a global PSQI score of ≥5) * ECOG performance status 0-2 (see Appendix A). Exclusion Criteria: * Known hypersensitivity to cyclobenzaprine or any of the inactive ingredients * Diagnosis of sleep apnea that is currently interfering with sleep or requiring CPAP, restless leg syndrome that is currently interfering with sleep or requiring medication, or Epworth sleepiness scale \>10. * Subjects with a history of hypothyroidism must have been on a stable dose of thyroid replacement medicine for at least 3 months prior to enrollment * Treatment with steroids within 1 month * Treatment with monoamine oxidase inhibitors (MAO-I) within 14 days of enrollment. * Concurrent treatment with bupropion, MAO inhibitors, phenothiazines (including thioridazine), selegiline, tramadol, or medications known to prolong the QT interval (www.azcert.org/medical-pros/drug-lists/drug-lists.cfm) * Currently primary psychiatric diagnosis (schizophrenia, psychosis) or suicidal ideation, history of bipolar disorder, or seizure disorder * Known moderate or severe hepatic impairment * History of congestive heart failure or cardiac arrhythmia (other than atrial fibrillation); myocardial infarction within the past 6 months * Uncontrolled narrow-angle glaucoma * Pregnant or breast feeding * Serious or unstable medical condition that could likely lead to hospitalization during the course of the study or compromise study participation