Comparing Bioavailability When Preservative-free Makena® (Hydroxyprogesterone Caproate Injection, 250 mg/mL) is Administered as an Intramuscular Manual Injection or as a Subcutaneous Injection Using an Auto-injector in Healthy Post-menopausal Women

Inclusion Criteria: 1\. Naturally or surgically postmenopausal women, with or without an intact uterus, aged 50 to 75 years of age, inclusive. FSH levels greater than 40 mIU/mL Exclusion Criteria: 1. Currently taking any estrogen/progesterone hormone replacement therapy (HRT). 2. History of allergy or sensitivity to hydroxyprogesterone caproate, castor oil or any of the constituents of the study medications, or history of any drug hypersensitivity or intolerance 3. Poorly controlled diabetes. 4. History or current evidence of deep vein thrombosis, pulmonary embolism or arterial thromboembolic disease (e.g., stroke, myocardial infarction). 5. Known, suspected, or current history of carcinoma of the breast. 6. Subjects with a past history of breast cancer on aromatase inhibitors or selective estrogen receptor modulators. 7. Known, suspected, or current history of hormone dependent tumor within the last 5 years. 8. Any current or recent (within previous 12 months) genital bleeding of unknown etiology. 9. Receipt of any investigational drug within 30 days. 10. Receipt of any prescription or OTC medications that are known to alter CYP3A4 or CYP3A5 levels (e.g., carbamazepine, St. John's Wort, ketoconazole, rifampin, ritonavir, alprazolam, azithromycin, loratadine, etc.) within 14. 11. Any estrogen, progestin, or selective estrogen receptor modulator (SERM) treatment within specified time windows before the study start, ranging from 2 to 6 months. 12. High blood pressure at the screening evaluation, defined as systolic blood pressure \> 150 mm Hg or diastolic blood pressure \> 90 mm Hg. 13. History of excessive alcohol consumption (on average more than 14 units of alcohol/week) during the past 12 months. 14. Use of tobacco products within 30 days of the start of the study.