1. Aschenbrenner, Diane S. MS, RN


* Ospemifene (Osphena) is a new drug for postmenopausal women who suffer from painful intercourse (dyspareunia).


* The drug has estrogen agonist effects in the endometrium that increase the risks of endometriosis and endometrial cancer; estrogen antagonist effects elsewhere in the body increase the risk of thrombotic stroke and deep vein thrombosis.



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After menopause vaginal tissues can become thinner, drier, and more fragile, leading to pain during intercourse (dyspareunia). Ospemifene (Osphena) is a new drug that may be helpful to postmenopausal women who suffer from painful intercourse.


Ospemifene is an estrogen agonist and an estrogen antagonist: in the endometrium it has the same effects on the estrogen receptors that estrogen would have, whereas in other tissues of the body it attaches to estrogen receptors but has no effect. Because of its estrogen agonist effect on the endometrium, it has adverse effects similar to those of any replacement hormone given to postmenopausal women. Those adverse effects were identified in the landmark clinical trial known as the Women's Health Initiative and include endometriosis, endometrial cancer, stroke, and deep vein thrombosis. Ospemifene's label carries a boxed warning that it increases the risks of endometrial cancer (in postmenopausal women who have a uterus) and cardiovascular disorders. The warning states that adding a progestin to the estrogen helps to minimize the endometrial cancer risk.


Because of these serious risks, ospemifene is contraindicated if there is abnormal genital bleeding of unknown etiology (which may be a sign of cancer), known or suspected estrogen-susceptible cancers, a history of or active pulmonary embolism or deep vein thrombosis, or a history of or active thromboembolic disease (such as stroke or myocardial infarction). Ospemifene is also contraindicated in women who are or could possibly become pregnant because it's a pregnancy category X drug. Ospemifene hasn't been adequately studied in women with breast cancer, although the Women's Health Initiative did find that estrogen, when administered with progestin, increased the risk of breast cancer; therefore, ospemifene needs to be used with caution if the patient has a history of or is suspected to have breast cancer.


Ospemifene is metabolized by the cytochrome P-450 (CYP) isoenzymes CYP3A4 and CYP2C9 and others, and drug interactions through these pathways are possible. The label specifically states that fluconazole and ketoconazole (strong inhibitors of these isoenzymes) shouldn't be coadministered with ospemifene because the circulating levels of ospemifene will increase significantly, leading to an even greater risk of adverse effects. Rifampin decreases the circulating level of ospemifene by more than half and should therefore not be coadministered with ospemifene. Ospemifene is also highly (99%) protein bound. Ospemifene's most common adverse effects (occurring in at least 1% of patients) are hot flashes, vaginal discharge, muscle spasms, genital discharge, and excessive sweating.


Nurses caring for women prescribed ospemifene should provide sufficient patient education regarding its risks. Women should know the importance of seeking care if they experience vaginal bleeding while taking ospemifene. If the patient has a uterus, the nurse should confirm that a prescription for a progestin has also been provided; the prescriber should be contacted if there isn't a prescription for progestin. Nurses should carefully assess a patient's blood protein levels before and during ospemifene therapy; women with low circulating protein levels are at higher risk for adverse effects from ospemifene therapy. The prescriber should be contacted if the patient is deficient in protein. Nurses should also provide patients with information regarding a healthful diet, as warranted.


Complete Food and Drug Administration prescribing information can be found at