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The following serious adverse reactions are discussed elsewhere in the labeling:
- Cardiovascular Disorders [see BOXED WARNING, WARNINGS AND PRECAUTIONS].
- Malignant Neoplasms [see BOXED WARNING, WARNINGS AND PRECAUTIONS].
Clinical Trials Experience
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
In a 13-week clinical trial that included 225 postmenopausal women treated with Femring and 108 women treated with placebo vaginal rings, adverse reactions that occurred at a rate of ≥ 2 percent are summarized in Table 1.
Table 1: Incidence of Adverse Reactions Occurring in ≥
2 Percent of Subjects Presented in Descending Frequency of Preferred Term
(n = 108)
|Estradiol 0.05 mg/day
(n = 113)
|Estradiol 0.10 mg/day
(n = 112)
|n (percent)||n (percent)||n (percent)|
|Headache (NOS)||10 (9.3)||8 (7.1)||11 (9.8)|
|Intermenstrual Bleeding||2 (1.9)||9 (8.0)||11 (9.8)|
|Vaginal Candidiasis||3 (2.8)||7 (6.2)||12 (10.7)|
|Breast Tenderness||2 (1.9)||7 (6.2)||12 (10.7)|
|Back Pain||4 (3.7)||7 (6.2)||4 (3.6)|
|Abdominal Distension||3 (2.8)||8 (7.1)||3 (2.7)|
|Sinusitis (NOS)||2 (1.9)||2 (1.8)||4 (3.6)|
|Uterine Pain||1 (0.9)||2 (1.8)||5 (4.5)|
|Urinary Tract Infection (NOS)||2 (1.9)||1 (0.9)||4 (3.6)|
|AE = adverse event; NOS = not otherwise specified|
- A few cases of toxic shock syndrome (TSS) have been reported in women using vaginal rings. TSS is a rare, but serious disease that may cause death. Warning signs of TSS include fever, nausea, vomiting, diarrhea, muscle pain, dizziness, faintness, or a sunburn-rash on face and body.
- A few cases of ring adherence to the vaginal or bladder wall, making ring removal difficult, have been reported in women using vaginal rings. Patients should be carefully evaluated for vaginal or bladder wall ulceration or erosion. If an ulceration or erosion has occurred, consideration should be given to leaving the ring out and not replacing it until healing is complete to prevent the ring from adhering to the vaginal tissue.
- A few cases of bowel obstruction associated with vaginal ring use have been reported. Persistent abdominal complaints consistent with obstruction should be carefully evaluated.
- A few cases of inadvertent ring insertion into the urinary bladder, which may require surgical removal, have been reported for women using vaginal rings. Persistent unexplained urinary symptoms should be carefully evaluated.
The following additional adverse reactions have been identified during post-approval use of Femring. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Blindness, contact lens intolerance.
Central Nervous System
Dizziness, headache, depression, nervousness, mood disturbances, irritability.
Read the Femring (estradiol acetate) Side Effects Center for a complete guide to possible side effects
No drug interaction studies have been conducted for Femring.
In vitro and in vivo studies have shown that estrogens are metabolized partially by cytochrome P450 3A4 (CYP3A4). Therefore, inducers or inhibitors of CYP3A4 may affect estrogen drug metabolism. Inducers of CYP3A4 such as St. John's wort (Hypericum perforatum) preparations, phenobarbital, carbamazepine and rifampin may decrease the plasma concentration of estrogens, possibly resulting in a decrease in therapeutic effects and/or changes in the uterine bleeding profile. Inhibitors of CYP3A4 such as erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir and grapefruit juice may increase the plasma concentration of estrogens and may result in side effects.
Read the Femring Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 6/12/2014
Additional Femring Information
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