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Mechanism Of Action
When taken immediately before ovulation is to occur, ella postpones follicular rupture. The likely primary mechanism of action of ulipristal acetate for emergency contraception is therefore inhibition or delay of ovulation; however, alterations to the endometrium that may affect implantation may also contribute to efficacy.
Ulipristal acetate is a selective progesterone receptor modulator with antagonistic and partial agonistic effects (a progesterone agonist/antagonist) at the progesterone receptor. It binds the human progesterone receptor and prevents progesterone from occupying its receptor.
The pharmacodynamics of ulipristal acetate depends on the timing of administration in the menstrual cycle. Administration in the mid-follicular phase causes inhibition of folliculogenesis and reduction of estradiol concentration. Administration at the time of the luteinizing hormone peak delays follicular rupture by 5 to 9 days. Dosing in the early luteal phase does not significantly delay endometrial maturation but decreases endometrial thickness by 0.6 ± 2.2 mm (mean ± SD).
Following a single dose administration of ella in 20 women under fasting conditions, maximum plasma concentrations of ulipristal acetate and the active metabolite, monodemethyl-ulipristal acetate, were 176 and 69 ng/ml and were reached at 0.9 and 1 hour, respectively.
Figure 1: Mean (± SD) Plasma
Concentration-time Profile of Ulipristal Acetate and Monodemethyl-ulipristal
Acetate Following Single Dose Administration of 30 mg Ulipristal Acetate
Table 2: Pharmacokinetic
Parameter Values Following Administration of ella (ulipristal acetate) Tablet
30 mg to 20 Healthy Female Volunteers under Fasting Conditions
|Mean (± SD)|
|C max (ng/ml)||AUC0-t (ng•hr/ml)||AUC0-∞ (ng•hr/ml)||tmax (hr)*||t½ (hr)|
|Ulipristal acetate||176 (89)||548 (259)||556 (260)||0.9 (0.5-2.0)||32 (6.3)|
|Monodemethyl-ulipristal acetate||69 (26)||240 (59)||246 (59)||1.00 (0.8-2.0)||27 (6.9)|
|Cmax = maximum concentration
AUC0-t = area under the drug concentration curve from time 0 to time of last determinable concentration
AUC0-∞ = area under the drug concentration curve from time 0 to infinity
tmax = time to maximum concentration
t½ = elimination half-life
* Median (range)
Effect of food: Administration of ella together with a high-fat breakfast resulted in approximately 40 -45% lower mean Cmax, a delayed tmax (from a median of 0.75 hours to 3 hours) and 20 -25% higher mean AUC0-∞ of ulipristal acetate and monodemethyl-ulipristal acetate compared with administration in the fasting state. These differences are not expected to impair the efficacy or safety of ella to a clinically significant extent; therefore, ella can be taken with or without food.
Ulipristal acetate is metabolized to mono-demethylated and di-demethylated metabolites. In vitro data indicate that this is predominantly mediated by CYP3A4. The mono-demethylated metabolite is pharmacologically active.
The terminal half-life of ulipristal acetate in plasma following a single 30 mg dose is estimated to 32.4 ± 6.3 hours.
CYP3A4 inducers: When a single 30 mg dose of ulipristal acetate was administered following administration of the strong CYP3A4 inducer, rifampin 600 mg once daily for 9 days, Cmax and AUC of ulipristal acetate decreased by 90% and 93% respectively. The Cmax and AUC of monodemethyl-ulipristal acetate decreased by 84% and 90% respectively [see DRUG INTERACTIONS].
CYP3A4 inhibitors: When a single 10 mg dose of ulipristal acetate was administered following administration of the strong CYP3A4 inhibitor, ketoconazole 400 mg once daily for 7 days, Cmax and AUC of ulipristal acetate increased by 2and 5.9-fold, respectively. While the AUC of monodemethyl-ulipristal acetate increased by 2.4-fold, Cmax of monodemethyl-ulipristal acetate decreased by 47%. There was no in vivo drug-drug interaction study between ulipristal acetate 30 mg and CYP3A4 inhibitors [see DRUG INTERACTIONS].
P-glycoprotein (P-gp) transporters: When a single 60 mg dose of fexofenadine, a substrate of P-gp glycoprotein, was administered 1.5 hours after the administration of a single 10 mg dose of ulipristal acetate, there was no increase in Cmax or AUC of fexofenadine.
Two multicenter clinical studies evaluated the efficacy and safety of ella. An open-label study provided the primary data to support the efficacy and safety of ulipristal acetate for emergency contraception when taken 48 to 120 hours after unprotected intercourse. A single-blind comparative study provided the primary data to support the efficacy and safety of ulipristal acetate for emergency contraception when taken 0 to 72 hours after unprotected intercourse and provided supportive data for ulipristal acetate for emergency contraception when taken > 72 to 120 hours after unprotected intercourse. Women in both studies were required to have a negative pregnancy test prior to receiving emergency contraception. The primary efficacy analyses were performed on subjects less than 36 years of age who had a known pregnancy status after taking study medication.
Table 3: Summary of Clinical Trial Results for Women
Who Received a Single Dose of ella (30 mg Ulipristal Acetate)
|Open-Label Study 48 to 120 Hours *
N = 1,242
|Single-Blind Comparative Study 0 to 72 Hours *
N = 844
|Expected Pregnancy Rate **||5.5||5.6|
|Observed Pregnancy Rate ** (95% confidence interval)||2.2 (1.5, 3.2)||1.9 (1.1, 3.1)|
|* Time after unprotected
intercourse when ella was taken
** Number of pregnancies per 100 women at risk for pregnancy
This study was a multicenter open-label trial conducted at 40 family planning clinics in the United States. Healthy women with a mean age of 24 years who requested emergency contraception 48 to 120 hours after unprotected intercourse received a dose of 30 mg ulipristal acetate (ella). The median BMI for the study subjects was 25.3 and ranged from 16.1 to 61.3 kg/m² .
Twenty-seven pregnancies occurred in 1,242 women aged 18 to 35 years evaluated for efficacy. The number of pregnancies expected without emergency contraception was calculated based on the timing of intercourse with regard to each woman's menstrual cycle. ella statistically significantly reduced the pregnancy rate, from an expected rate of 5.5% to an observed rate of 2.2%, when taken 48 to 120 hours after unprotected intercourse.
Single-Blind Comparative Study
This study was a multicenter, single-blind, randomized comparison of the efficacy and safety of 30 mg ulipristal acetate (ella) to levonorgestrel (another form of emergency contraception). Subjects were enrolled at 35 sites in the U.S., the United Kingdom and Ireland, with the majority (66%) having been enrolled in the U.S. Healthy women with a mean age of 25 years who requested emergency contraception within 120 hours of unprotected intercourse were enrolled and randomly allocated to receive ella or levonorgestrel 1.5 mg. The median BMI for the study subjects was 25.3 and ranged from 14.9 to 70.0 kg/m² .
In the ella group, 16 pregnancies occurred in 844 women aged 16 to 35 years when emergency contraception was taken 0 to 72 hours after unprotected intercourse. The number of pregnancies expected without emergency contraception was calculated based on the timing of intercourse with regard to each woman's menstrual cycle; ella statistically significantly reduced the pregnancy rate, from an expected 5.6% to an observed 1.9%, when taken within 72 hours after unprotected intercourse. There were no pregnancies observed in the women who were administered ella more than 72 hours after unprotected intercourse (10% of women who received ella).
Data from the two studies were pooled to provide a total efficacy population of women treated with ulipristal acetate up to 120 hours after UPI. Time Trend analysis for the five 24-hour intervals from 0 to 120 hours between unprotected intercourse and treatment was conducted. There were no significant differences in the observed pregnancy rates across the five time intervals.
Subgroup analysis of the pooled data by BMI showed that for women with BMI > 30 kg/m² (16% of all subjects), the observed pregnancy rate was 3.1% (95% CI: 1.7, 5.7), which was not significantly reduced compared to the expected pregnancy rate of 4.5% in the absence of emergency contraception taken within 120 hours after unprotected intercourse. In the comparative study, a similar effect was seen for the comparator emergency contraception drug, levonorgestrel 1.5 mg. For levonorgestrel, when used by women with BMI > 30 kg/m², the observed pregnancy rate was 7.4% (95% CI: 3.9, 13.4), compared to the expected pregnancy rate of 4.4% in the absence of emergency contraception taken within 72 hours after unprotected intercourse.
Last reviewed on RxList: 6/30/2014
This monograph has been modified to include the generic and brand name in many instances.
Additional Ella Information
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