Elagolix
Elagolix is FDA approved for the treatment of pelvic pain caused by endometriosis. I reviewed the key studies resulting in FDA approval in the November 2018 issue of OBG Management.10
In the Elaris Endometriosis-I study, 872 women with endometriosis and pelvic pain were randomly assigned to treatment with 1 of 2 doses of elagolix (high-dose [200 mg twice daily] and low-dose [150 mg once daily]) or placebo.11 After 3 months of therapy, a clinically meaningful reduction in dysmenorrhea pain was reported by 76%, 46%, and 20% of the women in the high-dose elagolix, low-dose elagolix, and placebo groups, respectively (P<.001 for comparisons of elagolix to placebo). After 3 months of therapy, a clinically meaningful reduction in nonmenstrual pain or decreased or stable use of rescue analgesics was reported by 55%, 50%, and 37% of the women in the high-dose elagolix, low-dose elagolix, and placebo groups, respectively (P<.01 low-dose elagolix vs placebo and P<.001 high-dose elagolix vs placebo).
Hot flashes that were severe enough to be reported as an adverse event by the study participants were reported by 42%, 24%, and 7% of the women in the high-dose elagolix, low-dose elagolix, and placebo groups. Bone density was measured at baseline and after 6 months of treatment. Lumbar bone density changes were -2.61%, -0.32%, and +0.47% and hip femoral neck bone density changes were -1.89%, -0.39%, and +0.02% in the high-dose elagolix, low-dose elagolix, and placebo groups, respectively.
Another large clinical trial of elagolix for the treatment of pelvic pain caused by endometriosis, Elaris EM-II, involving 817 women, produced results very similar to those reported in Elaris EM-I. The elagolix continuation studies, Elaris EM-III and -IV, demonstrated efficacy and safety of elagolix through 12 months of treatment.12
In my 2018 review,10 I noted that elagolix dose adjustment can be utilized to attempt to achieve maximal pain relief with minimal vasomotor symptoms. Elagolix at 200 mg twice daily produces a mean estradiol concentration of 12 pg/mL, whereas elagolix at 150 mg daily resulted in a mean estradiol concentration of 41 pg/mL.13 The estrogen threshold hypothesis posits that in women with endometriosis a stable estradiol concentration of 20 to 30 pg/mL is often associated with decreased pain and fewer vasomotor events.14 To achieve the target estradiol range of 20 to 30 pg/mL, I often initiate elagolix treatment with 200 mg twice daily. This enables a rapid onset of amenorrhea and a reduction in pelvic pain. Once amenorrhea has been achieved and a decrease in pelvic pain has occurred, I adjust the dose downward to 200 mg twice daily on even calendar days of each month and 200 mg once daily on odd calendar days each month. Some women will have continued pain relief and amenorrhea when the dose is further decreased to 200 mg once daily. If bothersome bleeding recurs and/or pain symptoms increase in severity, the dose can be increased to 200 mg twice daily or an alternating regimen of 200 mg twice daily and 200 mg once daily, every 2 days. An alternative to dose adjustment is to combine elagolix with NEA, which can reduce the severity of hot flashes and reduce bone loss caused by hypoestrogenism.15,16
Health insurers and pharmacy benefits managers may require a prior authorization before approving and dispensing elagolix. The prior authorization process can be burdensome for clinicians, consuming limited healthcare resources, contributing to burnout and frustrating patients.17 Elagolix is less expensive than depot-leuprolide acetate and nafarelin nasal spray and somewhat more expensive than a goserelin implant.18,19
Elagolix is not approved as a contraceptive. In the Elaris EM-I and -II trials women were advised to use 2 forms of contraception, although pregnancies did occur. There were 6 pregnancies among 475 women taking elagolix 150 mg daily and 2 pregnancies among 477 women taking elagolix 200 mg twice daily.20 Women taking elagolix should be advised to use a contraceptive, but not an estrogen-progestin contraceptive.
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