Elagolix, an orally active non-peptidic GnRH antagonist, has been approved by 
the Food and Drug Administration for the management of moderate to severe pain 
associated with endometriosis. As the degree of ovarian suppression obtained 
with elagolix is dose-dependent, pain relief may be achieved by modulating the 
level of hypo-oestrogenism while limiting side effects. Elagolix may thus be 
considered a novelty in terms of its endocrine and pharmacological properties 
but not for its impact on the pathogenic mechanisms of endometriosis, as the 
target of this new drug is, yet again, alteration of the hormonal milieu. Given 
the oestrogen-dependent nature of endometriosis, a reduction of side effects may 
imply a proportionate decrease in pain relief. Furthermore, if low elagolix 
doses are used, ovulation is not consistently inhibited, and patients should use 
non-hormonal contraceptive systems and perform serial urine pregnancy tests to 
rule out unplanned conception during periods of treatment-induced amenorrhoea. 
If high elagolix doses are used to control severe pain for long periods of time, 
add-back therapies should be added, similar to that prescribed when using GnRH 
agonists. To date, the efficacy of elagolix has only been demonstrated in 
placebo-controlled explanatory trials. Pragmatic trials comparing elagolix with 
low-dose hormonal contraceptives and progestogens should be planned to verify 
the magnitude of the incremental benefit, if any, of this GnRH antagonist over 
currently used standard treatments. The price of elagolix may impact on patient 
adherence and, hence, on clinical effectiveness. In the USA, the manufacturer 
AbbVie Inc. priced elagolix (OrilissaTM) at around $10 000 a year, i.e. $845 per 
month. When faced with unaffordable treatments, some patients may choose to 
forego care. If national healthcare systems are funded by the tax payer, the 
approval and the use of a new costly drug to treat a chronic condition, such as 
endometriosis, means that some finite financial resources will be diverted from 
other areas, or that similar patients will not receive the same level of care. 
Thus, defining the overall 'value' of a new drug for endometriosis also has 
ethical implications, and trade-offs between health outcomes and costs should be 
carefully weighed up.