Switching the 3.75 mg triptorelin depot injection from every 4 weeks to every 6 weeks still controls pain from endometriosis just as well, but cuts the drug cost by about a third (roughly €744 a year). The review found solid data for this schedule in 4 studies involving 171 women, while other cheaper dosing ideas lacked clear evidence.

Is it possible to reduce the cost of GnRH agonist treatment for endometriosis by using non-standard dosing regimens? An extended-interval dosing regimen of a 3.75 mg depot formulation of triptorelin injected every 6 weeks instead of every 4 weeks reduces the cost by one-third without compromising the effect on pain relief. Cost constitutes a limit to prolonged GnRH agonists use. Alternative modalities to reduce the economic burden of GnRH agonist treatment have been anecdotally attempted. A systematic review was conducted to evaluate and compare the effect of three alternative modalities for GnRH use in women with endometriosis, i.e. intermittent oestrogen deprivation therapy, reduced drug dosage, and extended-interval dosing regimens of depot formulations. A PubMed and Embase search was initially conducted in October 2022 and updated in January 2023 using the following search strings: (endometriosis OR adenomyosis) AND (GnRH-agonists OR gonadotropin-releasing hormone agonists OR triptorelin OR leuprorelin OR goserelin OR buserelin OR nafarelin). Full-length articles published in English in peer-reviewed journals since 1 January 1980, and reporting original data on GnRH agonist treatment of pain symptoms associated with endometriosis were selected. Information was extracted on study design, GnRH-agonist used, dosage, total duration of therapy, side effects, treatment adherence, and pelvic pain relief. Reviews, commentaries, conference proceedings, case reports, and letters to the editor were excluded. Of the 1664 records screened, 14 studies regarding clinical outcomes associated with the 3 considered alternative modalities for GnRH agonist use were eventually included (intermittent oestrogen deprivation therapy, n = 2; low-dose or 'draw-back' therapy, n = 8; extended-interval dosing regimen, n = 4). Six studies were randomized controlled trials (RCTs) (double blind, n = 2) and eight adopted a prospective cohort design (non-comparative, n = 6; comparative, n = 2). A total of 776 women with endometriosis were recruited in the above studies (intermittent oestrogen deprivation therapy, n = 77; low-dose or 'draw-back' therapy, n = 528; extended-interval dosing regimen, n = 171). Robust data demonstrating cost saving without detrimental clinical consequences were available for the extended-interval dosing regimen only. In particular, the 3.75 mg triptorelin depot preparation inhibits ovarian function for a longer period compared with the 3.75 mg leuprorelin depot preparation, allowing injections every 6 instead of 4 weeks. Based on the cost indicated by the Italian Medicine Agency for the 3.75 mg triptorelin depot preparation, this would translate in a yearly saving of €744.60 (€2230.15-€1485.55; -33.4%). The quality of the evidence reported in the selected articles was not formally evaluated and a quantitative synthesis could not be performed. Some studies were old and the tested therapeutic approaches were apparently obsolete. Only cost containment associated with GnRH analogue use, and not cost-effectiveness, has been addressed. Consuming less resources without negatively impacting on health outcomes carries ethical and practical implications for individuals and the community, as this approach may result in overall increased healthcare access. This study was supported by the Italian Ministry of Health (Ricerca Corrente 2023, IRCCS Ca' Granda Ospedale Maggiore Policlinico Milano). E.S. discloses payments from Ferring for research grants and honoraria from Merck-Serono for lectures. All other authors declare they have no conflict of interest. N/A.