Nomegestrol Acetate
A 19-norprogesterone-derived progestin with moderate anti-androgenic and no estrogenic or androgenic activity. Paired with estradiol in a monophasic combined contraceptive (Zoely/Naemis) and used in HRT and gynaecological indications.
01 Overview
Nomegestrol acetate (NOMAC) is a highly selective progestin derived from 19-norprogesterone. It has potent progestogenic and mild anti-androgenic activity without estrogenic, androgenic or glucocorticoid effects, and it strongly suppresses ovulation.
Its main modern use is in a combined oral contraceptive with 17-beta-estradiol (Zoely/Naemis), one of the few pills using bioidentical estradiol rather than ethinylestradiol, which may offer a more favourable metabolic and possibly thrombotic profile. It is also used in HRT and menstrual disorders.
02 Mechanism
Selective progesterone-receptor agonist with anti-androgenic activity and strong gonadotropin/ovulation suppression, with no significant estrogenic or androgenic action.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Combined contraceptive | 2.5–5 mg/day | Oral | 2.5 mg with estradiol (Zoely); 5 mg for gynaecological indications. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Ovulation suppression / contraceptionReliable ovulation inhibition in the estradiol-combined pill. | Clinical | ||
| Neutral metabolic profileEstradiol-based combination may spare lipids and clotting factors versus EE pills. | Observational |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Altered bleeding / amenorrhoeaAbsent or infrequent withdrawal bleeds are common. | Mild | Common | Clinical | |
| Meningioma (prolonged high-dose)Regulatory reviews flagged meningioma risk with prolonged high-dose use (as with related progestins). | Severe | Rare, dose-dependent | Observational |