Source: Alfred Pasieka / Science Photo Library
Polarised light micrograph of crystals of estradiol, the active ingredient of oral contraceptive Zoely
Estradiol-containing oral contraceptive Zoely cannot be recommended over established combined oral contraceptives (COC), according to the authors of an evidence summary in Drug and Therapeutics Bulletin (DTB)1.
Zoely, marketed by MSD, is taken as an extended regimen of 24 active and 4 inactive tablets. It has not been shown to be safer than other COCs, has not been compared with Bayer’s Qlaira (another extended regimen COC, with 26 active and 2 inactive tablets) and is more expensive than most other COCs.
It is also unclear whether the lighter, shorter or absent withdrawal bleeds with Zoely will prove acceptable to women used to the bleed pattern associated with other COCs, they say.
Zoely is the second extended-regimen COC to be licensed in the UK, after Qlaira. It delivers 17β-estradiol, which is structurally identical to endogenous oestrogen, and is taken for 24 days followed by a four-day inactive pill interval (most other combined oral contraceptives are taken as 21/7 regimens). Unlike Qlaira, which follows a quadraphasic regimen, Zoely is monophasic, meaning that all active pills contain the same dose of estradiol (as hemihydrate) and progestogen (as nomegestrol acetate).
The DTB review notes that a shorter inactive-tablet interval is claimed to result in a greater margin of contraceptive efficacy. In two large clinical trials, contraceptive efficacy with Zoely was comparable to Yasmin (drospirenone/ethinylestradiol) when taken on a standard 21-day regimen.
In trials, women taking Zoely experienced lighter and fewer, absent or irregular withdrawal bleeds compared with women taking Yasmin. In addition, acne and weight gain were more frequently reported by users of Zoely than users of Yasmin.
Women will need to be counselled about the pattern of vaginal bleeding with Zoely, say the review authors. Zoely users may find the instructions on what to do if they forget to take a tablet complicated to follow — the action required depends on when the tablet is missed. Zoely costs £5.50 per cycle, compared with £4.90 for Yasmin and £8.39 for Qlaira.
References
- Zoely: a new combined oral contraceptive. Drug and Therapeutics Bulletin 2014;52:90–93. Available from: doi: 10.1136/dtb.2014.8.0270
