Progestogen
Pregnancy: §4.6: Cyclogest should not be used during pregnancy except as indicated during the second and third trimesters to prevent preterm birth in high-risk pregnant women with a singleton pregnancy. There is limited and inconclusive data on the risk of congenital anomalies, including genital abnormalities in male or female infants, following intrauterine exposure. Lactation: progesterone is excreted in human milk and Cyclogest should not be used during breast-feeding.
Vaginal progesterone is a micronised natural progesterone delivered by the vaginal route, used for luteal-phase support in assisted reproduction and to reduce the risk of preterm birth in selected women.
Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.
Adult dose
Dose:Premenstrual syndrome and puerperal depression (first regimen in §4.2): 200 mg daily to 400 mg twice a day, by vaginal or rectal insertion.
Route: Vaginal insertion (the same product may also be given rectally for premenstrual syndrome/puerperal depression; the preterm-birth regimen in notes is vaginal only)
Frequency: Once daily up to twice daily, according to the dose used; for premenstrual syndrome, commence on day 14 of the menstrual cycle and continue until the onset of menstruation (commence on day 12 if symptoms are present at ovulation)
UK SPC for Cyclogest 200 mg pessaries (https://www.medicines.org.uk/emc/product/5568/smpc). SECOND LICENSED INDICATION — PREVENTION OF PRETERM BIRTH in high-risk pregnant women with a singleton pregnancy: 200 mg administered VAGINALLY ONCE A DAY AT BEDTIME, starting between 16 and 24 weeks and continued until at least 34 weeks of pregnancy, for women with either (a) a history of spontaneous preterm birth (up to 34+0 weeks of pregnancy) or mid-trimester loss (from 16+0 weeks of pregnancy onwards), or (b) a transvaginal ultrasound scan carried out between 16+0 and 24+0 weeks of pregnancy showing a cervical length of 25 mm or less. Before starting this indication, §4.4 requires shared decision making: the risks and benefits of all options with the potential to prevent preterm birth should be discussed and the treatment chosen jointly. After starting in pregnancy: any kind of vaginal bleeding should always be investigated; preterm premature rupture of membranes (PPROM) should be excluded, and if rupture of membranes occurs during treatment, further treatment should be discontinued (PPROM is a contraindication). Cyclogest is not indicated in threatened miscarriage, and treatment should be discontinued in the event of a missed miscarriage. ROUTE POINT FOR THE PREMENSTRUAL SYNDROME / PUERPERAL DEPRESSION INDICATION: §4.4 directs rectal use if barrier methods of contraception are being used. SPECIAL POPULATIONS: there is no experience with use in patients with impaired liver or renal function; no clinical data have been collected in patients over age 65. PAEDIATRIC: §4.2 states 'There is no relevant use of Cyclogest in the paediatric population', so no paediatric dose is recorded. DISCONTINUATION: §4.4 warns that abrupt discontinuation of progesterone dosing may cause increased anxiety, moodiness and increased sensibility to seizures. MONITORING: patients with a history of depression need to be closely observed (consider discontinuation if symptoms worsen); progesterone may cause some degree of fluid retention, so conditions that might be influenced by this (epilepsy, migraine, asthma, cardiac or renal dysfunction) require careful observation; diabetic patients should be carefully observed.
Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.
Contraindications
Hypersensitivity to the active substance or to any of the excipients (§4.3)
Undiagnosed vaginal bleeding
Known or suspected progesterone sensitive malignant tumours
Porphyria
Severe hepatic dysfunction or disease
Known missed abortion or ectopic pregnancy
Active arterial or venous thromboembolism or severe thrombophlebitis, or a history of these events
Preterm premature rupture of membranes (PPROM)
Side effects
Common — abdominal pain and abdominal discomfort
Common — breast pain
Common — application site soreness, and some leakage of the pessary base
Uncommon — somnolence
Not known — hypersensitivity reactions (e.g. rash, pruritus); menstruation may occur earlier than expected or, more rarely, be delayed; diarrhoea and flatulence may occur with rectal administration
Clinical monograph
How it works
It provides progestational support to the endometrium, promoting secretory transformation and maintaining a quiescent uterus to support early pregnancy.
Prescribing in practice
Vaginal use achieves high local endometrial exposure with first-uterine-pass targeting, but progesterone treatment must be stopped and pregnancy reassessed if signs of ectopic pregnancy, miscarriage or thromboembolism arise.
In threatened or recurrent miscarriage and in prevention of preterm birth it is used in defined groups following an individualised assessment in line with national guidance.
Local vaginal irritation or discharge is common, and absorption may be affected by concurrent intravaginal products.
Monitoring
Monitoring is largely clinical, following pregnancy viability and symptoms rather than routine progesterone levels.
Counselling the patient
Insert the pessary or gel high into the vagina as directed, and expect some discharge.
Continue treatment for the full course advised by your fertility or maternity team and do not stop abruptly without advice.
Report severe abdominal pain, heavy bleeding, or calf swelling and breathlessness urgently.
Evidence & guidelines
NICE guidance supports vaginal progesterone to reduce preterm birth in women with a short cervix or previous preterm birth, and the PRISM trial informed its use in early pregnancy bleeding with prior miscarriage.
Reference: PRISM Trial (Coomarasamy et al, NEJM 2019); ESHRE ART Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing.
The structured dose values shown have been reviewed by a clinician.
Monograph status: clinician-reviewed (2026-07-04).
Related
Curated clinical cross-links plus same-class fallbacks.
