How Does Femodette Work in the Body
Chemical Composition, Mechanism of Action & Metabolic Effects Explained
Key Takeaways: How Femodette Works
- Active Ingredients: Gestodene (75mcg, third-generation progestin) and Ethinylestradiol (20mcg, oestrogen).
- Triple Mechanism: Prevents pregnancy by inhibiting ovulation, thickening cervical mucus, and inducing endometrial atrophy.
- Onset & Duration: Peak serum levels within 1 hour; contraceptive protection is immediate if started on day 1 of cycle. Steady state reached in second half of treatment cycle.
- Metabolism: Gestodene metabolised in liver (reduction, hydroxylation); ethinylestradiol undergoes first-pass metabolism (CYP3A4). Excreted via urine and faeces.
- Protein Binding: Gestodene highly bound to SHBG (64%) and albumin; ethinylestradiol bound to albumin (98.5%).
Femodette combines two synthetic hormones—gestodene and ethinylestradiol—to provide reliable contraception by targeting the reproductive axis at multiple points: the brain, the cervix, and the uterine lining. This guide explains the precise pharmacological pathways behind its action.
Important Medical Advice
Femodette does not protect against HIV or STIs. Seek urgent medical attention if you experience signs of a blood clot: sudden swelling/pain in one leg, sudden chest pain, breathlessness, or severe headache. Do not take Femodette if you are pregnant or think you may be pregnant.
Chemical Composition & Molecular Structure
Femodette tablets contain two active pharmaceutical ingredients: gestodene (a progestogen) and ethinylestradiol (an oestrogen). The tablet core and coating include several excipients for stability and delivery [citation:5][citation:8].
Structural & Formulation Details
13β-Ethyl-18,19-dinor-17α-pregna-4,15-dien-20-yn-17β-ol-3-one
A third-generation progestin derived from 19-nortestosterone. It contains a unique δ15 double bond, which increases progestogenic potency and affects its binding to sex hormone-binding globulin (SHBG) [citation:1].
17α-Ethynylestra-1,3,5(10)-triene-3,17β-diol
A synthetic oestrogen with an ethinyl group at C17, which slows hepatic metabolism and allows oral activity. It is the standard oestrogen component in most combined oral contraceptives.
Excipients (Inactive Ingredients)
| Ingredient | Function |
|---|---|
| Lactose monohydrate | Filler/bulking agent |
| Maize starch | Disintegrant |
| Povidone | Binder |
| Magnesium stearate (E572) | Lubricant |
| Sucrose, Macrogol 6000 | Coating agents |
| Calcium carbonate (E170) | Coating filler |
| Talc, Montan glycol wax | Polishing/glazing agents |
🗒️ Pharmaceutical insight: Femodette contains lactose and sucrose; patients with rare hereditary sugar intolerance should consult their doctor before use [citation:4].
Mechanism of Action: Triple Contraceptive Pathway
Femodette prevents pregnancy through three complementary mechanisms, creating a multi‑layered barrier to conception [citation:3][citation:5][citation:8].
- Ovulation inhibition (primary mechanism): Gestodene and ethinylestradiol exert negative feedback on the hypothalamus and pituitary, suppressing GnRH pulsatility and reducing FSH and LH secretion. This prevents follicular development and abolishes the mid‑cycle LH surge, thus inhibiting ovulation [citation:2][citation:5].
- Cervical mucus thickening: Under the influence of gestodene, the cervical mucus becomes thick, viscid, and acellular, forming a physical barrier that impedes sperm penetration and migration [citation:4].
- Endometrial alteration: The endometrium becomes thin, atrophic, and unreceptive to implantation. Even if fertilisation were to occur (a rare event), the altered endometrium prevents implantation [citation:3].
| Target Site | Primary Hormone | Effect |
|---|---|---|
| Hypothalamus/Pituitary | Both | Suppression of GnRH/FSH/LH → no ovulation |
| Cervix | Gestodene | Thick, impenetrable mucus |
| Endometrium | Gestodene | Atrophic, non‑receptive lining |
| Fallopian tubes | Both | Altered motility disrupting gamete transport |
🗒️ Physiological insight: The triple action ensures high contraceptive efficacy (Pearl Index <1) even if one mechanism is partially compromised [citation:3].
Absorption & Distribution (Pharmacokinetics)
Both components are rapidly absorbed after oral administration, with distinct pharmacokinetic profiles influenced by first‑pass metabolism and protein binding [citation:2][citation:6].
Gestodene Absorption
Rapidly and completely absorbed; peak serum concentrations (~4 ng/ml) occur about 1 hour post‑dose. Bioavailability is exceptionally high (96‑99%) due to minimal first‑pass effect [citation:2][citation:6].
Ethinylestradiol Absorption
Rapidly absorbed; peak serum levels (~80 pg/ml) reached within 1‑2 hours. Absolute bioavailability is ~60% due to presystemic conjugation in gut mucosa and liver (first‑pass metabolism) [citation:2].
Protein Binding & Distribution
| Parameter | Gestodene | Ethinylestradiol |
|---|---|---|
| SHBG binding | ~64% | None |
| Albumin binding | ~34% | 98.5% |
| Free fraction | 1‑2% | 1.5% |
| Volume of distribution | 0.7 L/kg | 5 L/kg |
🗒️ Clinical note: Ethinylestradiol increases hepatic synthesis of SHBG, leading to a 3‑fold rise in SHBG during the cycle. This increases the bound fraction of gestodene, contributing to its accumulation at steady state [citation:2][citation:6].
Metabolic Pathways & Elimination
Gestodene metabolism: Completely metabolised via reduction and hydroxylation (CYP3A4). No unchanged gestodene is excreted. Metabolites are eliminated in urine and bile at a ratio of approximately 6:4, with a terminal half‑life of 12‑15 hours. Metabolic clearance rate: 0.8 ml/min/kg [citation:2].
Ethinylestradiol metabolism: Extensively metabolised by aromatic hydroxylation (CYP3A4) and conjugation to glucuronide and sulphate metabolites. The terminal half‑life is about 24 hours, with metabolites excreted in urine and bile (ratio 4:6). Metabolic clearance: 5 ml/min/kg [citation:2].
⚠️ Metabolic caution: Drugs that induce hepatic enzymes (e.g., rifampicin, carbamazepine, St John's Wort) can accelerate metabolism of both components, reducing contraceptive efficacy and increasing breakthrough bleeding risk [citation:4][citation:5].
Clinical Pharmacology & Receptor Profile
Gestodene exhibits a distinct receptor binding profile that contributes to its pharmacological effects and side effect profile [citation:1][citation:9].
| Receptor | Affinity (% vs reference) | Activity |
|---|---|---|
| Progesterone receptor (PR) | 90‑432% | Strong progestogenic (anti‑ovulatory) |
| Androgen receptor (AR) | 85% | Weak androgenic (acne, lipid effects) |
| Glucocorticoid receptor (GR) | 27‑38% | Minimal glucocorticoid activity |
| Mineralocorticoid receptor (MR) | 97‑290% | Weak antimineralocorticoid (mild diuretic effect) |
| Oestrogen receptor (ER) | 0% | No direct oestrogenic activity |
Ethinylestradiol is a potent oestrogen receptor agonist, responsible for cycle control, increased SHBG, and beneficial effects on bone mineral density [citation:9].
Steady‑State Kinetics
During a 21‑day cycle, gestodene serum levels increase approximately 4‑fold, reaching steady state in the second half of the cycle due to SHBG elevation. Ethinylestradiol reaches steady state after 3‑4 days (30‑40% higher than single dose) [citation:2][citation:6].
Femodette FAQs
How long does it take for Femodette to start working?
If started on day 1 of your period, protection is immediate. If started any other day, use additional contraception (e.g., condoms) for the first 7 days [citation:3][citation:8].
What makes gestodene different from other progestins?
Gestodene is a third‑generation progestin with very high progestogenic potency, high bioavailability (~99%), and a unique δ15 double bond that influences SHBG binding. It has lower androgenicity than second‑generation progestins [citation:1][citation:9].
Does Femodette cause weight gain or acne?
Weight gain is reported uncommonly. Acne may improve due to the anti‑androgenic effect of increased SHBG (which binds free testosterone) and low androgenic activity of gestodene [citation:1][citation:9].
How does Femodette affect the menstrual cycle?
It creates a regular 28‑day cycle (21 active pills, 7 placebo). Periods usually become lighter, less painful, and more predictable due to endometrial thinning [citation:3][citation:4].
Can I take Femodette if I smoke?
Smoking increases the risk of serious cardiovascular side effects, especially over age 35. If you smoke and are over 35, your doctor will likely advise against combined contraceptives [citation:5][citation:8].
Need Femodette with Expert Guidance?
If you are considering Femodette, a UK‑registered doctor can assess your medical history and suitability online.
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Clinical References & Sources
Medical Content Manager
Nabeel is a co-founder, and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
Medical Doctor
Dr. Feroz is a GMC-registered doctor and a medical reviewer at Chemist Doctor. He oversees acute condition and urgent care guidance.
Medical Director
Usman is a co-founder, and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 15 March 2026
Next Review: 15 September 2026
Published on: 15 March 2026
Last Updated: 15 March 2026