How Does Lizinna Work in the Body
Chemical Composition, Mechanism of Action & Metabolic Effects Explained
Key Takeaways: How Lizinna Works
- Active Ingredients: 250 µg norgestimate (progestogen) and 35 µg ethinylestradiol (oestrogen).
- Primary Actions: Prevents ovulation, thickens cervical mucus to block sperm, and alters endometrium to inhibit implantation.
- Onset & Duration: Full contraceptive effect after 7 days of correct use; each pill provides 24‑hour coverage.
- Metabolism: Norgestimate is a prodrug rapidly converted to active metabolites norelgestromin and levonorgestrel; both hormones undergo hepatic metabolism (CYP3A4) and renal/fecal excretion.
- Usage: Taken daily for 21 days followed by a 7‑day pill‑free break (withdrawal bleed).
Lizinna combines two hormones to prevent pregnancy by suppressing ovulation and creating barriers to sperm and implantation. This dual‑action provides highly effective, reversible contraception when taken correctly.
Important Medical Advice
Seek immediate medical help if you experience: sudden severe chest pain, breathlessness, coughing up blood (possible blood clot in lung); painful swelling or redness in one leg (DVT); severe headache, fainting, or vision loss (possible stroke); yellowing of skin/eyes (jaundice) or severe upper abdominal pain (liver problems).
Chemical Composition & Molecular Structure
Lizinna tablets contain two active pharmaceutical ingredients: norgestimate (a third‑generation progestogen) and ethinylestradiol (a synthetic oestrogen). Each uncoated blue tablet (diameter 6.4 mm, debossed '146' on one side) provides 250 micrograms norgestimate and 35 micrograms ethinylestradiol. The excipients include lactose anhydrous, lactose monohydrate, povidone K‑25, dl‑α‑tocopherol, microcrystalline cellulose, croscarmellose sodium, pregelatinised starch (Starch 1500), magnesium stearate, and indigo carmine aluminium lake (E 132) as colouring.
Structural Details
(8R,9S,10R,13S,14S,17R)-17-(acetyloxy)-13-ethyl-17-ethynyl-1,2,6,7,8,9,10,11,12,14,15,16-dodecahydrocyclopenta[a]phenanthren-3-one oxime
A prodrug with high progestogenic activity after metabolic conversion. Its 17α-ethinyl group delays hepatic inactivation, providing prolonged half‑life.
19-nor-17α-pregna-1,3,5(10)-trien-20-yne-3,17-diol
A synthetic oestrogen with an ethinyl group at C17 that slows metabolism, making it orally active and suitable for once‑daily dosing.
Key Pharmaceutical Properties
| Property | Norgestimate (prodrug) | Ethinylestradiol |
|---|---|---|
| Lipophilicity (logP) | ~3.9 (active metabolites) | ~3.7 |
| Protein binding | >97% (albumin, SHBG) | ~98% (albumin) |
| Oral bioavailability | High (prodrug fully converted) | ~45% (first‑pass effect) |
| Receptor affinity | High progesterone receptor (via norelgestromin) | High oestrogen receptor |
🗒️ Pharmaceutical insight: The lactose carrier ensures tablet integrity; the blue colour comes from indigo carmine (E 132), an approved food dye.
Mechanism of Action: Dual Hormonal Pathway
Lizinna exerts its contraceptive effect through three complementary mechanisms, typical of combined oral contraceptives.
- Ovulation suppression (primary): Ethinylestradiol inhibits hypothalamic GnRH secretion, reducing pituitary FSH and LH release. This prevents follicular development and the mid‑cycle LH surge, thereby inhibiting ovulation. Norgestimate (via its active metabolites) reinforces this negative feedback.
- Cervical mucus thickening: The progestogenic action of norelgestromin and levonorgestrel renders cervical mucus thick, scant, and tenacious, forming a physical barrier that impedes sperm penetration and migration.
- Endometrial alteration: The combination induces an atrophic, secretory endometrium that is unfavourable for implantation, providing a third layer of protection should fertilisation occur.
| Feature | Norgestimate (via metabolites) | Ethinylestradiol |
|---|---|---|
| Onset of action | Within hours (cervical mucus); full effect after 7 days | Gradual over first cycle |
| Peak effect | After 7 consecutive pills | After 7 consecutive pills |
| Duration | 24 hours (requires daily dosing) | 24 hours |
🗒️ Physiological insight: The 7‑day initiation rule is based on the time needed to reliably suppress ovarian activity. If starting on day 1 of menstruation, protection is immediate.
Absorption & Distribution (Pharmacokinetics)
Following oral administration, both hormones are rapidly and almost completely absorbed from the gastrointestinal tract. However, ethinylestradiol undergoes significant first‑pass metabolism in the gut wall and liver, reducing its systemic bioavailability to approximately 45%.
Norgestimate absorption
Norgestimate is rapidly hydrolysed to its primary active metabolite norelgestromin during absorption and first pass; peak plasma concentrations of norelgestromin occur 1–2 hours after dosing. A secondary metabolite, levonorgestrel, appears later.
Ethinylestradiol absorption
Peak plasma concentrations are reached within 1.5 hours. The volume of distribution is approximately 4 L/kg, indicating extensive tissue distribution.
Distribution
Both hormones are highly protein‑bound: ethinylestradiol binds to albumin; norelgestromin binds to albumin and sex hormone‑binding globulin (SHBG). Ethinylestradiol increases hepatic synthesis of SHBG, which may affect free hormone levels over time.
Metabolic Effects & Elimination
Norgestimate: Undergoes rapid first‑pass metabolism to norelgestromin (by hydrolysis of the oxime group) and further to levonorgestrel (by reduction and hydroxylation). These metabolites are primarily conjugated (glucuronide and sulphate) and excreted in urine and faeces. Less than 1% of norgestimate is excreted unchanged.
Ethinylestradiol: Metabolised mainly by CYP3A4 in the liver, undergoing aromatic hydroxylation to various hydroxylated metabolites, which are then methylated or conjugated. It also undergoes extensive conjugation (glucuronidation, sulphation) in the gut wall and liver. Enterohepatic recirculation occurs. Excretion is approximately 50% in urine and 35% in faeces, mostly as metabolites.
⚠️ Metabolic caution: CYP3A4 inducers (e.g., rifampicin, certain anticonvulsants) can accelerate ethinylestradiol metabolism, reducing contraceptive efficacy. Use of such drugs requires alternative or additional contraceptive measures.
Half‑life summary
| Compound | Half‑life |
|---|---|
| Ethinylestradiol | 12–18 hours |
| Norelgestromin | ~28 hours |
| Levonorgestrel | 20–30 hours |
Clinical Efficacy in Contraception
When taken correctly (no missed pills, consistent timing), the combined oral contraceptive pill has a Pearl Index of less than 1 (fewer than 1 pregnancy per 100 woman‑years). Typical use (including occasional omissions) yields a Pearl Index around 5–8. Lizinna is indicated for women of reproductive age. Efficacy is maintained during the 7‑day pill‑free interval, provided the preceding 21 pills were taken correctly.
In addition to contraceptive benefits, users often experience lighter, more regular withdrawal bleeds, reduced dysmenorrhoea, and decreased risk of ovarian and endometrial cancer with long‑term use. Non‑contraceptive benefits are supported by epidemiological data.
Important: Lizinna does not protect against sexually transmitted infections (STIs); consistent condom use is recommended for STI prevention.
Lizinna FAQs
How long does it take for Lizinna to become effective?
If started on day 1 of your period, protection is immediate. If started at any other time, use additional contraception (e.g., condoms) for the first 7 days.
Can I get pregnant if I miss one pill?
Missing one pill (less than 24 hours late) does not reduce protection. Take it as soon as you remember and continue the strip normally. No extra contraception needed.
What are the most common side effects of Lizinna?
Very common: headache, nausea, breakthrough bleeding, painful periods. Common: mood changes, breast tenderness, weight gain, acne. These often improve after 2–3 cycles.
Does Lizinna increase the risk of blood clots?
Like all combined pills, Lizinna carries a small increased risk of venous thromboembolism. The absolute risk remains low; your doctor will assess personal risk factors before prescribing.
Can I take Lizinna while breastfeeding?
Combined pills are generally not recommended during breastfeeding as oestrogen may reduce milk production. Progestogen‑only pills are preferred. Discuss with your doctor.
Need Lizinna with Expert Guidance?
If you are considering Lizinna for contraception, a UK‑registered doctor can review your medical history and provide a prescription online after a suitable consultation.
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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