Synphase

Most combined pills deliver the same hormone dose in every tablet throughout the active course. Synphase does not. The progestogen dose changes twice across the 21-tablet cycle, stepping up in the middle and back down again at the end, while the oestrogen stays constant throughout. This graduated approach places Synphase in the triphasic category alongside Logynon — but the two pills use different progestogens and different dose architectures, making them clinically distinct preparations.

Synphase contains norethisterone as its progestogen and ethinylestradiol 35 micrograms as the fixed oestrogen. It is licensed in the United Kingdom for the prevention of pregnancy and is manufactured by Pfizer Limited. The triphasic design means the pack must be taken in strict colour-coded sequence — and unlike monophasic pills, the tablets you take in week one are not the same as those you take in week three. This page explains the clinical rationale for the triphasic structure, how Synphase compares to norethisterone monophasic alternatives, and what you need to know before starting a consultation./p>

Synphase is a triphasic combined oral contraceptive. Triphasic means the pack contains three distinct tablet types, each delivering a different dose of the progestogen component. The oestrogen dose – ethinylestradiol 35 micrograms – is identical in every tablet across all three phases. The progestogen – norethisterone – changes.

The pack contains 21 tablets in two colours, arranged in a three-phase sequence:

The blue tablets that open and close the pack contain 500 micrograms of norethisterone each. The white tablets in the middle phase contain 1 milligram. This means you are taking a lower progestogen dose at the start of the cycle, a higher dose during the main active phase, and returning to the lower dose at the end. The oestrogen remains constant throughout all 21 days.

Norethisterone is a first-generation synthetic progestogen. It appears in several other contraceptive preparations at this site – Norimin at 1 mg per tablet, Brevinor at 500 mcg per tablet, and Noriday at 350 mcg in the progestogen-only formulation. Synphase is the only triphasic preparation using norethisterone in UK licensed contraceptives. Logynon is the other triphasic combined pill available at Pharmacy Planet, but it uses levonorgestrel rather than norethisterone.

The contraceptive mechanisms in Synphase are shared with all combined pills: ovulation suppression, cervical mucus thickening, and endometrial change. What is specific to Synphase is how those mechanisms are achieved through a variable progestogen dose rather than a fixed one.

The Variable Norethisterone Logic

In a standard monophasic combined pill, the same dose of progestogen is delivered every day throughout the active phase. In Synphase, the lower norethisterone dose at the start of the cycle (phase 1, 500 mcg) is sufficient to establish cervical mucus thickening and begin ovulation suppression. The higher dose in phase 2 (1 mg) maintains and deepens the suppressive effect during the central active phase. The return to 500 mcg in phase 3 allows a more controlled hormonal decline as the end of the cycle approaches, supporting a predictable withdrawal bleed during the seven-day break.

The oestrogen component remains fixed across all three phases. Ethinylestradiol 35 micrograms acts jointly with norethisterone to suppress the pituitary hormones – follicle-stimulating hormone and luteinising hormone – that drive ovulation. Without the luteinising hormone surge, the ovary does not release an egg.

Cervical Mucus and Endometrial Effects

Norethisterone thickens the cervical mucus from the first tablet onwards. Even during phase 1, when the norethisterone dose is at its lower level, the mucus-thickening effect is active and provides secondary contraceptive protection. The endometrial lining is also altered by the combined hormonal environment, reducing its receptivity to implantation throughout the cycle.

The Withdrawal Bleed on Synphase

After the 21st active tablet, both ethinylestradiol and norethisterone clear from circulation. The drop in hormone levels triggers a withdrawal bleed during the seven-day break. Because Synphase ends with a lower norethisterone phase rather than abruptly cutting off from the highest dose, the hormonal descent into the break is somewhat more graduated than in a flat-dose monophasic pill. Some women find this produces a more predictable bleed pattern, though individual responses vary and this cannot be guaranteed.

Synphase must be taken in the exact sequence printed on the blister strip. The two tablet colours represent three phases – and taking a phase 2 white tablet when you should be on phase 1 blue tablets, or vice versa, disrupts the intended hormonal pattern. The strips are clearly labelled. Follow the arrows.

Starting for the First Time

Begin on day 1 of your period with the first blue phase 1 tablet. Starting on day 1 gives immediate contraceptive protection. If you start between days 2 and 5, use barrier contraception for the first seven days.

Switching from a monophasic combined pill: take your first Synphase tablet the day after the last active tablet of the previous pack. If your previous pill included inactive placebo tablets, start after the last one. Protection is continuous with no gap.

Switching from another triphasic pill such as Logynon: take the first Synphase tablet the day after the last active tablet from the Logynon pack. Note that Logynon uses levonorgestrel; Synphase uses norethisterone. These are different progestogens with different receptor profiles. A prescriber will confirm whether switching is appropriate before the change takes place.

Switching from a progestogen-only pill: start Synphase on any day and use barrier contraception for seven days.

The 21-Day Course

One tablet every day in sequence for 21 consecutive days. After the 21st tablet, stop for seven days. Begin the new pack on day 29. The seven-day break must be exactly seven days. A break longer than seven days risks follicle development beginning before the new pack re-establishes suppression. Do not wait for the withdrawal bleed to finish before restarting.

Missed Tablets

Under 24 hours late: take the missed tablet immediately. Continue the pack in sequence. Protection is maintained.

More than 24 hours late: take the missed tablet immediately. Take the next one at the usual time, even if two fall on the same day. Continue the pack in sequence. Use barrier contraception for seven days.

Two or more consecutive tablets missed: take only the most recently missed tablet. Discard the others. Continue the pack in correct sequence. Use condoms for seven days. If missed tablets were in week one and unprotected sex occurred in the preceding seven days, contact your prescriber or pharmacist about emergency contraception without delay.

Because Synphase is triphasic, the phase in which tablets are missed matters. Always refer to the Patient Information Leaflet for Synphase specifically when dealing with a missed tablet situation, particularly if it involves a phase change point.

Synphase delivers norethisterone across two dose levels within a single 21-tablet pack, with ethinylestradiol fixed at 35 micrograms throughout. The full phase-by-phase composition is shown below:

Total norethisterone across the 21-day course: (7 x 500 mcg) + (9 x 1,000 mcg) + (5 x 500 mcg) = 3,500 + 9,000 + 2,500 = 15,000 micrograms (15 milligrams).

Total ethinylestradiol across the 21-day course: 21 x 35 mcg = 735 micrograms.

Synphase Versus Norethisterone Monophasic Alternatives

Three other combined pills at Pharmacy Planet use norethisterone at fixed doses: Norimin (1 mg + ethinylestradiol 35 mcg) and Brevinor (500 mcg + ethinylestradiol 35 mcg). Synphase delivers both of these doses within a single pack, using 500 mcg in phases 1 and 3 and 1 mg in phase 2. A prescriber comparing these preparations may choose Synphase when a graduated norethisterone profile is preferred over a fixed dose, particularly for women who have experienced progestogenic side effects at the full 1 mg monophasic dose.

No Generic Equivalent

Synphase does not have a generic equivalent in the current UK market. It is manufactured by Pfizer Limited. Supply difficulties should be discussed with your prescriber, who may need to consider a clinically comparable alternative.

Synphase shares the general side effect profile of combined oral contraceptives, with some specific considerations arising from the norethisterone progestogen and the triphasic dose structure.

Norethisterone and Androgenic Activity

Norethisterone is a first-generation progestogen with mild androgenic activity. It binds weakly to androgen receptors in addition to progesterone receptors. For most women taking Synphase, this has no observable consequence. In women with androgen-sensitive skin, it may contribute to acne or oiliness, particularly in the higher-dose phase 2 portion of the cycle. If you have previously experienced androgen-related skin effects on norethisterone-containing preparations, discuss this with your prescriber before starting Synphase.

Bleeding Pattern and Phase-Change Effects

Some women experience spotting or irregular bleeding during the first one to three cycles of Synphase. This is more common in triphasic preparations than in monophasic pills because the dose transitions at phase change points can occasionally cause brief endometrial instability. This usually settles as the body adjusts to the triphasic pattern. Persistent spotting beyond three cycles warrants a prescriber review.

Common Side Effects

1. Headache
2. Nausea, particularly in the first few weeks
3. Breast tenderness
4. Mood changes, including low mood
5. Changes in libido
6. Changes in vaginal discharge

Less Common Effects

1. Weight changes
2. Contact lens intolerance
3. Chloasma: skin darkening on the face, worsened by sun exposure

Serious Signs Requiring Immediate Action

Stop taking Synphase and get urgent medical help if you notice:

1. Sudden chest pain, difficulty breathing, or coughing up blood
2. Swelling, heat, redness, or pain in one leg
3. A sudden severe headache unlike your usual headaches, or any loss of vision, slurred speech, or one-sided weakness
4. Severe acute abdominal pain
5. Yellowing of the skin or whites of the eyes

Blood Clot Risk

All combined pills raise VTE risk above the baseline for women not using hormonal contraception. Norethisterone-containing combined pills including Synphase sit in the same general VTE risk category as levonorgestrel-based preparations, which MHRA guidance places below the risk associated with third-generation progestogen pills. The oestrogen dose in Synphase is 35 micrograms, which is within the standard combined pill range. Your prescriber assesses your individual risk factors before any prescription is issued.

Drug Interactions

Enzyme-inducing medicines reduce the circulating levels of both ethinylestradiol and norethisterone, compromising contraceptive effectiveness. These include rifampicin, several antiepileptic medicines including phenytoin, carbamazepine, phenobarbital, and topiramate, some HIV antiretrovirals, and St John's Wort. Declare every medicine, supplement, and herbal product at every consultation.

Eligibility for Synphase covers both the standard combined pill checklist and a consideration specific to its triphasic format: whether you can reliably take tablets in the correct sequence every day.

Synphase Is Not Suitable If You:

1. Have ever had a blood clot: DVT, pulmonary embolism, stroke, or heart attack
2. Have migraine with aura: an absolute contraindication to all oestrogen-containing combined pills
3. Have uncontrolled high blood pressure
4. Have liver disease, liver tumours, or a history of pill-related jaundice
5. Have or have had breast cancer or any oestrogen-sensitive malignancy
6. Are pregnant
7. Are breastfeeding a baby under six weeks old
8. Smoke and are aged 35 or older
9. Have diabetes with established vascular complications

Synphase May Be Appropriate If You:

1. Are a healthy adult woman with no contraindications to oestrogen-containing contraception
2. Have previously experienced progestogenic side effects such as mood changes or acne at the full 1 mg norethisterone dose in Norimin, and a prescriber is considering whether a graduated dose pattern may produce better tolerability
3. Are already established on Synphase and are seeking a continuation prescription
4. Can reliably follow a colour-coded tablet sequence every day and understand that Synphase tablets are not interchangeable between phases
5. Have no personal or family history suggesting elevated VTE risk

Talk to Your Prescriber First If You:

1. Smoke and are under 35
2. Have a BMI above 30
3. Have a first-degree family member who had a blood clot before the age of 50
4. Have migraines of any type
5. Have previously experienced androgenic skin effects on norethisterone-containing preparations
6. Are planning long-haul travel or a period of extended immobility
7. Have a history of depression or are currently receiving treatment for a mood disorder

A prescription for Synphase at Pharmacy Planet requires a clinical consultation reviewed by a registered prescriber. Synphase is not a first-line prescription. It occupies a specific clinical space: the norethisterone triphasic combined pill for women for whom a variable progestogen dose is considered preferable to a fixed one.

The prescriber's assessment for Synphase is not simply whether you are eligible for a combined pill. It also covers whether the triphasic norethisterone format is appropriate for your specific circumstances, whether you have previously tolerated norethisterone at the 1 mg and 500 mcg doses, and whether you can manage the sequence-dependent dosing that Synphase requires. A woman who finds pill-taking formats involving multiple tablet types difficult to maintain consistently may be better suited to a monophasic preparation.

The outcome may be a prescription for Synphase, a recommendation for a norethisterone monophasic alternative such as Norimin or Brevinor, a suggestion to consider a different progestogen class, a request for more information, or a referral for a face-to-face review. Completing the questionnaire opens the clinical conversation. It does not determine the outcome. Repeat prescriptions are reviewed individually with no automatic renewal.

Store Synphase below 25°C, away from direct heat, light, and humidity. The original blister strip is essential for this preparation: it shows the day-by-day sequence across all three phases, with colour coding to distinguish phase 1 and 3 blue tablets from phase 2 white tablets. Removing tablets from the blister strip in bulk increases the risk of taking the wrong tablet at the wrong phase point. Keep tablets in the strip until the moment you take them.

Store out of reach of children. Check the expiry date on the outer carton before each new pack. Return unused or expired tablets to any UK pharmacy for safe disposal under Duty of Care regulations.

This reference guide compares the contraceptive preparations available at Pharmacy Planet, grouped by delivery method and formulation type. Every preparation is a Prescription Only Medicine. A registered prescriber will review your individual health profile, contraceptive history, and risk factors before recommending any preparation. This table is a clinical reference, not a recommendation.

Multiphasic combined pills change hormone doses at defined points across the active tablet course. The table below compares the triphasic and quadriphasic preparations available at Pharmacy Planet by progestogen stepping, oestrogen stepping, VTE risk, and key distinguishing features.

Important: This comparison is for general information only and does not replace medical advice. A prescriber will decide which treatment is suitable for you following an online consultation.

Synphase is not a pill that suits every woman who is eligible for combined hormonal contraception. Its triphasic norethisterone structure makes it appropriate for a defined clinical context: women for whom a graduated progestogen dose offers better tolerability than either of the fixed-dose norethisterone alternatives. Arriving at that decision requires a prescriber who has read your history with norethisterone-containing preparations and considered whether Synphase's specific dose pattern addresses your previous experience.

At Pharmacy Planet, every Synphase consultation is reviewed by a registered prescriber who makes that clinical judgement individually. If Synphase is not the right preparation for your profile, the prescriber will say so and explain which alternative is more appropriate for you.

• Pfizer Limited. Synphase tablets – Summary of Product Characteristics. Available at: www.medicines.org.uk/emc. Accessed May 2026.
• Faculty of Sexual and Reproductive Healthcare (FSRH). Combined Hormonal Contraception – Clinical Guidance. Available at: www.fsrh.org. Accessed May 2026.
• NHS. Combined pill – your contraception guide. Available at: www.nhs.uk/conditions/contraception/combined-contraceptive-pill. Accessed May 2026.
• British National Formulary (BNF). Ethinylestradiol with norethisterone. Available at: bnf.nice.org.uk. Accessed May 2026.
• MHRA. Combined hormonal contraceptives and venous thromboembolism. Available at: www.gov.uk. Accessed May 2026.