Mercilon

What is Mercilon?

Mercilon is a combined oral contraceptive pill that contains two synthetic hormones, desogestrel (a progestogen) and ethinylestradiol (oestrogen). It is a type of reversible contraception that doesn't interrupt sex and can make periods lighter, more regular and less painful.

When used perfectly, Mercilon is over 99% effective at preventing an unwanted pregnancy. However, when typical use, such as missing pills or being sick or having severe diarrhoea, is taken into consideration, Mercilon is closer to being 91% effective. That means that 9 in 100 Mercilon users will get pregnant in a year.

Please be aware that Mercilon does not protect you against sexually transmitted infections (STIs). Only condoms are effective at preventing the spread of STIs.

How Does Mercilon Work?

Mercilon contains 150 micrograms (mcg) of desogestrel and 20 mcg of ethinylestradiol, which means it is a low-oestrogen pill. This may be a more suitable combined pill option for anyone who struggles to tolerate oestrogen or would prefer not to take a high dose. These synthetic hormones work together to prevent pregnancy by:

1. Stopping ovulation so your ovaries do not release a mature egg each month. This is Mercilon's main mechanism of action.
2. Thickening the cervical mucus to make it difficult for sperm to travel to the womb to fertilise an egg.
3. Thinning the womb lining so a fertilised egg cannot implant itself there.

How Do I Take Mercilon?

Mercilon is a 21-day pill; each strip contains 21 tablets, each marked with the day of the week. You should take one Mercilon pill every day at around the same time for 21 days, followed by a 7-day pill-free break.

During the 7 days in which you do not take Mercilon, you should have a withdrawal bleed similar to a period. On day 8, start a new strip of Mercilon pills.

When Should I Start Taking Mercilon?

If you are starting Mercilon for the first time, or are coming back after a break, take it on day 1 of your next period so you are protected against pregnancy straight away. Alternatively, if your period has already begun, wait until day 5 before commencing treatment and use extra contraception, such as condoms, until you have taken the first 7 pills correctly.

What Should I Do if I Forget to Take Mercilon?

If you miss a Mercilon pill, what you need to do depends on how late you are.

If it has been less than 12 hours since you should have taken your pill:

• Take the missed pill straight away and continue taking your pills as usual, even if that means taking 2 pills on the same day.
• You will still be protected against pregnancy.

If your last pill was more than 12 hours ago, or if you've missed more than one pill:

• Take the most recently missed pill right away
• Leave any earlier missed pills in the strip
• Take subsequent pills as usual. This may mean taking 2 in one day
• Use additional contraception for the next 7 days

Your next course of action will depend on the number of pills remaining in your current Mercilon pack.

7 or More Pills in the Pack:

• Use extra precautions, such as condoms, for the next 7 days
• When you've finished the strip, take the usual 7-day pill-free break before starting the next one

Fewer than 7 Pills in the Pack:

• Take additional precautions for the next 7 days
• When you've finished your current strip, start the next one the following day without taking a pill-free break
• If you don't have a withdrawal bleed after finishing the second strip, take a pregnancy test before beginning another strip

Should you miss one or more tablets from the first week of your strip (days 1 to 7) and have unprotected sex during that week, you could become pregnant. Contact a medical professional for advice as soon as possible, as they may recommend emergency contraception.

If you miss Mercilon pills and don't experience a withdrawal bleed during your first pill-free break, there's a chance you may be pregnant. Take a pregnancy test and consult your doctor as soon as possible.

Your protection may also be reduced if you delay starting a new strip of Mercilon pills or extend your 7-day break. If you have unprotected sex in the last 7 days in either of these circumstances, you may need emergency contraception. You should also consult a medical professional for further advice and use an additional form of contraception for 7 days.

What If I Take More Mercilon Than I Should?

If you take more Mercilon than you should, it's unlikely to cause any significant harm. That being said, you may end up feeling sick, vomiting, or experiencing vaginal bleeding. Should you get any of these symptoms, consult your clinician for further advice.

What If I Am Sick or Have Diarrhoea When Taking Mercilon Pills?

If you are sick or have severe diarrhoea within 3 to 4 hours of taking Mercilon, you should follow the missed-pill advice, as your body may not have had time to absorb all the active ingredients.

If you have severe diarrhoea for more than 12 hours after taking Mercilon, follow the instructions for a missed pill that is more than 12 hours late.

If your symptoms do not improve or get worse, speak to your clinician, as they may recommend an alternative method of contraception.

How to Switch to Mercilon From Another Contraceptive Pill

You can switch to Mercilon from another pill, but how you should do this will depend on the type of pill you are currently taking.

• If you are currently taking a combined 21-day pill, start by taking Mercilon the next day after the end of the previous strip. You will be protected against pregnancy immediately and should have a withdrawal bleed after you finish your first strip of Mercilon.
• If you are currently taking a combined 28-day pill, start taking Mercilon the day after your last active pill. You will be protected against pregnancy with your first pill and should have a withdrawal bleed after you finish the first Mercilon strip.
• If you are switching to Mercilon from a progesterone-only pill (POP or mini pill), start taking Mercilon on the first day of bleeding, even if you have already taken the POP for that day. You will be protected against pregnancy straight away. If you do not usually bleed while taking the mini pill, you can stop taking it on any day and start Mercilon the next day. You will need to use condoms for the next 7 days.

Cautions and Side Effects of Mercilon

Different treatments have different ingredients and work in different ways. This means what is useful or suitable for one individual may not be right for another.

When researching the most appropriate treatment for your circumstances, it's essential to familiarise yourself with potential side effects and warnings, so you can make an informed decision. You should also speak with a clinician if you ever feel unsure.

Mercilon Side Effects

All medications have the potential to cause side effects, and Mercilon is no exception. Not everyone will experience the symptoms listed, and some people won't have any issues at all. Regardless, it's crucial to inform yourself of any possible adverse effects before you start Mercilon pills. Potential Mercilon side effects include:

It's important to note that the above is not a complete list of Mercilon side effects. For more information about what you could expect, refer to the treatment's Patient Information Leaflet.

Should you experience any adverse reactions to Mercilon, whether listed or not, it's a good idea to inform your doctor or clinician. You can also report them directly to the Yellow Card Scheme.

Risk of Allergic Reaction

Do not take Mercilon if you are allergic to desogestrel, ethinylestradiol, or any other ingredients listed in the patient information leaflet.

Signs of an allergic reaction are:

• Swelling of the lips, face, tongue, or throat
• Difficulty breathing or swallowing
• Hives

If you get any of these symptoms, call 999 or get emergency medical help immediately. Be sure to take the packaging and any remaining pills with you, so doctors have a clear understanding of what and how much you have taken.

Mercilon also contains lactose, so you should speak to a clinician before starting treatment if you are intolerant to some sugars.

Potential for Blood Clots

Mercilon and other combined pills can slightly increase the risk of blood clots in users compared to people who do not take the combined pill. Although the risk is small, it should still be considered.

The potential of blood clots developing in different scenarios is displayed in the table below:

Your first year of Mercilon treatment is typically when the risk of developing blood clots is at its highest. The same is true if you're restarting the medication after a gap of 4 weeks or more. Certain external factors can also affect the potential of complications developing, such as if you smoke, are overweight, or have a family history of blood clots.

If you're planning on having elective surgery or you're likely to have mobility issues for an extended period, Mercilon pills may not be suitable for everyone. Another form of contraception might be more beneficial.

You can find out more about the risk of developing a blood clot while taking Mercilon in section 4.4 of the Summary of Product Characteristics (SmPC).

Mercilon and the Risk of Breast Cancer

If you have breast cancer or you have had it in the past, you must not take the combined pill because it slightly increases your risk of breast cancer. While the overall risk of developing the condition is small, it increases the longer you are on the pill, but returns to normal about 10 years after stopping it.

Your risk of developing breast cancer is higher if you:

• Have a close relative who has had it
• Are seriously overweight

You can find out more about the risk of developing breast cancer while taking Mercilon in section 4.4 of the Summary of Product Characteristics (SmPC) or speak to your clinician for more advice.

Mercilon Warnings and Interactions

Mercilon may not be suitable for everyone. Its ingredients may interact with other treatments you might be taking, potentially reducing Mercilon's effectiveness. Alternatively, certain medical conditions could render the medication unsuitable. Your clinician will assess your suitability before prescribing the treatment.

Do not take Mercilon if you:

• Are allergic to any of the ingredients
• Have or have ever had a blood clot in your legs, lungs, or other organs
• Have a blood-clotting disorder
• Need an operation or are going to be off your feet for a while
• Have ever had a heart attack or stroke
• Have or have ever had angina pectoris or a transient ischaemic attack (TIA)
• Have severe diabetes with blood vessel damage, very high blood pressure, very high blood fat levels, or hyperhomocysteinaemia
• Have or have ever had a migraine with aura
• Have or have recently had severe liver disease
• Have ever had a liver tumour
• Have or have ever had pancreatitis
• Are or think you might be pregnant
• Have unexplained vaginal bleeding
• Have hepatitis C and are taking ombitasvir/paritaprevir/ritonavir and dasabuvir or glecaprevir/pibrentasvir

In general terms, Mercilon and other combined oral contraceptives are not recommended if you're aged 35 or older and smoke, with those who smoke 15 cigarettes or more a day advised not to use them at all. This is due to the potential for cardiovascular issues like blood clots, stroke, or heart attack.

Your medical history and how you react to hormonal medications can also impact whether Mercilon is suitable for use. If you're ever unsure, speak to your clinician, as they may recommend an alternative treatment like the mini pill.

Mercilon and Other Medications

Tell the clinician before taking Mercilon if you are taking any prescribed, over-the-counter, or herbal medications. Some medicines can stop Mercilon from working properly, such as those used to treat:

• Epilepsy (primidone, phenytoin, phenobarbital, carbamazepine, oxcarbazepine, topiramate, felbamate, modafinil)
• Tuberculosis (rifampicin)
• HIV (ritonavir, nelfinavir, nevirapine, efavirenz)
• Hepatitis C
• Other infectious conditions (griseofulvin)
• High blood pressure in the lungs (bosentan)
• Depressive moods (St John's Wort)

Most antibiotics are safe to use with combined pills and will not negatively affect their effectiveness. However, this is not the case for medications that affect liver enzymes, such as rifabutin and rifampicin, as they can reduce Mercilon's efficacy.

Pregnancy and Breastfeeding

Do not take Mercilon if you think you are pregnant. You should take a pregnancy test to confirm. If you are pregnant, stop taking Mercilon straight away.

Mercilon is not recommended while breastfeeding, as combined oral contraceptives could affect milk supply. Speak to your clinician or family planning nurse about alternative contraception if you are breastfeeding.

Frequently Asked Questions About Mercilon Pills

Sources

• EMC (2024): Mercilon Tablets.
• EMC (2024): Patient Information Leaflet.
• NHS (2024): How to take the combined pill.
• NHS (2024): How well contraception works at preventing pregnancy.
• Cochrane (2011): Combination contraceptives: effects on weight.
• Cochrane (2012): Combined oral contraceptive pills for treatment of acne.