• Keep this leaflet. You may need to read it again.
• If you have any further questions, ask your doctor or pharmacist.
• This medicine has been prescribed for you only. Do not pass it on to others. It may harm them, even if their signs of illness are the same as yours.
• If you get any side effects, talk to your doctor or pharmacist. This includes any possible side effects not listed in this leaflet. See section 4.

1. What Opsumit is and what it is used for
2. What you need to know before you take Opsumit
3. How to take Opsumit
4. Possible side effects
5. How to store Opsumit
6. Contents of the pack and other information

• if you are allergic to macitentan, soya or any of the other ingredients of this medicine (listed in section 6).
• if you are pregnant, if you are planning to become pregnant, or if you could become pregnant because you are not using reliable birth control (contraception). See section ‘Pregnancy and breastfeeding’.
• if you are breastfeeding. See section ‘Pregnancy and breastfeeding’.
• if you have liver disease or if you have very high levels of liver enzymes in your blood. Talk to your doctor, who will decide whether this medicine is suitable for you.

If any of these apply to you, please tell your doctor.

Talk to your doctor or pharmacist before taking Opsumit.

You will need blood tests, as indicated by your doctor:

Your doctor will take blood test before you start treatment with Opsumit and during treatment to test:

• whether you have anaemia (a reduced number of red blood cells)
• whether your liver is working properly

If you have anaemia (a reduced number of red blood cells), you may have the following signs:

• dizziness
• fatigue/malaise/weakness
• fast heart rate, palpitations
• pallor

If you notice any of these signs, tell your doctor.

Signs that your liver may not be working properly include:

• feeling sick (nausea)
• vomiting
• fever
• pain in your stomach (abdomen)
• yellowing of your skin or the whites of your eyes (jaundice)
• dark-coloured urine
• itching of your skin
• unusual tiredness or exhaustion (lethargy or fatigue)
• flu-like syndrome (joint and muscle pain with fever)

If you notice any of these signs, tell your doctor immediately.

If you have kidney problems, talk to your doctor before using Opsumit. Macitentan may lead to more reduction of blood pressure and decrease in haemoglobin in patients with kidney problems.

In patients with pulmonary veno-occlusive disease (obstruction of the lung veins), the use of medicines for treatment of PAH, including Opsumit, may lead to pulmonary oedema. If you have signs of pulmonary oedema when using Opsumit, such as a sudden, important increase in breathlessness and low oxygen, tell your doctor immediately. Your doctor may perform additional tests, and will determine what treatment regimen is most suitable for you.

Do not give this medicine to children and adolescents below 18 years because Opsumit has not been tested in children.

Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicine. Opsumit can affect other medicines.

If you take Opsumit together with other medicines including those listed below, the effects of Opsumit or the other medicines might be altered. Please talk to your doctor or pharmacist if you are taking any of the following medicines:

• rifampicin, clarithromycin, telithromycin, ciprofloxacin, erythromycin (antibiotics used to treat infections)
• phenytoin (a medicine used to treat seizures)
• carbamazepine (used to treat depression and epilepsy)
• St. John’s Wort (an herbal preparation used to treat depression)
• ritonavir, saquinavir (used to treat HIV infections)
• nefazodone (used to treat depression)
• ketoconazole (except shampoo), fluconazole, itraconazole, miconazole, voriconazole (medicines used against fungal infections)
• amiodarone (to control the heartbeat)
• cyclosporine (used to prevent organ rejection after transplant)
• diltiazem, verapamil (to treat high blood pressure or specific heart problems)

If you are taking piperine as a dietary supplement, this may alter how the body responds to some medicinal products, including Opsumit. Please talk to your doctor or pharmacist should this be the case.

If you are pregnant or breastfeeding, think you may be pregnant or are planning to have a baby, ask your doctor for advice before taking this medicine.

Opsumit may harm unborn babies conceived before, during or soon after treatment.

• If it is possible you could become pregnant, use a reliable form of birth control (contraception) while you are taking Opsumit. Talk to your doctor about this.
• Do not take Opsumit if you are pregnant or planning to become pregnant.
• If you become pregnant or think that you may be pregnant while you are taking Opsumit, or shortly after stopping Opsumit (up to 1 month), see your doctor immediately.

If you are a woman who could become pregnant, your doctor will ask you to take a pregnancy test before you start taking Opsumit and regularly (once a month) while you are taking Opsumit.

It is not known if Opsumit is transferred to breast milk. Do not breastfeed while you are taking Opsumit. Talk to your doctor about this.

If you are a man taking Opsumit, it is possible that this medicine may lower your sperm count. Talk to your doctor if you have any questions or concerns about this.

Opsumit can cause side effects such as headaches and hypotension (listed in section 4), and the symptoms of your condition can also make you less fit to drive.

Opsumit contains a sugar called lactose. If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicine.

Opsumit contains lecithin derived from soya. If you are allergic to soya, do not use this medicine (see section 2 ‘Do not take Opsumit’).

This medicine contains less than 1 mmol sodium (23 mg) per tablet, that is to say essentially ‘sodium-free’.

If you have taken more tablets than you have been told to take, you may experience headache, nausea, or vomiting. Ask your doctor for advice.

If you forget to take Opsumit, take a dose as soon as you remember, then continue to take your tablets at the usual times. Do not take a double dose to make up for a forgotten tablet.

Opsumit is a treatment that you will need to keep on taking to control your PAH. Do not stop taking Opsumit unless you have agreed this with your doctor.

If you get any side effects, talk to your doctor or pharmacist. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.

• The active substance is macitentan. Each tablet contains 10 mg macitentan.
• The other ingredients are lactose monohydrate (see section 2 “Opsumit contains lactose, lecithin from soya and sodium”), microcrystalline cellulose (E460i), povidone, sodium starch glycolate Type A (see section 2 “Opsumit contains lactose, lecithin from soya and sodium”), magnesium stearate (E572), polysorbate 80 (E433), polyvinyl alcohol (E1203), titanium dioxide (E171), talc (E553b), soya bean lecithin (E322) (see section 2 “Opsumit contains lactose, lecithin from soya and sodium”) and xanthan gum (E415).

Opsumit 10 mg tablets are white to off-white, biconvex, round, film-coated tablets with “10” on both sides.

Opsumit is supplied as 10 mg film-coated tablets in blister packs of 30 tablets.

For information in large print, tape, CD or Braille, telephone 0800 7318450.