Asunaprevir is used in combination with other medications (such as daclatasvir, peginterferon alfa, ribavirin) to treat chronic (long-lasting) hepatitis C, a viral infection of the liver. The combination treatment reduces the amount of hepatitis C virus in your body, which helps your immune system fight the infection and may help your liver recover. Chronic hepatitis C infection can cause serious liver problems such as scarring (cirrhosis) or liver cancer.

It is not known if this treatment can prevent you from passing the virus to others. Do not share needles, and practice "safer sex" (such as the use of latex condoms) to lower the risk of passing the virus to others.

Asunaprevir must be used in combination treatment to have the best effect. Taking it by itself can make your treatment less effective.

Read the Patient Information Leaflet if available from your pharmacist before you start taking asunaprevir and each time you get a refill. If you have any questions, ask your doctor or pharmacist. Also read the drug information for your other antiviral medication(s).

Take this medication by mouth with or without food as directed by your doctor, usually twice daily (every 12 hours).

The dosage is based on your medical condition and response to treatment.

For the best effect, take asunaprevir at evenly spaced times. To help you remember, take this medication at the same times every day.

Continue to take asunaprevir and the other medication(s) in the combination treatment for the full length of time prescribed, even if symptoms disappear after a short time. Stopping any of the drugs too early may result in a return of the infection.

See also Warning section.

Headache or tiredness may occur. If either of these effects lasts or gets worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking asunaprevir, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• other liver problems (such as hepatitis B)
• kidney disease
• diabetes

If you have diabetes, your blood sugar may be lower with hepatitis C treatment. This can increase your risk of low blood sugar, so your doctor may adjust your diabetes treatment plan. Tell your doctor right away if you have symptoms of low blood sugar such as sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

During pregnancy, asunaprevir should be used only when clearly needed. Discuss the risks and benefits with your doctor.

If this medication is used in combination with ribavirin, it must not be used during pregnancy by either the pregnant woman or her male partner. Ribavirin may harm an unborn baby. If either sexual partner is using asunaprevir with ribavirin, use reliable forms of birth control during treatment. Female patients should keep using birth control for 9 months after stopping treatment. Male patients should keep using birth control for 6 months after stopping treatment. If you or your partner becomes pregnant, or if you think you or your partner may be pregnant, tell your doctor right away.

It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• flecainide
• gemfibrozil
• mavacamten
• propafenone
• thioridazine

Other medications can affect the removal of asunaprevir from your body, which may affect how asunaprevir works. Examples include azole antifungals (such as ketoconazole, itraconazole), dexamethasone, elagolix, macrolide antibiotics (such as erythromycin, clarithromycin), HIV NNRTIs (such as efavirenz, etravirine, nevirapine), HIV protease inhibitors (such as atazanavir), rifamycins (such as rifabutin, rifampin), ritonavir, St. John's wort, telithromycin, certain drugs used to treat seizures (such as carbamazepine, phenobarbital, phenytoin), among others.

This medication may decrease the effectiveness of hormonal birth control such as pills, patch, or ring. This could cause pregnancy. Discuss with your doctor or pharmacist if you should use reliable backup birth control methods while using this medication. Also tell your doctor if you have any new spotting or breakthrough bleeding, because these may be signs that your birth control is not working well.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab tests (such as liver function, tests for hepatitis B and C) should be done before you start using this medication, while you are using it, and after completing treatment. Keep all medical and lab appointments.

If you are taking this medication with ribavirin, it is recommended that female patients or female partners of male patients take a pregnancy test before starting this medication. Pregnancy tests should continue to be done while using this medication and for some time after this medication is stopped to make sure no pregnancy occurs (for 9 months for female patients and for 6 months for female partners of male patients).

If you miss a dose, take it as soon as you remember. If it is more than 8 hours after the missed dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store in the original container at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.