Asunaprevir is an antiviral agent. Specifically, it belongs to the class of medications known as protease inhibitors. Protease is an enzyme that viruses need for reproduction. Asunaprevir blocks the action of protease, slowing the growth of the virus.

This medication is used in combination with other medications such as daclatasvir, peginterferon alfa, and ribavirin, to treat chronic (long-term) hepatitis C that is not worsening. It is effective only against "genotype 1" and "genotype 4" strains of the hepatitis C virus.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended dose of asunaprevir is 100 mg taken by mouth, twice daily. The capsule should be swallowed whole with fluids and not crushed or chewed. Ideally, you should take asunaprevir at the same times each day. It may be taken with food or on an empty stomach.

Asunaprevir must be taken in combination with daclatasvir or with daclatasvir, peginterferon alfa, and ribavirin, depending on the type of hepatitis C you have. It is usually taken for 24 weeks, at which time, your doctor will determine effectiveness of the combination of medications through blood tests.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important that this medication be taken exactly as prescribed by your doctor and not reduced. Reducing the dose may cause the medication to fail. If you miss a dose, and it is less than 8 hours since the missed dose, take it as soon as possible and continue with your regular schedule. If it is more than 8 hours past the time of your missed dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature in its original package, protect it from light and moisture, and keep it out of the reach of children.

Do not take asunaprevir if you:

• are allergic to asunaprevir or any ingredients of the medication
• cannot take peginterferon alfa, ribavirin, or daclatasvir
• are pregnant or plan to become pregnant
• are the male partner of a woman who is pregnant, may become pregnant or is planning to become pregnant
• have moderately-to-severely decreased liver function
• are taking other medications such as
• "azole" antifungals (e.g., fluconazole, itraconazole, ketoconazole, voriconazole)
• bosentan
• calcium channel blockers (e.g., diltiazem, verapamil)
• cobicistat
• cyclosporine
• gemfibrozil
• dexamethasone
• flecainide
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delaviridine, efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• gemfibrozil
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• modafinil
• propafenone
• rifabutin, rifampin, or rifapentine
• seizure medications (e.g., carbamazepine, oxcarbazepine, phenobarbital, phenytoin)
• St. John's wort

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• flu-like symptoms
• hair loss
• headache
• irritability
• itchiness
• nausea
• skin rash
• tiredness
• trouble sleeping
• weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• signs of anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• signs of infection (symptoms may include fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Birth control: The effect of asunaprevir on the development of an unborn baby has not been studied, however for certain types of hepatitis C, asunaprevir must be used with interferon alfa and ribavirin. Treatment with ribavirin can cause severe birth defects to an unborn child. Both partners should use a reliable form of birth control while taking this medication and for 6 months afterwards (the time it takes for ribavirin to be cleared from the body).

For women, your doctor will not give you asunaprevir until you have had a negative pregnancy test. Your doctor should have you continue to do monthly pregnancy tests to ensure that you do not become pregnant while using this medication.

Methods of birth control that use hormones, such as a birth control pill, patch, or injection, may not be fully reliable as asunaprevir interacts with many medications and may change the way that your body uses the hormones. If you are taking ribavirin along with asunaprevir at least 2 forms of non-hormonal birth control (condom, diaphragm) must be used while you are taking this medication.

Hepatitis C virus response: Only genotype 1 and genotype 4 hepatitis C viruses have been studied and determined to respond to asunaprevir. The safety and effectiveness of using asunaprevir to treat other strains of hepatitis C virus have not been determined.

Hepatitis B Infection: People who have hepatitis B infection that is dormant may experience the infection returning, causing further liver dysfunction or liver failure. If you have a history of hepatitis B, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

If you experience symptoms of worsening liver function, such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Infection with HIV: The safety and effectiveness of treatment with asunaprevir have not been established for people who also have human immunodeficiency virus (HIV).

Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. Asunaprevir may reduce liver function and in severe cases, cause liver failure. Asunaprevir is not recommended for people with active, worsening liver disease, or moderately-to-severely reduced liver function. If you have a history of reduced liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Organ transplantation: The safety and effectiveness of treatment with asunaprevir have not been established for people with liver or other organ transplants. Asunaprevir may interact with medications used to prevent rejection of the transplanted organ.

Pregnancy: Asunaprevir has not been studied for use by pregnant women. For certain types of hepatitis C it must be taken with daclatasvir, peginterferon alfa, and ribavirin. Ribavirin has been shown to cause serious problems in the developing fetus. As a result, asunaprevir (plus daclatasvir, peginterferon alfa, and ribavirin) should not be used by pregnant women or by men whose partners are pregnant. Both partners should use a reliable form of birth control while taking this medication and for 6 months afterwards. Tell your doctor immediately if you become pregnant while using this medication.

Breast-feeding: It is not known if asunaprevir passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Breast-feeding should be stopped before starting treatment with asunaprevir.

Children: The safety and effectiveness of using this medication have not been established for children.

There may be an interaction between asunaprevir and any of the following:

• abiraterone
• aliskiren
• amiodarone
• anticancer medications(e.g., cabazitaxel, docetaxel, doxorubicin, etoposide, ifosfamide, irinotecan, vincristine)
• antihistamines (e.g., cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• aprepitant
• atomoxetine
• "azole" antifungals (e.g., itraconazole, ketoconazole, voriconazole)
• certain beta-adrenergic blockers (e.g., bisoprolol, carvedilol, metoprolol, propranolol, nadolol, timolol)
• bicalutamide
• birth control pills
• bosentan
• calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
• captopril
• carbamazepine
• chloroquine
• cobicistat
• codeine
• colchicine
• conivaptan
• cyclosporine
• dabigatran
• deferasirox
• dexamethasone
• dextromethorphan
• digoxin
• dronedarone
• eltrombopag
• enzalutamide
• estrogens (e.g., conjugated estrogen, estradiol, ethinyl estradiol)
• fesoterodine
• flecainide
• gemfibrozil
• grapefruit juice
• hepatitis protease inhibitors (e.g., boceprevir, ledipasvir, simeprevir, sofosbuvir)
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delaviridine, efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• hydrocortisone
• lidocaine
• lomitapide
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• methamphetamine
• mexiletine
• midazolam
• mifepristone
• mirtazapine
• modafinil
• naloxegol
• nefazodone
• oxcarbazepine
• phenobarbital
• phenytoin
• primaquine
• primidone
• progestins (e.g., dienogest, levonorgestrel, medroxyprogesterone, norethindrone, norgestimate)
• procainamide
• propafenone
• protein kinase inhibitors (e.g., bosutinib, dasatinib, erlotinib, imatinib, nilotinib)
• prucalopride
• quinidine
• quinine
• rifabutin
• rifampin
• rifapentine
• rivaroxaban
• St. John's wort
• selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, duloxetine, fluoxetine, paroxetine, sertraline)
• serotonin/norepinephrine reuptake inhibitors (e.g., desvenlafaxine, duloxetine, venlafaxine)
• silodosin
• siltuximab
• sirolimus
• "statin" anti-cholesterol medications (e.g., atorvastatin, lovastatin, simvastatin)
• tacrolimus
• tamoxifen
• teriflunomide
• tetrabenazine
• tocilizumab
• tolterodine
• tramadol
• tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.