Dasabuvir, ombitasvir, paritaprevir, and ritonavir (Viekira) is a combination antiviral medicine used to treat chronic hepatitis C virus (HCV) in adults. Viekira is sometimes given in combination with another antiviral medicine called ribavirin.

Viekira treats specific genotypes of hepatitis C, and only in certain people. Use only the medications prescribed for you. Do not share your medicine with other people.

Viekira is sometimes used in people who also have HIV. This medicine is not a treatment for HIV or AIDS.

Viekira may also be used for purposes not listed in this medication guide.

You should not use Viekira if you are allergic to dasabuvir, ombitasvir, paritaprevir, or ritonavir, or if:

• you have moderate to severe liver disease; or
• you have ever had a severe skin rash after taking ritonavir (Norvir).

If you take Viekira with ribavirin: There may be other reasons you should not take this combination treatment. Tell your doctor about all your medical conditions.

Many drugs can interact and cause dangerous effects. Some drugs should not be used together with Viekira. Your doctor may change your treatment plan if you also use:

• alfuzosin;
• apalutamide;
• colchicine;
• dronedarone;
• efavirenz (Atripla, Sustiva, Symfi);
• ranolazine;
• rifampin;
• sildenafil (Revatio), when taken for pulmonary artery hypertension (PAH);
• St. John's wort;
• oral midazolam (Versed), or triazolam;
• anti-psychotic medicine--lurasidone, pimozide;
• birth control pills or patches--Lo Loestrin FE, Norinyl, Ortho Tri-Cyclen Lo, Ortho Evra, and others;
• hormone replacement therapy such as Fem HRT;
• a vaginal ring such as NuvaRing;
• cholesterol-lowering medicine--atorvastatin, gemfibrozil, lomitapide, lovastatin, simvastatin (Zocor, Vytorin, Simcor);
• an immunosuppressant--everolimus, sirolimus, tacrolimus;
• ergot medicine--dihydroergotamine, ergotamine, methylergonovine; or
• seizure medicine--carbamazepine, phenytoin, phenobarbital.

Before you start taking Viekira, you must stop using medicine that contains ethinyl estradiol. This includes certain birth control pills or hormone replacement medicines. Ask your doctor about using non-hormonal birth control (condom, diaphragm with spermicide) to prevent pregnancy while taking Viekira and for 2 weeks after your treatment ends.

Tell your doctor if you have ever had:

• liver problems other than hepatitis C (such as cirrhosis or hepatitis B);
• HIV (human immunodeficiency virus);
• a liver transplant; or
• if you use a blood thinner (warfarin, Coumadin, Jantoven) and you have routine "INR" or prothrombin time tests.

Viekira is sometimes used in combination with ribavirin. Both men and women using ribavirin should use effective birth control to prevent pregnancy. Ribavirin can cause birth defects, miscarriage, or death to an unborn baby if the mother or father is using this medicine.

You should not take ribavirin if you are pregnant, or if you are a man and your sex partner is pregnant. Use effective birth control to prevent pregnancy. Keep using birth control for at least 6 months after your last dose of ribavirin.

Tell your doctor right away if a pregnancy occurs while either the mother or the father is using ribavirin.

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.

Use Viekira Pak (Dasabuvir, Ombitasvir, Paritaprevir, And Ritonavir) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have new or worsening symptoms such as:

• confusion;
• loss of appetite, upper stomach pain;
• dark urine, clay-colored stools; or
• jaundice (yellowing of the skin or eyes).

Common side effects may include:

• nausea;
• itching, skin rash or redness;
• sleep problems (insomnia); or
• feeling weak or tired.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Do not drink alcohol within 4 hours after you take Viekira XR.

Using this medicine will not prevent your disease from spreading. Do not have unprotected sex or share razors or toothbrushes. Talk with your doctor about safe ways to prevent HCV transmission during sex. Sharing drug or medicine needles is never safe, even for a healthy person.