Viekira Pak

Viekira Pak is a combination of drugs used to treat patients with hepatitis C virus (HCV) genotype 1. It contains four medicines, dasabuvir, ombitasvir, paritaprevir, and ritonavir. Viekira Pak belongs to a class of drugs called direct-acting antiviral agents. Similar drugs include

• boceprevir (Victrelis), 
• sofosbuvir (Sovaldi),
• simeprevir (Olysio),
• telaprevir (Incivek), and
• ombitasvir, paritaprevir, ritonavir (Technivie).

Dasabuvir, ombitasvir, and paritaprevir are antivirals that work in three different ways to help stop HCV from multiplying. They block the effect of proteases which are enzymes that HCV uses for making new virus, leading to reduced numbers of HCV copies in the body. Ombitasvir blocks HCV NS5A protease while paritaprevir blocks HCV NS3/4A protease. Dasabuvir blocks a viral structure called NS5B palm polymerase which is also needed for replication of HCV. Ritonavir is not active against the HCV virus. It is used to increase blood levels of paritaprevir by inhibiting the breakdown of paritaprevir.

In clinical studies Viekira Pak, with or without ribavirin (Rebetol) HCV was cured in 95% to 100% of patients treated. Cure was defined as undetectable levels of HCV in the blood 3 months after treatment. The FDA approved Viekira Pak in December 2014.

The most common side effects of Viekira Pak when used with ribavirin include

• tiredness,
• nausea,
• itching,
• skin reactions such as redness or rash,
• sleep problems (insomnia), and
• feeling weak.

The most common side effects of Viekira Pak when used without ribavirin include

• nausea,
• itching, and
• problems sleeping.

Other side effects include

• allergic reactions,
• anemia, and
• increases in liver enzymes and bilirubin.

• Viekira Pak is supplied in monthly cartons that contain enough medicine for 28 days. Each daily dose pack contains four tablets: two 12.5/75/50 mg ombitasvir, paritaprevir, ritonavir tablets and two 250 mg dasabuvir tablets.
• The recommended dose of Viekira Pak is two tablets containing ombitasvir, paritaprevir, ritonavir in the morning and one dasabuvir tablet in the morning and evening. Viekira Pak should be taken with meals.
• Certain patients may also be treated with ribavirin. The dosage of ribavirin is based on weight and is usually administered twice daily with food.
• The recommended treatment regimen and duration of treatment for each type of HCV infection is as follows:
  • Patients with HCV genotype 1a without cirrhosis may be treated with Viekira Pak plus ribavirin for 12 weeks.
  • Patients with HCV genotype 1a with cirrhosis may be treated with Viekira Pak plus ribavirin for 24 weeks. (Some patients who have had prior treatment with other drugs may be considered for a shorter treatment duration of 12 weeks.)
  • Patients with HCV genotype 1b without cirrhosis may be treated with Viekira Pak for 12 weeks.
  • Patients with HCV genotype 1b with cirrhosis may be treated with Viekira Pak plus ribavirin for 12 weeks.
• No dosage adjustment is required in patients with mild liver impairment. Viekira Pak is not recommended for patients with moderate liver impairment and is contraindicated in patients with severe liver impairment.

• Viekira Pak interacts with many drugs. The prescribing information should be consulted for a complete list of drugs that interact with Viekira Pak. Viekira Pak should not be used with the following medications:
• Afluzosin hydrochloride (Uroxatral), a medicine used to treat benign prostate hyperplasia (BPH), due to the risk of hypotension (low blood pressure).
• Certain anti-seizure medications, including carbamazepine (Tegretol), phenytoin (Dilantin), and phenobarbital (Luminal), may decrease the blood concentrations of Viekira Pak and reduce the effectiveness of treatment.
• Rifampin (Rifadin, Rimactane), a component of many tuberculosis treatment regimens, may decrease the blood concentrations of Viekira Pak, reducing the effectiveness of treatment.
• Ergot derivatives which are used to treat migraine headaches should not be used with Viekira Pak due to the risk of ergot toxicity.
• Combination birth control pills that contain ethinyl estradiol should be avoided due to the potential for liver damage.
• St. John's Wort may decrease the blood concentrations of Viekira Pak, resulting in reduced effectiveness of treatment.
• Commonly used cholesterol lowering agents, lovastatin (Mevacor) and simvastatin (Zocor), should be avoided due to the risk for serious muscle pain and injury, including rhabdomyolysis.
• Combining Viekira Pak and pimozide (Orap) may increase the risk for abnormal heart beats.
• Combining efavirenz (Sustiva) and Viekira Pak may increase the risk of liver damage.
• Combining Viekira Pak with sildenafil (Viagra, Revatio) and similar drugs may increase the risk of vision problems, low blood pressure, fainting, and priapism (painful, long lasting erection).
• Viekira Pak increases blood levels of triazolam (Halcion) and midazolam, leading to increased sedation and respiratory depression.

Viekira Pak has not been evaluated in pregnant women. Therefore, Viekira Pak should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

When Viekira Pak is administered with ribavirin, the combination regimen should not be used in pregnant women and in men who can father children. Ribavirin is known to cause birth defects and should be avoided during pregnancy.

There is an antiretroviral pregnancy registry that monitors the use of products such as Viekira Pak in HCV/HIV-1 co-infected women. Patients are advised to enroll in this program to help study and understand the safety of antiretroviral therapy during pregnancy.

It is not known whether any of the drugs contained in Viekira Pak are excreted into human milk. Due to the lack of conclusive safety data, Viekira Pak should be used cautiously in nursing mothers.

What preparations of Viekira Pak are available?

Tablets: 12.5/75/50 mg ombitasvir, paritaprevir, ritonavir co-packaged with 250 mg dasabuvir tablets.

How should I keep Viekira Pak stored?

Viekira Pak should be stored at room temperature between 15 C and 30 C (59 F and 86 F). Viekira Pak as well as all medicines should be kept out of the reach of children and pets.