Published: 8 December 2016


Safe Prescribing of Direct-Acting Antivirals for Treatment of Hepatitis C — It’s Complicated

This article is more than five years old. Some content may no longer be current.

Prescriber Update 37(4): 50-51
December 2016

Key Messages

  • Direct-Acting Antivirals (DAAs) are used for the treatment of hepatitis C infection.
  • Viekira Pak, Viekira Pak-RBV and Harvoni are funded by PHARMAC.
  • Beware of the many potential drug interactions when prescribing or dispensing DAAs.

Direct-acting antivirals (DAAs) are recently approved medicines indicated for the treatment of hepatitis C infection. The World Health Organization (WHO) now recommends DAA regimens for the treatment of persons with hepatitis C infection, rather than regimens with pegylated interferon and ribavirin1. The NZ Society of Gastroenterology HCV Treatment Guidelines and PHARMAC funding have been updated to align with the WHO recommendations2,3.

What are DAAs?

DAAs are used for the treatment of hepatitis C infection with the goal of curing the patient. DAAs work by blocking the action of hepatitis C virus proteins required for viral replication.

Treatment regimens with DAAs have a short treatment duration (usually 12 weeks), are administered orally and are very effective (sustained virological response rates of ≥ 90%)1.

There are a number of DAAs approved in New Zealand. This article focuses on Viekira Pak, Viekira Pak-RBV and Harvoni, which are funded by PHARMAC.

Viekira Pak contains ombitasvir, ritonavir and paritaprevir in a combination tablet packaged together with dasabuvir tablets. Viekira Pak-RBV also contains ribavirin in the same package.

Harvoni is a combination tablet containing ledipasvir and sofosbuvir.

In some countries DAAs are marketed under different brand names and in different combinations. Be aware that patients who have been importing DAA products from overseas may be taking a different combination from those funded in New Zealand.

Things to remember when prescribing DAAs

Genotype of hepatitis C

Prior to starting the treatment, determine the hepatitis C virus genotype and measure the viral load, as this will direct the choice of DAA and the treatment duration (Table 1).


DAAs are known to interact and postulated to interact with a substantial list of medicines. These interactions may be severe. Comorbidities are common in patients with hepatitis C so it is important to know what other medicines the patient is taking. Be careful when prescribing DAAs with medicines metabolised or transported by4,5,6:

  • CYP3A4
  • Organic Anion Transporting Polypeptides (OATP) family and Organic Cation Transporter 1 (OCT1)
  • Breast Cancer Resistance Protein (BCRP)
  • P-glycoprotein (P-gp) in the intestine
  • glucuronidation (UGT1A1)
  • CYP2C19
  • CYP1A2

The University of Liverpool provides an online interactions tool that is quick and easy to use (see below).

What do I need to look out for?

Hepatitis B reactivation has also been reported in temporal association with DAA treatment. The Medicines Adverse Reactions Committee (MARC) recently reviewed the information on this possible risk. Although patients may get flares of hepatitis B at any time, the MARC considered that patients who are being prescribed DAAs should be assessed, tested and closely monitored for hepatitis B (

Advise patients to report any signs and symptoms of hepatotoxicity with Viekira Pak or Viekira Pak-RBV to their healthcare professionals. Patients who develop evidence of hepatic decompensation with the use of Viekira Pak or Viekira Pak-RBV should discontinue treatment4,5.

Table 1: Summary table for Viekira Pak, Viekira Pak-RBV and Harvoni4,5,6

  Viekira Pak Viekira Pak-RBV Harvoni
Genotypes Genotype 1b Genotype 1a All genotypes
Contraindications Hypersensitivity to any component
Severe hepatic impairment  
Patients taking other medicines with significant interactions
  Pregnant women or patients with a pregnant partner
Severe pre-existing cardiac disease
Main adverse effects Fatigue, nausea, itchy skin, insomnia, anaemia Fatigue, nausea, headache, rash
Hypersensitivity reactions including tongue and lip swelling Symptomatic bradycardia when co-administered with amiodarone
Hepatic decompensation and hepatic failure

Please report any adverse reactions with DAAs, including interactions, to the Centre for Adverse Reactions Monitoring (CARM). These are new medicines, and the safety profile has not yet been fully identified. Reports can be submitted on paper or electronically ( These reports will help CARM and Medsafe identify any trends or patterns in New Zealand that may require action to ensure DAAs continue to be used safely.

Where can I look for more information?

Links to some useful resources are provided below.

  1. World Health Organization. 2016. Guidelines for the Screening, Care and Treatment of Persons with Chronic Hepatitis C Infection: Updated Version. URL: (accessed 20 July 2016).
  2. Gane E, Stedman C. 2016. NZ Society of Gastroenterology HCV Treatment Guidelines. URL: (accessed 4 August 2016).
  3. PHARMAC. 2016. Hepatitis C treatments: information about new listings from 1 July 2016. URL: (accessed 14 September 2016).
  4. AbbVie Limited. 2016. Viekira Pak New Zealand Data Sheet. 25 August 2016. URL: (accessed 27 September 2016).
  5. AbbVie Limited. 2016. Viekira Pak-RBV New Zealand Data Sheet. 25 August 2016. URL: (accessed 27 September 2016).
  6. Gilead Sciences (NZ). 2016. Harvoni New Zealand Data Sheet. 26 May 2016. URL: (accessed 27 July 2016).
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