What pharmacists need to know about oral antiviral treatments for COVID-19

Less than a month after being provisionally approved, two new oral antiviral treatments for COVID-19 are being rolled out into aged care and remote communities. Here’s what pharmacists need to know.

The federal government has secured 300,000 courses of molnupiravir (Lagevrio) and 500,000 courses of nirmatrelvir plus ritonavir (Paxlovid) for use during 2022. 

From yesterday (1 March) molnupiravir has been listed on the PBS for eligible adults who test positive for COVID-19 and are at risk of developing severe disease requiring hospitalisation.

Initially, both medicines will be available through the National Medical Stockpile for residential aged care facilities (RACFs), rural and remote communities (particularly regions with high Aboriginal and Torres Strait Islander populations) and to state and territory governments for distribution to those at highest risk in the community, including people with disability. 

‘The advantage of these oral medications is that people will be able to receive treatment for COVID-19 in their own homes or in residential aged care facilities without the need to travel to hospital for treatment as an inpatient,’ Deputy Chief Medical Officer Professor Michael Kidd said during a Department of Health webinar last week.

Molnupiravir has already been placed in some RACFs to support the timely administration of the medicine to eligible patients, once it has been prescribed by their general practitioner. The aim is to transition to PBS arrangements as supply continues to grow. 

‘As supply increases the treatments are expected to become more widely available and … it may be that one or both of these medications will be available in the coming months for prescription on the PBS by general practitioners and for dispensing by community pharmacists right across the country,’ Prof Kidd said.

The first deliveries of molnupiravir and nirmatrelvir plus ritonavir have also already gone out to Aboriginal Community Controlled Health Organisations (ACCHOs), COVID-19 Primary Care Response First Assistant Secretary Dr Lucas de Toca said during the webinar.

‘Initially we have prioritised the states where there are currently large outbreaks impacting Aboriginal and Torres Strait Islander people,’ he said.

PSA Education and Training Delivery General Manager Simone Diamandis said the importance of timely administration of these medicines, combined with how new they are, meant it was important that pharmacists were familiar with them.

‘It is essential that pharmacists don’t rely on prescribing software for drug-drug interactions and take the time to review the product information and the patient’s history,’ she said.

On 9 March, PSA will run a webinar focused on helping pharmacists identifying appropriate patients and facilitating oral COVID-19 treatment.

The Oral COVID-19 Treatment Update: Evidence, access and suitable patients webinar will provide pharmacists with current evidence and clinical considerations, from dosing and administration to reviewing and managing the range of drug-drug interactions that they should be aware of.

How the treatments work

Molnupiravir and nirmatrelvir plus ritonavir work by blocking the ability of the SARS-CoV-2 virus to replicate in the human body.

They have been granted provisional approval for the treatment of patients who:

• are 18 years and older 
• do not require supplemental oxygen due to COVID-19
• are at high risk of progressing to severe disease.  

Both treatments should be started as soon as possible after a patient is diagnosed with COVID-19, and within 5 days of the start of symptoms. 

A course of molnupiravir is 800 mg (four 200 mg capsules) twice a day (every 12 hours) for 5 days. A course of nirmatrelvir plus ritonavir is 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet) taken together orally every 12 hours for 5 days.

Prof Kidd said the earlier treatment is started, the better the likely outcomes. 

‘There’s no evidence that either of the treatments are of any benefit if administered more than 5 days after symptoms have commenced,’ he said.

Neither of the medicines are recommended during pregnancy or breastfeeding.

Prof Kidd said the medicines would likely be of most benefit to people aged 60 and above, and those who have significant medical conditions, such as diabetes, obesity, heart disease, chronic lung disease or cancer.

While the introduction of the treatments ‘represents an important new landmark’ in Australia’s response to the COVID-19 pandemic, he emphasised they should not be seen as a replacement for vaccines.

‘Vaccination remains the most effective way of protecting your health and the health of loved ones during this pandemic,’ Prof Kidd said. ‘And so we continue to urge everyone who hasn’t received the first or second dose to do so and everyone who is eligible for a booster dose not to hesitate in arranging their booster dose.’

Contraindications and interactions

Nirmatrelvir plus ritonavir is not being distributed in RACFs due to ‘significant contraindications to the use of Paxlovid with many commonly prescribed medications’ which ‘may make it unsuitable for use in many frail residents of aged care facilities,’ Prof Kidd said.

Contraindicated medicines for Paxlovid include pethidine, simvastatin, diazepam and rivaroxaban.

Nirmatrelvir plus ritonavir is also contraindicated in patients with severe renal impairment and patients with severe hepatic impairment.

For a full list of contraindications and drug-drug interactions, see the TGA Paxlovid product information.

Molnupiravir does not have the same drug interactions.

Quick facts

Secure your spot at the Oral COVID-19 Treatment Update: Evidence, access and suitable patients webinar.