The Morrison government has added a self-administering pen to the Pharmaceutical Benefits Scheme, saving patients with severe asthma thousands of dollars.

Australians living with severe asthma will have access to a cheaper home treatment when a self-injecting pen is listed on the Pharmaceutical Benefits Scheme.

Patients with severe eosinophilic asthma - where levels of inflammation-causing white blood cells are elevated in the lungs - can already purchase the drug Fasenra from pharmacies.

But currently it is only available as a course of injections to be administered at a hospital or GP clinic.

About 10 per cent of Australians suffer from asthma with around 170,000 people suffering from a severe form of the condition.

Fasenra, or benralizumab, is prescribed to young people over the age of 12 with uncontrolled eosinophilic asthma who are already using other medication, such as an asthma puffer.

It is injected under the skin with a thin 29-gauge needle once a month for the first three doses and once every eight weeks thereafter.

It can help stabilise the condition and prevent severe attacks.

"Having severe asthma can be a constant battle, with frequent symptoms and flare-ups which can be really debilitating," said Michele Goldman, chief executive of Asthma Australia.

Without the PBS listing, one dose of Fasenra can cost about $3358, with a standard treatment course costing more than $25,000.

Federal Health Minister Greg Hunt will announce the drug's listing on Friday, immediately taking the cost down to less than $41 per dose, or just over $300 a year.

The listing is timely as asthma sufferers are particularly vulnerable to COVID-19.

Severe asthma places a major psychological and financial burden on sufferers and is linked to high rates of depression and anxiety.

More than 70 per cent of Australians living with the illness say they are impaired at work while almost 30 per cent say they have taken time off due to their health.