Australians have been urged not to take medicines being touted as a cure or preventative for COVID-19 with a doctor warning they can be "downright dangerous".

Australians have been reminded there's no treatment or cure for COVID-19 and have been urged to refrain from buying any medication in the belief it could help prevent or treat the deadly virus.

Health organisation NPS MedicineWise urged people to not ask for or try to obtain any medication for coronavirus after the Australian Border Force reported an increase in illegally imported substances.

MedicineWise medical adviser Dr Anna Samecki warned people of the risks of taking such medication especially if it has been purchased online with some websites selling out-of-date, poor quality, contaminated or fake medicines.

"All medicines come with risks, and taking medicines in the belief they will help prevent or treat COVID-19 can be downright dangerous," she said in a statement on Wednesday.

Hydroxychloroquine is one medicine that some have claimed will prevent or treat COVID-19 but Dr Samecki insists there is no reliable evidence for this and if used incorrectly, it can be toxic.

Another is remdesivir which is an antiviral medicine that can help some people in hospital with severe COVID-19 but doesn't help people with a milder infection.

Dexamethasone can reduce the risk of people with serious COVID-19 from dying in hospital but doesn't help those with a milder infection, with Dr Samecki warning it can make things worse.

She reiterated there were no medicines yet that have been found to be effective against COVID-19 outside of intensive care.