There is no specific treatment for Covid-19. It is a new disease and drug development takes many years, so doctors are using re-purposed drugs on coronavirus patients in the hope that they work.
These are drugs approved for other diseases and so are known to be mostly safe for humans.
Some of the ones used to treat the disease include experimental antiviral drug remdesivir, which was originally developed to combat Ebola, a HIV-drug combination, malaria drug chloroquine and antiviral drug favipiravir, which China has approved for use for Covid-19.
There is also the rheumatoid arthritis drug tocilizumab, which has been used to treat those with severe lung damage.
Scientists have identified 69 potential drugs or drug combinations that can be used to treat Covid-19, and several hundred trials are being done to find an effective treatment.
As multiple small trials with different methodologies may not give clear, strong evidence about which treatments help to save lives, the World Health Organisation (WHO) announced last week that it is organising a multi-country drug trial.
The WHO's Solidarity trial will test the four most promising therapies: remdesivir, a combination of the HIV drugs lopinavir and ritonavir, the two HIV drugs plus interferon beta, and chloroquine.
It will compare their effectiveness to what is called standard of care - the regular support hospitals treating Covid-19 patients use now. Hospitals have used care options such as supplementary oxygen, mechanical ventilatory support and extracorporeal membrane oxygenation.
So far, the first trial of HIV drugs - which have been used on coronavirus patients in Singapore and elsewhere - has shown disappointing results.
Researchers from China conducted a small high-quality trial involving 199 patients from a hospital in Wuhan and found that a combination of the two HIV drugs lopinavir and ritonavir - sold under the brand name Kaletra - did not help the very sick coronavirus patients.
They had given standard care to 100 patients, and the HIV-drug combo plus standard care to 99 patients, and found no significant difference between the two groups.
"In hospitalised adult patients with severe Covid-19, no benefit was observed with lopinavir-ritonavir treatment beyond standard care," they wrote in a study published last week in the New England Journal of Medicine. It remains to be seen if combining this HIV drug combination with other antiviral agents, which have been used to treat severe acute respiratory syndrome (Sars) and is now being studied for use against the Middle East respiratory syndrome, can help, they said.
Singapore has also used the lopinavir-ritonavir combination on patients with variable clinical outcomes.
It is involved in large remdesivir trials initiated by the manufacturer Gilead Sciences and the National Institutes of Health in the United States.