Untested drugs can be used to treat patients infected with the Ebola virus, the World Health Organization says.
The WHO said it was ethical in light of the scale of the outbreak and high number of deaths – more than 1,000 people have died in West Africa.
The statement was made after its medical experts met in Switzerland on Monday to discuss the issue.
But officials warned there were very limited supplies of potential treatments
The WHO said where experimental treatments are used there must be informed consent and the results of the treatment collected and shared.
In a statement, it said: “In the particular circumstances of this outbreak, and provided certain conditions are met, the panel reached consensus that it is ethical to offer unproven interventions with as yet unknown efficacy and adverse effects, as potential treatment or prevention.”
But the organisation conceded there were still many questions to be answered including how data could be gathered effectively while the focus remained on providing good medical care.
It was also unclear where the funding for the treatment would come from.
Last week the WHO declared the Ebola outbreak was a global health emergency.
The move came as Liberia said it was getting an experimental drug, Zmapp, after requests to the US government.
But the WHO said there were only 12 doses.
Zmapp has been used on two US aid workers who have shown signs of improvement, although it is not certain what role the medication played in this.
A Roman Catholic priest, infected with Ebola in Liberia, who died after returning home to Spain is also thought to have been given the drug.
However, the drug has only been tested on monkeys and has not yet been evaluated for safety in humans.
What drugs exist currently ?
There a handful of drugs that have been shown to work well in animals.
One is Zmapp – the drug requested by the Liberian government. This contains a cocktail of antibodies that attack proteins on the surface of the virus.
Only one drug has moved onto early safety testing in humans. Known as TKM-Ebola this interrupts the genetic code of the virus and prevents it from making disease causing proteins.
The drug was trialled in healthy volunteers at the beginning of 2014 but the American medicines regulator asked for further safety information. The manufacturer says human studies may soon resume.
Another option would be to use serum from individuals who have survived the virus – this is a part of the blood that may contain particles able to neutralise the virus.
Vaccines to protect against acquiring the disease have also been shown to work in primates. American authorities are considering fast-tracking their development and say they could be in use in 2016. Trials are likely to start soon according to the WHO.
But experts warn ultimately the only way to be sure a drug or vaccine is effective is to see if it works in countries affected by Ebola.
There is no cure for Ebola, which has infected at least 1,779 people since the outbreak was first reported in Guinea in February.
The Liberian government said it was aware of the risks associated with Zmapp, but the alternative was to allow many more people to die.
“The alternative for not testing this is death, a certain death,” Information Minister Lewis Brown told the BBC.
“This is not even the rock and the hard place for us.
“We think those who have been infected should be given the chance to have that tested on them if they give their consent to do so.
“We know there may be risks associated with it,” the minister added, “but choosing a risk and choosing dying I am sure many would prefer to see that risk happen”.
Ebola’s initial flu-like symptoms can lead to external haemorrhaging from areas like eyes and gums, and internal bleeding which can lead to organ failure. Patients have a better chance of survival if they receive early treatment.
Fatality rate can reach 90% – but the current outbreak is about 55%
Incubation period is two to 21 days
There is no vaccine or cure
Supportive care such as rehydrating patients who have diarrhoea and vomiting can help recovery
Fruit bats are considered to be virus’ natural host