Allowing GPs to prescribe the medication for patients suffering conditions, such as multiple sclerosis and chronic pain, brings WA into line with other states including NSW, Queensland and Victoria.

But doctors must still seek specialist approval when prescribing for children under the age of 16 and patients who are drug dependent or have a history of drug abuse.

Medicinal cannabis products are not approved by the Therapeutic Goods Administration or funded by the Pharmaceutical Benefit Scheme, which is the responsibility of the federal government.

"It is important for the Commonwealth to have a flexible system that expedites affordable access to new and emerging healthcare treatments," Health Minister Roger Cook said on Tuesday.

Australian Medical Association WA president Andrew Miller backed the state government's decision and said the potential for "doctor shopping" was low.

He said medicinal cannabis had been shown to help children with epilepsy and patients with neurological conditions.

"At this stage, the evidence for this use more widely for things such as nausea or for chronic pain is not very good at all," he told reporters.

"We already have quite good drugs for these things ... so, we'll need to collect a lot more data and see some proper trials coming forward from the drug companies before we'll be supporting widespread use."

Australian Associated Press