A safety warning has been issued by the national medicines regulator over a so-called "Hollywood drug" used to treat type 2 diabetes and obesity.

The Therapeutic Goods Association has updated its product information for the relatively new class of medicines known as GLP-1 receptor agonists, warning of an increased risk of potential suicidal ideation.

The class includes semaglutide, the drug marketed in Australia as Ozempic.

The drug is taken as a weekly injection to treat diabetes, but is also widely used for weight loss, making it popular among celebrities.

Other GLP-1 receptor agonists included in the warning were semaglutide sold as Wegovy; liraglutide sold as Saxenda; dulaglutide (Trulicity) and tirzepatide (Mounjaro).

The TGA said patients taking any of these medicines should tell their health professional if they experienced new or worsening depression, suicidal thoughts or any unusual changes in mood or behaviour.

The updates have been issued after investigations by the TGA and other international regulators.

The product warning for tirzepatide (Mounjaro) was also updated to reflect a risk of decreased effectiveness of oral contraception when first taking or increasing the dose of the drug.

The TGA advised patients taking tirzepatide to switch to a non-oral contraceptive or add a barrier method of contraception for four weeks after first taking the medicine, and for four weeks after each increase in the dose.

It added that no GLP-1 receptor agonists should be used during pregnancy and that individuals with child-bearing potential should use effective contraception when using the drugs.

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