The TGA has renewed warnings about the use of promethazine (Phenergan) and other first-generation sedating antihistamines for respiratory symptoms and sleep disturbances in children, after adverse events quadrupled in four years.

Up until 24 May, there were 226 adverse event reports involving newborns, infants and children given products containing first-generation antihistamines, compared to 45 as of late 2017.

This was despite all OTC products carrying warnings not to give them to children under two for any indication.

Oral cough, cold and flu products additionally warn against use in children under six and to seek medical advice before administering to children six to 11, the medicines regulator said on Wednesday.