I feel I have a glue-like phlegm stuck in my throat for weeks already. I as advised to take antihistamine after which I had dry mouth. I as browsing the internet when I came across blog posts regarding the efficacy of robitussin to cases such as mine. I want to try it but am afraid it would interact with the PPI (omepron for my hyperacidity) whih I am taking. Pls advice. ## The Robitussin LiquiGels contain Dextromethorphan and there are no interactions listed between it and the Omeprazole in the Omepron, however, you should check with your doctor or pharmacist to be sure. It may cause side effects, such as: nausea, dry mouth and drowsiness. Read more: Are there any other comments or questions?