... hours. I recently had pneumonia and continued using it as above along with prescription antibiotic (I did check w pharmacist). 3 weeks ago I started hyperventilating, having palpitations, weakness, fatigue and anxiety, rather like a panic attack. When I found out that sudafed can cause those symptoms I stopped taking it forever. The symptoms continue. Does anyone know for how long this might go on? I was given a clean bill of heart health 3 months ago. Anything I can do? I drink plenty of water