Ephedrine. Computer graphic of a molecule of the drug ephedrine (C10.H15.N.O). The atoms (spheres) of the molecule are colour-coded: carbon (yellow), hydrogen (white), oxygen (red) and nitrogen (blue). Ephedrine is a stimulant drug that has similar effects to the natural body stimulant adrenaline. It stimulates the heart, dilates the bronchi (airways of the lungs) and constricts the blood vessels. It is used as a nasal decongestant and to treat asthma, and is administered by mouth or by inhalation. Side effects may include nausea, insomnia, headache and nervousness.