8b85b910_d_s_Flow___Scientific_American__2
[0] Decongestants [1] Ephedrine, Sudafed [3] Pseudoephedrine, the active ingredient in most decongestants, also causes tightening in the blood vessels in the brain, which can trigger insomnia, restlessness and anxiety, as well as headache if the blood vessels narrow too quickly. [2] 
Decongestants vanquish runny noses by causing swollen blood vessels in the mucus membrane of the nose and sinuses to tighten. When taken in pill form, this effect extends throughout the body.
Common Prescription Drugs Alter Blood’s Flow - Scientific American
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