Pseudoephedrine stays in the body for three to four hours before being eliminated by your kidneys, according to Drugs.com. Extended-release versions last eight to 12 hours.
Pseudoephedrine is a decongestant that works by shrinking the blood vessels in the nose and sinuses that cause congestion, also known as a stuffy nose. This medication is the active ingredient of Sudafed, Triaminic Softchew Cold and Allergy, and many other medications for adults and children, states Drugs.com. Possible side effects include anxiety, high blood pressure and increased heartbeat. Individuals should check with a doctor before using this medication if they have certain health conditions such as hypertension or are taking an MAO inhibitor.