In popular culture
In the pilot episode of Breaking Bad, Walter White first synthesizes methamphetamine through the Nagai route, using  red phosphorus and iodine to reduce pseudoephedrine. In the episode "Vitamin D" of Glee, Terri takes a job as the school nurse to stop her husband, Will Schuester, from becoming closer to guidance counsellor Emma Pillsbury (Jayma Mays), but is fired after giving the students performance-enhancing pseudoephedrine tablets. In her 2013 single "Avant Gardener", Australian rock musician Courtney Barnett refers to the effects of pseudoephedrine: "Reminds me of the time / When I was really sick and I / Had too much pseudoephedrine and I / Couldnt sleep at night". In her 2017 album Melodrama, pop artist Lorde references pseudoephedrine on the song "Writer in the Dark". The lyric reads: "I still feel you, now and then / Slow like pseudoephedrine / When you see me, will you say Ive changed?" Synthesis
Although pseudoephedrine occurs naturally as an alkaloid in certain plant species (for example, as a constituent of extracts from the Ephedra species, also known as ma huang, in which it occurs together with other isomers of ephedrine), the majority of pseudoephedrine produced for commercial use is derived from yeast fermentation of dextrose in the presence of benzaldehyde. In this process, specialized strains of yeast (typically a variety of Candida utilis or Saccharomyces cerevisiae) are added to large vats containing water, dextrose and the enzyme pyruvate decarboxylase (such as found in beets and other plants).
Increase of ectopic pacemaker activity can occur when pseudoephedrine is used concomitantly with digitalis. Antacids increase the rate of pseudoephedrine absorption, while kaolin decreases it. Mechanism of action
Pseudoephedrine is a sympathomimetic amine. Its principal mechanism of action relies on its direct action on the adrenergic receptor system. The vasoconstriction that pseudoephedrine produces is believed to be principally an α-adrenergic receptor response.Pseudoephedrine acts on α- and β2-adrenergic receptors, to cause vasoconstriction and relaxation of smooth muscle in the bronchi, respectively. α-Adrenergic receptors are located on the muscles lining the walls of blood vessels. When these receptors are activated, the muscles contract, causing the blood vessels to constrict (vasoconstriction). The constricted blood vessels now allow less fluid to leave the blood vessels and enter the nose, throat and sinus linings, which results in decreased inflammation of nasal membranes, as well as decreased mucus production. Thus, by constriction of blood vessels, mainly those located in the nasal passages, pseudoephedrine causes a decrease in the symptoms of nasal congestion. Activation of β2-adrenergic receptors produces relaxation of smooth muscle of the bronchi,  causing bronchial dilation and in turn decreasing congestion (although not fluid) and difficulty breathing. Other uses
There have been reports of off-label uses of pseudoephedrine for its stimulant properties. Long-distance truck drivers and athletes, for example, have reportedly used pseudoephedrine as a stimulant to increase their state of alertness/awareness.A study has also found that pseudoephedrine can reduce milk production in breastfeeding women.