Pseudoephedrine

Pseudoephedrine is a sympathomimetic medication commonly used as a decongestant. It is a stereoisomer of ephedrine and belongs to the class of phenethylamines that stimulate the sympathetic nervous system. In pharmaceutical use, pseudoephedrine occurs in several stereoisomeric forms, with one enantiomer providing the principal decongestant activity. It is formulated for oral administration, including tablets, and is frequently found in combination products with analgesics or cough suppressants.

Pseudoephedrine is used to relieve nasal and sinus congestion due to colds, allergies, or sinusitis; it is not a cure for infection or inflammation. It is usually taken for short periods and not advised for chronic use.

Pseudoephedrine acts as an alpha-adrenergic receptor agonist, causing constriction of nasal blood vessels and reduced swelling of nasal mucosa. Central nervous system stimulation can cause insomnia or agitation.

After oral dosing, pseudoephedrine is absorbed and reaches peak plasma concentrations within a few hours. The elimination half-life is generally several hours and is influenced by urine pH; the drug is largely excreted unchanged in urine. Interactions include potential hypertensive effects with monoamine oxidase inhibitors and other stimulants.

Because pseudoephedrine can be diverted for illicit synthesis of methamphetamine, many countries regulate its sale. Purchases may be restricted to pharmacies, require identification, and be subject to limits. Adverse effects include insomnia, dizziness, tachycardia, and elevated blood pressure; it is contraindicated in certain heart conditions, severe hypertension, hyperthyroidism, and in some pregnancy contexts.

Pseudoephedrine is derived from natural ephedra alkaloids in the 20th century and has since become a standard decongestant in many over-the-counter products.