Pseudoephedrine

Pseudoephedrine is an indirect sympathomimetic from the chemical class of phenethylamines and amphetamines. It is used as a decongestant for the nose and sinuses in cold symptoms and in permanent erection of the penis (priapism). It can also be used as a stimulant or, in higher doses, as an awakening agent, and is often abused for these effects. It was first characterized in 1889 by the German chemists Ladenburg and Oelschlägel of the Merck company in Darmstadt. These isolated the substance from a sample of the plant from Ephedra vulgaris, which has long been used in traditional Eastern medicine. The decongestant effect of pseudoephedrine was first described in 1927 in animal experiments.

Pharmacodynamics

Pseudoephedrine causes vasoconstriction leading to a decongestant effect. It has a short duration of action. Pseudoephedrine acts mainly as an agonist at alpha-adrenergic receptors and less strongly as an agonist at beta-adrenergic receptors. This agonism causes vasoconstriction of the blood vessels, giving them less surface area for fluid to pass through, leading to decongestion of the affected regions. Less mucus is also produced in the upper airways, relieving symptoms.

Pharmacokinetics

Pseudoephedrine is approximately 6% bound to human serum albumin. The majority of the administered dose of pseudoephedrine is excreted unmetabolized in the urine. The mean elimination half-life of pseudoephedrine is approximately 6 hours.

Drug Interactions

Use of pseudoephedrine together with other sympathomimetics (tricyclic antidepressants, MAO inhibitors, psychostimulants, amfetamine-type anorectics, etc.) may result in an increase in blood pressure. Pseudoephedrine may weaken the effect of antihypertensive agents (e.g., beta-blockers).

Side effects

Common adverse drug reactions include.

• stimulation of the central nervous system
• insomnia
• nervousness
• excitability
• Dizziness
• Bladder emptying disorders
• Anxiety

Rare adverse reactions include:

• Tachycardia
• Palpitations
• mydriasis (dilated pupils)
• Hallucinations
• Cardiac arrhythmias
• Hypertension
• Seizures
• ischemic colitis

Contraindications

• hypersensitivity or allergy to pseudoephedrine
• Hypertension
• pre-existing bladder emptying disorders
• severe hepatic or renal insufficiency
• cardiovascular disease
• cardiac arrhythmias
• Pregnancy and breastfeeding