Final answer:
Pseudoephedrine and ephedrine are used as decongestants and stimulants, extracted historically from the Ephedra plant and incorporated into modern medication. Phenylephrine is another decongestant often used as an alternative. While these substances relieve symptoms of nasal congestion, they have been scrutinized due to their potential in illicit drug production.
Step-by-step explanation:
Pseudoephedrine is a sympathomimetic drug used primarily as a decongestant for relieving nasal and sinus congestion, but also has stimulant properties. Its effects are due to its ability to act on adrenergic receptors and promote vasoconstriction, reducing swelling and allowing for easier breathing. However, its utility has been somewhat limited due to its role as a precursor in the illegal synthesis of methamphetamine.
Ephedrine, another alkaloid from Ephedra plants, shares similar properties and has been used as a stimulant and to treat asthma, hay fever, and congestion. Both substances have a history in traditional medicine and were later synthesized for use in modern medicinal practices.
Phenylpropanolamine (PPA) and phenylephrine are related compounds also used for their decongestant effects. Phenylephrine, which is less effective than pseudoephedrine due to partial breakdown in the digestive tract before absorption, is frequently found in over-the-counter preparations. It is an α₁-adrenergic agonist and works by binding to adrenergic receptors in the bronchioles and dilating them, aiding in mucus clearance.
It's important to understand that while cold and allergy medications containing these decongestants can relieve symptoms, some substances like cough suppressants do not always show measurable benefits. They can also be combined with other pharmaceuticals, such as antihistamines and expectorants, to treat a wider range of symptoms like cough, runny nose, and watery eyes associated with allergies.