How Do Systemic Decongestants Work?

Systemic decongestants are adrenergic agonists used to treat sinus and nasal congestion. Congestion may be caused by cold, allergies, or upper respiratory tract infections.

Decongestants cause shrinkage of blood vessels in the nasal passages (vasoconstrict). Vasoconstriction reduces nasal congestion by preventing fluid from draining from blood vessels into the tissues lining the nasal passages.

Phenylephrine is approved by the U.S. Food and Drug Administration (FDA) for the treatment of sinus congestion. Phenylephrine works by binding to alpha 1-adrenergic receptors present in the walls of arterioles and causes systemic arterial vasoconstriction (narrowing of blood vessels).

Pseudoephedrine is a sympathomimetic drug approved by the U.S. FDA for the treatment of sinus/nasal congestion. Pseudoephedrine causes vasoconstriction by stimulating alpha-adrenergic receptors present in the walls of arterioles. This drug also stimulates beta-adrenergic receptors and causes relaxation of the bronchus leading to increased heart rate and contractility.

Systemic decongestants are administered orally to treat:

• Sinus congestion
• Nasal congestion (stuffy nose)

Off-label use includes:

• Priapism (prolonged erection of the penis, usually without sexual arousal)

Side effects of systemic decongestants may include:

• Nausea and vomiting
• Restlessness
• Insomnia
• Headache
• Tremor
• Nervousness
• Premature ventricular contractions (extra heartbeats in the lower chambers of the heart)
• Atrial fibrillation (irregular rapid beating of upper chambers of the heart)
• Myocardial infarction (heart attack)
• Respiratory distress
• Gastric irritation
• Severe hypertension
• Ischemic colitis (inflammation of the large intestine) 
• Anaphylaxis (life-threatening allergic reactions)

The information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of systemic decongestants include:

• Nexafed
• Phenylephrine PO
• Pseudoephedrine
• Sudafed
• Sudafed PE Sinus Congestion
• Zephrex-D