Decongestants

Decongestants

Decongestants may be classified as systemic or topical, depending on how they’re administered.

Types of decongestants

As sympathomimetic drugs, systemic decongestants stimulate the sympathetic nervous system to reduce swelling of the respiratory tract’s vascular network. Systemic decongestants include:

• ephedrine
• phenylephrine
• pseudoephedrine.

Topical concerns

Topical decongestants are also powerful vasoconstrictors. When applied directly to swollen mucous membranes of the nose, they provide immediate relief from nasal congestion. These drugs include:

• ephedrine, epinephrine, and phenylephrine (sympathomimetic amines)
• naphazoline and tetrahydrozoline (imidazoline derivatives of sympathomimetic amines).

Pharmacokinetics

The pharmacokinetic properties of decongestants vary.

Absorbed quickly…

When taken orally, the systemic decongestants are absorbed readily from the GI tract and widely distributed throughout the body into various tissues and fluids, including cerebrospinal fluid, the placenta, and breast milk.

…metabolized slowly

Systemic decongestants are slowly and incompletely metabolized by the liver and excreted largely unchanged in urine within 24 hours of oral administration.

Direct action

Topical decongestants act locally on the alpha receptors of the vascular smooth muscle in the nose, causing the arterioles to constrict. As a result of this local action, absorption of the drug is negligible.

Warning!

Adverse reactions to acetylcysteine

During administration, acetylcysteine has a “rotten egg” odor that may cause nausea. With prolonged or persistent use, acetylcysteine may produce:

• bronchospasm
• drowsiness
• nausea and vomiting
• severe runny nose
• stomatitis.

Acetylcysteine isn’t recommended for the patient with asthma because it may cause bronchospasm.

Pharmacodynamics

The properties of systemic and topical decongestants vary slightly.

System(ic) analysis

Systemic decongestants cause vasoconstriction by stimulating alpha-adrenergic receptors in the blood vessels of the body. This reduces the blood supply to the nose, which decreases swelling of the nasal mucosa. They also cause contraction of urinary and GI sphincters, dilated pupils, and decreased insulin secretion.

Indirect hit

These drugs may also act indirectly, causing the release of norepinephrine from storage sites in the body, which results in peripheral vasoconstriction.

On topic(al)

Like systemic decongestants, topical decongestants stimulate alpha-adrenergic receptors in the smooth muscle of nasal blood vessels, resulting in vasoconstriction. The combination of reduced blood flow to the nasal mucous membranes and decreased capillary permeability reduces swelling. This action improves respiration by helping to drain sinuses, clear nasal passages, and open eustachian tubes.

Pharmacotherapeutics

Systemic and topical decongestants are used to relieve the symptoms of swollen nasal membranes resulting from:

• acute coryza (profuse discharge from the nose)
• allergic rhinitis (hay fever)
• the common cold
• sinusitis
• vasomotor rhinitis.

Team tactics

Systemic decongestants are commonly given with other drugs, such as antihistamines, antimuscarinics, antipyretic analgesics, and antitussives.

Advantage, topical

Topical decongestants provide two major advantages over systemics: minimal adverse reactions and rapid symptom relief.

Drug interactions

Because they produce vasoconstriction, which reduces drug absorption, topical decongestants seldom produce drug interactions.

Systemic decongestants, however, may interact with other drugs.

Warning!

Adverse reactions to decongestants

Most adverse reactions to decongestants result from central nervous system stimulation and include:

• nervousness

• restlessness
• insomnia
• nausea
• palpitations
• tachycardia
• difficulty urinating
• elevated blood pressure.

Systemic decongestants exacerbate hypertension, hyperthyroidism, diabetes, benign prostatic hypertrophy, glaucoma, and heart disease. They’re also secreted in breast milk in a breast-feeding woman.

Topical decongestants

The most common adverse reaction associated with prolonged use (more than 5 days) of topical decongestants is rebound nasal congestion.

Other reactions include:

• burning and stinging of the nasal mucosa

• sneezing
• mucosal dryness or ulceration.

Issue of sensitivity

The patient who’s hypersensitive to other sympathomimetic amines may also be hypersensitive to decongestants.

• Increased CNS stimulation may occur when systemic decongestants are taken with other sympathomimetic drugs, including epinephrine, norepinephrine, dopamine, dobutamine, isoproterenol, metaproterenol, terbutaline, and phenylephrine, and tyramine-containing foods.
• Use of systemic decongestants with MAOIs may cause severe hypertension or a hypertensive crisis, which can be life-threatening. These drugs shouldn’t be used together.
• Alkalinizing drugs may increase the effects of pseudoephedrine by reducing its urinary excretion.