Decongestants

Decongestants are medicines that relieve congestion by reducing swelling, inflammation, and mucus formation within the nasal passages or the eye.  They have no other effect on symptoms such as a runny nose or sneezing.

Decongestants may be taken orally to help relieve congestion that is affecting the nose, sinuses, and eyes or sprayed directly in the nose or instilled in the eye for a more local effect.

The inside of the nose is lined with small blood vessels. Blood flow is increased to these blood vessels when our immune system detects the presence of an allergen (such as a virus or pollen). This causes swelling within the blood vessels which can block the nasal passageway, making nasal inhalation difficult. In addition, mucous glands within the nose secrete more mucus to trap the allergen which also contributes to nasal congestion and creates a sensation of “stuffiness”.

Most decongestants work by activating alpha-adrenergic receptors either by binding directly to them or stimulating the release of norepinephrine, a chemical transmitter. Activation of these receptors causes vasoconstriction (a narrowing of the blood vessels within that area). This decreases blood flow and helps to shrink swollen tissue, relieving congestion. They are often used in combination with antihistamines.

Decongestants are available as nose drops or nasal sprays, eye drops, and as tablets, capsules, and syrup.

What are decongestants used for?

Decongestants are typically used for conditions associated with nasal or eye congestion, such as:

• a cold
• allergies
• hay fever
• rhinitis
• sinusitis.

Decongestants only provide short-term relief from congestion and do not cure the underlying cause or condition.

What are the differences between decongestants?

Decongestants differ by their duration of action, their formulation availability and their propensity for side effects. Federal regulations require that pseudoephedrine is sold behind the pharmacy or service counter because it can be used illegally to manufacture methamphetamine.

Nasal decongestants are usually either short-acting (3 to 4 hours), such as levmetamfetamine or phenylephrine, or long-acting (8 to 12 hours) such as xylometazoline and oxymetazoline.

Topical decongestants (such as xylometazoline or oxymetazoline) have a more rapid onset of action and stronger effect than oral decongestants. They are less likely to cause side effects although there have been rare reports of seizures in children.

Oral decongestants do not cause rebound congestion (see “Are decongestants safe?”, below), but they are not as effective as topical formulations.

Are decongestants safe?

There are not many good quality studies that have investigated the effectiveness of decongestants, or reported on adverse effects. Most studies excluded children, therefore, most experts recommend not giving decongestants to children under the age of 12 because their effectiveness and risk of side effects is unknown.

Some decongestants (such as pseudoephedrine) have been associated with heart-related side effects such as elevated blood pressure, palpitations, tachycardia. Because decongestants act on alpha adrenoreceptors which are also located in other areas of the body, they may increase intraocular pressure in the eye and aggravate urinary obstruction.

Using nasal decongestants regularly and for longer than three to five days has been associated with rebound congestion. This is when nasal congestion recurs almost immediately once you stop using the decongestant, prompting repeat use of the nasal decongestant. If use continues unabated, a form of rhinitis called rhinitis medicamentosa will develop, which is very difficult to treat.

In some people, even recommended dosages of decongestants can aggravate already high blood pressure or cause heart palpitations or a fast heartbeat. Decongestants may also produce side effects such as CNS stimulation and may not be suitable for people including those with heart disease, high blood pressure, urinary problems, or taking certain medications (such as monoamine oxidase inhibitors).

If taken in overdose, decongestants can cause kidney failure, psychotic symptoms, strokes, and seizures.

What are the side effects of decongestants?

Insomnia and irritability are the most common side effects of oral decongestants and these side effects can occur in up to 25% of people taking these medicines. Other side effects may include:

• dizziness
• a headache
• excitability
• nervousness
• tremors.

For a complete list of side effects, please refer to the individual drug monographs.