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Allergies > Doctors: Decongestants


Decongestants are effective at reducing nasal congestion, a symptom not well controlled by antihistamines alone.

Mode of Action

Nasal congestion is a common symptom of allergic rhinitis. It is caused when inflammatory mediators such as histamine, bradykinin, prostaglandins, leukotrienes, platelet-activating factor, and neuropeptides induce nasal vasodilation. This leads to tissue swelling, reduced internal nasal diameter, and increased resistance to air flow. Nasal secretions may also reduce airflow.

Decongestants reduce nasal congestion by causing nasal vasoconstriction. They contain sympathomimetic agents and thus mimic the actions of the neural transmitter norepinephrine, resulting in the activation of adrenergic receptors alpha 1 and alpha 2.

- Activation of alpha 1 receptors causes vasoconstriction that reduces the volume of blood in the mucosa and the mucosa volume, leading to decreased congestion

- Activation of alpha 2 receptors causes vasoconstriction that reduces blood flow into the capillary bed of the nasal mucosa, reducing the extracellular fluid that is associated with congestion and rhinorrhoea

Decongestants may also displace norepinephrine from storage vesicles (sometimes also preventing its re-uptake).


Decongestants are available in oral and topical preparations, both of which are effective at reducing congestion.

Topical decongestants are slightly more effective than oral decongestants, but they may cause rebound vasodilation

Safety Decongestants

All decongestants should be used with care in children <1 year old because of the narrow range between therapeutic and toxic doses.

Oral decongestants

The primary side effects are nervousness, irritability, tachycardia, palpitations, headache, and insomnia. Blood pressure may be increased from generalised constriction of blood vessels. They should therefore be used with caution in patients at risk from complications of high blood pressure.

Pseudoephedrine is contraindicated in children <1 year old, adults >60 years old, pregnant women, and in patients with hypertension, cardiopathy, hyperthyroidism, prostatic hypertrophy, glaucoma, and psychiatric disorders, and to patients taking beta-blockers or MAO inhibitors.

Topical decongestants

Topical applications do not have systemic side effects, but prolonged use (>10 days) may lead to tachyphylaxis, rebound congestion, and rhinitis medicamentosa.

Use of Decongestants

Short courses of decongestants can be used to reduce nasal blockage promptly while co-administering other drugs for other symptoms.

Van Cauwenberge et al recommend that topical decongestants should be limited to a duration of <10 days because of the risk of rhinitis medicamentosa

Drug Information - Oral Preperations

The following table gives the major oral decongestants available in the UK, US, and Canada. Links to prescribing information or summary of product characteristics are provided for most drugs. Only brand names are given, but generic versions may also be available.

Active ingredients Brand names and county where licensed
Pseudoephedrine hydrochloride Galpseud (UK), Sudafed products (UK, Canada, US). Other US brand names include Dimetapp, Cenofed
Phenylpropanolamine In November 2000, the Food and Drug Administration (FDA) issued a public health warning regarding phenylpropanolamine (PPA) due to the risk of hemorrhagic stroke. The FDA, supported by results of a research program, requested that manufacturers voluntarily discontinue marketing products that contain PPA and that consumers work with their healthcare providers to select alternative products.

Combination Treatments

Antihistamines and decongestants

Antihistamines are effective at reducing rhinorrhoea, sneezing and nasal itching, but have limited effects on nasal obstruction. In combination with oral decongestants, which do effectively reduce nasal congestion, combination treatment can counteract all the symptoms of allergic rhinitis. There are various proprietary combined formulations; these tend to be more effective than individual components alone.

Antihistamines and topical corticosteroids

Topical corticosteroids and antihistamines given together do not out-perform corticosteroids given alone. Despite this, in patients not fully controlled by corticosteroids, the addition of antihistamines may be useful, particularly when they suffer from eye symptoms.


Gentile DA, Friday GA, Skoner DP. Management of allergic rhinitis. Antihistamines and decongestants. Immunol Allergy Clin North Am 2000;20:355–368.EFFICACY

van Cauwenberge P, Bachert C, Passalacqua G, et al. Consensus statement on the treatment of allergic rhinitis. European Academy of Allergology and Clinical Immunology. Allergy 2000;55:116–134.

Dykewicz MS, Fineman S, Skoner DP, et al. Diagnosis and management of rhinitis: complete guidelines of the Joint Task Force on Practice Parameters in Allergy, Asthma and Immunology. Ann Allergy Asthma Immunol 1998;81:478–518.

Sussman GL, Mason J, Compton D, Stewart J, Ricard N. The efficacy and safety of fexofenadine HCl and pseudoephedrine, alone and in combination, in seasonal allergic rhinitis. J Allergy Clin Immunol 1999;104:100–106.

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