August 24, 2012

Q&A: Acute Urticaria Treatment

Acute urticaria may progress to life-threatening angioedema and/or anaphylactic shock in a very short time, although it usually presents as rapid-onset shock with no urticaria or angioedema.

In this article:
What is urticaria?
What is acute urticaria? And who gets acute urticaria?
MCQ: clinical scenario
MCQ: answer
MCQ: explanation
Understanding antihistamines

What is urticaria?

Urticaria is characterised by weals (hives) or angioedema (swellings, in 10%) or both (in 40%). There are several types of urticaria. The name urticaria is derived from the common European stinging nettle 'Urtica dioica'.

A weal (or wheal) is a superficial skin-coloured or pale skin swelling, usually surrounded by erythema (redness) that lasts anything from a few minutes to 24 hours. Usually very itchy, it may have a burning sensation.

Angioedema is deeper swelling within the skin or mucous membranes and can be skin-coloured or red. It resolves within 72 hours. Angioedema may be itchy or painful but is often asymptomatic.

What is acute urticaria? And who gets acute urticaria?

Acute urticaria is urticaria, with or without angioedema, that is present for less than 6 weeks. It is often gone within hours to days.

One in five children or adults has an episode of acute urticaria during their lifetime. It is more common in atopic individuals. It affects all races and both sexes.

See separate article, Allergies and Allergic reaction.

MCQ: clinical scenario

You are the doctor on call, and are called by the nurse on duty to review a patient. You discover that this patient with allergic rhinitis has developed acute urticaria.

This condition is best relieved by:

a) Antigen avoidance
b) Combination of H1 and H2 antagonists
c) Antihistamine-decongestant preparation
d) Systemic corticosteroids
e) Oral adrenergic agonist

MCQ questions & answers on medicalnotes.info

MCQ exam: answer

The correct answer is B.
Among the answer options listed, acute urticaria is best relieved by a combination of H1 and H2 antagonists

MCQ: explanation

The main treatment for acute urticaria in adults and in children is with an oral second-generation antihistamine. While first-generation H1 antihistamines have a central effect and, thus, are also used as sedatives, second-generation H1 antihistamines have less central effects and are primarily used as antiallergic drugs.

For the treatment of acute urticaria, the combination of H1 and H2 antagonists is more effective than the H1 antagonist alone. But for the treatment of pruritus from acute allergic reactions, the H1 antagonist is more effective than the H2 antagonist, and the combination offers no additional benefit.

Understanding antihistamines

Histamine is a biologically active substance that potentiates the inflammatory and immune responses of the body, regulates physiological function in the gut, and acts as a neurotransmitter. Antihistamines are drugs that antagonize these effects by blocking or inhibiting histamine receptors (H receptors), and they are categorized as either H1 or H2 according to the type of H receptor targeted.

H1 antihistamines are mostly used to treat allergic reactions and mast cell-mediated disorders. This subtype is further divided into two generations. While first-generation H1 antihistamines have a central effect and, thus, are also used as sedatives, second-generation H1 antihistamines have less central effects and are primarily used as antiallergic drugs. H2 antihistamines are indicated primarily for gastric reflux disease because they reduce the production of stomach acid by reversibly blocking the H2 histamine receptors in the parietal cells of the gastric mucosa.

Most H1 and H2 antihistamines are contraindicated during pregnancy and childhood. First-generation H1 antihistamines are specifically contraindicated in angle-closure glaucoma and pyloric stenosis.

Reference(s)
1). Medscape: How might acute urticaria progress?. Available online: https://www.medscape.com/answers/137362-92967/how-might-acute-urticaria-progress
2). DermNet NZ: Acute urticaria. Available online: https://dermnetnz.org/topics/acute-urticaria/
3). AMBOSS: Antihistamines summary. Available online: https://www.amboss.com/us/knowledge/Antihistamines

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