Adrenergic antagonist drug

Urticaria (Hives) overview

• It is defined as smooth, slightly raised, pink or red areas of the skin of various sizes and shapes associated with pruritus.
• Urticaria is classified as type 1 hypersensitivity “immediate hypersensitivity”.
• Urticaria lesions usually appear after hours of exposure “immediate“  to allergen and resolve rapidly when the drug is withdrawn. Lesions commonly last for 20 minutes to 3 hours, disappear, and  then reappear in the other skin areas.
• The development of urticaria is often an isolated event without systemic reaction. Rarely, it can be prelude to the development of anaphylactic shock.

Management of urticaria

• It is essential to identify the allergen and avoiding further exposure to it “may be food or drug or other substances”.
• Oral antihistamines are the primary agents used in the management of urticaria. First-line therapy is oral antihistamine “second generation antihistamines are preferred” because of the adverse effects of first generation antihistamines such as drowsiness, anticholinergic effects and cognitive effects), which may continue until the next day so they are not recommended as first choice unless a specific need is present.
• Examples of second generation antihistamines “non-sedating antihistamines” are loratadine, desloratadine, acrivastine, cetirizine, fexofenadine or mizolastine.

Summary of management of urticaria

1. Avoid the exposure to the allergen.
2. Administration of non-sedating antihistamines “second generation antihistamines” unless there is a specific need is present (in the case of children, sedating effect of first generation is needed so they are preferred in children over second generation).

What if the patient is not responding sufficiently to the standard dose of antihistamines ?

1. Reach up to 4 folds of the dose of antihistamine.
2. Combination of H1 antihistamines and H2 blockers can be used.
3. For refractory cases the patient should go for topical corticosteroids.

Topical corticosteroids therapeutic considerations

• Topical corticosteroids are classified into 4 main groups according to potency: mild, moderate, potent and very potent. 

The approximate potencies of some topical corticosteroids:

 

• The choice of topical corticosteroid is dependent on the site and severity of skin legions.

• Site of legions:

• Whenever possible, use only mild steroids in the delicate sites such as the face, genitals and flexures.
• Avoid corticosteroid application on the periorbital region because of the thin skin increasing the likelihood of absorption and risk of cataracts or glaucoma.

• Severity of legions:

Mild to moderate potency corticosteroids are the groups used in most urticaria.

Adverse drug reactions of topical corticosteroids:

The adverse effects are mainly local:

• Stretch marks “striae”.
• Telangiectasia “visible dilated small blood vessels”.
• Epidermal thinking.
• Purpura “bruising”.
• Perioral dermatitis.
• Poor wound healing.

• Frequency of dosing of topical corticosteroids

Topical corticosteroids should be applied no more than twice daily “increasing the frequency from twice daily to four daily does not provide superior response and may lead to increased severity of adverse effects.

• Dosing of topical corticosteroids

• The recommended amount used can be quantified using a fingertip unit.
• Each 1 fingertip unit is sufficient to cover an area of the size of 2 palms.

The recommended amount of a topical corticosteroids corresponding to one fingertip unit:

 

References

EEACI/GA2LEN/EDF/WAO guideline management of urticaria.