Oral antihistamines for treatment of chronic idiopathic urticaria
Oral antihistamines have been the first line treatment for all patients with chronic or idiopathic urticaria. Non-sedating 2nd generation H1 antihistamines are used with good treatment response. When itching is intense, especially in the night, sedative first generation H1 antihistamines are given in the night and non-sedating 2nd generation H1 antihistamines are given during the day for the idiopathic urticaria patient. Increasing the dosage up to four fold is recommended if the response to the initial dosage is found inadequate during chronic idiopathic urticaria treatment.First generation H1 antihistamines for chronic or idiopathic urticaria
Chlorpheniramine, hydroxyzine, and diphenhydramine are the first generation H1 antihistamines having side effect of sedation. Though these antihistamines have proven record of efficacy in urticaria treatment, with the advent of second generation drugs their sedative effects appear as a big drawback in the treatment of chronic idiopathic urticaria.
Non–sedating 2nd generation H1 antihistamines in urticaria treatment
Loratadine, fexofenadine, cetirizine, levocetirizine, terfenadine, desloratadine and mizolastine are non sedating second generation H1 antihistamines very much in use in the treatment of chronic idiopathic urticaria.
Nonsedating H2 antihistamines for chronic idiopathic urticaria
Cimetidine, ranitidine, famotidine and nizatadine are H2 antihistamines having no sedating side effect. These drugs have been used successfully along with H1 drugs for the treatment of chronic or idiopathic urticaria.
Treatment of antihistamine –resistant chronic idiopathic urticaria
Some forms of chronic idiopathic urticaria do not respond well to antihistamine treatment. In some patients chronic idiopathic urticaria may become antihistamine -resistant. In such instances non antihistamine medications like systemic corticosteroids, leukotriene modifiers or immunosuppressants may be considered during urticaria treatment. However their use has many limitations due to their side effects.Role for systemic corticosteroids
Systemic glucocorticoids like prednisone have been used for lessening swelling, inflammation and itch in chronic idiopathic urticaria. However they can be used only for a short treatment periods as they have serious side effects like Cushing syndrome, skin damage, increased blood glucose levels, sleep disturbances, weight gain and psychological effects. Corticosteroids can weaken the immune system and worsen the existing infections of patients with idiopathic urticaria.
Leukotriene modifiers for chronic idiopathic urticaria
Asthma medications like montelukast and zafirlukast are leukotriene receptor antagonists (LTRA). They have been found to be effective in the treatment of chronic idiopathic urticaria when used along with non–sedating 2nd generation H1 antihistamines like loratadine. Side effects of leukotriene modifiers include gastrointestinal disturbances, headaches, general hypersensitivity, insomnia, sleep disorders, aggression, anxiousness, hallucinations, depression, irritability, and increased bleeding tendency.
Immunosuppressant drugs
Immunosuppressant drugs like cyclosporine and cyclosporin G are useful in the treatment especially of chronic autoimmune urticaria. As immunosuppressants they suppress the activity of the immunological system by obstructing the activity and growth of T cells. Treatment with immunosuppressants may be associated with a number of potentially serious adverse drug reactions (ADRs) like gastrointestinal disturbances, peptic ulcers, pancreatitis, convulsions, kidney and liver dysfunction, increased vulnerability to opportunistic infections and flare-up of current infections. Ciclosporin is listed as IARC Group 1 carcinogens as sufficient evidence of carcinogenicity in humans has been established.
Maintenance treatment
Once the symptoms resolve the treatment must be continued and tapered off after three months. The dosage of the medication is gradually reduced every two weeks. In many cases relapse has occurred when the medication is withdrawn soon after the resolution of symptoms.
Topical agents
Certain topical agents like calamine lotion, menthol with aqueous cream, and crotamiton lotion have been found to soothe the inflammation and itching. Applying cold compress or ice to the affected area for about 15 minutes relieves swelling, itching and pain. This may be followed up with application of calamine lotion.
Considerations for children
There are specific approvals and restrictions by FDA for use of various antihistamine medications in children considering their age. Please check the drug information provided by the manufacturer for use in children before usage.
Considerations for pregnant women
First-generation antihistamine such as chlorpheniramine is the safest choice for treatment of chronic idiopathic urticaria in pregnant women. Considerable usage experience is gained in its long term use without any fetal harm.
For drugs like cetirizine and loratadine there are no controlled data in human pregnancy and have been assigned to pregnancy category B by the FDA. These drugs are recommended for use during pregnancy when need benefit outweighs risk. They are excreted into human milk. Hence their use is not recommended in nursing mothers.
Like cetrizine, montelukast and zafirlukast have been assigned to pregnancy category B by the FDA.
Cyclosporine and prednisone have been assigned to pregnancy category C by the FDA and are potentially harmful to fetus.
Avoidance of triggers or exacerbating factors
In some cases of chronic urticaria the triggers are identifiable. In such cases avoiding the trigger itself is the treatment. However in idiopathic urticaria the causes are not known. Avoiding the possible causes may bring relief to the patient affected by the idiopathic allergy.- Avoid tight fitting clothes, shoes and belts.
- Try to keep your surroundings cool.
- Avoid hot or cold baths.
- Avoid stress and tension.
- Do not do strenuous exercise.
- Inform the doctor about your proneness to urticaria when he prescribes medications.
- Avoid possible food triggers.
- Avoid exposure to sun.
- Avoid exposure to cold winds.
- Avoid exposure to germicides, pesticides and detergents.
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Topic of interest:
Types of urticaria - Types of physical urticaria
Reference:
1. Kaplan AP, Greaves M. Pathogenesis of chronic urticaria. Clin Exp Allergy. 2009 Jun;39(6):777-87. Epub 2009 Apr 22.
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