Management
First-generation antihistamines
H1 antihistamines, which compete with histamine for the H1 receptor sites, are the first-line therapy for urticaria. First-generation antihistamines—such as diphenhydramine, chlorpheniramine, and hydroxyzine—can be very effective, particularly in acute cases. Diphenhydramine and chlorpheniramine are available over-the-counter and are relatively inexpensive. Hydroxyzine still requires a prescription, and it is thought to be more potent than diphenhydramine and chlorpheniramine.
The sedation experienced with these agents may help reduce pruritus, but it may also be a danger when a patient is driving or operating machinery. Because people respond to these medicines differently, you must weigh the bene fits and risks for each person based on their response to the medicine.
The pathophysiology of urticaria and angioedema can be mediated by immunoglobulin E, complement, physical stimuli, or autoantibodies, or it may be idiopathic. These mechanisms lead to mast cell degranulation, resulting in the release of histamine. Histamine and other inflammatory mediators produce the wheals, edema, and pruritus.
Second-generation antihistamines
Second-generation H1 antihistamines—such as astemizole, loratadine, desloratadine, and cetirizine—cause less sedation and are better for long-term daytime use. While more expensive, they are valuable in the management of chronic urticaria.
In the most refractory cases, combinations of various antihistamines may be useful in suppressing symptomatology. A nonsedating H1 antihistamine in the daytime can be combined with a sedating H1antihistamine and doxepin at night. An H2antihistamine can be added to this regimen before starting oral prednisone (level of evidence=5 for all the treatment regimes cited, based on expert opinion without explicit critical appraisal and based on physiology).
This patient’s treatment
The patient understood that he must stop taking the trimethoprim-sulfamethoxazole tablets and was given a fluoroquinolone for his chronic prostatitis. He took 1 dose of diphenhydramine (Benadryl, in this case) in the office, and the itching and wheals began to subside.
He was also told the could purchase diphenhydramine over the counter to continue to relieve his itching and wheals. He was advised that if it made him sleepy, he could call the office for a prescription for a nonsedating antihistamine.
This patient’s outcome
The patient was significantly better the next day and never needed additional medications for urticaria. His chronic prostatitis did resolve with a 2-month course of fluoroquinolone.