From the Research
For this patient with an allergic reaction presenting with diffuse hives but no facial swelling, I recommend administering methylprednisolone 125 mg IV as the steroid of choice, given its effectiveness in reducing inflammation and preventing progression to anaphylaxis, as supported by the treatment guidelines for allergic emergencies 1. Given the patient's weight of 107.95 kg, this standard dose is appropriate as steroid dosing for allergic reactions is not typically weight-based. In addition to the Benadryl (diphenhydramine) 50 mg the patient has already taken, consider adding famotidine 20 mg IV as an H2 blocker for synergistic antihistamine effect. Diagnostic testing should include:
- A basic metabolic panel to assess baseline renal function
- A complete blood count to evaluate for eosinophilia or other abnormalities No specific allergy testing is needed acutely. The patient should be monitored for at least 4-6 hours to ensure the reaction doesn't progress to anaphylaxis, with particular attention to vital signs, respiratory status, and any developing angioedema, as anaphylaxis can be difficult to recognize clinically and has a high incidence and potentially life-threatening nature 2. Steroids work by suppressing inflammatory mediator release and reducing vascular permeability, which helps resolve the urticarial reaction. Upon discharge, prescribe a 5-day oral prednisone taper (60 mg daily for 2 days, then 40 mg, 20 mg, and 10 mg for one day each) along with an oral antihistamine regimen to prevent rebound symptoms. It's also important to note that while methylprednisolone is the recommended steroid, there have been reports of immediate allergic reactions to methylprednisolone, although these are rare 3, 4.