Severe serum sickness-like reaction to oral penicillin drugs: three case reports.

Background: Because the use of heterologous sera has diminished, the incidence of serum sickness has declined. However, serum sickness-like reactions to nonprotein drugs continue to occur.

Methods: We report three cases of severe serum sickness-like reactions in adults to oral penicillin drugs.

Results: In each patient, significant symptom resolution occurred within 24 hours of starting therapy with oral corticosteroids.

Conclusions: Serum sickness-like reactions to oral penicillin drugs may be more common than reported in the literature and can be very severe. No specific laboratory finding is universally present or definitively diagnostic. As with classic serum sickness, the diagnosis of serum sickness-like reaction is made clinically. In severe cases such as those presented here with debilitating joint symptoms or life-threatening angioedema, a diagnostic-therapeutic trial of prednisone, 40 to 60 mg at least once daily, is warranted.