THE CASE
A 24-year-old man with no past medical history was referred to a nephrologist for a 5-month history of leg swelling and weight gain. His only medication was furosemide 40 mg/d, prescribed by his primary care physician. His physical examination was unremarkable except for lower extremity and scrotal edema.
Laboratory values included a creatinine of 0.8 mg/dL (reference range, 0.6 to 1.2 mg/dL); hemoglobin concentration, 14.4 g/dL (reference range, 14 to 18 g/dL); albumin, 1.9 g/dL (reference range, 3.5 to 5.5 g/dL); and glucose, 80 mg/dL (reference range, 74 to 106 mg/dL). Electrolyte levels were normal. Urinalysis revealed 3+ blood and 4+ protein on dipstick, as well as the presence of granular and lipid casts on microscopic exam. A 24-hour urine collection contained 10.5 g of protein. Antinuclear antibody titers, complement levels, hepatitis serologies, and antineutrophil cytoplasmic antibody titers were all normal.
A renal biopsy revealed idiopathic focal segmental glomerulosclerosis. The patient was started on oral prednisone 40 mg twice daily.
Two days later, he developed a diffuse pruritic maculopapular rash. He stopped taking the prednisone, and the rash resolved over the next 3 to 5 days. He was then instructed to restart the prednisone for his nephrotic syndrome. When he developed a new but similar rash, the prednisone was discontinued. The rash again resolved.
THE DIAGNOSIS
Since the patient had already been taking furosemide for 6 weeks without an adverse reaction, it was presumed that the prednisone tablet was causing his rash. It would be unusual for prednisone itself to cause a drug eruption, so an additive or coloring agent in the tablet was thought to be responsible for the reaction.
We noted that the patient had been taking a 20-mg orange tablet of prednisone. So we opted to “tweak” the prescription and prescribe the same daily dose but in the form of 10-mg white tablets. The patient tolerated this new regimen without any adverse effects and completed a full 9 months of prednisone therapy without any recurrence of skin lesions. His glomerular disease went into remission.
DISCUSSION
Excipients are inert substances that are added to a food or drug to provide the desired consistency, appearance, or form. They are also used as a preservative for substance stabilization.
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