Marked decrease of tacrolimus blood concentration caused by compound Chinese herbal granules in a patient with refractory nephrotic syndrome

What is known and objective The blood concentration of tacrolimus can be affected by co‐administrated drugs. The objective is to draw more attention to herb‐drug interactions in China, where herbal medicines are commonly used. Case description The blood concentration of tacrolimus in a girl with refractory nephrotic syndrome decreased nearly a half despite no change in dose. Nebulizer therapy, cyclophosphamide and a compound Chinese herbal medicine were the only additional treatments than usual. What is new and conclusion The most possible cause of the decrease in tacrolimus concentration was the administration of Radix Astragali among compound Chinese herbal medicine granules. The blood concentration of tacrolimus in a girl with refractory nephrotic syndrome decreased nearly a half despite no change in dose. The most possible cause was the co‐administration of Radix Astragali among compound Chinese herbal medicine granules.