A .beta.-glucuronidase inhibitor comprising at least one compound selected from the group consisting of baicalin, oroxylin A-7-O-glucuronide and luteolin-3'-glucuronide; an extract of scutellaria root (baikal skullcap; Scutellariae Radix) and/or schizonepeta spike (Japanese catnip; Schizonepelae Spica); or a Chinese and Japanese traditional prescription comprised of scutellaria root (baikal skullcap; Scutellariae Radix) and/or schizonepeta spike (Japanese catnip; Schizonepelae Spica) as a crude drug. The .beta.-glucuronidase inhibitor can relieve the adverse effect, especially diarrhea, caused in the administration of a compound represented by the following formula I ##STR1##

Tsumura &amp; Co.

nepeta trachonitica/gin diare

.beta.-glucuronidase inhibitor

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