Compounds, compositions and methods are provided that comprise selective β-glucuronidase inhibitors for both aerobic and anaerobic bacteria, especially enteric bacteria normally associated with the gastrointestinal tract. The compounds, compositions and methods can be for inhibiting bacterial β-glucuronidase and for improving efficacy of camptothecin-derived antineoplastic agents or glucuronidase-substrate agents or compounds by attenuating the side effects caused by reactivation by bacterial β-glucuronidases of glucuronidated metabolites of camptothecin-derived antineoplasatic agents or glucuronidase-substrate agents or compounds.