A prodrug utilizes an enzyme whose enzymatic activity is different in between the target site of the drug and the site to express side effects, the prodrug having a substituent cleavable with the enzyme and being activated by cleaving the substituent with the enzyme. As the target site of the drug, for example, a respiratory organ can be mentioned and as the site to express side effects, for example, the heart can be mentioned. As the example of the drug, a bronchodilator can be mentioned and as the example of the enzyme, a glycosidase (for example, .beta.-glucuronidase) can be mentioned. Furthermore, the substituent is, for example, a glycosyl group composed of a monosaccharide or an oligosaccharide. Use of the enzyme enables reducing the side effects of a drug of the type whose target site is different from the site to express side effects.