2-(6-Cyano-1-hexyn-1-yl)adenosine, 2-(6-cyano-1-hexyn-1-yl)adenosine 5'-monophosphate, or salts thereof; and drugs containing the same as an active ingredient. The compounds have excellent effects of lowering ocular tension, promoting blood flow in retina, and protecting optic nerve failure and are highly soluble in water. Owing to these characteristics, the compounds are useful as drugs such as remedies for glaucoma and ocular hypertension.