Table 2.

Number of drugs containing non-aromatic rings or bridge rings in the whole database and five sub-databases.

Number of Non-Aromatic Rings	All Drugs	Oral Drug	CNS Drugs	Cardiovascular Drugs	Anti-Infective Drugs	Anti-Cancer Drugs
0	2985	435	416	466	372	182
1	2164	343	443	332	293	117
2	854	147	199	138	140	61
3	258	47	29	35	60	31
>3	464	55	8	33	27	43
bridge rings	166	24	27	17	13	8