| Record No. | Name | No. of Entries |
| 276 | Colchicine,oxo- | 1 |
| 277 | Colchicoinamide,N-Methyl- | 1 |
| 278 | Columbamine | 33 |
| 279 | Columbamine chloride | 1 |
| 280 | Columbamine,iodide | 1 |
| 281 | Combunox | 1 |
| 282 | Compound oxycodone | 1 |
| 283 | Coptisine | 1 |
| 284 | Coralyne | 3 |
| 285 | Coreximine | 1 |
| 286 | Corlumine | 1 |
| 287 | Corpaine | 4 |
| 288 | Corydaline | 7 |
| 289 | Corydine | 3 |
| 290 | Corydine methyl ether | 1 |
| 291 | Corynoline | 2 |
| 292 | Corytuberine | 1 |
| 293 | Crebanine | 1 |
| 294 | Crebanine N-oxide | 1 |
| 295 | CSH 068 | 1 |
| 296 | Cularicine | 1 |
| 297 | Cularidine | 2 |
| 298 | Cularimine | 2 |
| 299 | Cularine | 7 |
| 300 | Curarine | 1 |