| Record No. | Name | No. of Entries |
| 451 | Macarpine | 5 |
| 452 | Macoline | 1 |
| 453 | Magnoflorine | 96 |
| 454 | Magnoflorine styphnate | 1 |
| 455 | Magnoflorine,iodide | 1 |
| 456 | Melosmine | 1 |
| 457 | Menisperine | 2 |
| 458 | Menisperine iodide | 1 |
| 459 | Merobustinine | 1 |
| 460 | Methoxymethyldihydromorphine | 1 |
| 461 | Methyl hydrastine | 1 |
| 462 | METHYLDESORPHINE | 1 |
| 463 | Methyldihydrocodeine | 1 |
| 464 | Methyldihydromorphine | 1 |
| 465 | Methylenedioxy-N-propylnoraporphine | 1 |
| 466 | Metocurine | 3 |
| 467 | METOCURINE CHLORIDE | 1 |
| 468 | Metvine | 1 |
| 469 | Migraeflux-green | 1 |
| 470 | Migraine-Kranit | 1 |
| 471 | Migraleve | 1 |
| 472 | Mivacurium | 1 |
| 473 | MLS000069811 | 1 |
| 474 | MLS000860063 | 1 |
| 475 | MLS001076557 | 1 |