List of drugs commonly associated with HA21
| Drug | Cases of HA | Serious events (%) | Fatal events (%) | |
| 1 | Valproate | 1260 | 768 (61) | 54 (4) |
| 2 | Fluorouracil | 221 | 213 (96) | 20 (9) |
| 3 | Topiramate | 96 | 65 (68) | 0 (0) |
| 4 | Oxaliplatin | 74 | 68 (92) | 12 (16) |
| 5 | Asparaginase | 71 | 50 (70) | 6 (8) |
Column 3 lists the absolute number of cases associated with HA for each drug. Columns 4 and 5 list the absolute number and % in brackets of serious events and fatal events. For serious events these were defined as severe case, death, life-threatening, caused or prolonged hospitalisation, disabling/incapacitating, congenital anomaly/birth defect, other medically important condition. For seriousness criteria it was possible to choose more than one.
HA, hyperammonaemia.