| Parameter | Varenicline 1 mg twice daily(n = 376) | Nicotine titrated from 21 mg patches(n = 370) |
| Any adverse event | 319 (84.8) | 260 (70.3) |
| Treatment discontinuations due to adverse events | 30 (8.0) | 16 (4.3) |
| Dose reductions or temporary withdrawal from study medication | 44 (11.7) | 25 (6.8) |
| Deaths | 0 (0.0) | 0 (0.0) |
| Serious adverse events | 2 (0.5) | 8 (2.2) |
| Most frequent adverse events | ||
| Nausea | 140 (37.2) | 36 (9.7) |
| Insomnia | 80 (21.3) | 71 (19.2) |
| Headache | 72 (19.1) | 36 (9.7) |
| Abnormal dreams | 44 (11.7) | 31 (8.4) |
| Constipation | 31 (8.2) | 9 (2.4) |
| Dizziness | 28 (7.4) | 13 (3.5) |
| Disturbance in attention | 24 (6.4) | 5 (1.4) |
| Vomiting | 23 (6.1) | 4 (1.1) |
| Diarrhoea | 22 (5.9) | 10 (2.7) |
| Flatulence | 22 (5.9) | 5 (1.4) |
| Dysgeusia | 22 (5.9) | 4 (1.1) |
| Abdominal pain (upper) | 21 (5.6) | 4 (1.1) |
| Fatigue | 21 (5.6) | 9 (2.4) |
Data presented as n (%).