Patients randomized and reason for withdrawal from the tiotropium and ipratropium groups
| Tiotropium n (%) | Ipratropium n (%) | |
| Randomized | 356 (100) | 179 (100) |
| Completed trial | 302 (84.8) | 141 (78.8) |
| Withdrawn due to adverse events | 36 (10.1) | 23 (12.8) |
| Worsening of COPD | 11 (3.1) | 11 (6.1) |
| Worsening of other pre-existing disease | 2 (0.6) | 4 (2.2) |
| Other adverse event | 23 (6.5) | 8 (4.5) |
| Withdrawn due to lack of efficacy | 3 (0.8) | 3 (1.7) |
| Withdrawn for other reasons | 15 (4.2) | 12 (6.7) |
| Noncompliant with protocol | 3 (0.8) | 3 (1.7) |
| Lost to follow-up | 2 (0.6) | 0 (0.0) |
| Consent withdrawn | 5 (1.4) | 4 (2.2) |
| Miscellaneous | 5 (1.4) | 5 (2.8) |
COPD: chronic obstructive pulmonary disease