Differences in the proportion of cumulative days on codeine, tramadol or piritramide between patients with normal magnesium levels and patients with high magnesium levels
| Mean serum magnesium | Difference in proportion (95% CI) | ||
| ≤1.0 mmol/l | >1.0 mmol/l | ||
| Proportion of days (%) on: | |||
| Codeine | 37% | 44% | −7% (−1 to −14%) |
| Tramadol | 31% | 32% | −1% (−7 to 5%) |
| Piritramide | 21% | 16% | 5% (0 to 10%) |