A total of 18 studies (n=3,453) were included in the review.
Dental.
Among the dental studies all treatments, except for codeine 60 mg, showed significantly greater pain relief than with placebo. There was a clear dose-response for tramadol.
For tramadol 50 mg, the RR was 2.9 (95% CI: 1.6, 5.2) and the NNT was 9.1 (95% CI: 6.1, 18.8).
For tramadol 75 mg, the RR was 2.7 (95% CI: 1.1, 6.5) and the NNT was 9.1 (95% CI: 5.1, 64.5).
For tramadol 100 mg, the RR was 3.8 (95% CI: 2.4, 5.8) and the NNT was 4.6 (95% CI: 3.6, 6.4).
For tramadol 150 mg, the RR was 4.8 (95% CI: 2.1, 11.1) and the NNT was 4.2 (95% CI: 2.9, 7.3).
For codeine 60 mg, the RR was 1.3 (95% CI: 0.8, 2.1) and the NNT was 50 (95% CI: 16.3, infinity).
For aspirin 650 mg plus codeine 60 mg, the RR was 3.8 (95% CI: 2.2, 6.8) and the NNT was 6.3 (95% CI: 4.5, 9.8).
For acetaminophen 650 mg plus propoxyphene 100 mg, the RR was 4.0 (95% CI: 1.7, 9.4) and the NNT was 5.3 (95% CI: 3.4, 11.4).
Postsurgical.
All treatments showed statistically significantly superior analgesia compared with placebo. There was a clear dose-response for tramadol.
For tramadol 50 mg, the RR was 2.4 (95% CI: 1.4, 4.4) and the NNT was 7.1 (95% CI: 4.6, 17.9).
For tramadol 75 mg, the RR was 2.4 (95% CI: 1.7, 3.5) and the NNT was 4.5 (95% CI: 3.1, 7.0).
For tramadol 100 mg, the RR was 3.2 (95% CI: 1.8, 5.6) and the NNT was 4.8 (95% CI: 3.4, 8.2).
For tramadol 150 mg, the RR was 3.5 (95% CI: 2.5, 4.9) and the NNT was 2.4 (95% CI: 2.0, 3.1).
For codeine 60 mg, the RR was 1.9 (95% CI: 1.3, 2.7) and the NNT was 9.1 (95% CI: 6.0, 23.4).
For aspirin 650 mg plus codeine 60 mg, the RR was 5.8 (95% CI: 2.1, 15.9) and the NNT was 3.6 (95% CI: 2.5, 6.3).
For acetaminophen 650 mg plus propoxyphene 100 mg, the RR was 2.7 (95% CI: 1.9, 3.8) and the NNT was 5.3 (95% CI: 3.0, 5.7).
Overall, there was a clear dose-response for tramadol (p<0.0001, Kruskal-Wallis test).
Adverse events. There was also a dose-related effect for adverse effects in dental extraction patients, but not postsurgical patients.