The efficacy of the tricyclic antidepressant, amoxapine, was investigated in 20 subjects suffering from somatoform pain disorder, consisting of chronic lower back and leg pain with no identifiable organic cause and resistant to treatment. Evaluation of efficacy was made both prior to and 6 months after administration using the visual analogue scale (VAS) and self-rating depression scale (SDS). VAS and SDS improved significantly after amoxapine administration. If a VAS improvement rate ≥50% is defined as effective and < 50% as ineffective, then there were 10 subjects where the treatment could be rated as effective and 10 as ineffective. Correlations between pain response to amoxapine and subject background factors were consequently examined, but no predictive factors could be identified. The onset of the effect was 1 week in 7 subjects, and after 2, 3 and 4 weeks in 1 subject, respectively. The strongest effect tended to be shown in those subjects where the onset was earliest. These results indicate amoxapine administration may be an intervention worthy of consideration in cases of lower back and leg pain with no identifiable organic cause and resistant to other forms of treatment and that the efficacy can be evaluated in relatively short period of time.
