Adverse effects. ^*Nefopam (NFP) increased the frequency of dry mouth, dizziness, nausea and ataxia, in order of frequency, during the initial period of the study days 1 to 6 (P < 0.05 compared to those of normal saline [NS] group). There was no difference between the groups in overall frequencies of occurrence for each adverse effect. Dry mouth in both groups was an intolerable adverse effect which showed a never-decreasing and even-increasing symptom till the end of the study days.