Within each group (n=9) 3 volunteers were randomised to receive placebo and the remaining 6 volunteers to receive BIA 2-093. No volunteer was a member of more than one treatment group. In each group, the study consisted of a single-dose period (Phase A) followed by a 7-day multiple-dose period (Phase B). The multiple-dose phase started 96 h post single-dose. Progression to the 2400 mg dose (Group 2) only occurred if the 1800 mg dose (Group 1) was considered to be safe and well tolerated. An appropriate interval separated the investigation of the two groups in order to permit a timely review and evaluation of safety data.