The trial will recruit 400 eligible patients over 1 year (200 Penthrox and 200 tramadol). Patients managed by SCDF EAS for treatment of acute pain and who meet the eligibility criteria will be recruited into the study. Half of SCDF's 30 ambulances (15 ambulances), will be randomly assigned, equipped and trained to carry the new medication (Penthrox). The other half (15 ambulances), will be trained and equipped with tramadol. Allocation will be on a per station level. After 6 months, they will cross over to Penthrox and tramadol respectively.