A method of treating pain, e.g., acute post-operative pain, by administering to a human patient(s) a therapeutically effective dose of tramadol intravenously in a dosing regimen which includes one or more loading doses administered at shortened intervals as compared to dosing at steady-state is disclosed. In certain embodiments, the dose of tramadol about 25 mg and the second (and optionally) third doses are intravenously administered at intervals of about 2 hours, and thereafter the tramadol is intravenously administered at a dosing interval of about 4 hours, until the patient no longer requires treatment with tramadol.
