It is a centrally acting analgesic, used for treating moderate to severe pain.
It possesses agonist actions at the u-opioid receptor and affects reuptake at the noradrenergic and serotonergic systems; it is also a NMDA-antagonist.
In practice tramadol 100 mg is equivalent to morphine 10 mg.
Onset of action: 30 minutes
Time to peak: 2 h
Duration of action: 4-6 h
Usual oral doses are 50–100 mg q 6 h–q 4 h; maximum recommended dose 400 mg/day.
Adverse drug reactions: pruritus, constipation, nausea, vomiting, dizziness, headache, somnolence