Author: Nick Hatch, M.D. Educational Pearls Tramadol acts at multiple receptors and is a partial agonist at the mu opioid receptor, but also blocks reuptake of serotonin and norepinephrine throughout the body among others.   One major side effect to be aware of is that it lowers the seizure threshold. Useful in setting of pain control in patients with contraindications to NSAIDs who are poor opioid candidates. Use with caution as it potential for abuse.   References Hennies HH, Friderichs E, Schneider J (July 1988). "Receptor binding, analgesic and antitussive potency of tramadol and other selected opioids". Arzneimittel-Forschung. 38 (7): 877–80. "Tramadol Hydrochloride". The American Society of Health-System Pharmacists. Retrieved Dec 1, 2014. "Withdrawal syndrome and dependence: tramadol too". Prescrire Int. 12 (65): 99–100. 2003