Tramadol, sold under the brandname Ultram among others, is an opioid pain medication used to treat moderate to moderately severe pain. When taken as an immediate-release oral formulation, the onset of pain relief usually occurs within about an hour. It has two different mechanisms. First, it works by binding to the μ-opioid receptor. Second, it inhibits the reuptake of serotonin and norepinephrine. It is often combined with paracetamol as this is known to improve the efficacy of tramadol in relieving pain.