Tramadol: a new centrally acting analgesic.

The pharmacology, pharmacokinetics, efficacy, adverse effects, and dosage and administration of tramadol are reviewed. Tramadol is a synthetic analogue of codeine that binds to mu opiate receptors and inhibits norepinephrine and serotonin reuptake. It is rapidly and extensively absorbed after oral doses and is metabolized in the liver. Analgesia begins within one hour and starts to peak in two hours. In patients with moderate postoperative pain, i.v. or i.m. tramadol is roughly equal in efficacy to meperidine or morphine; for severe acute pain, tramadol is less effective than morphine. Oral tramadol can also be effective after certain types of surgery. Tramadol and meperidine are equally effective in postoperative patient-controlled analgesia. In epidural administration for pain after abdominal surgery, tramadol is more effective than bupivacaine but less effective than morphine. In patients with ureteral calculi, both dipyrone and butylscopolamine are more effective than tramadol. For labor pain, i.m. tramadol works as well as meperidine and is less likely to cause neonatal respiratory depression. Oral tramadol is as effective as codeine for acute dental pain. In several types of severe or refractory cancer pain, tramadol is effective, but less so than morphine; for other types of chronic pain, such as low-back pain, oral tramadol works as well as acetaminophen-codeine. Common adverse effects of tramadol include dizziness, nausea, dry mouth, and sedation. The abuse potential seems low. The recommended oral dosage is 50-100 mg every four to six hours. Tramadol is an effective, if expensive, alternative to other analgesics in some clinical situations.