Demerol is used to help relieve moderate to severe pain. It belongs to a class of drugs known as opioid (narcotic) analgesics and is similar to morphine. It works in the brain to change how your body feels and responds to pain.Meperidine should not be used to treat long-term or ongoing pain. It should only be used to treat sudden episodes of moderate to severe pain. See also Precautions section. Initial Dosage Adults Initiate treatment with DEMEROL Tablets or Oral Solution in a dosing range of 50 mg to 150 mg orally, every 3 or 4 hours as needed for pain. Pediatric Patients Initiate treatment with DEMEROL Tablets or Oral Solution in a dosing range of 1.1 mg/kg to 1.8 mg/kg orally, up to the adult dose, every 3 or 4 hours as necessary. Dosage Modification With Concomitant Use With Phenothiazines The dose of DEMEROL Tablets or Oral Solution should be reduced by 25 to 50% when administered concomitantly with phenothiazines and other tranquilizers. Within USA: 6 to 24 hours Canada: 1 to 2 Days International Delivery: 3 to 4 Days