Australian researchers reviewed three randomized trials that compared acetaminophen with a placebo for the relief of spinal pain, and 10 trials that compared their use for easing the pain of
osteoarthritis. All together, the analysis included 5,366 patients. Acetaminophen was given orally in doses between 3,000 and 4,000 milligrams a day, except for one study in which a dose of 1,000 milligrams was administered intravenously.