A single dose of paracetamol provides effective analgesia for about half of patients with acute postoperative pain, for a period of about four hours, and is associated with few, mainly mild, adverse events.
A double-blind randomized study of an aspirin/caffeine combination versus acetaminophen/aspirin combination versus acetaminophen versus placebo in patients with moderate to severe post-partum pain.
In a double-blind, randomized controlled trial among 500 post-partum patients experiencing moderate to severe pain, a single oral dose of an aspirin/caffeine combination (800 mg aspirin, 65 mg caffeine) provided significantly more pain relief at 2 hours than did a higher dose of an acetaminophen/aspirin combination (648 mg acetaminophen, 648 mg aspirin) and a higher dose of acetaminophen alone (1000 mg acetaminophen). At 3 and 4 hours, the acetaminophen/aspirin combination as well as the aspirin/caffeine combination were significantly superior to acetaminophen alone. At all times, all three drugs were significantly superior to placebo. There were no clinically significant adverse reactions. These results provide evidence of a potentiating effect of caffeine on aspirin's analgesic potency.