Tylenol or ibuprofen: which does more for the pain?

The review rates most of its own evidence as low quality, chiefly because the trials reported their methods poorly, and the studies disagreed with each other substantially on the main pain comparison. Fifty-nine per cent of the trials were commercially funded and a further 31% did not say who paid. No one drug in the class could be shown safer or more effective than another, because most head-to-head comparisons rested on very few small trials.

No drug was tested against another here. These are numbers from separate trials in separate people, lined up side by side. The authors flag 13 of the drug and dose pairs as possibly affected by publication bias. All of it is a single dose for pain after an operation, which says nothing about taking either drug for weeks. And the arithmetic that makes the pair work is the same arithmetic that makes an unnoticed second acetaminophen product dangerous.