Get with it guys, we’re almost there:
Because acetaminophen is a weak inhibitor in vitro of both cyclooxygenase (COX)-1 and COX-2, the possibility exists that it inhibits a so far unidentified form of COX, perhaps COX-3. In animal studies, COX enzymes in homogenates of different tissues vary in sensitivity to the inhibitory action of acetaminophen. This may be evidence that there are >2 isoforms of the enzyme. Recently, a variant of COX-2 induced with high concentrations of nonsteroidal anti-inflammatory drugs was shown to be highly sensitive to inhibition by acetaminophen. Therefore COX-3 may be a product of the same gene that encodes COX-2, but have different molecular characteristics.