Can a 5mg oxycodone hydrochloride be broken in half to take?

Was just curious. Have never taken it before and wanted to be cautious. Was nit sure if it was extended release. The marking is K 18

It was probably IR (immediate release) oxycodone pill. If it were and extended release (ER) form of oxycodone pill, it would be marked oxy-contin (oxycodone continuous release) or oxy- followed by ER (extended release) or XR (extended release. If there aren't these letters after the oxycodone or oxy-whatever. Then it is an IR form of oxycodone in pill or liquid form, which means it is released once it enters the gut and will exert the pain relieving effect for 4 to 6 hours. Then if needed another pill needs to be taken. Extended release pain pills have a pain relieving effect that last for 12 to 24 hours (depending on the med) before another pill needs to be taken.