A preliminary study of hydrocodone and hydromorphone to oxycodone ratios for distinguishing impurities from independent opioid use

•Hydrocodone is an impurity in oxycodone pills that can be detected in urine.•Hydromorphone is also detectable in trace amounts in patients taking oxycodone.•Ratios of hydromorphone and hydrocodone to oxycodone can help identify impurities.•If the ratio to oxycodone is <1 %, then the source is the pill itself.