Examples include heroin, hydrocodone, and hydromorphone. Fully synthetic opioids are not derived from an opiate but still bind the opioid receptor. Examples include fentanyl and methadone [2]. Opioids are often used medically for pain relief but are also used non-medically for their psychoactive and euphoric effects.
A clear liquid diet on the day before your colonoscopy helps clear out your intestines, as well as helping to maintain your hydration.
1 Upper endoscopy: No food or drink is allowed for six hours before the procedure. An empty stomach allows for the best view and safest exam.  Colonoscopy: Drink only clear liquids for at least 24 hours before the procedure.