Oral use of heroin is less common than other methods of administration, mainly because there is little to no "rush", and the effects are less potent.[57] Heroin is entirely converted to morphine by means of first-pass metabolism, resulting in deacetylation when ingested. Heroin's oral bioavailability is both dose-dependent (as is morphine's) and significantly higher than oral use of morphine itself, reaching up to 64.2% for high doses and 45.6% for low doses; opiate-naive users showed far less absorption of the drug at low doses, having bioavailabilities of only up to 22.9%. The maximum plasma concentration of morphine following oral administration of heroin was around twice as much as that of oral morphine.[58]