 For constant pain, the relieving effect of extended-release morphine given once (for Kadian) or twice (for MS Contin) every 24 hours is roughly the same as multiple administrations of "immediate release" (or "regular") morphine.Extended-release morphine can be administered together with "rescue doses" of immediate-release morphine as needed in case of breakthrough pain, each generally consisting of 5% to 15% of the 24-hour extended-release dosage.Morphine and its major metabolites, morphine-3-glucuronide and morphine-6-glucuronide, can be detected in blood, plasma, hair, and urine using an immunoassay.