Question: Which heroin metabolite is unique to heroin and manifests a longer half-life than heroin itself?
Answer: The cited reference notes that 6-monoacetylmorphine (6-MAM) is unique to heroin with a substantially longer half-life than heroin itself. (Raja AS et al. Case 37-2017: A 36-year-old man with unintentional opioid overdose. 2017 NEJM 377(22): 2181-2188)