[refurb]

Typical dose of fentanyl in the medical setting for an adult is 100 ug (0.1 mg). For heroin (diamorphine in the UK), it’s 5 mg. A 50x difference.

[robbiep]

A typical dose is 25 mcg, I certainly wouldn’t give an opioid naive person 100mcg in a go. Dose low and go again if relief not adequate