This week we have seen some interesting uses of naloxone in the Sinai ED, so let’s review:
Naloxone for pruritis? Why yes. Several randomized controlled trials have shown Naloxone to be efficacious in all sorts of pruritic conditions – chronic urticarial, atopic dermatitis, Psoriasis Vulgaris – to name a few. The dose range is high, but most studies started with 50 mg/day. I’d explain the mechanism but this image below will do a far better job.
Naloxone for ACE-I overdose? Duh, apparently. It seems that naloxone is a quite well known antidote for ACE-I overdose within the tox community, although there isn’t a ton of literature to support it. The proposed mechanism is that naloxone works to block the central (as opposed to the peripheral vasodilatory actions of angiotensin), by “blocking the b-endorphin inhibition of angiotensin II and thus augmenting the vasopressor response of the latter agent.” 
Phan NQ, Bemhard JD, Luger TA, Stander S. Antipruritic treatment with systemic u-opioid receptor antagonists: a review. J Am Acad Dermatol. 2010 Oct;63(4):680-688 doi:10.1016/j/jaad.2009.08.052
Varon J, Duncan SR. Naloxone reversal of hypotension due to captopril overdose. Ann Emerg Med. 1991. Oct;20(10):1125-7.