That's interesting, when a drug passes through the intestines it first goes to the liver for potential metabolism before systemic circulation.
en.wikipedia.org
As I understand it, N does not require metabolism to work, but it is metabolised by the liver before excretion.
You can see there is a paper about N in patient's with liver disease from the 50s here, and it says there is no evidence the individuals were more sensitive to N who had liver disease and so impaired inactivation of N:
Sessions, John T., et al. "The effect of barbiturates in patients with liver disease."
The Journal of clinical investigation 33.8 (1954): 1116-1127.
I'd guess it would be the other way round, people with impaired livers would be more sensitive to N and not less (although this paper says there is no effect).
You might want to speak with some one who is a medical doctor, although phrasing the question might be a bit tricky, haha.