Oh, one more thing to clarify:
It is not MORE physically dangerous for one to take narcotics while taking naltrexone, in fact, it would technically be SAFER to take narcotics while ON naltrexone than while NOT on naltrexone.
Why? Because ON naltrexone, narcotics simply will not work. They will do NOTHING. No, one will NOT be kinda 'high without knowing' it as was suggested above. One can most certainly NOT overdose more easily on narcotics while on naltrexone, though it would theoretically still be possible to do so given the infinite ratios of the amounts of antagonist vs. agonist one could have in one's system.
The 'neutralization effect' of a strong opioid antagonist like naltrexone over an agonist is basically 'total'. That's WHY they give it to people who are overdosing and it revives them and saves their lives, you see?
And the only time that taking naltrexone along with narcotics causes withdrawals is in persons who would be in withdrawals if they weren't on narcotics, i.e. active addicts.
Again, not a doctor, look it up for yourselves or ask a real doctor. Pretty sure I know from whence I speak, though.