Typical response of, no offense intended, the opioid naïf (naive- in terms of tolerance, and by consequence, naive in what is liked about the differing drugs). The nausea is due, I find most often, to *technically* (but not seriously) overdosing; not in a way for which your body cannot retort; even if while holding it down without succumbing to emesis (regurgitating / emergent stomach evac), your body can adjust but we have 'safe rather than sorry' automatic reactions if our body doesn't have it pinned or know exactly what the potency is for the speed of onset with the same route; taking many differing sub-varieties of opioids in the beginning can do this:
Now Dilaudid is many times stronger than morphine, but like morphine, has poor oral bioavailability (unlike oxycodone which has great oral/ingested route blood -absorption; i.e. doesn't get broken down into inactive metabolites by stomach acid &/or first-pass metabolism prior to reaching a saturation point into the blood stream as regular ol' feen does.)
Vicodin is, widely, considered one that does *nothing* for a highly opioid dependent (for years on end; sorry Doctor House, but your plot is too thin to hold water to real opiophiles, esp. one w/ a PhD.). I have heard others say they like oxycodone but not heroin; just makes them itchy, etc., all the *negatives* (too potent for their tolerance) but once they up the ante, the others don't do much for them. H-morphone has no legs for me, and I don't even feel it unless injected, but when injected, it's rush is one of the most intense, euphoric of the opioids configured for a fast onset route.