Final answer:
Morphine, propofol, and ketamine are drugs that are associated with pain on intravenous injection.
Step-by-step explanation:
When it comes to pain on intravenous injection, some drugs are more associated with this side effect than others. The drugs that are commonly known to cause pain on intravenous injection include morphine, propofol, and ketamine. Fentanyl, on the other hand, is typically well-tolerated and does not cause significant pain when administered intravenously.