[dreamcompiler]

Oxymetazoline is an extremely effective nasal decongestant. It works almost instantly and it lasts 24 hours.

It also creates dependency. A drug that is ineffective cannot cause dependency.

[admash]

Of course it can. You take drug A for 5 days to get rid of symptom X. The symptom X does not go away. It is ineffective! You stop taking drug A and immediately experience brutal migraines that go away when you start taking drug A again. Ergo, you have become dependent on drug A for normal functioning, even though it is ineffective at ridding you of symptom X.