Only ant nectar causes this addiction; fire ant nectar is not addictive. This is the one addiction that cannot be cured by employing My First Laboratory. The Lone Wanderer must employ a doctor to cure this addiction.
Fallout: New VegasEdit
It is possible to become addicted to the normal ant nectar, though the 5% chance is one of the lowest addiction rates of any consumable in the game. It is further reduced by Chem Resistant, Old World Gourmet ( ) and Big Brained ( ) perks producing a very small 0.75% chance (likely rounded up to 1%) of addiction. The Courier will still become addicted with a 100% chance after frequent use due to the UMON effect. The effect can be avoided through the use of the Logan's Loophole trait, however.
Ant nectar addiction used to be incurable due to a bug, but this was fixed in Fallout: New Vegas patch 126.96.36.199x. The console command Player.RemoveSpell 0006dc6e will immediately remove the addiction on the PC version.