Supposedly fusion of deuterium doesn't yield enough power to allow a ship to go to warp, but it might yield enough power to replicate stuff. Doesn't mean that fusing a kilogram of deuterium would give enough power to replicate a kilogram of deuterium, though.
But if the replicators could create antideuterium with the same ease they supposedly create deuterium with, then annihilating 1+1 kg of the stuff might well yield enough power to create more than 1+1 kg of the stuff, considering how efficient replicators otherwise appear to be (that is, they seem to do better than E=mcc if a household unit can create enough food and water for survival out of pure energy, or then future households have pretty formidable power sources), and then we have a perpetual motion machine. Hopefully, there are some limitations to that process that negate the drama-ruining potential! (Although it's very difficult to see why antimatter would be any more difficult to replicate than matter, as long as replication involves transmutation of elements - which is certainly appears to do, as per "Night Terrors" and the like.)
Clearly, starships can't "bootstrap" themselves by going to warp to gather high volumes of deuterium with ramscoops so that they can turn that to fuel to go to warp to get more of the stuff, hence the perfectly reasonable yet much-maligned VOY episode "Demon". You have to get deuterium from a naturally or industrially enriched source to make any practical use of it. Where you get antideuterium is never explained, but perhaps by fusing a hundred kilograms of deuterium you get enough power for a doodad that creates a gram of antideuterium, so by sitting next to a deuterium well, you can eventually fill both your matter and antimatter tanks.