ConcoctionDatabase.handleQueue( ..., KoLConstants.CONSUME_EAT ) will "eat" things from the Food section.
ConcoctionDatabase.consumeItem( <munchies pill>, <n>, KoLConstants.CONSUME_EAT ) will "eat" the munchies pills
UseItemRequest.getInstance( KoLConstants.CONSUME_EAT, <n munchies pills> ) will make the request to "eat" the munchies pills.
Since consumptionType is KoLConstants.CONSUME_EAT, it does a new EatItemRequest( <n munchies pill> )
That, in turn, does super( ItemDatabase.getConsumptionType( item.getItemId() ), item ), which results in
UseItemRequest( KoLConstants.CONSUME_MULTIPLE, <n munchies pill> )
That should make a request with URL of "multiuse.php?whichitem=1619", this.consumptionTpe = KoLConstants.CONSUME_MULTIPLE, and this.item <n munchie pill>.
And when the request is actually run(), since this.consumptionType is KoLConstants.CONSUME_MULTIPLE, it should add "action=useitem" and "quantity=<n>".
At least, looking at the code, that looks like how it should work. But, you are reporting that the request that is submitted is simply "multiuse.php?whichitem=1619"? Not even "inv_use.php?whichitem=1619"? How odd.
I think I'll try stepping through this with Eclipse.