Antidote to Veritaserum

An antidote to Veritaserum exists to counteract the effects of the said truth serum. Professor Horace Slughorn is said to be keeping one with him ever since Albus Dumbledore tried to relieve him a memory that Slughorn was too ashamed to give, in case Dumbledore ever attempted to use Veritaserum to bring out the said memory.

Appearances

 * Harry Potter and the Half-Blood Prince