Antidote

Antidotes cure the imbiber instantly from poisoning, but unlike the Elixir of Health, they don't heal hit points which may have been lost from poison. This items appears in Baldur's Gate, Baldur's Gate: Enhanced Edition and Baldur's Gate. In Baldur's Gate, this potion is sold at Sorcerous Sundries and many temples.

In-game description
"As the name implies, this potion will neutralize any poison of which the imbiber is currently suffering the effects.  The cleansing is instant and the potion may only be used once."