Antidote

Cures Poison.
Cures Poison
Price 75 gil (50 gil on Easy)
Value 37 gil (25 gil on Easy)
Sold In Crescent Lake, Desert Caravan, Gaia, Pravoca, Cornelia, Elfheim, Onlak
Cures one character of Poison.

Because Esuna is a fourth-level Spell, you'll always want to have a decent supply of Antidotes on hand. For 75 gil, they are expensive early in the game, but once you have a bunch of them you probably won't need to buy more. You will definitely regret not having Antidotes, though, since Poison does 5% of your max HP in damage every turn in combat, and drains HP while walking around as well. It's not fun stuff.
Compare Antidote to other Items
Shops: Where Antidote is sold – 7 shown
Map Shop
Cornelia Items
Pravoca Items
Elfheim Items
Crescent Lake Items
Gaia Items
Desert Caravan Items
Onlak Items
Treasures: Containing Antidote – 5 shown
Map
The specifics of where this treasure can be found
Notes
Matoya's Cave Found in a chest in Matoya's room
Terra Cavern B1 Found in the western chest in the southeastern room (guarded)
Mt. Gulg B2 Found in the central chest between two other chests on the south wall in the southwest treasure area in the large room (guarded)
Mt. Gulg B4 Found in a chest in the western room
Sunken Shrine 5F Found in a chest in one of the treasure rooms
Potion Gold Needle

Related

PURE Potion

Cures Poison
Price 75 G
Sold In Crescent Lake, Gaia, Pravoka, Coneria, ElfLand, Onrac
Cures one character of Poison.

You won't be able to cast the PURE Spell in the early game, so PURE Potions are your primary means of curing Poison for some time. You won't go through PURE Potions as quickly as HEAL Potions, so an initial investment of a handful of PURE Potions can last for most of the game.

Antidote

Price 200 gil
Value 100 gil
Spell Cast Antidote 1 (Self)
Sold In Altair, Bafsk, Fynn, Gatrea, Paloom, Poft, Salamand, Mysidia
Dropped By Death Flower, Poison Toad, Queen Bee, Soldier, Vampire Thorn
The Antidote heals Poison, though in combat it can only be used on the Character holding it, making it much more useful outside of combat. They're also worth selling in the early game, as few Monsters inflict Poison (and it's not difficult to heal with Spells, especially with Minwu around), and they're worth a decent amount of gil.

Antidote

Sprite
Accuracy +100%
Type Special Magic
Effect Cures the target of poison
Cures Poison
Cast By Items Antidote
The Antidote "Spell" powers the Antidote Item, and cures the Character of Poison

Antidote

Item Type Anywhere
Price 80 gil
Value 40 gil
Spell Effect Poisona

Antidote

Game Name Antidote
Price 40 gil
Value 20 gil
Effect Cure Poison
Spell Antidote (targeting one)

Antidote

Type Special Magic
Effect Cure Poison
Reflectable No

Antidote

Cures "Poison" status
Price 50 GP
Value 25 GP
Status Poison
World of Balance Shops Figaro Castle (v2), Jidoor, Kohlingen, Phantom Train (v2, v3), South Figaro
World of Ruin Shops Figaro Castle, Kohlingen
Antidotes cure Poison, so they are very useful to have on-hand. Both Terra and Celes learn Antdot early on, so you will not likely need many Antidotes, but being caught Poisoned without a way to cure it will likely result in a Character being Wounded so be careful.

Antidote

Description Cures [Poison]
Target One ally
Status Effect Remove: Poison
Use in Field? No
Price 80 gil
Value 40 gil
Shops Sector 7 Item Shop, Sector 5 Slums Item Shop, Wall Market Item Shop, Sector 7 General Store, Shinra Building Item Shop, Kalm Item Shop, Upper Junon Item Store, Costa del Sol Item Shop, Gold Saucer Hotel Shop, Mideel Item Store
Stolen from Brain Pod, Kelzmelzer
Dropped by Blood Taste, Special Combatant
Morph Kelzmelzer, Zolokalter

Antidote

Type Medicine
Description Cures Poison
Value 50 gil (75 gil with the Sell-High menu ability)
Used in Battle Yes
Menu Effect One party member
Status Effect Poison

Antidote

Type Consumable
Description Removes Poison from one ally.
Chapter 5
Retail Network Unicorn Mart
Availability Chapter 5
Price 100 gil
Value 50 gil

Antidote

Description Removes Poison from one ally.
Removes Status Poison
Price 100 gil
Value 50 gil