Using an attack potion will temporarily raise the player's Attack by 1-8 (1 + 8% of Attack level), rounded down. If the player adds roe to a 2-dose potion then it will become a 2-dose attack mix which heals 30 life points. Using an attack potion will not allow you to use higher level equipment. For example, if you have an attack of 39, and you use an attack potion, you will not be able to wield rune weapons. F2P players can also now use Attack Potions.
A better alternative to using attack potions for combat are buying combat potions. They give the bonuses of both a strength potion and attack potion in only one item slot and are cheaper, only costing 294 coins for 3 doses.