Antioxidant preventing biodegration of LA by preventing oxidation of vasopressor by oxygen

• A. Sodium bisulfite
• B. Sodium metabisulfite
• C. Ascorbic acid
• D. Sodium chloride

Answer: (A)

The key idea is that these local anesthetic solutions with a vasopressor are stabilized by an antioxidant to prevent the vasopressor from oxidizing in the presence of oxygen. Epinephrine, the vasopressor used, is prone to oxidation which reduces its effectiveness and can cause color change. Sodium bisulfite acts as an antioxidant preservative that scavenges oxygen-related oxidants, keeping epinephrine in its active form and extending shelf life. The other options don’t provide this stabilizing antioxidant effect in these formulations: sodium chloride is just a salt, and ascorbic acid, while an antioxidant, isn’t the standard stabilizer used in typical dental LA with vasopressor; sodium metabisulfite is another sulfite antioxidant but is less commonly the chosen stabilizer in standard dental cartridges.