What is commonly added to local anesthesia to prolong its effects?

Epinephrine is commonly added to local anesthesia to prolong its effects because it acts as a vasoconstrictor. This means that it narrows the blood vessels in the area where the anesthesia has been administered. By doing so, it reduces blood flow to the site, which helps to keep the local anesthetic in the area longer and slows down its absorption into the bloodstream. As a result, this extended duration of action allows for prolonged pain relief during dental procedures.

In contrast, sodium chloride is used to make the anesthetic solution isotonic, and hydrochloric acid is used to adjust the pH of the solution but does not impact the duration of the anesthetic effect. Adrenaline, another name for epinephrine, is typically added in circumstances that are standard rather than special because it is routinely used with local anesthetics for the purposes stated above.