Which formulation of local anesthetic contains a low concentration of epinephrine?

The formulation that contains a low concentration of epinephrine is 1:200,000 epinephrine in lidocaine. Lower concentrations of epinephrine are often used in local anesthetic formulations to provide vasoconstrictive effects without significantly increasing the risk of systemic absorption, which can lead to increased heart rate and other cardiovascular effects.

In the context of local anesthesia, epinephrine is added to prolong the duration of action by reducing blood flow to the area, which decreases the rate of absorption of the anesthetic into the bloodstream. A concentration of 1:200,000 is considered a lower dose compared to options with higher concentrations, such as 1:100,000 or 1:50,000. The 1:400,000 formulation is even more dilute, but when considering typical usage and effects, 1:200,000 strikes a balance between efficacy and safety, making it a common choice for many local anesthetic applications.

This understanding reflects the importance of titrating the concentration to achieve the desired clinical effect while minimizing side effects associated with excessive vasoconstriction or systemic exposure to epinephrine.