What term describes a positively charged ion that represents the active form of a local anesthetic?

A positively charged ion is referred to as a cation, which is indeed the active form of many local anesthetics. Local anesthetics function primarily by blocking sodium channels in nerve membranes, and their effectiveness depends on their ionization state in relation to the physiological pH.

Local anesthetics are typically weak bases and can exist in both ionized (cation) and unionized (neutral) forms. However, it is the cationic form that is responsible for the binding to sodium channels, leading to the desired anesthetic effect. At physiological pH, the ionized form is more prevalent, especially in inflamed or infected tissues where pH is often lower, which enhances the cationic form’s ability to interact with receptors in the sodium channels.

Understanding the concept of cations in the context of local anesthetics is essential because it highlights how pH and ionization affect the efficiency and onset of anesthesia.