Why Do Topical Anesthetics Require a Higher Concentration of Drug

Why do topical anesthetics require a higher concentration of drug than the same drug used as an injectable local anesthetic?

A) More base molecules of drug are needed to diffuse through membranes barriers
B) They are less likely to produce toxicity when applied topically
C) Decreased amounts are applied topically than when locally injected
D) They do not contain vasoconstrictors