Which is NOT a requirement for a local anesthetic drug?

 # Which is NOT a requirement for a local anesthetic drug? 

A. Lipid solubility. 

B. Water solubility. 

C. Precipitate in interstitial fluid. 

D. Depression of nerve conduction. 

The correct answer is C. Precipitate in interstitial fluid.

Local anesthetics must be lipid soluble in order for the drug to cross various barriers in the tissue. Local anesthetics must be water soluble to prevent the drug from precipitating when exposed to interstitial fluids. Local anesthetics must NOT precipitate in interstitial fluid because then they would be ineffective as anesthetics. A local anesthetic’s intended purpose is to block pain; therefore, it must depress nerve conduction.