Question

Which is true of drugs that decrease membrane permeability to sodium ions? some are used as local. they may block nerve impulses from moving along the axon. they may prevent the perception of pain. they work by blocking sodium channels in the cell membrane. all of these are true?

Answer 1

The right answer is: they work by blocking sodium channels in the cell membrane.

These drugs are used systemic and not local.
they block sodium channels in the cell membrane in the synapses between neurons, and not along axons. 
Many drug acts by blocking sodium channel, in a specific location, like antiepileptics in the nervous system, and digoxin and antiarrhythmic in the heart.