Final answer:
A drug can raise the threshold for an action potential in a cell by increasing the membrane's resistance to depolarization.
Step-by-step explanation:
An action potential is a brief reversal of the resting membrane potential of a neuron, and it is triggered when the membrane depolarizes to a certain threshold. One way a drug can raise the threshold for an action potential is by increasing the membrane's resistance to depolarization. This can be accomplished by blocking sodium channels or reducing the number of available sodium ions, preventing the membrane from reaching the threshold and thus raising it.