A new medication for the treatment of cardiac arrhythmias has been developed. The drug has a high affinity for both activated and inactivated sodium channels but a low affinity for resting sodium channels. An experiment is designed to keep sodium channels inactive for an extended period of time while they are exposed to the new drug. The speed of the drug's dissociation from the sodium channels is recorded and shown below after allowing the sodium channels to return to their resting state. For comparison, the dissociation curve for quinidine is provided. The pharmacologic action of the new drug is most similar to which of the following drugs?

Question

A new medication for the treatment of cardiac arrhythmias has been developed. The drug has a high affinity for both activated and inactivated sodium channels but a low affinity for resting sodium channels. An experiment is designed to keep sodium channels inactive for an extended period of time while they are exposed to the new drug. The speed of the drug's dissociation from the sodium channels is recorded and shown below after allowing the sodium channels to return to their resting state. For comparison, the dissociation curve for quinidine is provided.  The pharmacologic action of the new drug is most similar to which of the following drugs?

Quizplus · Accepted Answer

Eductional Objective: The sodium-channel-binding strength of class I antiarrhythmics is IC > IA > IB. Higher heart rates cause increased sodium channel blockade due to cumulative blocking effects over multiple cardiac cycles, which is referred to as use dependence. Because of their slow dissociation from the receptor, class IC antiarrhythmics have the highest use dependence, while class IB drugs have the lowest use dependence due to their rapid dissociation.

A New Medication for the Treatment of Cardiac Arrhythmias Has