Channel blockers - potassium

Potassium channels are the most widely distributed type of ion channel and are found in virtually all living organisms. They are found in most cell types and control a wide variety of cell functions.  Potassium is key to establishing an ‘action potential’ that enables the nerve to ‘fire’.  Potassium is used to set the resting membrane potential. 

They too can be the target of various toxins.  Charybdotoxin,  iberiotoxin and some dendrotoxins act on these channels.  Any blockade or irregularity of these channels can be life threatening.  For example, malfunction of potassium channels in the heart may cause life-threatening arrhythmias. Malfunction of the beta cells in the pancreas can lead to diseases such as diabetes.  Potassium deficiencies do the same thing.

Potassium channel blockers are agents which interfere with conduction through potassium channels.  In general they are used solely in the treatment of cardiac arrhythmias.  By blocking the potassium channels, they theoretically ‘prolong repolarization’.

But as the literature says “Because of the reverse use-dependence of these agents, at low heart rates they may paradoxically be more arrhythmogenic”.  These agents include a risk of torsades de pointes which is a variety of ventricular tachycardia.