Editing Threshold potential (section)

====Use of medications====
A variety of drugs can present prolongation of the [[QT interval]] as a side effect. Prolongation of this interval is a result of a delay in sodium and calcium channel inactivation; without proper channel inactivation, the threshold potential is reached prematurely and thus arrhythmia tends to result.{{sfn|Nelson|Leung|2011|p=292}} These drugs, known as pro-arrhythmic agents, include antimicrobials, antipsychotics, methadone, and, ironically, [[antiarrhythmic agents]].{{sfn|Nelson|Leung|2011|p=291}} The use of such agents is particularly frequent in intensive care units, and special care must be exercised when QT intervals are prolonged in such patients: arrhythmias as a result of prolonged QT intervals include the potentially fatal [[torsades de pointes]], or TdP.{{sfn|Nelson|Leung|2011|p=292}}