Antimuscarinic agents are the main drugs used to treat patients with the
overactive bladder (OAB) syndrome, defined as urgency, with or without urgency incontinence, usually with increased daytime frequency and
nocturia. Since the treatment is not curative and since OAB is a
chronic disease, treatment may be life-long.
Antimuscarinics are generally considered to be ‘safe’ drugs, but among the more serious concerns related to their use is the risk of cardiac adverse effects, particularly increases in heart rate (HR) and QT prolongation and induction of polymorphic
ventricular tachycardia (
torsade de pointes). An elevated resting HR has been linked to overall increased morbidity and mortality, particularly in patients with
cardiovascular diseases. QT prolongation and its consequences are not related to blockade of
muscarinic receptors, but rather linked to inhibition of the hERG
potassium channel in the heart. However, experience with
terodiline, an
antimuscarinic drug causing
torsade de pointes in patients, has placed the whole
drug class under scrutiny. The potential of the different
antimuscarinic agents to increase HR and/or prolong the QT time has not been extensively explored for all agents in clinical use. Differences between drugs cannot be excluded, but risk assessments based on available evidence are not possible.