Risk Factors for Calcium Channel Blocking Agent Toxicity

Risk factors for increased toxicity:

(1) excessive dosage

(2) impaired cardiac conduction

(2a) sinus node dysfunction

(2b) atrioventricular block

(2c) drugs that impair cardiac conduction or increase heart block (digitalis, class I anti-arrhythmic agents such as quinidine, amiodarone)

(3) impaired cardiac contractility and cardiac output

(3a) congestive heart failure

(3b) drugs that impair myocardial contractility or cardiac output (beta blockers, disopyramide)

(3c) drugs that cause dehydration (diuretic agents)

(4) accumulation due to impaired hepatic metabolism

(4a) hepatic failure

(4b) drugs that impair hepatic metabolism or blood flow (cimetidine)