Верапамил

Использование

Verapamil is primarily used as an antiarrythmic for treating ventricular arrhythmias; however, currently it is being forced out gradually by adenosine.

Определение

ChEBI: A tertiary amino compound that is 3,4-dimethoxyphenylethylamine in which the hydrogens attached to the nitrogen are replaced by a methyl group and a 4-cyano-4-(3,4-dimethoxyphenyl)-5-methylhexyl group.

Общее описание

Verapamil, 5-[. Hemodynamically, verapamil causesa change in the preload, afterload, contractility, heart rate,and coronary blood flow. The drug reduces systemic vascularresistance and mean blood pressure, with minor effectson cardiac output.
Verapamil is a synthetic compound possessing slightstructural similarity to papaverine. It can be separated intoits optically active isomers, of which the levorotatory enantiomeris the most potent. It is absorbed rapidly after oraladministration. The drug is metabolized quickly and, as aresult, has low bioavailability. The liver is the main siteof first-pass metabolism, forming several products. Thepreferential metabolic step involves N-dealkylation, followedby O-demethylation, and subsequent conjugation ofthe product before elimination. The metabolites have no significantbiological activity. Verapamil has an eliminationhalf-life of approximately 5 hours.

Механизм действия

Verapamil is used as an antiarrythmic drug in treating supraventricular arrythmia such as paroxysmal atrial tachycardia, and for controlling atrial fibrillation. By blocking entrance of Ca2+ in the cell, verapamil exhibits a negative inotropic effect, and therefore it cannot be combined with β-adrenoblockers or cynidine since that would lead to an increased inotropic effect.

Клиническое использование

Verapamil (Isoptin, Covera), in addition to its use as an antiarrhythmic agent, has been employed extensively in the management of variant (Prinzmetal’s) angina and effort-induced angina pectoris. It selectively inhibits the voltage-gated calcium channel that is vital for action potential genesis in slowresponse myocytes, such as those found in the sinoatrial and A-V nodes.
Verapamil is useful for slowing the ventricular response to atrial tachyarrhythmias, such as atrial flutter and fibrillation. Verapamil is also effective in arrhythmias supported by enhanced automaticity, such as ectopic atrial tachycardia and idiopathic left ventricular tachycardia.

Побочные эффекты

Orally administered verapamil is well tolerated by most patients. Most complaints are of constipation and gastric discomfort. Other complaints include vertigo, headache, nervousness, and pruritus.

Меры предосторожности

Verapamil must be used with extreme caution or not at all in patients who are receiving -adrenoceptor blocking agents. Normally, the negative chronotropic effect of verapamil will in part be overcome by an increase in reflex sympathetic tone. The latter is be prevented by simultaneous administration of a β-adrenoceptor blocking agent, which exaggerates the depressant effects of verapamil on heart rate, A-V node conduction, and myocardial contractility. The use of verapamil in children less than 1 year of age is controversial.