Disopyramide is an antiarrhythmic drug. It is therefore used in particular for the drug therapy of cardiac arrhythmias. The active ingredient disopyramide has similarities to the drugs procainamide and quinidine. In most cases, the drug is administered orally. Excretion of the active ingredient from the human body is largely renal.
What is disopyramide?
The active ingredient disopyramide is classified as a first-in-class antiarrhythmic agent. It is administered either orally or by intravenous injection. In this case, the bioavailability of the drug disopyramide is more than 80 percent. In the blood, approximately 40 percent of the active ingredient binds to the proteins present in the plasma. In principle, the plasma half-life of the drug is about seven hours. Subsequently, the drug is metabolized by the hepatic system (centered on the liver). Thereafter, the drug is excreted from the organism predominantly renally, i.e. via the kidneys. The drug disopyramide was patented in 1962. In practical use, the active ingredient disopyramide is present as a racemate.
Pharmacologic action
The drug disopyramide acts primarily as a so-called sodium channel antagonist. Thus, the drug causes fewer sodium ions to enter the myocardium. As a result, the excitability of the heart is reduced. In this way, the drug disopyramide exerts its negative bathmotropic effect. Finally, the substance also causes the refractory period to be prolonged. As a result, negative chronotropy occurs. Primarily, the active ingredient disopyramide blocks those sodium channels that are located on the cell membranes inside the heart muscle. These are the cells responsible for regulating the heart rhythm. In this way, the active ingredient prolongs the action potential. Basically, the drug disopyramide is characterized by anti-parasympathetic effects and is thus similar to the substance atropine. Moreover, the drug shows no efficacy in connection with specific adrenoceptors in the sympathetic nervous system. In addition, the drug reduces the refractory period of the ventricles as well as their atria. The drug disopyramide significantly decreases the efficiency of the left ventricle. In addition, it causes dilation of the arterial blood vessels. As a result, blood pressure drops. The active substance is therefore problematic for people whose pumping function is impaired. In such cases, treatment with the drug disopyramide should be refrained from.
Medical use and application
Disopyramide is suitable for the therapy of numerous diseases and health complaints. Indications primarily represent certain functional disorders of the heart. These include, for example, ventricular tachycardia and extrasystoles, as well as ventricular fibrillation. Therapy with the drug disopyramide is also possible for supraventricular tachycardia, such as atrial flutter or fibrillation. Disopyramide can be combined with other drugs from the group of antiarrhythmic agents if a single drug does not have sufficient effect. In addition, disopyramide is able to prevent recurrence of atrial fibrillation following cardioversion. Before the first application of the active substance disopyramide, it is necessary to check the ventricular frequency. In this way, a so-called 1:1 conduction can be avoided. In addition, disopyramide is suitable for the treatment of neurogenic syncope and hypertrophic cardiomyopathy.
Risks and Side Effects
Various adverse symptoms and side effects are possible while taking the drug disopyramide. However, these do not occur in every patient and vary in frequency. For example, constipation and urinary retention as well as dry mouth are possible. Also, in some cases, disturbances of accommodation and narrow-angle glaucoma occur. In addition, the performance of the left ventricle of the heart may be impaired. The risk of this increases if the affected patient already has heart failure. In the course of treatment with disopyramide, the QT time is also prolonged in some cases. In addition, torsade de pointes tachycardia is possible.Some patients experience hypotension (drop in blood pressure) or circulatory problems when taking the drug disopyramide. Other potential side effects include agranulocytosis and glaucoma. Acute heart failure, which has been observed in some individuals, is also a dangerous complication. In addition, some contraindications to the drug disopyramide exist. For example, if there is decompensated heart failure or bradycardia, the drug disopyramide should not be administered. If the affected patient has coronary artery disease, the drug disopyramide is not the drug of first choice. This is because the risk of mortality is increased in this case. If the active ingredient disopyramide is nevertheless to be used, an examination by means of a cardiac catheterization is necessary before the first dose. The drug should also not be administered in cases of hypersensitivity to the drug or cardiac insufficiency. Other contraindications include sick sinus syndrome, disturbed electrolyte balance, and liver or kidney weakness. In addition, interactions with other substances are possible, which is why concomitant use is not recommended. Tricyclic antidepressants, erythromycin as well as neuroleptics lead to a prolongation of the half-life of disopyramide. As a result, they enhance the effect of the drug. As a general rule, all undesirable side effects and complaints caused by the drug disopyramide should prompt consultation with a physician. He or she may then prescribe an alternative drug.
