11.7: Antianginal Drugs: Calcium Channel Blockers and Ranolazine
Angina pectoris, a primary symptom of ischemic heart disease, requires careful pharmacological interventions. In this context, calcium channel blockers (CCBs) and ranolazine have emerged as crucial pharmacotherapeutic agents, providing deep insights into the complexities of angina management.
CCBs, a diverse class that includes dihydropyridines (nifedipine) and diphenylalkylamines (verapamil and diltiazem), exert their effect by blocking calcium channels in cardiac and smooth muscle cells. This blockade reduces the influx of calcium ions, leading to vasodilation and a decrease in myocardial oxygen demand. These agents, which are administered orally, undergo extensive metabolism. Certain compounds, such as verapamil and diltiazem, can also be administered intravenously. However, using CCBs may result in side effects, including headaches, dizziness, and peripheral edema.
In contrast, ranolazine, a sodium-channel blocker, operates through a more nuanced mechanism. It inhibits the late-phase sodium current in cardiac cells during repolarization, thereby preventing calcium entry via the sodium-calcium exchanger. This intricate regulation reduces intracellular sodium and calcium levels, promoting relaxation within the cardiac muscle and increasing coronary blood flow. Following oral administration, ranolazine undergoes substantial metabolism, primarily mediated by CYP3A enzymes. However, its therapeutic use is associated with side effects such as dizziness, headaches, constipation, and nausea.
The interplay between CCBs and ranolazine in treating angina pectoris highlights the delicate balance between precision and complexity. The careful regulation of calcium dynamics and sodium currents outlines a path toward relief, although it is challenging.
