Ranolazine

• Chronic Stable Angina
• Refractory Angina
• Coronary Artery Disease

Ranolazine (Ranexa) is an antianginal medication used to treat chronic stable angina pectoris in patients with coronary artery disease. Unlike nitrates, beta-blockers, and calcium channel blockers, which work by reducing heart rate, blood pressure, or preload, ranolazine improves myocardial oxygen efficiency without significant hemodynamic effects. This makes it particularly useful as add-on therapy for patients whose angina remains poorly controlled despite optimized first-line antianginal therapy or who cannot tolerate dose increases of those agents because of low blood pressure or bradycardia. It is prescribed by primary care and cardiovascular clinicians as part of a comprehensive ischemic heart disease program.

Mechanism of Action

Ranolazine inhibits the late inward sodium current (late INa) in cardiac myocytes. Under ischemic conditions, late INa is pathologically increased, leading to sodium accumulation inside the cell. This sodium overload reverses the sodium-calcium exchanger and drives calcium into the cell, producing calcium overload that impairs diastolic relaxation, increases myocardial wall tension, and compresses the small coronary vessels that perfuse the inner heart layers during diastole. By selectively blocking late INa while sparing the much larger peak sodium current responsible for normal conduction, ranolazine reduces intracellular calcium overload, improves diastolic relaxation, lowers wall tension, and enhances diastolic coronary perfusion to the ischemic myocardium.

The net clinical effect is reduced angina frequency, increased exercise duration before ST-segment depression, and improved time to onset of angina during stress testing. Importantly, ranolazine accomplishes this without lowering heart rate or blood pressure meaningfully. It also exerts modest antiarrhythmic effects, partly by reducing late INa-mediated triggered activity. The drug is metabolized predominantly by CYP3A4 with secondary contribution from CYP2D6, and it is also a P-glycoprotein substrate. These pathways underlie its drug interaction profile. Ranolazine prolongs the QT interval in a dose-dependent manner by approximately 6 milliseconds at therapeutic doses, but proarrhythmia in clinical trials has not been observed at usual exposures. The American Heart Association recognizes ranolazine as a reasonable add-on agent in chronic angina.

Clinical Use

Ranolazine is FDA-approved for the treatment of chronic angina. It is typically used in combination with amlodipine, beta-blockers, or nitrates rather than as a substitute. According to the American College of Cardiology and acpjournals.org guideline summaries, first-line therapy for chronic stable angina includes a beta-blocker or non-dihydropyridine calcium channel blocker, often combined with a long-acting nitrate. When symptoms persist despite optimized first-line therapy, or when blood pressure or heart rate constraints prevent dose escalation, ranolazine is a reasonable second-line addition. It is particularly attractive in patients with low resting heart rate, hypotension, or sinus node dysfunction where adding more rate-lowering agents is risky.

Ranolazine does not provide acute relief during an anginal episode; sublingual nitroglycerin remains the rescue medication. It is also not a substitute for revascularization in patients with high-risk anatomy. Some clinicians use ranolazine in patients with diabetes for an associated modest improvement in HbA1c observed in clinical trials, though it is not approved for this indication. Patient selection includes those with chronic stable angina, no severe hepatic impairment or QT prolongation, and a medication regimen that does not include strong CYP3A4 inhibitors or inducers. Our article on early warning signs of heart attack helps patients distinguish stable angina from acute coronary syndrome.

How to Take It

Ranolazine is supplied as 500 mg and 1000 mg extended-release tablets. The starting dose is 500 mg twice daily, with the option to titrate to 1000 mg twice daily based on tolerance and response after one week. Tablets must be swallowed whole and not crushed, broken, or chewed because crushing destroys the extended-release matrix and produces dangerously high peak concentrations. The medication can be taken with or without food, but consistency from day to day improves predictable absorption. Grapefruit and grapefruit juice should be avoided because they inhibit CYP3A4 and can substantially increase ranolazine exposure.

A missed dose should be taken as soon as remembered unless the next dose is within a few hours; doubling up is not appropriate. Patients should continue all other antianginal medications including nitroglycerin for acute symptoms. During the first week patients may notice constipation, mild dizziness, nausea, or headache. Most of these settle. Constipation responds to increased fluid, fiber, or polyethylene glycol. If dizziness is significant, blood pressure and heart rate should be checked, particularly in patients on multiple antihypertensives. Patients should be instructed about which medications to avoid during ranolazine therapy, including over-the-counter or alternative agents.

Monitoring and Follow-Up

Before initiation, baseline ECG, basic metabolic panel including renal function, and liver enzymes are recommended. A baseline QTc interval helps with subsequent comparison. Follow-up in two to four weeks evaluates symptom response, blood pressure, heart rate, and side effects. A repeat ECG within the first month confirms QTc has not lengthened excessively; a QTc above 500 milliseconds or an increase of more than 60 milliseconds from baseline should prompt reassessment, dose reduction, or discontinuation. Renal function, liver enzymes, and ECG can be rechecked annually thereafter or sooner if dose changes occur or interacting medications are added.

Response is measured by reduction in weekly angina episodes, decreased nitroglycerin use, and improved exercise tolerance. A meaningful response is typically a reduction of at least one to two episodes per week or improvement in functional class. If no benefit is seen after dose titration, alternative strategies should be considered. Red numbers include syncope, presyncope on standing, palpitations with documented arrhythmia, marked QTc prolongation, creatinine doubling, or LFT elevation more than three times upper normal. Severe constipation requiring repeated intervention may also justify dose adjustment.

Special Populations

Elderly patients have higher plasma levels of ranolazine than younger patients but generally tolerate the drug; starting at 500 mg twice daily and titrating cautiously is wise. Renal impairment increases exposure substantially; severe renal impairment was associated with higher rates of acute renal failure in trials, so caution is needed and the lowest effective dose used. Hepatic cirrhosis is a contraindication because impaired metabolism markedly elevates levels and the risk of QT prolongation. Pregnancy data are limited; ranolazine should be used only when potential benefit clearly outweighs risk. It is unknown whether the drug is excreted in human breast milk. Pediatric safety has not been established. Patients with congenital long QT, baseline QTc above 500, or known proarrhythmic conditions should not receive ranolazine. Patients on strong CYP3A4 inhibitors such as ketoconazole, clarithromycin, or HIV protease inhibitors should not receive the drug; with moderate inhibitors such as diltiazem or verapamil the maximum dose is 500 mg twice daily. Information from MedlinePlus and the National Heart, Lung, and Blood Institute provides additional patient guidance.

When to Contact Your Doctor

Call the office promptly for new or worsening chest pain not relieved by sublingual nitroglycerin, palpitations, lightheadedness with standing, fainting, or sudden shortness of breath. These could represent acute coronary syndrome and may warrant immediate emergency evaluation. Severe constipation that does not respond to over-the-counter measures, persistent nausea, ankle swelling, or a marked drop in urine output deserve evaluation. Notify the office before adding any new prescription, over-the-counter, or herbal product so interactions and QT effects can be screened. Pregnancy or planned pregnancy should prompt medication review.

Lifestyle measures remain the foundation of chronic angina care alongside any medication. These include consistent aerobic activity within prescribed limits, weight management, a Mediterranean-style diet, smoking cessation, blood pressure control, lipid optimization with statin therapy when indicated, and tight diabetes control when present. Cardiac rehabilitation is recommended after coronary events, after revascularization, and increasingly for stable angina without revascularization, since structured exercise and risk-factor modification reduce future cardiac events. Patients should also recognize that ranolazine is not a substitute for evaluation of new or progressive symptoms; any change in the pattern, frequency, intensity, or precipitants of chest pain warrants prompt reassessment because it can signal disease progression that may benefit from imaging, stress testing, or revascularization. Coordination between the primary care physician and cardiologist ensures that medication adjustments, procedural decisions, and risk-factor goals remain aligned.

If chest pain is interfering with your activity despite first-line therapy, our internal medicine team can help review your antianginal regimen and coordinate cardiology consultation. Contact us or schedule a visit to discuss whether ranolazine fits your plan.