Razine Mechanism of Action

Pharmacology: Pharmacodynamics: Mechanism of Action: The mechanism of action of ranolazine's antianginal effects has not been determined. Ranolazine has anti-ischemic and antianginal effects that do not depend upon reductions in heart rate or blood pressure. It does not affect the rate-pressure product, a measure of myocardial work, at maximal exercise. Ranolazine at therapeutic levels can inhibit the cardiac late sodium current (INa). However, the relationship of this inhibition to angina symptoms is uncertain.
The QT prolongation effect of ranolazine on the surface electrocardiogram is the result of inhibition of IKr, which prolongs the ventricular action potential.
Pharmacokinetics: Ranolazine is extensively metabolized in the gut and liver and its absorption is highly variable. For example, at a dose of 1000 mg twice daily, the mean steady-state Cmax was 2600 ng/mL with 95% confidence limits of 400 and 6100 ng/mL. The pharmacokinetics of the (+) R- and (-) S-enantiomers of ranolazine are similar in healthy volunteers. The apparent terminal half-life of ranolazine is 7 hours. Steady state is generally achieved within 3 days of twice-daily dosing with Ranolazine. At steady state over the dose range of 500 to 1000 mg twice daily, Cmax and AUC0-_T increase slightly more than proportionally to dose, 2.2- and 2.4-fold, respectively. With twice-daily dosing, the trough: peak ratio of the ranolazine plasma concentration is 0.3 to 0.6. The pharmacokinetics of ranolazine is unaffected by age, gender, or food.
Absorption and Distribution: After oral administration of Ranolazine, peak plasma concentrations of ranolazine are reached between 2 and 5 hours. After oral administration of 14C-ranolazine as a solution, 73% of the dose is systemically available as ranolazine or metabolites. The bioavailability of ranolazine from Ranolazine tablets relative to that from a solution of ranolazine is 76%. Because ranolazine is a substrate of P-gp, inhibitors of P-gp may increase the absorption of ranolazine.
Food (high-fat breakfast) has no important effect on the Cmax and AUC of ranolazine. Therefore, Ranolazine may be taken without regard to meals. Over the concentration range of 0.25 to 10 μg/mL, ranolazine is approximately 62% bound to human plasma proteins.
Metabolism and Excretion: Ranolazine is metabolized mainly by CYP3A and, to a lesser extent, by CYP2D6. Following a single oral dose of ranolazine solution, approximately 75% of the dose is excreted in urine and 25% in feces. Ranolazine is metabolized rapidly and extensively in the liver and intestine; less than 5% is excreted unchanged in urine and feces. The pharmacologic activity of the metabolites has not been well characterized. After dosing to steady state with 500 mg to 1500 mg twice daily, the four most abundant metabolites in plasma have AUC values ranging from about 5 to 33% that of ranolazine, and display apparent half-lives ranging from 6 to 22 hours.