Mechanism of Action
The mechanism of action of ranolazine'sanginal 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.
Pharmacodynamics
Hemodynamic Effects
Patients with chronic angina treated with Ranexa in controlled clinical studies had minimal changes in mean heart rate ( < 2 bpm) and systolic blood pressure ( < 3 mm Hg). Similar results were observed in subgroups of patients with CHF NYHA Class I or II, diabetes, or reactive airway disease, and in elderly patients.
Electrocardiographic Effects
Dose and plasma concentration-related increases in the QTc interval [see WARNINGS
and PRECAUTIONS], reductions in T wave amplitude,
and, in some cases, notched T waves, have been observed in patients treated
with Ranexa. These effects are believed to be caused by ranolazine and not by
its metabolites. The relationship between the change in QTc and ranolazine plasma
concentrations is linear, with a slope of about 2.6 msec/1000 ng/mL, through
exposures corresponding to doses several-fold higher than the maximum recommended
dose of 1000 mg twice daily. The variable blood levels attained after a given
dose of ranolazine give a wide range of effects on QTc. At Tmax following repeat
dosing at 1000 mg twice daily, the mean change in QTc is about 6 msec, but in
the 5% of the population with the highest plasma concentrations, the prolongation
of QTc is at least 15 msec. In subjects with mild or moderate hepatic impairment,
the relationship between plasma level of ranolazine and QTc is much steeper
[see CONTRAINDICATIONS].
Age, weight, gender, race, heart rate, congestive heart failure, diabetes, and renal impairment did not alter the slope of the QTc-concentration relationship of ranolazine.
No proarrhythmic effects were observed on 7-day Holter recordings in 3,162
acute coronary syndrome patients treated with Ranexa. There was a significantly
lower incidence of arrhythmias (ventricular tachycardia, bradycardia, supraventricular
tachycardia, and new atrial fibrillation) in patients treated with Ranexa (80%)
versus placebo (87%), including ventricular tachycardia ≥ 3 beats (52% versus
61%). However, this difference in arrhythmias did not lead to a reduction in
mortality, a reduction in arrhythmia hospitalization, or a reduction in arrhythmia
symptoms.
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 Ranexa. At steady state over the dose range of 500 to 1000 mg twice
daily, Cmax and AUC0-τ 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 Ranexa, 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 Ranexa 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, Ranexa 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.
Reproductive Toxicology Studies
Animal reproduction studies with ranolazine were conducted in rats and rabbits.
There was an increased incidence of misshapen sternebrae and reduced ossification of pelvic and cranial bones in fetuses of pregnant rats dosed at 400 mg/kg/day (2 times the MRHD on a surface area basis). Reduced ossification of sternebrae was observed in fetuses of pregnant rabbits dosed at 150 mg/kg/day (1.5 times the MRHD on a surface area basis). These doses in rats and rabbits were associated with an increased maternal mortality rate.
Clinical Studies
Chronic Stable Angina
CARISA (Combination Assessment of Ranolazine In Stable Angina) was a study in 823 chronic angina patients randomized to receive 12 weeks of treatment with twice-daily Ranexa 750 mg, 1000 mg, or placebo, who also continued on daily doses of atenolol 50 mg, amlodipine 5 mg, or diltiazem CD 180 mg. Sublingual nitrates were used in this study as needed.
In this trial, statistically significant (p < 0.05) increases in modified
Bruce treadmill exercise duration and time to angina were observed for each
Ranexa dose versus placebo, at both trough (12 hours after dosing) and peak
(4 hours after dosing) plasma levels, with minimal effects on blood pressure
and heart rate. The changes versus placebo in exercise parameters are presented
in Table 1. Exercise treadmill results showed no increase in effect on exercise
at the 1000 mg dose compared to the 750 mg dose.
Table 1: Exercise Treadmill Results (CARISA)
| |
Mean Difference from Placebo (sec) |
| Study |
CARISA (N = 791) |
| Ranexa Twice-daily Dose |
750 mg |
1000 mg |
| Exercise Duration |
| Trough |
24* |
24* |
| Peak |
34** |
26* |
| Time to Angina |
| Trough |
30* |
26* |
| Peak |
38** |
38** |
| Time to 1 mm ST-Segment Depression |
| Trough |
20 |
21 |
| Peak |
41** |
35** |
| * p-value ≤ 0.05 ** p-value ≤ 0.005 |
The effects of Ranexa on angina frequency and nitroglycerin use are shown in
Table 2.
Table 2: Angina Frequency and Nitroglycerin Use (CARISA)
| |
|
Placebo |
Ranexa
750 mga |
Ranexa
1000 mga |
| Angina Frequency (attacks/week) |
N |
258 |
272 |
261 |
| Mean |
3.3 |
2.5 |
2.1 |
| p-value vs placebo |
— |
0.006 |
< 0.001 |
| Nitroglycerin Use (doses/week) |
N |
252 |
262 |
244 |
| Mean |
3.1 |
2.1 |
1.8 |
| p-value vs placebo |
— |
0.016 |
< 0.001 |
| a Twice daily |
Tolerance to Ranexa did not develop after 12 weeks of therapy. Rebound increases
in angina, as measured by exercise duration, have not been observed following
abrupt discontinuation of Ranexa.
Ranexa has been evaluated in patients with chronic angina who remained symptomatic
despite treatment with the maximum dose of an antianginal agent. In the ERICA
(Efficacy of Ranolazine In Chronic Angina) trial, 565 patients were randomized
to receive an initial dose of Ranexa 500 mg twice daily or placebo for 1 week,
followed by 6 weeks of treatment with Ranexa 1000 mg twice daily or placebo,
in addition to concomitant treatment with amlodipine 10 mg once daily. In addition,
45% of the study population also received long-acting nitrates. Sublingual nitrates
were used as needed to treat angina episodes. Results are shown in Table 3.
Statistically significant decreases in angina attack frequency (p = 0.028) and
nitroglycerin use (p = 0.014) were observed with Ranexa compared to placebo.
These treatment effects appeared consistent across age and use of long-acting
nitrates.
Table 3: Angina Frequency and Nitroglycerin Use (ERICA)
| |
Placebo |
Ranexaa |
Angina Frequency
(attacks/week) |
N |
281 |
277 |
| Mean |
4.3 |
3.3 |
| Median |
2.4 |
2.2 |
Nitroglycerin Use
(doses/week) |
N |
281 |
277 |
| Mean |
3.6 |
2.7 |
| Median |
1.7 |
1.3 |
| a1000 mg twice daily |
Gender
Effects on angina frequency and exercise tolerance were considerably smaller in women than in men. In CARISA, the improvement in Exercise Tolerance Test (ETT) in females was about 33% of that in males at the 1000 mg twice-daily dose level. In ERICA, where the primary endpoint was angina attack frequency, the mean reduction in weekly angina attacks was 0.3 for females and 1.3 for males.
Race
There were insufficient numbers of non-Caucasian patients to allow for analyses of efficacy or safety by racial subgroup.
Lack of Benefit in Acute Coronary Syndrome
In a large (n = 6,560) placebo-controlled trial (MERLIN-TIMI 36) in patients
with acute coronary syndrome, there was no benefit shown on outcome measures.
However, the study is somewhat reassuring regarding proarrhythmic risks, as
ventricular arrhythmias were less common on ranolazine [see CLINICAL PHARMACOLOGY],
and there was no difference between Ranexa and placebo in the risk of all-cause
mortality (relative risk ranolazine:placebo 0.99 with an upper 95% confidence
limit of 1.22).
REFERENCES
M.A. Suckow et al. The anti-ischemia agent ranolazine promotes the development of intestinal tumors in APC (min/+) mice. Cancer Letters 209(2004):165 9.
Last updated on RxList: 12/29/2008