CLINICAL PHARMACOLOGY
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.
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 cirrhotic 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 3162 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.
Drug Interactions
Effect of Other Drugs on Ranolazine
In vitro data indicate that ranolazine is a substrate of
CYP3A and, to a lesser degree, of CYP2D6. Ranolazine is also a substrate of
P-glycoprotein.
Strong CYP3A Inhibitors
Plasma levels of ranolazine with RANEXA 1000 mg twice
daily are increased by 220% when co-administered with ketoconazole 200 mg twice
daily [see CONTRAINDICATIONS].
Moderate CYP3A Inhibitors
Plasma levels of ranolazine with RANEXA 1000 mg twice
daily are increased by 50 to 130% by diltiazem 180 to 360 mg, respectively.
Plasma levels of ranolazine with RANEXA 750 mg twice daily are increased by
100% by verapamil 120 mg three times daily [see DRUG INTERACTIONS].
Weak CYP3A Inhibitors
The weak CYP3A inhibitors simvastatin (20 mg once daily)
and cimetidine (400 mg three times daily) do not increase the exposure to
ranolazine in healthy volunteers.
CYP3A Inducers
Rifampin 600 mg once daily decreases the plasma
concentrations of ranolazine (1000 mg twice daily) by approximately 95% [see CONTRAINDICATIONS].
CYP2D6 Inhibitors
Paroxetine 20 mg once daily increased ranolazine
concentrations by 20% in healthy volunteers receiving RANEXA 1000 mg twice
daily. No dose adjustment of RANEXA is required in patients treated with CYP2D6
inhibitors.
Digoxin
Plasma concentrations of ranolazine are not significantly
altered by concomitant digoxin at 0.125 mg once daily.
Effect of Ranolazine on Other Drugs
In vitro ranolazine and its O-demethylated metabolite are
weak inhibitors of CYP3A and moderate inhibitors of CYP2D6 and P-gp. in vitro
ranolazine is an inhibitor of OCT2.
CYP3A Substrates
The plasma levels of simvastatin, a CYP3A substrate, and
its active metabolite are increased by 100% in healthy volunteers receiving 80
mg once daily and RANEXA 1000 mg twice daily [see DRUG INTERACTIONS].
Mean exposure to atorvastatin (80 mg daily) is increased by 40% following
co-administration with RANEXA (1000 mg twice daily) in healthy volunteers.
However, in one subject the exposure to atorvastatin and metabolites was
increased by ~400% in the presence of RANEXA.
Diltiazem
The pharmacokinetics of diltiazem is not affected by
ranolazine in healthy volunteers receiving diltiazem 60 mg three times daily
and RANEXA 1000 mg twice daily.
P-gp Substrates
Ranolazine increases digoxin concentrations by 50% in
healthy volunteers receiving RANEXA 1000 mg twice daily and digoxin 0.125 mg
once daily [see DRUG INTERACTIONS].
CYP2D6 Substrates
RANEXA 750 mg twice daily increases the plasma
concentrations of a single dose of immediate release metoprolol (100 mg), a
CYP2D6 substrate, by 80% in extensive CYP2D6 metabolizers with no need for dose
adjustment of metoprolol. In extensive metabolizers of dextromethorphan, a
substrate of CYP2D6, ranolazine inhibits partially the formation of the main
metabolite dextrorphan.
OCT2 Substrates
In subjects with type 2 diabetes mellitus, the exposure
to metformin is increased by 40% and 80% following administration of ranolazine
500 mg twice daily and 1000 mg twice daily, respectively. If co-administered
with RANEXA 1000 mg twice daily, do not exceed metformin doses of 1700 mg/day [see
DRUG INTERACTIONS].
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)
Study |
Mean Difference from Placebo (sec) |
CARISA
(N=791) |
RANEXA Twice-daily Dose |
750 mg |
1000 mg |
Exercise Duration |
Trough |
24a |
24a |
Peak |
34b |
26a |
Time to Angina |
Trough |
30a |
26a |
Peak |
38b |
38b |
Time to 1 mm ST-Segment Depression |
Trough |
20 |
21 |
Peak |
41b |
35b |
a p-value ≤ 0.05 b 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 |
a 1000 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=6560) 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
Pharmacodynamics], 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.