Eplerenone 25 mg Tablet, Film Coated, 30-count — NDC 31722-049-30 (Billing 31722-0049-30)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action Eplerenone binds to the mineralocorticoid receptor and blocks the binding of aldosterone, a component of the renin-angiotensin-aldosterone-system (RAAS). Aldosterone synthesis, which occurs primarily in the adrenal gland, is modulated by multiple factors, including angiotensin II and non-RAAS mediators such as adrenocorticotropic hormone (ACTH) and potassium. Aldosterone binds to mineralocorticoid receptors in both epithelial (e.g., kidney) and nonepithelial (e.g., heart, blood vessels, and brain) tissues and increases blood pressure through induction of sodium reabsorption and possibly other mechanisms.

Eplerenone has been shown to produce sustained increases in plasma renin and serum aldosterone, consistent with inhibition of the negative regulatory feedback of aldosterone on renin secretion. The resulting increased plasma renin activity and aldosterone circulating levels do not overcome the effects of eplerenone. Eplerenone selectively binds to human mineralocorticoid receptors relative to its binding to recombinant human glucocorticoid, progesterone, and androgen receptors.

12.2Pharmacodynamics There was no significant change in average heart rate among patients treated with eplerenone in the combined clinical studies. No consistent effects of eplerenone on heart rate, QRS duration, or PR or QT interval were observed in 147 normal subjects evaluated for electrocardiographic changes during pharmacokinetic studies.

12.3Pharmacokinetics Eplerenone is cleared predominantly by cytochrome P450 (CYP) 3A4 metabolism, with an elimination half-life of 3 to 6 hours. Steady state is reached within 2 days. Absorption is not affected by food.

Inhibitors of CYP3A (e.g., ketoconazole, saquinavir) increase blood levels of eplerenone. Absorption and Distribution Mean peak plasma concentrations of eplerenone are reached approximately 1.5 to 2 hours following oral administration. Absorption is not affected by food.

The absolute bioavailability of eplerenone is 69% following administration of a 100 mg oral tablet. Both peak plasma levels (C max ) and area under the curve (AUC) are dose proportional for doses of 25 mg to 100 mg and less than proportional at doses above 100 mg. Upon repeat dosing, steady state levels are reached within 2 days.

The plasma protein binding of eplerenone is about 50% and it is primarily bound to alpha 1-acid glycoproteins. The apparent volume of distribution at steady state ranged from 42 to 90 L. Eplerenone does not preferentially bind to red blood cells.

Metabolism and Excretion Eplerenone metabolism is primarily mediated via CYP3A4. No active metabolites of eplerenone have been identified in human plasma. Less than 5% of an eplerenone dose is recovered as unchanged drug in the urine and feces.

Following a single oral dose of radiolabeled drug, approximately 32% of the dose was excreted in the feces and approximately 67% was excreted in the urine. The elimination half-life of eplerenone is approximately 3 to 6 hours. The apparent plasma clearance is approximately 10 L/hr.

Age, Gender, and Race The pharmacokinetics of eplerenone at a dose of 100 mg once daily has been investigated in the elderly (≥65 years), in males and females, and in Blacks. At steady state, elderly subjects had increases in C max (22%) and AUC (45%) compared with younger subjects (18 to 45 years). The pharmacokinetics of eplerenone did not differ significantly between males and females.

At steady state, C max was 19% lower and AUC was 26% lower in Blacks [see Dosage and Administration ( 2.4 ) and Use in Specific Populations ( 8.5 )]. Renal Impairment The pharmacokinetics of eplerenone was evaluated in patients with varying degrees of renal impairment and in patients undergoing hemodialysis. Compared with control subjects, steady state AUC and C max were increased by 38% and 24%, respectively, in patients with severe renal impairment and were decreased by 26% and 3%, respectively, in patients u… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action Eplerenone binds to the mineralocorticoid receptor and blocks the binding of aldosterone, a component of the renin-angiotensin-aldosterone-system (RAAS). Aldosterone synthesis, which occurs primarily in the adrenal gland, is modulated by multiple factors, including angiotensin II and non-RAAS mediators such as adrenocorticotropic hormone (ACTH) and potassium. Aldosterone binds to mineralocorticoid receptors in both epithelial (e.g., kidney) and nonepithelial (e.g., heart, blood vessels, and brain) tissues and increases blood pressure through induction of sodium reabsorption and possibly other mechanisms.

Eplerenone has been shown to produce sustained increases in plasma renin and serum aldosterone, consistent with inhibition of the negative regulatory feedback of aldosterone on renin secretion. The resulting increased plasma renin activity and aldosterone circulating levels do not overcome the effects of eplerenone. Eplerenone selectively binds to human mineralocorticoid receptors relative to its binding to recombinant human glucocorticoid, progesterone, and androgen receptors.

12.3Pharmacokinetics Eplerenone is cleared predominantly by cytochrome P450 (CYP) 3A4 metabolism, with an elimination half-life of 3 to 6 hours. Steady state is reached within 2 days. Absorption is not affected by food.

Inhibitors of CYP3A (e.g., ketoconazole, saquinavir) increase blood levels of eplerenone. Absorption and Distribution Mean peak plasma concentrations of eplerenone are reached approximately 1.5 to 2 hours following oral administration. Absorption is not affected by food.

The absolute bioavailability of eplerenone is 69% following administration of a 100 mg oral tablet. Both peak plasma levels (C max ) and area under the curve (AUC) are dose proportional for doses of 25 mg to 100 mg and less than proportional at doses above 100 mg. Upon repeat dosing, steady state levels are reached within 2 days.

The plasma protein binding of eplerenone is about 50% and it is primarily bound to alpha 1-acid glycoproteins. The apparent volume of distribution at steady state ranged from 42 to 90 L. Eplerenone does not preferentially bind to red blood cells.

Metabolism and Excretion Eplerenone metabolism is primarily mediated via CYP3A4. No active metabolites of eplerenone have been identified in human plasma. Less than 5% of an eplerenone dose is recovered as unchanged drug in the urine and feces.

Following a single oral dose of radiolabeled drug, approximately 32% of the dose was excreted in the feces and approximately 67% was excreted in the urine. The elimination half-life of eplerenone is approximately 3 to 6 hours. The apparent plasma clearance is approximately 10 L/hr.

Age, Gender, and Race The pharmacokinetics of eplerenone at a dose of 100 mg once daily has been investigated in the elderly (≥65 years), in males and females, and in Blacks. At steady state, elderly subjects had increases in C max (22%) and AUC (45%) compared with younger subjects (18 to 45 years). The pharmacokinetics of eplerenone did not differ significantly between males and females.

At steady state, C max was 19% lower and AUC was 26% lower in Blacks [see Dosage and Administration ( 2.4 ) and Use in Specific Populations ( 8.5 )]. Renal Impairment The pharmacokinetics of eplerenone was evaluated in patients with varying degrees of renal impairment and in patients undergoing hemodialysis. Compared with control subjects, steady state AUC and C max were increased by 38% and 24%, respectively, in patients with severe renal impairment and were decreased by 26% and 3%, respectively, in patients undergoing hemodialysis.

No correlation was observed between plasma clearance of eplerenone and creatinine clearance. Eplerenone is not removed by hemodialysis [see Warnings and Precautions ( 5.1 )]. Hepatic Impairment The pharmacokinetics of eplerenone 400 mg has been investigated in patients with moderate (Child-Pugh Class B) hepatic impairment and compared with normal subjects.

Steady state C max and AUC of eplerenone were increased by 3.6% and 42%, respectively. Heart Failure The pharmacokinetics of eplerenone 50 mg was evaluated in 8 patients with heart failure (NYHA classification II–IV) and 8 matched (gender, age, weight) healthy controls. Compared with the controls, steady state AUC and C max in patients with stable heart failure were 38% and 30% higher, respectively.

Drug-Drug Interactions Eplerenone is metabolized primarily by CYP3A4. Inhibitors of CYP3A cause increased exposure [see Drug Interactions ( 7.1 )]. Drug-drug interaction studies were conducted with a 100 mg dose of eplerenone.

Following a single dose of eplerenone 100 mg and CYP3A inhibitor ketoconazole 200 mg twice a day, eplerone's C max was 1.7-fold and AUC was 5.4-fold compared with eplerone alone. Administration of eplerenone with moderate CYP3A inhibitors (e.g., erythromycin 500 mg BID, verapamil 240 mg once daily, saquinavir 1200 mg three times a day, fluconazole 200 mg once daily) resulted in increases in C max of eplerenone ranging from 40% to 60% and AUC from 100% to 190%. Grapefruit jui… [Excerpted — this section continues on DailyMed.]

12.2Pharmacodynamics There was no significant change in average heart rate among patients treated with eplerenone in the combined clinical studies. No consistent effects of eplerenone on heart rate, QRS duration, or PR or QT interval were observed in 147 normal subjects evaluated for electrocardiographic changes during pharmacokinetic studies.

14 CLINICAL STUDIES

14.1Heart Failure Post-Myocardial Infarction The eplerenone post-acute myocardial infarction heart failure efficacy and survival study (EPHESUS) was a multinational, multicenter, double-blind, randomized, placebo-controlled study in patients clinically stable 3 to 14 days after an acute MI with LV dysfunction (as measured by left ventricular ejection fraction [LVEF] ≤40%) and either diabetes or clinical evidence of HF (pulmonary congestion by exam or chest x-ray or S 3 ). Patients with HF of valvular or congenital etiology, patients with unstable post-infarct angina, and patients with serum potassium >5.0 mEq/L or serum creatinine >2.5 mg/dL were to be excluded.

Patients were allowed to receive standard post-MI drug therapy and to undergo revascularization by angioplasty or coronary artery bypass graft surgery. Patients randomized to eplerenone were given an initial dose of 25 mg once daily and titrated to the target dose of 50 mg once daily after 4 weeks if serum potassium was <5.0 mEq/L. Dosage was reduced or suspended anytime during the study if serum potassium levels were ≥5.5 mEq/L [see Dosage and Administration ( 2.1 )].

EPHESUS randomized 6,632 patients (9.3% U.S.) at 671 centers in 27 countries. The study population was primarily white (90%, with 1% Black, 1% Asian, 6% Hispanic, 2% other) and male (71%). The mean age was 64 years (range, 22 to 94 years).

The majority of patients had pulmonary congestion (75%) by exam or x-ray and were Killip Class II (64%). The mean ejection fraction was 33%. The average time to enrollment was 7 days post-MI.

Medical histories prior to the index MI included hypertension (60%), coronary artery disease (62%), dyslipidemia (48%), angina (41%), type 2 diabetes (30%), previous MI (27%), and HF (15%). The mean dose of eplerenone was 43 mg/day. Patients also received standard care including aspirin (92%), ACE inhibitors (90%), beta-blockers (83%), nitrates (72%), loop diuretics (66%), or HMG-CoA reductase inhibitors (60%).

Patients were followed for an average of 16 months (range, 0 to 33 months). The ascertainment rate for vital status was 99.7%. The co-primary endpoints for EPHESUS were (1) the time to death from any cause, and (2) the time to first occurrence of either cardiovascular mortality [defined as sudden cardiac death or death due to progression of HF, stroke, or other CV causes] or CV hospitalization (defined as hospitalization for progression of HF, ventricular arrhythmias, acute MI, or stroke).

For the co-primary endpoint for death from any cause, there were 478 deaths in the eplerenone group (14.4%) and 554 deaths in the placebo group (16.7%). The risk of death with eplerenone was reduced by 15% [hazard ratio equal to 0.85 (95% confidence interval 0.75 to 0.96; p = 0.008 by log rank test)]. Kaplan-Meier estimates of all-cause mortality are shown in Figure 1 and the components of mortality are provided in Table 5.

Figure 1. Kaplan-Meier Estimates of All-Cause Mortality Table 5. Components of All-Cause Mortality in EPHESUS Eplerenone (N=3,319) n (%) Placebo (N=3,313) n (%) Hazard Ratio p-value Death from any cause 478 (14.4) 554 (16.7) 0.85 0.008 CV Death 407 (12.3) 483 (14.6) 0.83 0.005 Non-CV Death 60 (1.8) 54 (1.6) Unknown or unwitnessed death 11 (0.3) 17 (0.5) Most CV deaths were attributed to sudden death, acute MI, and HF.

The time to first event for the co-primary endpoint of CV death or hospitalization, as defined above, was longer in the eplerenone group (hazard ratio 0.87, 95% confidence interval 0.79 to 0.95, p = 0.002). An analysis that included the time to first occurrence of CV mortality and all CV hospitalizations (atrial arrhythmia, angina, CV procedures, progression of HF, MI, stroke, ventricular arrhythmia, or other CV causes) showed a smaller effect with a hazard ratio of 0.92 (95% confidence interval 0.86 to 0.99; p = 0.028).

The combined endpoints, including combined all-cause hospitalization and mortality were driven primarily by CV mort… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility Eplerenone was non-genotoxic in a battery of assays including in vitro bacterial mutagenesis (Ames test in Salmonella spp. and E. Coli ), in vitro mammalian cell mutagenesis (mouse lymphoma cells), in vitro chromosomal aberration (Chinese hamster ovary cells), in vivo rat bone marrow micronucleus formation, and in vivo/ex vivo unscheduled DNA synthesis in rat liver. There was no drug-related tumor response in heterozygous P53 deficient mice when tested for 6 months at dosages up to 1000 mg/kg/day (systemic AUC exposures up to 9 times the exposure in humans receiving the 100 mg/day therapeutic dose).

Statistically significant increases in benign thyroid tumors were observed after 2 years in both male and female rats when administered eplerenone 250 mg/kg/day (highest dose tested) and in male rats only at 75 mg/kg/day. These dosages provided systemic AUC exposures approximately 2 to 12 times higher than the average human therapeutic exposure at 100 mg/day. Repeat dose administration of eplerenone to rats increases the hepatic conjugation and clearance of thyroxin, which results in increased levels of TSH by a compensatory mechanism.

Drugs that have produced thyroid tumors by this rodent-specific mechanism have not shown a similar effect in humans. Male rats treated with eplerenone at 1000 mg/kg/day for 10 weeks (AUC 17 times that at the 100 mg/day human therapeutic dose) had decreased weights of seminal vesicles and epididymides and slightly decreased fertility. Dogs administered eplerenone at dosages of 15 mg/kg/day and higher (AUC 5 times that at the 100 mg/day human therapeutic dose) had dose-related prostate atrophy.

The prostate atrophy was reversible after daily treatment for 1 year at 100 mg/kg/day. Dogs with prostate atrophy showed no decline in libido, sexual performance, or semen quality. Testicular weight and histology were not affected by eplerenone in any test animal species at any dosage.