A variety of clinical studies have demonstrated that elevated levels of total cholesterol (total-C), low density lipoprotein cholesterol (LDL-C), and apolipoprotein B (apo B), an LDL membrane complex, are associated with human atherosclerosis. Similarly, decreased levels of high density lipoprotein cholesterol (HDL-C) and its transport complex, apolipoprotein A (apo A I and apo A II) are associated with the development of atherosclerosis. Epidemiologic investigations have established that cardiovascular morbidity and mortality vary directly with the level of total-C, LDL-C, and triglycerides, and inversely with the level of HDL-C. The independent effect of raising HDL-C or lowering triglycerides (TG) on the risk of cardiovascular morbidity and mortality has not been determined.
Fenofibric acid, the active metabolite of fenofibrate, produces reductions in total cholesterol, LDL cholesterol, apolipoprotein B, total triglycerides, and triglyceride rich lipoprotein (VLDL) in treated patients. In addition, treatment with fenofibrate results in increases in high density lipoprotein (HDL) and apoproteins apo A I and apo A II.
The effects of fenofibric acid seen in clinical practice have been explained in vivo in transgenic mice and in vitro in human hepatocyte cultures by the activation of peroxisome proliferator activated receptor α (PPARα).
Through this mechanism, fenofibrate increases lipolysis and elimination of triglyceride-rich particles from plasma by activating lipoprotein lipase and reducing production of apoprotein C- III (an inhibitor of lipoprotein lipase activity). The resulting fall in triglycerides produces an alteration in the size and composition of LDL from small, dense particles (which are thought to be atherogenic due to their susceptibility to oxidation), to large buoyant particles. These larger particles have a greater affinity for cholesterol receptors and are catabolized rapidly. Activation of PPARα also induces an increase in the synthesis of apoproteins A- I, A- II and HDL-cholesterol.
Fenofibrate also reduces serum uric acid levels in hyperuricemic and normal individuals by increasing the urinary excretion of uric acid.
Plasma concentrations of fenofibric acid after multiple dose administration of Antara 130 mg capsules are equivalent, under low-fat fed conditions, to 200 mg fenofibrate capsules.
Absorption: The absolute bioavailability of fenofibrate cannot be determined as the compound is virtually insoluble in aqueous media suitable for injection. However, fenofibrate is well absorbed from the gastrointestinal tract. Following oral administration in healthy volunteers, approximately 60% of a single dose of radiolabelled fenofibrate appeared in urine, primarily as fenofibric acid and its glucuronate conjugate, and 25% was excreted in the feces. Peak plasma levels of fenofibric acid from Antara occur within 4 to 8 hours after administration.
There was less than dose-proportional increase in the systemic exposure of fenofibric acid from three strengths (43 mg, 87 mg, and 130 mg) of Antara under fasting conditions.
Doses of two- or three-capsules of 43 mg Antara given concurrently were dose-equivalent to single-capsule doses of 87 mg and 130 mg, respectively.
The extent of absorption of acid was unaffected when Antara was taken either in fasted state or with a low-fat meal. However, the Cmax of Antara increased in the presence of a low-fat meal. Tmax was unaffected in the presence of a low-fat meal. In the presence of a high-fat meal, there was a 26% increase in AUC and 108% increase in Cmax of fenofibric acid from Antara relative to fasting state.
Distribution: In healthy volunteers, steady-state plasma levels of fenofibric acid were shown to be achieved within a week of dosing and did not demonstrate accumulation across time following multiple dose administration. Serum protein binding was approximately 99% in normal and hyperlipidemic subjects.
Metabolism: Following oral administration, fenofibrate is rapidly hydrolyzed by esterases to the active metabolite, fenofibric acid; no unchanged fenofibrate is detected in plasma.
Fenofibric acid is primarily conjugated with glucuronic acid and then excreted in urine. A small amount of fenofibric acid is reduced at the carbonyl moiety to a benzhydrol metabolite which is, in turn, conjugated with glucuronic acid and excreted in urine.
In vivo metabolism data indicate that neither fenofibrate nor fenofibric acid undergo oxidative metabolism (e.g., cytochrome P450) to a significant extent.
Excretion: After absorption, fenofibrate is mainly excreted in the urine in the form of metabolites, primarily fenofibric acid and fenofibric acid glucuronide. After administration of radiolabelled fenofibrate, approximately 60% of the dose appeared in the urine and 25% was excreted in the feces.
Fenofibrate acid from Antara is eliminated with a half-life of 23 hours, allowing once daily administration in a clinical setting.
Geriatrics: In elderly volunteers 77– 87 years of age, the oral clearance of fenofibric acid following a single oral dose of fenofibrate was 1.2 L/h, which compares to 1.1 L/h in young adults. This indicates that a similar dosage regimen can be used in the elderly, without increasing accumulation of the drug or metabolites.
Pediatrics: Antara has not been investigated in adequate and well-controlled trials in pediatric patients.
Gender: No pharmacokinetic difference between males and females has been observed for fenofibrate.
Race: The influence of race on the pharmacokinetics of fenofibrate has not been studied; however, fenofibrate is not metabolized by enzymes known for exhibiting inter-ethnic variability. Therefore, inter-ethnic pharmacokinetic differences are very unlikely.
Renal insufficiency: In a study in patients with severe renal impairment (creatinine clearance <50 mL/min), the rate of clearance of fenofibric acid was greatly reduced, and the compound accumulated during chronic dosage. However, in patients having moderate renal impairment (creatinine clearance of 50 to 90 mL/min), the oral clearance and the oral volume of distribution of fenofibric acid are increased compared to healthy adults (2.1 L/h and 95 L versus 1.1 L/h and 30 L, respectively). Therefore, the dosage of Antara should be minimized in patients who have severe renal impairment, while no modification of dosage is required in patients having moderate renal impairment.
Hepatic insufficiency: No pharmacokinetic studies have been conducted in patients having hepatic insufficiency.
Drug-drug interactions: In vitro studies using human liver microsomes indicate that fenofibrate and fenofibric acid are not inhibitors of cytochrome (CYP) P450 isoforms CYP3A4, CYP2D6, CYP2E1, or CYP1A2. They are weak inhibitors of CYP2C19 and CYP2A6, and mild-to-moderate inhibitors of CYP2C9 at therapeutic concentrations.
Potentiation of coumarin-type anticoagulants has been observed with prolongation of the prothrombin time/INR.
Bile acid sequestrants have been shown to bind other drugs given concurrently. Therefore, fenofibrate should be taken at least 1 hour before or 4-6 hours after a bile acid binding resin to avoid impeding its absorption (see WARNINGS and PRECAUTIONS).
Hypercholesterolemia (Heterozygous Familial and Nonfamilial) and Mixed Dyslipidemia (Fredrickson Types IIa and IIb): The effects of fenofibrate at a dose equivalent to 130 mg Antara per day were assessed from four randomized, placebo-controlled, double-blind, parallel-group studies including patients with the following mean baseline lipid values: total-C 306.9 mg/dL; LDL-C 213.8 mg/dL; HDL-C 52.3 mg/dL; and triglycerides 191.0 mg/dL. Fenofibrate therapy lowered LDL-C, Total-C, and the LDL-C/HDL-C ratio. Fenofibrate therapy also lowered triglycerides and raised HDL-C (see Table 1).
Table 1. Mean Percent Change in Lipid Parameters at End of Treatment†
| Treatment Group || Total-C || LDL-C || HDL-C || TG |
|† Duration of study treatment was 3 to 6 months.|
|* p=<0.05 vs. placebo|
|Mean baseline lipid values (n=646)||306.9 mg/dL||213.8 mg/dL||52.3 mg/dL||191.0 mg/dL|
|All FEN (n=361)||-18.7%*||-20.6%*||+11.0%*||-28.9%*|
|Baseline LDL-C >160 mg/dL|
|and TG <150 mg/dL (Type II a)|
|Mean baseline lipid values (n=334)||307.7 mg/dL||227.7 mg/dL||58.1 mg/dL||101.7 mg/dL|
|All FEN (n=193)||-22.4%*||-31.4%*||+9.8%*||-23.5%*|
|Baseline LDL-C >160 mg/dL|
|and TG≥150 mg/dL (Type II b)|
|Mean baseline lipid values (n=242)||312.8 mg/dL||219.8 mg/dL||46.7 mg/dL||231.9 mg/dL|
|All FEN (n=126)||-16.8%*||-20.1%*||+14.6%*||-35.9%*|
In a subset of the subjects, measurements of apo B were conducted. Fenofibrate treatment significantly reduced apo B from baseline to endpoint as compared with placebo (-25.1% vs. 2.4%, p<0.0001, n=213 and 143 respectively).
Hypertriglyceridemia (Fredrickson Type IV and V): The effects of fenofibrate on serum triglycerides were studied in two randomized, double-blind, placebo-controlled clinical trials1 of 147 hypertriglyceridemic patients (Fredrickson Types IV and V). Patients were treated for eight weeks under protocols that differed only in that one entered patients with baseline triglyceride (TG) levels of 500 to 1500 mg/dL, and the other TG levels of 350 to 500 mg/dL. In patients with hypertriglyceridemia and normal cholesterolemia with or without hyperchylomicronemia (Type IV/V hyperlipidemia), treatment with fenofibrate at dosages equivalent to 130 mg Antara per day decreased primarily very low density lipoprotein (VLDL) triglycerides and VLDL cholesterol. Treatment of patients with Type IV hyperlipoproteinemia and elevated triglycerides often results in an increase of low density lipoprotein (LDL) cholesterol (see Table 2).
Table 2. Effects of Fenofibrate in Patients With Fredrickson Type IV/V Hyperlipidemia
| Study 1 || Placebo || Fenofibrate |
|*=p<0.05 vs. placebo|
|Baseline TG levels|
|350 to 499 mg/dL||Baseline||Endpoint||% Change||Baseline||Endpoint||% Change|
| Study 2 || Placebo || Fenofibrate |
|Baseline TG levels|
|500 to 1500 mg/dL||Baseline||Endpoint||% Change||Baseline||Endpoint||% Change|
The effect of Antara on serum triglycerides was studied in a double-blind, randomized, 3-arm parallel-group trial of 146 patients with Fredrickson Types IV and V dyslipidemia. The study population was comprised of 61% male and 39% female patients. Approximately 70% of patients had hypertension and 32% had diabetes. Patients were treated for eight weeks with either Antara 130 mg taken once daily with meals, Antara 130 mg taken once daily between meals, or placebo. Antara 130 mg, whether taken with meals or between meals, had comparable effects on TG and all lipid parameters (see Table 3).
Table 3. Effects of 130 mg Antara in Patients With Fredrickson Type IV/V Dyslipidemia
| Placebo (n=50) || Antara with meals (n=54) || Antara between meals (n=42) |
|*p=<0.05 vs. placebo|
|Baseline||Mean % change||Baseline||Mean % change||Baseline||Mean % change|
|(mean mg/dL)||at endpoint||(mean mg/dL)||at endpoint||(mean mg/dL)||at endpoint|
The effect of fenofibrate on cardiovascular morbidity and mortality has not been determined.