Felodipine is a calcium antagonist (calcium channel blocker). Felodipine is a dihydropyridine derivative that is chemically described as ± ethyl methyl 4-(2,3-dichlorophenyl)-1,4-dihydro-2, 6-dimethyl-3,5-pyridinedicarboxylate. Its molecular formula is C18H19Cl2NO4 and its structural formula is:

Felodipine, USP is a light yellow to yellow crystalline powder with a molecular weight of 384.26. It is insoluble in water and is freely soluble in acetone and in methanol; very slightly soluble in heptane. Felodipine is a racemic mixture.

Felodipine extended-release tablets provide extended release of felodipine. They are available as tablets containing 2.5 mg, 5 mg or 10 mg of felodipine, USP for oral administration. Inactive ingredients are: colloidal silicon dioxide, hydroxy propyl cellulose, hypromellose, lactose anhydrous, magnesium oxide, microcrystalline cellulose, polyoxyl 40 hydrogenated castor oil, propyl gallate, propylene glycol, sodium stearyl fumarate, talc, titanium dioxide and additional agents listed below:

2.5 mg tablets: Ferric oxide yellow and lake of indigo carmine

5 and 10 mg tablets: Ferric oxide red and ferric oxide yellow

Meets USP Dissolution Test 3.

Felodipine extended-release tablets are indicated for the treatment of hypertension.

Felodipine extended-release tablets may be used alone or concomitantly with other antihypertensive agents.

Felodipine extended-release tablets are contraindicated in patients who are hypersensitive to this product.

Patients should be instructed to take felodipine extended-release whole and not to crush or chew the tablets. They should be told that mild gingival hyperplasia (gum swelling) has been reported. Good dental hygiene decreases its incidence and severity.

NOTE: As with many other drugs, certain advice to patients being treated with felodipine extended-release is warranted. This information is intended to aid in the safe and effective use of this medication. It is not a disclosure of all possible adverse or intended effects.

CYP3A4 Inhibitors

Felodipine is metabolized by CYP3A4. Coadministration of CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, erythromycin, grapefruit juice, cimetidine) with felodipine may lead to several-fold increases in the plasma levels of felodipine, either due to an increase in bioavailability or due to a decrease in metabolism. These increases in concentration may lead to increased effects, (lower blood pressure and increased heart rate). These effects have been observed with coadministration of itraconazole (a potent CYP3A4 inhibitor). Caution should be used when CYP3A4 inhibitors are coadministered with felodipine. A conservative approach to dosing felodipine should be taken. The following specific interactions have been reported:

Itraconazole

Coadministration of another extended-release formulation of felodipine with itraconazole resulted in approximately 8-fold increase in the AUC, more than 6-fold increase in the Cmax, and 2-fold prolongation in the half-life of felodipine.

Erythromycin

Coadministration of felodipine with erythromycin resulted in approximately 2.5-fold increase in the AUC and Cmax, and about 2-fold prolongation in the half-life of felodipine.

Grapefruit Juice

Coadministration of felodipine with grapefruit juice resulted in more than 2-fold increase in the AUC and Cmax, but no prolongation in the half-life of felodipine.

Cimetidine

Coadministration of felodipine with cimetidine (a non-specific CYP-450 inhibitor) resulted in an increase of approximately 50% in the AUC and the Cmax, of felodipine.

Beta-Blocking Agents

A pharmacokinetic study of felodipine in conjunction with metoprolol demonstrated no significant effects on the pharmacokinetics of felodipine. The AUC and Cmax of metoprolol, however, were increased approximately 31 and 38%, respectively. In controlled clinical trials, however, beta-blockers including metoprolol were concurrently administered with felodipine and were well tolerated.

Digoxin

When given concomitantly with felodipine extended-release the pharmacokinetics of digoxin in patients with heart failure were not significantly altered.

Anticonvulsants

In a pharmacokinetic study, maximum plasma concentrations of felodipine were considerably lower in epileptic patients on long-term anticonvulsant therapy (e.g. phenytoin, carbamazepine, or phenobarbital) than in healthy volunteers. In such patients, the mean area under the felodipine plasma concentration-time curve was also reduced to approximately 6% of that observed in healthy volunteers. Since a clinically significant interaction may be anticipated, alternative antihypertensive therapy should be considered in these patients.

Tacrolimus

Felodipine may increase the blood concentration of tacrolimus. When given concomitantly with felodipine, the tacrolimus blood concentration should be followed and the tacrolimus dose may need to be adjusted.

Other Concomitant Therapy

In healthy subjects there were no clinically significant interactions when felodipine was given concomitantly with indomethacin or spironolactone.

Interaction with Food

See CLINICAL PHARMACOLOGY: Pharmacokinetics and Metabolism.

In a 2 year carcinogenicity study in rats fed felodipine at doses of 7.7, 23.1 or 69.3 mg/kg/day (up to 61 times1 the maximum recommended human dose on a mg/m2 basis), a dose related increase in the incidence of benign interstitial cell tumors of the testes (Leydig cell tumors) was observed in treated male rats. These tumors were not observed in a similar study in mice at doses up to 138.6 mg/kg/day (61 times1 the maximum recommended human dose on a mg/m2 basis). Felodipine, at the doses employed in the 2 year rat study, has been shown to lower testicular testosterone and to produce a corresponding increase in serum luteinizing hormone in rats. The Leydig cell tumor development is possibly secondary to these hormonal effects which have not been observed in man.

In this same rat study a dose related increase in the incidence of focal squamous cell hyperplasia compared to control was observed in the esophageal groove of male and female rats in all dose groups. No other drug-related esophageal or gastric pathology was observed in the rats or with chronic administration in mice and dogs. The latter species, like man, has no anatomical structure comparable to the esophageal groove.

Felodipine was not carcinogenic when fed to mice at doses up to 138.6 mg/kg/day (61 times1 the maximum recommended human dose on a mg/m2 basis) for periods of up to 80 weeks in males and 99 weeks in females.

Felodipine did not display any mutagenic activity in vitro in the Ames microbial mutagenicity test or in the mouse lymphoma forward mutation assay. No clastogenic potential was seen in vivo in the mouse micronucleus test at oral doses up to 2500 mg/kg (1,100 times1 the maximum recommended human dose on a mg/m2 basis) or in vitro in a human lymphocyte chromosome aberration assay.

A fertility study in which male and female rats were administered doses of 3.8, 9.6 or 26.9 mg/kg/day (up to 24 times1 the maximum recommended human dose on a mg/m2 basis) showed no significant effect of felodipine on reproductive performance.

Pregnancy Category C

Teratogenic Effects

Studies in pregnant rabbits administered doses of 0.46, 1.2, 2.3 and 4.6 mg/kg/day (from 0.8 to 8 times1 the maximum recommended human dose on a mg/m2 basis) showed digital anomalies consisting of reduction in size and degree of ossification of the terminal phalanges in the fetuses. The frequency and severity of the changes appeared dose related and were noted even at the lowest dose. These changes have been shown to occur with other members of the dihydropyridine class and are possibly a result of compromised uterine blood flow. Similar fetal anomalies were not observed in rats given felodipine.

In a teratology study in cynomolgus monkeys, no reduction in the size of the terminal phalanges was observed, but an abnormal position of the distal phalanges was noted in about 40% of the fetuses.

Nonteratogenic Effects

A prolongation of parturition with difficult labor and an increased frequency of fetal and early postnatal deaths were observed in rats administered doses of 9.6 mg/kg/day (8 times1 the maximum human dose on a mg/m2 basis) and above.

Significant enlargement of the mammary glands, in excess of the normal enlargement for pregnant rabbits, was found with doses greater than or equal to 1.2 mg/kg/day (2.1 times the maximum human dose on a mg/m2 basis). This effect occurred only in pregnant rabbits and regressed during lactation. Similar changes in the mammary glands were not observed in rats or monkeys.

There are no adequate and well controlled studies in pregnant women. If felodipine is used during pregnancy, or if the patient becomes pregnant while taking this drug, she should be apprised of the potential hazard to the fetus, possible digital anomalies of the infant, and the potential effects of felodipine on labor and delivery and on the mammary glands of pregnant females.

1 Based on patient weight of 50 kg

It is not known whether this drug is secreted in human milk and because of the potential for serious adverse reactions from felodipine in the infant, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

Safety and effectiveness in pediatric patients have not been established.

Clinical studies of felodipine did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. Pharmacokinetics, however, indicate that the availability of felodipine is increased in older patients (see CLINICAL PHARMACOLOGY: Geriatric Use). In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

In controlled studies in the United States and overseas, approximately 3,000 patients were treated with felodipine as either the extended-release or the immediate-release formulation.

The most common clinical adverse events reported with felodipine extended-release administered as monotherapy at the recommended dosage range of 2.5 mg to 10 mg once a day were peripheral edema and headache. Peripheral edema was generally mild, but it was age and dose related and resulted in discontinuation of therapy in about 3% of the enrolled patients. Discontinuation of therapy due to any clinical adverse event occurred in about 6% of the patients receiving felodipine extended-release, principally for peripheral edema, headache, or flushing.

Adverse events that occurred with an incidence of 1.5% or greater at any of the recommended doses of 2.5 mg to 10 mg once a day (felodipine extended-release, N = 861; Placebo, N = 334), without regard to causality, are compared to placebo and are listed by dose in the table below. These events are reported from controlled clinical trials with patients who were randomized to a fixed dose of felodipine extended-release tablets or titrated from an initial dose of 2.5 mg or 5 mg once a day. A dose of 20 mg once a day has been evaluated in some clinical studies. Although the antihypertensive effect of felodipine extended-release tablets is increased at 20 mg once a day, there is a disproportionate increase in adverse events, especially those associated with vasodilatory effects (see DOSAGE AND ADMINISTRATION).

Percent of Patients with Adverse Events in Controlled Trials* of Felodipine Extended-Release (N = 861) as Monotherapy without Regard to Causality (Incidence of discontinuations shown in parentheses)

Adverse events that occurred in 0.5% up to 1.5% of patients who received felodipine extended-release in all controlled clinical trials at the recommended dosage range of 2.5 mg to 10 mg once a day, and serious adverse events that occurred at a lower rate, or events reported during marketing experience (those lower rate events are in italics) are listed below. These events are listed in order of decreasing severity within each category, and the relationship of these events to administration of felodipine extended-release is uncertain:

Body as a Whole: Chest pain, facial edema, flu-like illness

Cardiovascular: Myocardial infarction, hypotension, syncope, angina pectoris, arrhythmia, tachycardia, premature beats

Digestive: Abdominal pain, diarrhea, vomiting, dry mouth, flatulence, acid regurgitation

Endocrine: Gynecomastia

Hematologic: Anemia

Metabolic: ALT (SGPT) increased

Musculoskeletal: Arthralgia, back pain, leg pain, foot pain, muscle cramps, myalgia, arm pain, knee pain, hip pain

Nervous/Psychiatric: Insomnia, depression, anxiety disorders, irritability, nervousness, somnolence, decreased libido

Respiratory: Dyspnea, pharyngitis, bronchitis, influenza, sinusitis, epistaxis, respiratory infection

Skin: Angioedema, contusion, erythema, urticaria, leukocytoclastic vasculitis

Special Senses: Visual disturbances

Urogenital: Impotence, urinary frequency, urinary urgency, dysuria, polyuria.

Gingival Hyperplasia: Gingival hyperplasia, usually mild, occurred in < 0.5% of patients in controlled studies. This condition may be avoided or may regress with improved dental hygiene. (See PRECAUTIONS: Information for Patients.)

Clinical Laboratory Test Findings

Serum Electrolytes

No significant effects on serum electrolytes were observed during short- and long-term therapy (see CLINICAL PHARMACOLOGY: Renal/Endocrine Effects).

Serum Glucose

No significant effects on fasting serum glucose were observed in patients treated with felodipine extended-release in the U.S. controlled study.

Liver Enzymes

One of two episodes of elevated serum transaminases decreased once drug was discontinued in clinical studies; no follow-up was available for the other patient.

Oral doses of 240 mg/kg and 264 mg/kg in male and female mice, respectively, and 2390 mg/kg and 2250 mg/kg in male and female rats, respectively, caused significant lethality.

In a suicide attempt, one patient took 150 mg felodipine together with 15 tablets each of atenolol and spironolactone and 20 tablets of nitrazepam. The patient's blood pressure and heart rate were normal on admission to hospital; he subsequently recovered without significant sequelae.

Overdosage might be expected to cause excessive peripheral vasodilation with marked hypotension and possibly bradycardia.

If severe hypotension occurs, symptomatic treatment should be instituted. The patient should be placed supine with the legs elevated. The administration of intravenous fluids may be useful to treat hypotension due to overdosage with calcium antagonists. In case of accompanying bradycardia, atropine (0.5 mg to 1 mg) should be administered intravenously. Sympathomimetic drugs may also be given if the physician feels they are warranted.

It has not been established whether felodipine can be removed from the circulation by hemodialysis.

To obtain up-to-date information about the treatment of overdose, consult your Regional Poison-Control Center. Telephone numbers of certified poison-control centers are listed in the Physicians' Desk Reference (PDR). In managing overdose, consider the possibilities of multiple-drug overdoses, drug-drug interactions, and unusual drug kinetics in your patient.

The recommended starting dose is 5 mg once a day. Depending on the patient's response, the dosage can be decreased to 2.5 mg or increased to 10 mg once a day. These adjustments should occur generally at intervals of not less than 2 weeks. The recommended dosage range is 2.5 mg to 10 mg once daily. In clinical trials, doses above 10 mg daily showed an increased blood pressure response but a large increase in the rate of peripheral edema and other vasodilatory adverse events (see ADVERSE REACTIONS). Modification of the recommended dosage is usually not required in patients with renal impairment.

Felodipine extended-release tablets should regularly be taken either without food or with a light meal (see CLINICAL PHARMACOLOGY, Pharmacokinetics and Metabolism). Felodipine extended-release tablets should be swallowed whole and not crushed or chewed.

Product: 63629-5418

NDC: 63629-5418-1 30 TABLET, EXTENDED RELEASE in a BOTTLE