Diltiazem Hydrochloride 120 mg Capsule, Extended Release, 500-count

WARNINGS Cardiac Conduction Diltiazem hydrochloride prolongs AV node refractory periods without significantly prolonging sinus node recovery time, except in patients with sick sinus syndrome. This effect may rarely result in abnormally slow heart rates (particularly in patients with sick sinus syndrome) or second, or third degree AV block (22 of 10,119 patients, or 0.2%); 41% of these 22 patients were receiving concomitant β-adrenoceptor antagonists versus 17% of the total group. Concomitant use of diltiazem with beta-blockers or digitalis may result in additive effects on cardiac conduction.

A patient with Prinzmetal’s angina developed periods of asystole (2 to 5 seconds) after a single 60 mg dose of diltiazem. Congestive Heart Failure Although diltiazem has a negative inotropic effect in isolated animal tissue preparations, hemodynamic studies in humans with normal ventricular function have not shown a reduction in cardiac index nor consistent negative effects on contractility (dp/dt). An acute study of oral diltiazem in patients with impaired ventricular function (ejection fraction of 24% ± 6%) showed improvement in indices of ventricular function without significant decrease in contractile function (dp/dt).

Worsening of congestive heart failure has been reported in patients with preexisting impairment of ventricular function. Experience with the use of diltiazem hydrochloride in combination with beta-blockers in patients with impaired ventricular function is limited. Caution should be exercised when using this combination.

Hypotension Decreases in blood pressure associated with diltiazem hydrochloride therapy may occasionally result in symptomatic hypotension. Acute Hepatic Injury Mild elevations of serum transaminases with and without concomitant elevation in alkaline phosphatase and bilirubin have been observed in clinical studies. Such elevations were usually transient and frequently resolved even with continued diltiazem treatment.

In rare instances, significant elevations in alkaline phoshatase, LDH, SGOT, SGPT, and other phenomena consistent with acute hepatic injury have been noted. These reactions tended to occur early after therapy initiation (1 to 6 weeks) and have been reversible upon discontinuation of drug therapy. The relationship to diltiazem is uncertain in some cases, but probable in some others.

(See PRECAUTIONS .)

ADVERSE REACTIONS Serious adverse reactions to diltiazem hydrochloride have been rare in studies with other formulations, as well as with diltiazem hydrochloride extended-release capsules. It should be recognized, however, that patients with impaired ventricular function and cardiac conduction abnormalities have usually been excluded from these studies. Hypertension The most common adverse events (frequency ≥1%) in placebo-controlled, clinical hypertension studies with diltiazem hydrochloride extended-release capsules using daily doses up to 540 mg, are listed in the table below with placebo-treated patients included for comparison.

MOST COMMON ADVERSE EVENTS IN DOUBLE-BLIND, PLACEBO-CONTROLLED HYPERTENSION TRIALS Adverse Events Diltiazem Hydrochloride Extended-Release Capsules Adverse events occurring in 1% or more of patients receiving diltiazem hydrochloride extended-release capsules. Placebo (COSTART Term) n=303 # pts (%) n=87 # pts (%) rhinitis 29 (9.6) 7 (8.0) headache 27 (8.9) 12 (13.8) pharyngitis 17 (5.6) 4 (4.6) constipation 11 (3.6) 2 (2.3) cough increase 9 (3.0) 2 (2.3) flu syndrome 7 (2.3) 1 (1.1) edema, peripheral 7 (2.3) 0 (0.0) myalgia 7 (2.3) 0 (0.0) diarrhea 6 (2.0) 0 (0.0) vomiting 6 (2.0) 0 (0.0) sinusitis 6 (2.0) 1 (1.1) asthenia 5 (1.7) 0 (0.0) pain, back 5 (1.7) 2 (2.3) nausea 5 (1.7) 1 (1.1) dyspepsia 4 (1.3) 0 (0.0) vasodilatation 4 (1.3) 0 (0.0) injury, accident 4 (1.3) 0 (0.0) pain, abdominal 3 (1.0) 0 (0.0) arthrosis 3 (1.0) 0 (0.0) insomnia 3 (1.0) 0 (0.0) dyspnea 3 (1.0) 0 (0.0) rash 3 (1.0) 1 (1.1) tinnitus 3 (1.0) 0 (0.0) Angina The most common adverse events (frequency ≥1%) in a placebo-controlled, short-term (2 week) clinical angina study with diltiazem hydrochloride extended-release capsules are listed in the table below with placebo-treated patients included for comparison.

In this trial, following a placebo phase, patients were randomly assigned to once daily doses of either 120, 240, or 480 mg of diltiazem hydrochloride extended-release capsules. MOST COMMON ADVERSE EVENTS IN A DOUBLE-BLIND, PLACEBO-CONTROLLED SHORT-TERM, ANGINA TRIALS Adverse Events Diltiazem Hydrochloride Extended-Release Capsules Adverse events occurring in 1% or more of patients receiving diltiazem hydrochloride extended-release capsules. Placebo (COSTART Term) n=139 # pts (%) n=50 # pts (%) asthenia 5 (3.6) 2 (4.0) headache 4 (2.9) 3 (6.0) pain, back 4 (2.9) 1 (2.0) rhinitis 4 (2.9) 1 (2.0) constipation 3 (2.2) 1 (2.0) nausea 3 (2.2) 0 (0.0) edema, peripheral 3 (2.2) 1 (2.0) dizziness 3 (2.2) 0 (0.0) cough, increased 3 (2.2) 0 (0.0) bradycardia 2 (1.4) 0 (0.0) fibrillation, atrial 2 (1.4) 0 (0.0) arthralgia 2 (1.4) 0 (0.0) dream, abnormal 2 (1.4) 0 (0.0) dyspnea 2 (1.4) 0 (0.0) pharyngitis 2 (1.4) 1 (2.0) Infrequent Adverse Events The following additional events (COSTART Terms), listed by body system, were reported infrequently (less than 1%) in all subjects, hypertensive (n=425) or angina (n=318) patients who received diltiazem hydrochloride extended-release capsules, or with other formulations of diltiazem.

Hypertension Cardiovascular: First-degree AV block, arrhythmia, postural hypotension, tachycardia, pallor, palpitations, phlebitis, ECG abnormality, ST elevation. Nervous System: Vertigo, hypertonia, paresthesia, dizziness, somnolence. Digestive System: Dry mouth, anorexia, tooth disorder, eructation.

Skin and Appendages: Sweating, urticaria, skin hypertrophy (nevus). Respiratory System: Epistaxis, bronchitis, respiratory disorder. Urogenital System: Cystitis, kidney calculus, impotence, dysmenorrhea, vaginitis, prostate disease.

Metabolic and Nutritional Disorders: Gout, edema. Musculoskeletal System: Arthralgia, bursitis, bone pain. Hemic and Lymphatic System: Lymphadenopathy.

Body as a Whole: Pain, unevaluable reaction, neck pain, neck rigidity, fever, chest pain, malaise. Special Senses: Amblyopia (blurred vision), ear pain. Angina Cardiovascular: Palpitations, AV block, sinus bradycardia, bigeminal extrasyst…

Drug Interactions Due to the potential for additive effects, caution and careful titration are warranted in patients receiving diltiazem hydrochloride concomitantly with any agents known to affect cardiac contractility and/or conduction. (See WARNINGS .) Pharmacologic studies indicate that there may be additive effects in prolonging AV conduction when using beta-blockers or digitalis concomitantly with diltiazem hydrochloride. (See WARNINGS .) As with all drugs, care should be exercised when treating patients with multiple medications.

Diltiazem hydrochloride undergoes biotransformation by cytochrome P-450 mixed function oxidase. Co-administration of diltiazem hydrochloride with other agents which follow the same route of biotransformation may result in the competitive inhibition of metabolism. Especially in patients with renal and/or hepatic impairment, dosages of similarly metabolized drugs, particularly those of low therapeutic ratio such as cyclosporine, may require adjustment when starting or stopping concomitantly administered diltiazem hydrochloride to maintain optimum therapeutic blood levels.

Concomitant administration of diltiazem with carbamazepine has been reported to result in elevated plasma levels of carbamazepine, resulting in toxicity in some cases. Beta-Blockers Controlled and uncontrolled domestic studies suggest that concomitant use of diltiazem hydrochloride and beta-blockers is usually well-tolerated, but available data are not sufficient to predict the effects of concomitant treatment in patients with left ventricular dysfunction or cardiac conduction abnormalities. Administration of diltiazem hydrochloride concomitantly with propranolol in five normal volunteers resulted in increased propranolol levels in all subjects and the bioavailability of propranolol was increased approximately 50%.

If combination therapy is initiated or withdrawn in conjunction with propranolol, an adjustment in the propranolol dose may be warranted. (See WARNINGS .) Cimetidine A study in six healthy volunteers has shown a significant increase in peak diltiazem plasma levels (58%) and area-under-the-curve (53%) after a 1 week course of cimetidine at 1,200 mg per day and diltiazem 60 mg per day. Ranitidine produced smaller, nonsignificant increases.

The effect may be mediated by cimetidine’s known inhibition of hepatic cytochrome P-450, the enzyme system responsible for the first-pass metabolism of diltiazem. Patients currently receiving diltiazem therapy should be carefully monitored for a change in pharmacological effect when initiating and discontinuing therapy with cimetidine. An adjustment in the diltiazem dose may be warranted.

Clonidine Sinus bradycardia resulting in hospitalization and pacemaker insertion has been reported in association with the use of clonidine concurrently with diltiazem. Monitor heart rate in patients receiving concomitant diltiazem and clonidine. Digitalis Administration of diltiazem hydrochloride with digoxin in 24 healthy male subjects increased plasma digoxin concentrations approximately 20%.

Another investigator found no increase in digoxin levels in 12 patients with coronary artery disease. Since there have been conflicting results regarding the effects of digoxin levels, it is recommended that digoxin levels be monitored when initiating, adjusting, and discontinuing diltiazem hydrochloride therapy to avoid possible over- or under-digitalization. (See WARNINGS .) Anesthetics The depression of cardiac contractility, conductivity, and automaticity as well as the vascular dilation associated with anesthetics may be potentiated by calcium channel blockers.

When used concomitantly, anesthetics and calcium channel blockers should be titrated carefully. Statins Diltiazem is an inhibitor of CYP3A4 and has been shown to increase significantly the AUC of some statins. The risk of myopathy and rhabdomyolysis with statins metabolized by CYP3A4 may be increased with concomitant use of diltiazem.

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