Professional Information — Diltiazem Hydrochloride

Indications and Usage

Diltiazem hydrochloride extended-release capsules are indicated for the treatment of hypertension. Diltiazem hydrochloride may be used alone or in combination with other antihypertensive medications, such as diuretics.

Diltiazem hydrochloride extended-release capsules are indicated for the management of chronic stable angina.

Dosage and Administration

Hypertensive or anginal patients who are treated with other formulations of diltiazem can safely be switched to diltiazem hydrochloride extended-release capsules at the nearest equivalent total daily dose. Subsequent titration to higher or lower doses may, however, be necessary and should be initiated as clinically indicated.

Studies have shown a slight increase in the rate of absorption of diltiazem hydrochloride extended-release capsules when ingested with a high-fat breakfast; therefore, administration in the morning on an empty stomach is recommended.

Patients should be cautioned that the diltiazem hydrochloride extended-release capsules should not be opened, chewed or crushed, and should be swallowed whole.

Dosage

Hypertension
Dosages must be adjusted to each patient’s needs, starting with 180 mg or 240 mg once daily. Based on the antihypertensive effect, the dose may be adjusted as needed. Individual patients, particularly ≥60 years of age, may respond to a lower dose of 120 mg. The usual dosage range studied in clinical trials was 180 mg to 480 mg once daily.

Current clinical experience with the 540 mg dose is limited; the dose may be increased to 540 mg with little or no increased risk of adverse reactions. Doses should not exceed 540 mg once daily.

While a dose of diltiazem hydrochloride extended-release capsules given once daily may produce an antihypertensive effect similar to the same total daily dose given in divided doses, individual dose adjustment may be needed.

Dosage

Angina
Dosages for the treatment of angina should be adjusted to each patient’s needs, starting with a dose of 120 mg once daily, which may be titrated to doses of up to 480 mg once daily. When necessary, titration may be carried out over a 7 to 14 day period.

Concomitant Use with Other Cardiovascular Agents

Sublingual Nitroglycerin may be taken as required to abort acute anginal attacks during diltiazem hydrochloride therapy.

Prophylactic Nitrate Therapy – Diltiazem hydrochloride may be safely co-administered with short- and long-acting nitrates.

Beta-blockers. (See WARNINGS and PRECAUTIONS.)

Antihypertensives – Diltiazem hydrochloride has an additive antihypertensive effect when used with other antihypertensive agents. Therefore, the dosage of diltiazem hydrochloride or the concomitant antihypertensives may need to be adjusted when adding one to the other.

Contraindications

Diltiazem hydrochloride is contraindicated in: (1) patients with sick sinus syndrome except in the presence of a functioning ventricular pacemaker; (2) patients with second or third degree AV block except in the presence of a functioning ventricular pacemaker; (3) patients with hypotension (less than 90 mmHg systolic); (4) patients who have demonstrated hypersensitivity to the drug; and (5) patients with acute myocardial infarction and pulmonary congestion as documented by X-ray on admission.

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 occurring in 1% or more of patients receiving diltiazem hydrochloride extended-release capsules.

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 occurring in 1% or more of patients receiving diltiazem hydrochloride extended-release capsules.

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 extrasystole, angina pectoris, hypertension, hypotension, myocardial infarct, myocardial ischemia, syncope, vasodilatation, ventricular extrasystole.

Nervous System: Abnormal thinking, neuropathy, paresthesia.

Digestive System: Diarrhea, dyspepsia, vomiting, colitis, flatulence, GI hemorrhage, stomach ulcers.

Skin and Appendages: Contact dermatitis, pruritus, sweating.

Respiratory System: Respiratory distress.

Urogenital System: Kidney failure, pyelonephritis, urinary tract infection.

Metabolic and Nutritional Disorders: Weight increase.

Musculoskeletal System: Myalgia.

Body as a Whole: Chest pain, accidental injury, infection.

Special Senses: Eye hemorrhage, ophthalmitis, otitis media, taste perversion, tinnitus.

There have been post-marketing reports of Stevens-Johnson syndrome and toxic epidermal necrolysis associated with the use of diltiazem hydrochloride.

To report SUSPECTED ADVERSE REACTIONS, contact Alembic Pharmaceuticals Limited at 1-866-210-9797 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Overdosage

Several literature reports have identified cases of diltiazem hydrochloride overdose, some with multiple drug ingestion, with both fatal and non-fatal outcomes. The reported events affected multiple body systems including the cardiovascular system (bradycardia, complete heart block, asystole, cardiac failure, arrhythmia, atrial fibrillation, palpitations, hypotension, ischemia, ECG changes), respiratory system (respiratory failure, hypoxia, dyspnea, pulmonary edema), central nervous system (loss of consciousness, convulsions, dizziness, confusion, agitation), gastrointestinal system (nausea, vomiting), skin and appendages (increased sweating), and other systems (hypotonia, iliac artery thrombosis, metabolic acidosis, increased blood glucose). The administration of ipecac to induce vomiting and activated charcoal to reduce drug absorption have been advocated as initial means of intervention. In addition to gastric lavage, the following measures should also be considered:

Bradycardia
Administer atropine (0.6 mg to 1 mg). If there is no response to vagal blockade, administer isoproterenol cautiously.

High-Degree AV Block
Treat as for bradycardia above. Fixed high-degree AV block should be treated with cardiac pacing.

Cardiac Failure
Administer inotropic agents (dopamine or dobutamine) and diuretics.

Hypotension
Vasopressors (e.g., dopamine or levarterenol bitartrate).

Actual treatment and dosage should depend on the severity of the clinical situation as well as the judgment and experience of the treating physician.

Due to extensive metabolism, plasma concentrations after a standard dose of diltiazem can vary over tenfold, which significantly limits their value in evaluating cases of overdosage.

Charcoal hemoperfusion has been used successfully as an adjunct therapy to hasten drug elimination. Overdoses with as much as 10.8 grams of oral diltiazem have been successfully treated using appropriate supportive care.

Description

Diltiazem hydrochloride, USP is a calcium ion influx inhibitor (slow channel blocker or calcium antagonist). Chemically, diltiazem hydrochloride, USP is 1,5-Benzothiazepin-4(5H)one, 3-(acetyloxy)-5-[2-(dimethylamino)ethyl]-2,3-dihydro-2-(4-methoxyphenyl)-, monohydrochloride, (+)-cis-. Its molecular formula is C₂₂H₂₆N₂O₄S•HCl and its molecular weight is 450.98. Its structural formula is as follows:

Diltiazem hydrochloride, USP is a white to off-white crystalline powder with a bitter taste. It is freely soluble in chloroform, formic acid, methanol and water, sparingly soluble in dehydrated ethanol and insoluble in ether.

Diltiazem hydrochloride extended-release capsules, USP contain 120 mg or 180 mg or 240 mg diltiazem hydrochloride and are formulated for the controlled release of diltiazem hydrochloride over a 24-hour period.

Inactive Ingredients: Diltiazem hydrochloride extended-release capsules, USP contain lactose monohydrate, hypromellose, colloidal silicon dioxide and magnesium stearate.

The 120 mg, 180 mg and 240 mg capsule shells contain FD&C Blue 1, FD&C Red 3, FD&C Red 40, titanium dioxide and gelatin.

Additionally, 120 mg capsule shell contains FD&C Yellow 6, 180 mg and 240 mg capsule shell contains D&C Red 33.

The capsules are printed with edible ink containing shellac, iron oxide black and potassium hydroxide.

For oral administration.

FDA approved dissolution test specifications differ from USP.

Clinical Pharmacology

The therapeutic benefits of diltiazem hydrochloride are believed to be related to its ability to inhibit the influx of calcium ions during membrane depolarization of cardiac and vascular smooth muscles.

Mechanism of Action

Hypertension
Diltiazem hydrochloride extended-release capsule produces its antihypertensive effect primarily by relaxation of vascular smooth muscle with a resultant decrease in peripheral vascular resistance. The magnitude of blood pressure reduction is related to the degree of hypertension; thus hypertensive individuals experience an antihypertensive effect, whereas there is only a modest fall in blood pressure in normotensives.

Angina
Diltiazem HCl has been shown to produce increases in exercise tolerance, probably due to its ability to reduce myocardial oxygen demand. This is accomplished via reductions in heart rate and systemic blood pressure at submaximal and maximal work loads.

Diltiazem has been shown to be a potent dilator of coronary arteries, both epicardial and subendocardial. Spontaneous and ergonovine-induced coronary artery spasms are inhibited by diltiazem.

In animal models, diltiazem interferes with the slow inward (depolarizing) current in excitable tissue. It causes excitation-contraction uncoupling in various myocardial tissues without changes in the configuration of the action potential. Diltiazem produces relaxation of coronary vascular smooth muscle and dilation of both large and small coronary arteries at drug levels which cause little or no negative inotropic effect. The resultant increases in coronary blood flow (epicardial and subendocardial) occur in ischemic and nonischemic models and are accompanied by dose-dependent decreases in systemic blood pressure and decreases in peripheral resistance.

Hemodynamic and Electrophysiologic Effects
Like other calcium antagonists, diltiazem decreases sinoatrial and atrioventricular conduction in isolated tissues and has a negative inotropic effect in isolated preparations. In the intact animal, prolongation of the AH interval can be seen at higher doses.

In man, diltiazem prevents spontaneous and ergonovine-provoked coronary artery spasm. It causes a decrease in peripheral vascular resistance and a modest fall in blood pressure in normotensive individuals. In exercise tolerance studies in patients with ischemic heart disease, diltiazem reduces the double product (HR x SBP) for any given work load. Studies to date, primarily in patients with good ventricular function, have not revealed evidence of a negative inotropic effect. Cardiac output, ejection fraction and left ventricular end diastolic pressure have not been affected. Such data have no predictive value with respect to effects in patients with poor ventricular function. Increased heart failure has, however, been reported in occasional patients with pre-existing impairment of ventricular function. There are as yet few data on the interaction of diltiazem and beta-blockers in patients with poor ventricular function. Resting heart rate is usually slightly reduced by diltiazem.

Diltiazem hydrochloride extended-release capsule produces antihypertensive effects both in the supine and standing positions. Postural hypotension is infrequently noted upon suddenly assuming an upright position. Diltiazem decreases vascular resistance, increases cardiac output (by increasing stroke volume), and produces a slight decrease or no change in heart rate. No reflex tachycardia is associated with the chronic antihypertensive effects.

During dynamic exercise, increases in diastolic pressure are inhibited while maximum achievable systolic pressure is usually reduced. Heart rate at maximum exercise does not change or is slightly reduced.

Diltiazem antagonizes the renal and peripheral effects of angiotensin II. No increased activity of the renin-angiotensin-aldosterone axis has been observed. Chronic therapy with diltiazem produces no change or an increase in plasma catecholamines. Hypertensive animal models respond to diltiazem with reductions in blood pressure and increased urinary output and natriuresis without a change in the urinary sodium/potassium ratio. In man, transient natriuresis and kaliuresis have been reported, but only in high intravenous doses of 0.5 mg/kg of body weight.

Diltiazem-associated prolongation of the AH interval is not more pronounced in patients with first-degree heart block. In patients with sick sinus syndrome, diltiazem significantly prolongs sinus cycle length (up to 50% in some cases). Intravenous diltiazem in doses of 20 mg prolongs AH conduction time and AV node functional and effective refractory periods approximately 20%.

In two short-term, double-blind, placebo-controlled studies, 303 hypertensive patients were treated with once daily diltiazem hydrochloride extended-release capsules in doses of up to 540 mg. There were no instances of greater than first-degree atrioventricular block, and the maximum increase in the PR interval was 0.08 seconds. No patients were prematurely discontinued from the medication due to symptoms related to prolongation of the PR interval.

Pharmacodynamics
In one short-term, double-blind, placebo-controlled study, diltiazem hydrochloride extended-release capsule 120, 240, 360, and 480 mg/day demonstrated a dose-related antihypertensive response among patients with mild to moderate hypertension. Statistically significant decreases in trough mean supine diastolic blood pressure were seen through 4 weeks of treatment: 120 mg/day (-5.1 mmHg); 240 mg/day (-6.9 mmHg); 360 mg/day (-6.9 mmHg); and, 480 mg/day (-10.6 mmHg). Statistically significant decreases in trough mean supine systolic blood pressure were also seen through 4 weeks of treatment: 120 mg/day (-2.6 mmHg); 240 mg/day (-6.5 mmHg); 360 mg/day (-4.8 mmHg); and 480 mg/day (-10.6 mmHg). The proportion of evaluable patients exhibiting a therapeutic response (supine diastolic blood pressure <90 mmHg or decrease >10 mmHg) was greater as the dose increased: 31%, 42%, 48%, and 69% with the 120, 240, 360, and 480 mg/day diltiazem groups, respectively. Similar findings were observed for standing systolic and diastolic blood pressures. The trough (24 hours after a dose) antihypertensive effect of diltiazem hydrochloride extended-release capsules retained more than one-half of the response seen at peak (3 to 6 hours after administration).

Significant reductions of mean supine blood pressure (at trough) in patients with mild to moderate hypertension were also seen in a short-term, double-blind, dose-escalation, placebo-controlled study after 2 weeks of once daily diltiazem hydrochloride extended-release capsules 180 mg/day (diastolic: -6.1 mmHg; systolic: -4.7 mmHg) and again, 2 weeks after escalation to 360 mg/day (diastolic: -9.3 mmHg; systolic: -7.2 mmHg). However, a further increase in dose to 540 mg/day for 2 weeks provided only a minimal further increase in the antihypertensive effect (diastolic: -10.2 mmHg; systolic: -6.7 mmHg).

Diltiazem hydrochloride extended-release capsules, given at 120 mg, 240 mg, and 480 mg/day, in a randomized, multicenter, double-blind, placebo-controlled, parallel group, dose-ranging study, in 189 patients with chronic angina, demonstrated a dose-related increase in exercise time by Exercise Tolerance Test (ETT) and a reduction in rates of anginal attacks (based on individual patient diaries). The improvement in total exercise time (using the Bruce protocol), measured at trough exercise periods, for placebo, 120 mg, 240 mg, and 480 mg, was 20, 37, 49, and 56 seconds, respectively.

Pharmacokinetics and Metabolism
Diltiazem is well absorbed from the gastrointestinal tract, and is subject to an extensive first-pass effect. When given as an immediate release oral formulation, the absolute bioavailability (compared to intravenous administration) of diltiazem is approximately 40%. Diltiazem undergoes extensive hepatic metabolism in which 2% to 4% of the unchanged drug appears in the urine. Total radioactivity measurement following short IV administration in healthy volunteers suggests the presence of other unidentified metabolites which attain higher concentrations than those of diltiazem and are more slowly eliminated; half-life of total radioactivity is about 20 hours compared to 2 to 5 hours for diltiazem. In vitro binding studies show diltiazem HCl is 70% to 80% bound to plasma proteins. Competitive in vitro ligand binding studies have also shown diltiazem HCl binding is not altered by therapeutic concentrations of digoxin, HCTZ, phenylbutazone, propranolol, salicylic acid, or warfarin. The plasma elimination half-life of diltiazem is approximately 3.0 to 4.5 hours. Desacetyldiltiazem, the major metabolite of diltiazem, which is also present in the plasma at concentrations of 10% to 20% of the parent drug, is approximately 25% to 50% as potent a coronary vasodilator as diltiazem. Therapeutic blood levels of diltiazem hydrochloride appear to be in the range of 40 to 200 ng/mL. There is a departure from linearity when dose strengths are increased; the half-life is slightly increased with dose.

A study that compared patients with normal hepatic function to patients with cirrhosis found an increase in half-life and a 69% increase in bioavailability in the hepatically impaired patients. Patients with severely impaired renal function showed no difference in the pharmacokinetic profile of diltiazem compared to patients with normal renal function.

Diltiazem hydrochloride extended-release capsules (Once-a-day dosage) contain a degradable controlled-release tablet formulation designed to release diltiazem over a 24-hour period. Controlled absorption of diltiazem begins within 1 hour, with maximum plasma concentrations being achieved 4 to 6 hours after administration. The apparent steady-state half-life of diltiazem following once daily administration of diltiazem hydrochloride extended-release capsules ranges from 5 to 10 hours. This prolongation of half-life is attributed to continued absorption of diltiazem rather than to alterations in its elimination.

The absolute bioavailability of diltiazem from a single dose of diltiazem hydrochloride extended-release capsules (compared to intravenous administration) is 41% (±14). The value was shown to be similar to the 40% systemic availability reported following administration of an immediate release diltiazem HCl formulation.

As the dose of diltiazem hydrochloride extended-release capsule is increased from a daily dose of 120 mg to 240 mg, there is an increase in the AUC of 2.3 fold. When the dose is increased from 240 mg to 360 mg, AUC increases 1.6 fold and when increased from  240 mg to 480 mg, AUC increases 2.4 fold.

In vivo release of diltiazem occurs throughout the gastrointestinal tract, with controlled release still occurring for up to 24 hours after administration, as determined by radio-labeled methods. As the once daily dose of diltiazem hydrochloride extended-release capsule was increased, departures from linearity were noted. There were disproportionate increases in area under the curve for doses from 120 mg to 480 mg.

The presence of food did not affect the ability of diltiazem hydrochloride extended-release capsules to maintain a controlled release of the drug and did not impact its sustained release properties over 24-hours after administration. However, simultaneous administration of diltiazem hydrochloride extended-release capsules with a high-fat breakfast resulted in increases in AUC of 13% and 19%, and in C_max by 37% and 51%, respectively.

How Supplied / Storage and Handling

Diltiazem hydrochloride extended-release capsules USP, 120 mg are pink opaque cap/light pink opaque body, hard gelatin capsules having imprinting “A250” in black ink on the cap. The capsule is filled with one white to off white oval shaped tablet.
Bottle of 100 capsules with child-resistant closure, NDC 62332-815-31
Bottle of 500 capsules, NDC 62332-815-71
Bottle of 1000 capsules, NDC 62332-815-91

Diltiazem hydrochloride extended-release capsules USP, 180 mg are lavender opaque cap/pink opaque body, hard gelatin capsules having imprinting “A251” in black ink on the cap. The capsule is filled with one white to off white oval shaped tablet.
Bottle of 100 capsules with child-resistant closure, NDC 62332-816-31
Bottle of 500 capsules, NDC 62332-816-71
Bottle of 1000 capsules, NDC 62332-816-91

Diltiazem hydrochloride extended-release capsules USP, 240 mg are blue opaque cap/pink opaque body, hard gelatin capsules having imprinting “A252” in black ink on the cap. The capsule is filled with one white to off white oval shaped tablet.
Bottle of 100 capsules with child-resistant closure, NDC 62332-817-31
Bottle of 500 capsules, NDC 62332-817-71
Bottle of 1000 capsules, NDC 62332-817-91

Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature].

Dispense in a tight, light-resistant container [see USP]. Keep tightly closed. 

Keep out of the reach of children.

Rx Only

Manufactured by:
Alembic Pharmaceuticals Limited
(Formulation Division),
Panelav 389350, Gujarat, India.

Manufactured for:
Alembic Pharmaceuticals, Inc.
Bedminster, NJ 07921, USA

Revised: 09/2023