Diltiazem

Cardizem IR and CD: chronic stable angina and angina due to coronary artery spasm; CD additionally treats hypertension. Cardizem LA treats hypertension and improves exercise tolerance in chronic stable angina. Tiazac treats hypertension and chronic stable angina. These selected oral labels do not list AF rate control as a labeled indication.

Selected IV products temporarily control rapid ventricular rate in AF/flutter and rapidly convert PSVT to sinus rhythm; WG explicitly indicates adults. Sagent describes AV-nodal reentry and reciprocating PSVT involving an accessory pathway, while AF/flutter WITH an accessory bypass tract is contraindicated. Do not conflate those rhythm situations. IV diltiazem rarely converts AF/flutter itself to sinus rhythm; it primarily slows ventricular rate.

The 2023 joint AF guideline supports acute diltiazem rate control in hemodynamically stable AF with EF > 40%, and selected long-term rate control according to comorbidities. Oral AF use is outside these selected oral labels’ indications. IV nondihydropyridine blockers should not be used with known moderate/severe LV systolic dysfunction, with or without decompensated HF; long-term use should not occur with LVEF < 40%. This focused reference does not supply a complete AF, cardioversion or anticoagulation algorithm.

Adult label regimens below require BP, pulse, angina-response and adverse-effect assessment.

Cardizem IR label permits swallowing whole, crushing or chewing; its 30 mg tablet must not be split. Do not transfer IR handling to ER. Cardizem LA: swallow whole, never chew/crush, once daily at the same time; food does not meaningfully change exposure. Tiazac can be swallowed whole or all beads sprinkled on cool, soft applesauce, swallowed immediately without chewing then cool water; do not store or subdivide contents. The selected CD label does not grant Tiazac’s sprinkle permission. CD/LA/Tiazac labels allow a supervised switch from another diltiazem regimen to the nearest equivalent total daily dose with close monitoring and possible further titration; do not substitute release forms independently. Avoid alcohol with Cardizem CD because it can accelerate release.

Continuous ECG, frequent BP measurement and immediately available defibrillator/emergency equipment are required. Confirm actual weight and rhythm.

Sagent 5 mg/mL vials require dilution for infusion with saline, D5W or D5W/0.45% saline per label; calculate final volume/concentration rather than treating vial concentration as infusion concentration. Use within 24 hours and refrigerate until use. WG 1 mg/mL bags are ready to administer without further dilution. Inspect solution, avoid mixing other drugs in the same container and use a dedicated line when possible due to incompatibilities. Cardizem LA specifies no renal adjustment and likely none for mild/moderate hepatic impairment; IR/other selected labels call for cautious organ-impairment titration without a fixed algorithm. Do not generalize LA wording to severe hepatic disease or every product.

Selected oral products: sick sinus syndrome or second/third-degree AV block unless a functioning ventricular pacemaker; systolic BP < 90 mm Hg; drug hypersensitivity; acute MI with pulmonary congestion. Selected IV products: the same pacemaker exceptions for sinus/AV disease, severe hypotension/cardiogenic shock, hypersensitivity, pre-excited AF/flutter and ventricular tachycardia. IV diltiazem and IV beta-blockers must not be given together; Sagent also forbids close proximity within a few hours. That is distinct from cautious supervised combinations with oral beta-blockers.

The selected current U.S. diltiazem labels have no boxed warning. Route-specific contraindications and risks of conduction block, hypotension and HF remain important.

Oral trial/reported effects include peripheral edema, dizziness, headache, fatigue, bradycardia/AV block, nausea/constipation and rash; serious HF, hepatic, skin or allergic reactions may occur. IV trials prominently report hypotension, injection-site reactions, flushing and arrhythmia; oral incidence cannot be assigned to IV use. Postmarketing events have uncertain frequency. Overdose can cause profound bradycardia, block, hypotension and cardiac failure; emergency/toxicology care is required (U.S. Poison Help 1-800-222-1222). ER toxicity may be prolonged; dialysis does not appear effective. Follow a specialist resuscitation plan rather than a home antidote.

Diltiazem is both substrate/inhibitor of CYP3A4 and P-gp; organ impairment can magnify exposure changes. This table highlights selected current label actions.

Do not mix with other drugs in the same container; dedicated line preferred. Selected labels report incompatibility with agents including furosemide, regular insulin, diazepam, phenytoin, bicarbonate and several antimicrobials/steroids. Check the complete product compatibility list before co-infusion rather than relying on this abbreviated list.

Current LA/WG summaries state decades-of-use published pregnancy data have not identified increased major-birth-defect, miscarriage or other adverse-outcome risk; animal developmental findings and evidence limits remain. Selected older IR/CD/Tiazac/Sagent labels advise use only when benefit justifies fetal risk. Diltiazem enters human milk. LA/WG weigh maternal need, breastfeeding benefit and potential infant effects, while selected older products advise alternative infant feeding if treatment is essential. Discuss the exact product and circumstances; do not infer universal safety.

Pediatric safety/effectiveness is not established for these selected products; no pediatric regimen is supplied. Older-adult trials are limited; use cautious low-end initial dosing in view of cardiac/hepatic/renal function, comorbidity and interactions. Monitor pulse, BP, dizziness/falls, conduction and HF rather than assigning a universal age-based dose.

LA states no renal adjustment and that mild/moderate hepatic impairment likely needs no adjustment. Other selected labels recommend cautious use/titration with organ impairment and periodic renal/hepatic testing; no universal percentage reduction exists. Cirrhosis can increase exposure/half-life; severe hepatic impairment requires individualized review. Assess LV function and HF separately from clearance.

Diltiazem inhibits calcium entry in cardiac/vascular muscle, dilates coronary/peripheral vessels and reduces AV-nodal conduction/refractoriness. BP and oxygen-demand reduction contribute to antianginal effects; AV slowing contributes to ventricular-rate control. Reduced contractility underlies HF precautions.

Disposition

Extensive first-pass/hepatic metabolism; oral absolute bioavailability ~40%, protein binding ~70–80%, only ~2–4% unchanged urinary drug.

Selected ER timing

CD peak ~10–14 hours / apparent half-life 5–8 hours; LA peak ~11–18 hours / apparent half-life 6–9 hours. These values do not make the two products interchangeable.

IV / nonlinear kinetics

IV half-life and clearance vary with dose/infusion; rate and daily oral mg do not form a universal direct conversion.

Organ effects

Cirrhosis can increase exposure and prolong half-life; interactions through CYP3A4/P-gp affect diltiazem and companion drugs.

Assess indication, BP/pulse, ECG/conduction when relevant, ventricular function/HF and interacting medicines before selection. Oral follow-up tracks angina/BP, edema, dizziness, bradycardia, liver/skin symptoms and renal/hepatic laboratory parameters as labels indicate. IV requires continuous ECG and frequent BP with emergency equipment; reassess block, hypotension, HF and infusion duration. Monitor companion drug levels/CK symptoms when relevant.

Know the exact release form and dosing schedule; LA must remain intact, and Tiazac’s sprinkle option does not apply to every capsule. Avoid alcohol with CD. Consult before starting/stopping other medicines, including OTC/supplements. Report fainting, unusually slow pulse, worsening dyspnea/edema, jaundice or rash promptly; severe symptoms need urgent care. Diltiazem is not an acute-angina rescue substitute; use the prescribed rescue plan. Discuss pregnancy/breastfeeding and individual missed-dose directions.

Cardizem CD 120 mg once-daily capsule: light turquoise body/cap, cardizem CD 120 mg imprint; example 30-count bottle NDC 0187-0795-30. Exact generic release/appearance is manufacturer-specific and cannot be inferred from color alone.

Selected oral brands: 25°C, excursions 15–30°C, avoid excess humidity; LA also avoids > 30°C and uses tight light-resistant container. Sagent vials: 2–8°C, no freezing; may remain at room temperature up to 1 month then destroy; discard remainder. Diluted Sagent infusion: use within 24 hours, refrigerate until use. WG bags: 2–8°C, no freezing; original overwrapped bag may remain 20–25°C up to 1 month, and use within 28 days after removal from aluminum overwrap. Keep route-specific storage/preparation instructions with the product.