DOSAGE AND ADMINISTRATION Direct Intravenous Single Injections (Bolus) The initial dose of diltiazem hydrochloride injection should be 0.25 mg/kg actual body weight as a bolus administered over 2 minutes (20 mg is a reasonable dose for the average patient). If response is inadequate, a second dose may be administered after 15 minutes. The second bolus dose of diltiazem hydrochloride injection should be 0.35 mg/kg actual body weight administered over 2 minutes (25 mg is a reasonable dose for the average patient). Subsequent intravenous bolus doses should be individualized for each patient. Patients with low body weights should be dosed on a mg/kg basis. Some patients may respond to an initial dose of 0.15 mg/kg, although duration of action may be shorter. Experience with this dose is limited. Continuous Intravenous Infusion For continued reduction of the heart rate (up to 24 hours) in patients with atrial fibrillation or atrial flutter, an intravenous infusion of diltiazem hydrochloride injection may be administered. Immediately following bolus administration of 20 mg (0.25 mg/kg) or 25 mg (0.35 mg/kg) diltiazem hydrochloride injection and reduction of heart rate, begin an intravenous infusion of diltiazem hydrochloride. The recommended initial infusion rate of diltiazem hydrochloride is 10 mg/h. Some patients may maintain response to an initial rate of 5 mg/h. The infusion rate may be increased in 5 mg/h increments up to 15 mg/h as needed, if further reduction in heart rate is required. The infusion may be maintained for up to 24 hours. Diltiazem shows dose-dependent, non-linear pharmacokinetics. Duration of infusion longer than 24 hours and infusion rates greater than 15 mg/h have not been studied. Therefore, infusion duration exceeding 24 hours and infusion rates exceeding 15 mg/h are not recommended. DILUTION To prepare diltiazem hydrochloride injection for continuous intravenous infusion, aseptically transfer the appropriate quantity (see chart) of diltiazem hydrochloride injection to the desired volume of either Normal Saline, D5W, or D5W/0.45% NaCl. Mix thoroughly. Use within 24 hours. Keep refrigerated until use. Diluent Volume Quantity of Diltiazem HCl Injection to Add Final Concentration Administration Dose 5 mg/h may be appropriate for some patients Infusion Rate 100 mL 125 mg (25 mL) Final Volume 125 mL 1 mg/mL 10 mg/h 15 mg/h 10 mL/h 15 mL/h 250 mL 250 mg (50 mL) Final Volume 300 mL 0.83 mg/mL 10 mg/h 15 mg/h 12 mL/h 18 mL/h 500 mL 250 mg (50 mL) Final Volume 550 mL 0.45 mg/mL 10 mg/h 15 mg/h 22 mL/h 33 mL/h Compatibility Diltiazem hydrochloride injection was tested for compatibility with three commonly used intravenous fluids at a maximal concentration of 1 mg diltiazem hydrochloride per milliliter. Diltiazem hydrochloride injection was found to be physically compatible and chemically stable in the following parenteral solutions for at least 24 hours when stored in glass or polyvinylchloride (PVC) bags at controlled room temperature 15º-30°C (59°-86°F) or under refrigeration 2°-8°C (36°-46°F). dextrose (5%) injection sodium chloride (0.9%) injection dextrose (5%) and sodium chloride (0.45%) injection Physical Incompatibilities Because of potential physical incompatibilities, it is recommended that diltiazem hydrochloride not be mixed with any other drugs in the same container. If possible, it is recommended that diltiazem hydrochloride not be co-infused in the same intravenous line. Physical incompatibilities (precipitate formation or cloudiness) were observed when diltiazem hydrochloride injection was infused in the same intravenous line with the following drugs: acetazolamide, acyclovir, aminophylline, ampicillin, ampicillin sodium/sulbactam sodium, cefamandole, cefoperazone, diazepam, furosemide, hydrocortisone sodium succinate, insulin (regular: 100 units/mL), methylprednisolone sodium succinate, mezlocillin, nafcillin, phenytoin, rifampin, and sodium bicarbonate. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. Transition to Further Antiarrhythmic Therapy Transition to other antiarrhythmic agents following administration of diltiazem hydrochloride injection is generally safe. However, reference should be made to the respective agent manufacturer’s package insert for information relative to dosage and administration. In controlled clinical trials, therapy with antiarrhythmic agents to maintain reduced heart rate in atrial fibrillation or atrial flutter or for prophylaxis of PSVT was generally started within 3 hours after bolus administration of diltiazem hydrochloride. These antiarrhythmic agents were intravenous or oral digoxin, Class 1 antiarrthythmics (e.g., quinidine, procainamide), calcium channel blockers, and oral beta-blockers. Experience in the use of antiarrhythmic agents following maintenance infusion of diltiazem hydrochloride injection is limited. Patients should be dosed on an individual basis and reference should be made to the respective manufacturer’s package insert for information relative to dosage and administration.