Diltiazem

Write for generic Diltiazem ER to allow pharmacist to substitute between multiple similar ER preparations
1. (2016) Presc Lett 23(7): 39-40

Non-Dihydropyridine Calcium Channel Blocker
AV Node effects
1. Slow AV Node Conduction
2. Prolong AV Node refractory period
Less negative hemodynamic effects than Verapamil
1. Potent negative chronotropic effect with decreased Heart Rate (but less than with Verapamil)
2. Minimal negative inotropic effect
3. Decreases Afterload via peripheral arterial vasodilation
4. Diltiazem affects Left Ventricular Dysfunction less than Verapamil
Coronary vasodilatation
1. Prevents sympathetic induced Coronary Artery spasm
2. May reduce Anginal episodes and increase Exercise tolerance in Stable Angina

Wolff-Parkinson-White Syndrome with Atrial Fibrillation
1. Paroxysmal accelerated ventricular response
2. Risk of progression into Ventricular Fibrillation
Wide Complex Tachycardia (unless supraventricular)
1. Risk of severe Hypotension
2. May progress into Ventricular Fibrillation
Sinus Node or AV Node dysfunction without Pacemaker
1. AV Block
2. Sick Sinus Syndrome
Severe Congestive Heart Failure or pulmonary congestion
Concurrent Intravenous Beta Blocker use
Hypotension

Regimen 1: One Bolus and then maintenance
1. Bolus: 0.25 mg/kg (to 20 mg) IV over 2 minutes
2. Maintenance: 10 mg/hour titrated to Heart Rate (typically 5-15 mg/hour)
3. Mnemonic: Rule of 15 for patient weight of 70 kg
  1. First: 15 mg IV over 2 minutes, then infusion at 15 mg/hour
  2. Titrate dosing between 5 to 15 mg/hour
Regimen 2: Two boluses and then maintenance
1. Bolus One: 0.25 mg/kg (to 20 mg) IV over 2 minutes
2. Bolus Two: 0.35 mg/kg (to 25 mg) IV over 2 minutes starting 15 minutes after first bolus
3. Maintenance: 10 mg/hour titrated to Heart Rate (typically 5-15 mg/hour)
Regimen 3: Hypotensive patient
1. "Bolus": 2.5 mg/min over 10-20 min infusion
  1. http://ehced.org/wp-content/site/Drips/dilt-load.pdf
2. Maintenance: 5 mg/hour titrated as Blood Pressure allows to Heart Rate (typically 5-15 mg/hour)
3. Pretreating with Calcium is unlikely to benefit Blood Pressure
  1. At best may offer transient Blood Pressure increase for 10 minutes (secondary to Catecholamine surge)
  2. Calcium infusion could be considered in Hypocalcemia (e.g. Calcium Chloride 0.5 to 1 g IV)
  3. Kolkebeck (2004) J Emerg Med 26(4): 395-400 [PubMed]
Oral dosing after intravenous rate control
1. Consider switching to Beta Blocker for chronic rate control (more efficacious than oral Diltiazem)
2. Diltiazem regular release starting at 30-60 mg orally three to four times daily
  1. Titrate 120 to 360 mg orally daily with extended release

Regular Release
1. Start 30 mg orally three times times daily
2. Maximum 360 mg/day
Extended Release
1. Long-acting formulations have variable release mechanisms and dosing regimens vary between products
  1. Extended Release (XR, XT, CD) formulations are dosed once daily
  2. Sustained Release (SR) formulations are dosed twice daily
  3. Extended release capsule contents may be sprinkled on food
2. Start 120-240 mg orally daily
3. Target: 240 to 360 mg/day
4. Maximum: 540 mg/day

Regular Release
1. Start 1.5 to 2 mg/kg/day orally divided 3 to 4 times daily
2. Maximum 3.5 mg/kg/day

Agents that prolong AV Node conduction (avoid)
1. Beta Blockers
2. Digoxin
3. Clonidine (case reports of severe episodes)
4. Ivabradine (contraindicated in combination)
Agents that have levels increased by Diltiazem
1. Propranolol
2. Buspirone
3. Lovastatin (limit to 20 mg daily)
4. Simvastatin (limit to 10 mg daily)
5. Quinidine
Agents that increase Diltiazem Levels
1. Cimetidine