Calcium Channel Blockers are cardiovascular agents that inhibit calcium influx into cardiac and smooth muscle cells, promoting vasodilation, lowering blood pressure, and treating conditions like hypertension, angina, and arrhythmias.
Name of the Calcium Channel Blockers drugs
- Dihydropyridines
- Nifedipine
- Amlodipine
- Felodipine
- Diltiazem
- Verapamil
Mechanism of action:
Calcium-channel blockers target L-type calcium channels and binds to them. These L-type calcium channels are located on the smooth muscle of vessels, cardiac myocytes, and nodal tissues in heart. These channels regulate the entry of calcium into muscle cells, which stimulates smooth muscle and cardiac myocyte to contract. Vasodilation occurs when calcium entry is blocked this way into cells. Hence there will be decrease in myocardial force generation (negative inotropy), decrease in heart rate (negative chronotropic), and decrease in conduction velocity within the heart (negative dromotropic).
Indications:
- Cardiac arrhythmias
- Hypertension
- SVT (verapamil and Diltiazem)
- Prophylaxis of angina pectoris
- Raynaud’s phenomenon (dihydropyridines only)
- Prophylaxis of migraine
| Amlodipine |
| Availability: Tablets: 2.5 mg, 5 mg, 10 mg |
| Administration/handling: PO: • May give without regard to food. |
| Hypertension PO: Adults: Initially, 5 mg/day as a single dose. May titrate every 7–14 days. Maximum: 10 mg/day. Small-frame, fragile, elderly, addition to other antihypertensives: 2.5 mg/day as a single dose. May titrate q7–14 days. Maximum: 10 mg/day. Children 6–17 YRS: 2.5–5 mg/day. |
| CAD PO: Adults: 5–10 mg/day as a single dose. Elderly, pts with hepatic insufficiency: 5 mg/day as a single dose. |
| Dosage in Hepatic Impairment : Adults, elderly: Hypertension: Initially, 2.5 mg/day. Angina: Initially, 5 mg/day. Titrate slowly in pts with severe impairment. |
| Nifedipine |
| Availability: Capsules: 10 mg, 20 mg. Tablets, Extended-Release: 30 mg, 60 mg, 90 mg |
| Administration/handling: PO • Do not break, crush, dissolve, or divide extended-release tablets. • Give without regard to food. • Grapefruit products may alter absorption; avoid use. Sublingual • Capsules must be punctured, chewed, and/or squeezed to express liquid into mouth. |
| Prinzmetal’s Variant Angina, Chronic Stable (Effort-Associated) Angina PO: (Extended-Release): Adults, elderly: Initially, 30–60 mg/day. May increase at 7- to 14-day intervals. Maximum: 120 mg/day. |
| Hypertension PO: (Extended-Release): Adults, elderly: Initially, 30–60 mg/day. May increase at 7- to 14-day intervals. Maximum: 90–120 mg/day. Children 1–17 yrs: Initially, 0.2–0.5 mg/kg/day. Maximum: 3 mg/kg/day or 120 mg/day. |
| Diltiazem |
| Availability: Injection, Solution: 25 mg/5 mL, 50 mg/10 mL, 125 mg/25 ml. Tablets, Immediate-Release: 30 mg, 60 mg, 90 mg, 120 mg. Capsules, Extended-Release, 24 Hour: 120 mg, 180 mg, 240 mg, 300 mg, 360 mg, 420 mg. Capsules, Extended Release, 12 Hour: 60 mg, 90 mg, 120 mg. Tablets, Extended-Release, 24 Hour: 120 mg, 180 mg, 240 mg, 300 mg, 360 mg, 420 mg. |
| Administration/handling: IV Reconstitution: Add 125 mg to 100 mL D5W, 0.9% NaCl to provide concentration of 1 mg/ml. Rate of administration: • Infuse per dilution/rate chart provided by manufacturer. Storage: Refrigerate vials. • After dilution, stable for 24 hrs. PO: Give immediate-release tablets before meals and at bedtime. • Tablets may be crushed. • Do not break, crush, dissolve, or divide sustained-release capsules or extended-release capsules or tablets. |
| Angina: PO: (Immediate-Release): Adults, elderly: Initially, 30 mg 4 times/day. Range: 120–320 mg/day. PO: (Extended-Release): Adults, elderly: Initially, 120–180 mg once daily. May increase at 7- to 14-day intervals. Range: 120–320 mg. Maximum: 480 mg/day. |
| Hypertension PO: (Extended-Release Capsule [once-daily dosing]) Initially, 180–240 mg/day. May increase after 14 days. Usual dose: 240–360 mg/day. Maximum: 480 mg/day. |
| Temporary Control of Rapid Ventricular Rate in Atrial Fibrillation/Flutter; Rapid Conversion of Paroxysmal Supraventricular Tachycardia to Normal Sinus Rhythm IV bolus: Adults, elderly: Initially, 0.25 mg/kg (average dose: 20 mg) actual body weight over 2 min. May repeat in 15 min at dose of 0.35 mg/kg (average dose: 25 mg) actual body weight. Subsequent doses individualized. IV infusion: Adults, elderly: After initial bolus injection, may begin infusion at 5–10 mg/hr; may increase by 5 mg/hr up to a maximum of 15 mg/hr. Continuous infusion longer than 24 hrs or infusion rate greater than 15 mg/hr are not recommended. Attempt conversion to PO therapy as soon as possible |
| Verapamil |
| Availability : Injection Solution: 2.5 mg/mL. Tablets: 40 mg, 80 mg, 120 mg. Capsules, Extended-Release: 100 mg, 120 mg, 180 mg, 200 mg, 240 mg, 300 mg, 360 mg. Tablets, Extended-Release: 120 mg, 180 mg, 240 mg. |
| Administration/handling: IV Reconstitution • May give undiluted. Rate of administration: Administer IV push over 2 min for adults, children; give over 3 min for elderly. • Continuous ECG monitoring during IV injection is required for children, recommended for adults. • Monitor ECG for rapid ventricular rate, extreme bradycardia, heart block, asystole, prolongation of PR interval. Notify physician of any significant changes. • Monitor B/P q5– 10min. • Pt should remain recumbent for at least 1 hr after IV administration. Storage • Store vials at room temperature PO • Do not give with grapefruit products. • Do not crush or cut extended-release tablets, capsules. Give extended-release tablets with food. • Sustained-release capsules may be opened and sprinkled on applesauce, then swallowed immediately (do not chew). |
| Supraventricular Tachyarrhythmias (SVT) : IV: Adults, elderly: Initially, 5–10 mg over 2 min. May give 10 mg 15–30 min after initial dose. Children 1–15 yrs: 0.1–0.3 mg/kg over 2 min. Maximum initial dose: 5 mg. May repeat in 15–30 min. Maximum second dose: 10 mg |
| Angina, Unstable Angina, Chronic Stable Angina PO: (Immediate-Release): ADULTS, ELDERLY: 80–60 mg 3 times day |
| Atrial Fibrillation (Rate Control) IV: ADULTS, ELDERLY: Initially, 0.075–0.15 mg/kg (usual: 5–10 mg) over 2 min. May repeat with 10 mg after 15–30 min. PO: (Immediate-Release): 240–480 mg/day in 3–4 divided doses. |
| Hypertension PO: (Immediate-Release): ADULTS, ELDERLY: Initially, 40–120 mg 3 times/day. Range: 240–480 mg/day in divided doses. PO: (Extended-Release [Calan SR]):ADULTS, ELDERLY: Initially, 120–180 mg once daily. May increase at wkly intervals to 240 mg once daily, then 180 mg twice daily. Maximum: 240 mg twice daily. |
| Chronic Atrial Fibrillation (Rate Control), SVT PO: (Immediate-Release): ADULTS, ELDERLY: 240–480 mg/day in 3–4 divided doses. Usual range: 120–360 mg/day |
Metabolism And Half- Life:
All extensively metabolized in the liver. T ½ for diltiazem is 3-5 h; t ½ for Verapamil is 6 hrs; t ½ for dihydropyridines is highly variable.
Monitoring:
- Monitor BP, HR, anginal symptoms.
- Monitor for side effects
Drug Interactions:
- Enhanced hypotensive effects with antihypertensives and alcohol.
- Increased risk AV block, bradycardia, severe hypotension and heart failure if verapamil or diltiazem are given with beta blockers. Plasma concentration of some calcium channel blockers is increased by grapefruit juice.
Cautions & Contraindications:
- Cardiogenic shock or hypotension
- LVF (Verapamil and diltiazem)
- Second or third – degree heart block (verapamil and diltiazem)
- Bradycardia (Verapamil and diltiazem)
- Unstable angina (dihydropyridines)
- Hepatic or renal impairment
- Use with caution in patients using digoxin
- Do not use with grapefruit.
Side –Effects:
- Bradycardia (verapamil and diltiazem)
- Reflex tachycardia, gingival hyperplasia (Dihydropyridines)
- Hypotension
- Vasodilatory effects (flushing, headache, peripheral edema, palpitations, dizziness)
- Constipation (Verapamil)
- Heart Failure (Verapamil) Hyperprolactinemia
NURSING CONSIDERATIONS:
Baseline assessment:
Vital signs, review lab results: CBC, electrolytes, Creatinine, BUN, Liver function tests, urine analysis, and ECG.
Obtain baseline ECG. Record onset, type (sharp, dull, squeezing), radiation, location, intensity, duration of anginal pain, precipitating factors (exertion, emotional stress). Check B/P for hypotension, pulse for bradycardia immediately before giving medication.
Client Education:
- Explain how the medication works
- Take medication exactly as instructed and not to stop abruptly.
- Extended -release tablets should not be divided, crushed or chewed.
- Avoid grapefruit juice
- Limit caffeine intake, as it can increase BP and HR.
- If peripheral edema occurs as side effect advice to elevate the legs few hours /day
- Good dental hygiene
Important Points:
- Verapamil and Diltiazem are Vaughan Williams class IV antiarrhythmics. Vascular selectivity of different calcium channel blockers is explained by voltage dependence; dihydropyridines are inactive at the hyperpolarized membrane potentials of the myocardium during diastole.
- Verapamil and diltiazem are less voltage dependent and hence less selective.
- Monitor ECG for cardiac changes, particularly prolongation of PR interval. Notify physician of any significant ECG interval changes.
REFERENCES
- Robert Kizior, Keith Hodgson, Saunders Nursing Drug handbook,1st edition 2024, Elsevier Publications. ISBN-9780443116070
- McGraw Hill- Drug Handbook, Seventh Edition, 2013, McGraw Hill Education Publications,9780071799430.
- April Hazard, Cynthia Sanoski, Davi’s Drug Guide for Nurses -Sixteenth Edition 2019, FA Davis Company Publications,9780803669451.
- Jones and Bartlet, Pharmacology for Nurses, Second Edition, 2020, Jones and Bartlet Learning Publications, ISBN 9781284141986.
- Nursebro.com, Search – Nursebro
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