Makindo Medical Notes

Important: Diltiazem must be prescribed by specific preparation (e.g., Tildiem LA, Adizem-SR, Viazem XL) as different modified-release formulations vary in pharmacokinetics and are not interchangeable. Always use the brand name when prescribing.

📖 About

• Non-dihydropyridine calcium channel blocker (benzothiazepine class).
• Often used as an alternative to β-blockers for angina or rate control in atrial fibrillation/flutter.
• Also licensed for hypertension.

⚙️ Mode of Action

• Blocks L-type calcium channels in the myocardium and vascular smooth muscle.
• ↓ Myocardial oxygen demand: reduces heart rate (negative chronotrope) and contractility (negative inotrope).
• Coronary and systemic vasodilation improves blood supply and lowers blood pressure.

🩺 Indications & Dosing (BNF – check product-specific SPC)

• Angina, Hypertension, AF/flutter (rate control):
  • Immediate-release: Start 30 mg three times daily, titrate up to 120 mg TDS (max daily dose ~360 mg).
  • Modified-release (brand-specific): Usually once or twice daily; total daily dose commonly 120–360 mg.
• Always prescribe by brand to avoid inadvertent switching between MR preparations.

🚫 Contraindications

• Second- or third-degree AV block (unless paced).
• Bradycardia or hypotension.
• Acute pulmonary oedema / left ventricular systolic dysfunction.
• Wolff–Parkinson–White syndrome with AF (may accelerate conduction).
• Use with caution in elderly, renal/hepatic impairment, or heart failure with reduced EF.

❗ Side Effects

• Bradycardia, AV block, fatigue.
• Ankle oedema (common).
• Gingival hyperplasia.
• Rash, flushing, headache, dizziness.
• GI upset: nausea, constipation (less than verapamil).

🔄 Interactions

• β-blockers: Additive bradycardia, AV block, and negative inotropy → avoid combination unless specialist advice.
• CYP3A4 inhibition: Diltiazem can ↑ plasma levels of statins (esp. simvastatin – dose limit applies), ciclosporin, tacrolimus.
• Other antihypertensives: Additive hypotension possible.

📋 Monitoring

• Check BP and heart rate regularly, especially during dose titration.
• Use lower starting doses in elderly patients.

📚 References

• BNF: Diltiazem
• Summary of Product Characteristics