Makindo Medical Notes

⚠️ Important: Side effects of Amiodarone can be severe. Long-term treatment is specialist-initiated only, reserved for life-threatening arrhythmias or where no safer alternative exists. 🫀 Amiodarone is a highly effective antiarrhythmic (Class III) but is irritant — extravasation can cause serious tissue injury. Patients must be fully counselled before long-term use.

📖 About

• 💊 Very effective antiarrhythmic with multi-class actions.
• 🩺 Long-term therapy only started by a cardiologist.
• ⚡ Originally an antianginal; later repurposed as antiarrhythmic.
• 🧂 Structurally related to thyroxine and contains iodine → thyroid effects common.

🧠 Mode of Action

• Primarily a K⁺ channel blocker (Class III) → prolongs action potential and refractory period.
• Also blocks Na⁺ (Class I) and Ca²⁺ (Class IV) channels.
• Exhibits alpha- & beta-blocking effects (Class II-like).
• Slows His–Purkinje conduction and accessory pathways (e.g., WPW).
• Has vagolytic + vasodilatory effects.

⚗️ Pharmacokinetics

• Highly lipophilic, accumulates in fat, liver, and muscle.
• Metabolised in the liver → active metabolite desethylamiodarone.
• 📅 Very long half-life: 20–100 days (longer in elderly) → delayed toxicity & interactions.

🩺 Indications

• 🚑 Emergency use: VF/pulseless VT (after 3rd shock).
• 💓 Ventricular arrhythmias (VT, VF).
• ⚡ Atrial fibrillation/flutter (esp. with structural heart disease or WPW).
• Wide-complex tachycardias of uncertain origin.

🚫 Contraindications

• Pre-existing thyroid disease (contains iodine).
• Marked sinus bradycardia or advanced AV block (unless paced).
• Severe hypotension, iodine hypersensitivity.

⚠️ Major Side Effects

• 🫀 Bradycardia, AV block, QT prolongation → risk of Torsades (rare vs other Class III).
• 🫁 Pulmonary toxicity: interstitial pneumonitis, fibrosis (potentially fatal).
• 🧂 Thyroid dysfunction: hypo- or hyperthyroidism.
• 🧠 Tremor, ataxia, peripheral neuropathy.
• 🩻 Slate-grey skin pigmentation, photosensitivity, rash.
• 👁️ Corneal microdeposits (reversible, halos around lights).
• 🫀 Rare: retroperitoneal fibrosis, orchitis, hepatitis.
• ⚡ IV use: hypotension & phlebitis if infused peripherally too fast.

🔗 Interactions

• ↑ INR with Warfarin (monitor closely).
• ↑ Digoxin and Phenytoin levels (reduce doses accordingly).
• Multiple CYP450 interactions → always check BNF.

💉 Dose Range (check BNF)

Indication	Dose	Route
🚑 Cardiac Arrest (VF/pulseless VT)	300 mg IV in 20–30 ml NS/D5W (after 3rd shock)	IV bolus
⚡ Acute Arrhythmia	150–300 mg IV over 30–60 min → then 900 mg/24h	IV infusion (central line preferred)
📅 Oral Loading	200 mg TDS × 1 wk → 200 mg BD × 1 wk → 200 mg OD	PO

🩺 Monitoring

• Baseline & 6-monthly: TFTs, LFTs, U&E.
• Annual: CXR (pulmonary toxicity).
• Ophthalmology review if visual symptoms.
• Advise on sun protection (photosensitivity risk).

📚 References

• BNF – Amiodarone
• Resus Council UK – ALS 2021