the iodine bomb
A Class III antiarrhythmic agent known for its efficacy in atrial and ventricular arrhythmias, but burdened by a massive iodine content and extensive end-organ toxicity (Thyroid, Lung, Liver, Skin).
- Mechanism: Class III (K+ channel blocker). Also has Class I (Na+), II (-block), and IV (Ca2+) properties.
- Dosing: Load: 150 mg IV bolus / infusion. PO loading protocols vary (e.g., 8–10g total load). Maintenance: 100–200 mg daily (lowest effective dose).
- PK: Half-life: ~100 days (huge volume of distribution). Effects persist months after stopping. Iodine content: 37% by weight.
indications
- Atrial Fibrillation: Rhythm control (esp. in structural heart disease/HF).
- Ventricular Tachycardia (VT) / VF: ACLS protocols and maintenance.
adverse effects (the checklist)
- Thyroid:
- Hypothyroidism (AIH): Wolff-Chaikoff effect. Treat with Levothyroxine.
- Thyrotoxicosis (AIT): Type 1 (Jod-Basedow) vs Type 2 (Destructive). See Amiodarone-related thyroid dysfunction.
- Pulmonary: Interstitial pneumonitis / fibrosis (exclude if new cough/dyspnea).
- Hepatic: Elevated LFTs common; cirrhosis rare.
- Ocular: Corneal microdeposits (universal, usually benign), Optic neuropathy (rare/blindness).
- Skin: Blue-grey discoloration (sun-exposed areas), Photosensitivity.
related pages: Amiodarone-related thyroid dysfunction