Cardarone contains amiodarone as its active component. Amiodarone belongs to the heart-and-blood-pressure therapeutic class and is supplied as an oral pill in strengths of 100 mg and 200 mg. In Hong Kong, Cardarone is a prescription-only medication regulated by the Pharmacy and Poisons Board of the Department of Health.
Amiodarone is a class III anti-arrhythmic agent. It prolongs the cardiac action potential by blocking potassium channels, which slows repolarisation and stabilises the heart rhythm. It also has additional effects on sodium, calcium channels and β-adrenergic receptors, giving it a broad anti-arrhythmic profile. After oral ingestion, amiodarone is well absorbed; its bioavailability is about 35 % because of extensive first-pass metabolism. The drug is highly lipophilic, leading to a large volume of distribution and a long elimination half-life (average 58 days), which is why steady-state concentrations are reached only after several weeks of therapy. These pharmacologic properties explain why Cardarone is effective for a wide range of sustained ventricular and supraventricular arrhythmias.
In Hong Kong, Cardarone is approved for the treatment of:
These indications follow the approvals granted by major regulatory agencies such as the U.S. FDA and the European EMA, which are also recognised by the Hong Kong Pharmacy and Poisons Board.
Current peer-reviewed evidence does not support routine off-label use of amiodarone for conditions such as heart failure without concurrent arrhythmia, or for prophylactic treatment of atrial fibrillation after cardiac surgery. When off-label use is considered, it must be under strict medical supervision and accompanied by a thorough risk-benefit assessment.
Major:
Warfarin - amiodarone can increase INR; more frequent coagulation monitoring is needed.
Digoxin - plasma levels may rise; dosage reduction of digoxin often required.
Simvastatin - increased risk of myopathy; consider using a statin with lower interaction potential.
Moderate:
CYP3A4 substrates (e.g., carbamazepine, phenytoin) - amiodarone inhibits metabolism, leading to higher plasma concentrations.
CYP2C8 substrates (e.g., repaglinide) - may increase hypoglycaemic risk.
Note: Patients should disclose all prescription medicines, over-the-counter drugs, supplements, and herbal products to their healthcare provider before starting Cardarone.
This article provides educational information about Cardarone and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.
If you remember the missed dose within 12 hours, take it as soon as possible. If it is close to the time of your next scheduled dose, skip the missed tablet and continue with your regular dosing schedule. Do not double the dose.
Co-administration is generally avoided because additive cardiac effects can increase the risk of bradycardia or heart block. Any combination must be prescribed and closely monitored by a cardiologist.
Early symptoms include a dry cough, shortness of breath on exertion, and low-grade fever. Prompt reporting to your clinician allows early imaging and possible discontinuation before serious fibrosis develops.
Mild hepatic impairment does not usually require dose reduction, but liver enzymes should be checked every 3 months. Significant hepatic dysfunction may necessitate a lower maintenance dose.
Cardarone tablets are round, white, and bear the imprint “C-100” for the 100 mg strength and “C-200” for the 200 mg strength. Packaging includes the Hong Kong Pharmacy and Poisons Board registration number.
Amiodarone is not a controlled substance and does not trigger standard workplace drug-screening panels. However, some specialized tests may detect it; inform your employer’s occupational health service if you are undergoing such testing.
Because grapefruit juice inhibits CYP3A4 enzymes that metabolise amiodarone, regular consumption can raise drug levels and increase toxicity risk. It is safest to limit or avoid grapefruit juice during therapy.
A baseline ophthalmologic exam is recommended before starting therapy, followed by annual checks to monitor for corneal deposits or visual disturbances.
There are no specific food bans, but a balanced diet with adequate iodine intake is advisable. Excessive iodine supplements should be avoided unless prescribed.
Clinical response varies; many patients notice rhythm control within 1-2 weeks of reaching their maintenance dose, though full therapeutic effect may take several weeks due to the drug’s long half-life.
