Pharmacology
Cardiovascular
Which of the following is NOT a common side effect of amiodarone:
Answer:
Common side effects of amiodarone include:- Bradycardia
- Nausea and vomiting
- Thyroid disorders - hypothyroidism and hyperthyroidism
- Persistent slate grey skin discoloration
- Photosensitivity
- Pulmonary toxicity (including pneumonitis and fibrosis)
- Hepatotoxicity
- Corneal microdeposits (sometimes with night glare)
- Peripheral neuropathy
- Sleep disorders
Amiodarone
Pharmacology / Cardiovascular
Last Updated: 17th April 2019
Amiodarone hydrochloride is used in the treatment of arrhythmias, particularly when other drugs are ineffective or contraindicated. However, its long-term use is often restricted by serious adverse effects such as photosensitivity, thyroid disorders, corneal microdeposits, neuropathy and pulmonary alveolitis.
Mechanism of Action
Amiodarone has blocking actions on several channels (e.g. K+ and inactivated Na+ channels) and beta-adrenoceptors. It acts by slowing repolarisation and prolonging the action potential and refractory period in all cardiac tissues, depressing sinus node automaticity and slowing conduction.
Indications
Amiodarone can be used for paroxysmal supraventricular, nodal and ventricular tachycardias, atrial fibrillation and flutter, and ventricular fibrillation. It can also be used for tachyarrhythmias associated with Wolff-Parkinson- White syndrome.
Intravenous injection of amiodarone hydrochloride can be used in cardiopulmonary resuscitation for ventricular fibrillation or pulseless tachycardia unresponsive to other interventions.
Contraindications
Amiodarone is contraindicated in:
- Severe conduction disturbances (unless pacemaker fitted)
- Sinus node disease (unless pacemaker fitted)
- Iodine sensitivity
- Sinoatrial heart block (except in cardiac arrest)
- Sinus bradycardia (except in cardiac arrest)
- Thyroid dysfunction
Intravenous use should be avoided in cardiomyopathy, congestive heart failure, circulatory collapse, severe arterial hypotension and severe respiratory failure.
Cautions
Amiodarone should be used with caution in:
- Acute porphyrias
- Conduction disturbances (in excessive dosage)
- Elderly
- Heart failure
- Hypokalaemia
- Severe bradycardia (in excessive dosage)
- Severe hepatocellular toxicity
- Concomitant therapy with drugs that prolong the QT interval
Side Effects
Common side effects of amiodarone include:
- Bradycardia
- Nausea and vomiting
- Thyroid disorders - hypothyroidism and hyperthyroidism
- Persistent slate grey skin discoloration
- Photosensitivity
- Pulmonary toxicity (including pneumonitis and fibrosis)
- Hepatotoxicity
- Corneal microdeposits (sometimes with night glare)
- Peripheral neuropathy
- Sleep disorders
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
