Amiodarone secretion

Amiodarone is contraindicated in patients with sick sinus syndrome and may cause severe bradycardia and second-and third-degree atrioventricular block. Amiodarone crosses the placenta and will affect the fetus, as evidenced by bradycardia and thyroid abnormalities. The drug is secreted in breast milk. 

Quinidine inhibits the tubular secretion of digoxin which consequently raises the plasma digoxin concentration, which may be associated with toxicity. Certain other drugs also increase the digoxin concentration like verapamil, amiodarone, spironolactone etc. 

Amiodarone-induced hyponatremia, due to the syndrome of inappropriate secretion of antidiuretic hormone, is rare (SEDA-21, 199 25). The mechanism is unknown. Unlike other adverse effects of amiodarone, it seems to occur rapidly and to resolve rapidly after withdrawal. 

A 62-year-old woman with paroxysmal atrial fibrillation who had taken amiodarone 300 mg/day had a serum sodium concentration of 120 mmol/1 with a normal serum potassium and a reduced serum osmolality (240 mmol/kg) the urinary sodium concentration was 141 mmol/1 and the urine osmolality 422 mmol/kg (25). There was no evident cause of inappropriate secretion of ADH and within 5 days of withdrawal of amiodarone the serum sodium concentration had risen to 133 mmol/ 1 and rose further to 143 mmol/1 14 days later. There was no rechallenge and no recurrence of hyponatremia during the next 6 months. Another case has been reported (28). 

Ikegami H, Shiga T, Tsushima T, Nirei T, Kasanuki H. Syndrome of inappropriate antidiuretic hormone secretion (SIADH) induced by amiodarone a report on two cases. J Cardiovasc Pharmacol Ther 2002 7(l) 25-8. 

Aslam MK, Gnaim C, Kutnick J, Kowal RC, McGuire DK. Syndrome of inappropriate antidiuretic hormone secretion induced by amiodarone therapy. Pacing Clin Electrophysiol 2004 27(6 Pt l) 831-2. 

Loratadine is well absorbed after oral administration, with peak plasma concentrations at approximately 1.5 hours. Clinically significant relief of symptoms is usually obtained within 2 to 4 hours of the first dose. Excretion of loratadine occurs almost equally through the urine and feces.This dual mechanism of secretion provides a measure of safety in patients with liver or kidney disease, but caution should be exercised in both groups. Also, torsades de pointes may occur with the concurrent use of loratadine and amiodarone. Desloratadine is a metabolite of loratadine. 

Amiodarone inhibits the renal tubular secretion of digoxin (SEDA-22, 201) and it has also been suggested that it increases its absorption (SEDA-10, 144) (SEDA-12,150). This interaction has also been reported with acetyldigoxin (SEDA-18,198) (221). 

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