*Reduced tolerance of digoxin may be seen in (factors predisposing to digitalis toxicity) :
- Advanced age
- Acute Myocardial Infarction/ Ischemia/ Hypoxemia
- Magnesium depletion (hypomagnesemia)
- Hypercalcemia (Calcium synergises with digitalis and precipitates its toxicity)
- Hypothyroidism (Both hyperthyroidism and hypothyroidism enhance digitalis toxicity. Thyrotoxicosis patients are more prone to develop digitalis arrhythmias and Myxedema enhances responsiveness to digitalis. Myxedema patients eliminate digoxin more slowly)
- Renal insufficiency (Digoxin is mainly excreted by kidneys)
- Electrical cardioversion
* Digitalis toxicity causes hyperkalemia, but hypokalemia enhances digitalis toxicity (by increasing its binding to Na+/K+ ATPase.
*The administration of the following drugs raises the serum concentration of digoxin :
- Quinidine
- Verapamil
- Procainamide
- Amiodarone
*MANAGEMENT OF DIGITALIS OVERDOSE :
- Withdrawl of the drug
- Potassium (administer cautiously and by oral route whenever possible if hypokalemia is present. Potassium must not be employed in the presence of A-V block or hyperkalemia.
- Phenytoin/Beta blocker or Lidocaine : Lidocaine is effective in treatment of digitalis induced ventricular tachyarrythmias.
- Cardiac pacemaker : may be required in digitalis induced A-V block.
- Electrical conversion : may be life saving in digitalis induced ventricular fibrillation
- FAB fragments/ digitalis antibodies : are potentially life saving in severe intoxication
- Hemodialysis is not useful in digoxin toxicity .
(Other conditions where hemodialysis is ineffective is Digoxin poisoning, Kerosene poisoning, Benzodiazepine poisoning and Organophosphate poisoning)
(Remember that Digoxin and Digitoxin are two different drugs, both derived from digitalis, But digitoxin is mainly excreted by liver and digoxin is mainly excreted by kidneys. Hence digoxin dosage need not be adjusted in liver failure and digitoxin dosage need not be adjusted in renal failure)
*The most lipid soluble cardiac glycoside is Digitoxin.
*The most rapidly absorbed oral glycoside is digitoxin.
1 comment:
These coldness issues can masquerade as thyroid problems, and in some cases may in fact be the primary cause of the hypothyroidism. Whatever helps to get your energy and temperature up is what is needed. I take bovine thyroid supplements and I can feel the benefits.
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