Factors that affect digoxin dosage include weight and age, and most importantly, the patient’s blood levels in response to the drug’s administration. The form of the medicine is an additional, critical consideration when determining how much is used. Further, kidney impairment consistently requires dosing at a lower level. Also, certain medications elevate or decrease digoxin serum levels and could necessitate changes in the amounts used.
All digoxin dosage is aimed at getting patients to a therapeutic serum blood level without inducing digoxin toxicity, which is extremely serious. This medication is very helpful in the right amounts and deadly when used in excess. General guidelines exist for dosage, but individual response is so varied these should never be assumed to be appropriate for everyone. The only way to make certain a patient doesn’t develop long-lasting serum toxicity is to regularly test digoxin levels, and accordingly adjust the drug. This is particularly important at the initiation of therapy, and continued checks are required during the maintenance phase.
The general guidelines for digoxin dosage are based on age and weight. Most patients begin with a higher initial dose, called a loading dose. It’s important to mention that the form of the drug influences the specific amount given. Lower doses are common with the intravenous (IV) form of the drug.
In a two-year-old, for example, the IV loading dose is calculated as 30-50 micrograms (mcg) per kilogram (kg) of weight. Thereafter, the maintenance IV dose is 7.5-12 mcg/kg. In contrast, oral suspension begins with a loading dose of 35-60 mcg/kg, and the maintenance dosage is 10-15 mcg/kg.
Adults typically take larger amounts of digoxin than children with loading doses that can range from 400-750 mcg depending on the drug form. IV, injections, tablets, and liquid-filled capsules are the forms available for adults. Capsules and injected or IV forms of the drug usually are taken in lower microgram amounts. Weight still influences the total amount given, but so does serum concentration, which helps to inform doctors whether the patient’s response is within therapeutic range. An average adult dose could be 125-500 mcg daily, depending on all of these factors.
Kidney impairment affects digoxin dosage because it limits how quickly the medication is cleared from the body. The standard guideline is to reduce the loading dose by 50% in those with kidney problems. The maintenance amount is 25-75% of normal. Creatinine levels are carefully evaluated to make certain kidney disease isn’t worsening. With these recommendations, most adults would likely use about 125 mcg per day.
Another influential factor in digoxin dosage is medications that may react with it. The drug’s serum levels can be elevated by diuretics, heart medications like verapamil and amiodarone, and the benzodiazepine, alprazolam. Conversely, some antibiotics, antacids and thyroid medications may reduce serum levels of digoxin and require increased amounts of it to remain in the therapeutic range.