Digoxin Dosing Calculator
Determination of initial loading and maintanance dose.
Monitoring: Obtain blood samples at least 4 hrs after IV dose and 6-8hrs after an oral dose. Serum levels: 0.5 to 2.0 ng/ml. Obtain the first level within 24 hours of digitalization. Monitor BUN and serum creatinine q2days (qd if unstable). Monitor apical pulse daily. Onset/peak: IV: 5-30min/ 1-4hrs Oral: 1-2hrs/ 2-8 hrs. Time to steady state: 5-7 days (average) ESRD: 15-20 days. Half-life: 38-48 hrs. (anephric: 4-6 days).
Factors that increase the likelihood of digoxin toxicity: Hypokalemia, hypomagnesemia, hypothyroidism, renal dysfunction, interacting drugs (eg quinidine, verapamil).
Distribution: only a small fraction of digoxin in present in the blood (little is removed by hemodialysis). Digoxin distributes very little into body fat–doses must be based on lean body weight. Distribution is not altered by obesity. There appears to be a gradual contraction in the volume of distribution as renal function deteriorates. Therefore, extreme caution is necessary when dosing patients with renal failure.
Maximal response from any maintenance dose of digoxin will be obtained when serum concentrations are at steady state and maximal body stores for that dose have been obtained. It should be noted that any adjustment of dose or change in the elimination of digoxin requires a waiting period of 4-5 times the half-life (1 week with normal renal function) before the new steady state concentration is achieved.
If steady state levels are available, use this table
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