Lanoxin Injection Pediatric Dosage
Generic name: DIGOXIN 100ug in 1mL
Dosage form: injection, solution
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Recommended dosages of digoxin may require considerable modification because of individual sensitivity of the patient to the drug, the presence of associated conditions, or the use of concurrent medications.
Parenteral administration of digoxin should be used only when the need for rapid digitalization is urgent or when the drug cannot be taken orally. Intramuscular injection can lead to severe pain at the injection site, thus intravenous administration is preferred. If the drug must be administered by the intramuscular route, it should be injected deep into the muscle followed by massage. No more than 200 mcg (2 mL) should be injected into a single site.
LANOXIN Injection Pediatric can be administered undiluted or diluted with a 4-fold or greater volume of Sterile Water for Injection, 0.9% Sodium Chloride Injection, or 5% Dextrose Injection. The use of less than a 4-fold volume of diluent could lead to precipitation of the digoxin. Immediate use of the diluted product is recommended.
If tuberculin syringes are used to measure very small doses, one must be aware of the problem of inadvertent overadministration of digoxin. The syringe should not be flushed with the parenteral solution after its contents are expelled into an indwelling vascular catheter.
Slow infusion of LANOXIN Injection Pediatric is preferable to bolus administration. Rapid infusion of digitalis glycosides has been shown to cause systemic and coronary arteriolar constriction, which may be clinically undesirable. Caution is thus advised and LANOXIN Injection Pediatric should probably be administered over a period of 5 minutes or longer. Mixing of LANOXIN Injection Pediatric with other drugs in the same container or simultaneous administration in the same intravenous line is not recommended.
In selecting a dose of digoxin, the following factors must be considered:
- The body weight of the patient. Doses should be calculated based upon lean (i.e., ideal) body weight.
- The patient’s renal function, preferably evaluated on the basis of estimated creatinine clearance.
- The patient’s age. Infants and children require different doses of digoxin than adults. Also, advanced age may be indicative of diminished renal function even in patients with normal serum creatinine concentration (i.e., below 1.5 mg/dL).
- Concomitant disease states, concurrent medications, or other factors likely to alter the pharmacokinetic or pharmacodynamic profile of digoxin (see PRECAUTIONS).
Serum Digoxin Concentrations
In general, the dose of digoxin used should be determined on clinical grounds. However, measurement of serum digoxin concentrations can be helpful to the clinician in determining the adequacy of digoxin therapy and in assigning certain probabilities to the likelihood of digoxin intoxication. About two-thirds of adults considered adequately digitalized (without evidence of toxicity) have serum digoxin concentrations ranging from 0.8 to 2.0 ng/mL. However, digoxin may produce clinical benefits even at serum concentrations below this range. About two-thirds of adult patients with clinical toxicity have serum digoxin concentrations greater than 2.0 ng/mL. However, since one-third of patients with clinical toxicity have concentrations less than 2.0 ng/mL, values below 2.0 ng/mL do not rule out the possibility that a certain sign or symptom is related to digoxin therapy. Rarely, there are patients who are unable to tolerate digoxin at serum concentrations below 0.8 ng/mL. Consequently, the serum concentration of digoxin should always be interpreted in the overall clinical context, and an isolated measurement should not be used alone as the basis for increasing or decreasing the dose of the drug.
To allow adequate time for equilibration of digoxin between serum and tissue, sampling of serum concentrations should be done just before the next scheduled dose of the drug. If this is not possible, sampling should be done at least 6 to 8 hours after the last dose, regardless of the route of administration or the formulation used. On a once-daily dosing schedule, the concentration of digoxin will be 10% to 25% lower when sampled at 24 versus 8 hours, depending upon the patient’s renal function. On a twice-daily dosing schedule, there will be only minor differences in serum digoxin concentrations whether sampling is done at 8 or 12 hours after a dose.
If a discrepancy exists between the reported serum concentration and the observed clinical response, the clinician should consider the following possibilities:
- Analytical problems in the assay procedure.
- Inappropriate serum sampling time.
- Administration of a digitalis glycoside other than digoxin.
- Conditions (described in WARNINGS and PRECAUTIONS) causing an alteration in the sensitivity of the patient to digoxin.
- Serum digoxin concentration may decrease acutely during periods of exercise without any associated change in clinical efficacy due to increased binding of digoxin to skeletal muscle.
Infants and Children
In general, divided daily dosing is recommended for infants and young children (under age 10). In the newborn period, renal clearance of digoxin is diminished and suitable dosage adjustments must be observed. This is especially pronounced in the premature infant. Beyond the immediate newborn period, children generally require proportionally larger doses than adults on the basis of body weight or body surface area. Children over 10 years of age require adult dosages in proportion to their body weight. Some researchers have suggested that infants and young children tolerate slightly higher serum concentrations than do adults.
Digitalization may be accomplished by either of two general approaches that vary in dosage and frequency of administration, but reach the same endpoint in terms of total amount of digoxin accumulated in the body.
- If rapid digitalization is considered medically appropriate, it may be achieved by administering a loading dose based upon projected peak digoxin body stores. Maintenance dose can be calculated as a percentage of the loading dose.
- More gradual digitalization may be obtained by beginning an appropriate maintenance dose, thus allowing digoxin body stores to accumulate slowly. Steady-state serum digoxin concentrations will be achieved in approximately five half-lives of the drug for the individual patient. Depending upon the patient’s renal function, this will take between 1 and 3 weeks.
Rapid Digitalization With a Loading Dose
LANOXIN Injection Pediatric can be used to achieve rapid digitalization, with conversion to an oral formulation of LANOXIN for maintenance therapy. If patients are switched from intravenous to oral digoxin formulations, allowances must be made for differences in bioavailability when calculating maintenance dosages (see Table 1 in CLINICAL PHARMACOLOGY: Pharmacokinetics and dosing Table 5).
Intramuscular injection of digoxin is extremely painful and offers no advantages unless other routes of administration are contraindicated.
Peak digoxin body stores of 8 to 12 mcg/kg should provide therapeutic effect with minimum risk of toxicity in most patients with heart failure and normal sinus rhythm. Because of altered digoxin distribution and elimination, projected peak body stores for patients with renal insufficiency should be conservative (i.e., 6 to 10 mcg/kg) (see PRECAUTIONS).
Digitalizing and daily maintenance doses for each age group are given in Table 5 and should provide therapeutic effect with minimum risk of toxicity in most patients with heart failure and normal sinus rhythm. These recommendations assume the presence of normal renal function.
The loading dose should be administered in several portions, with roughly half the total given as the first dose. Additional fractions of this planned total dose may be given at 4- to 8-hour intervals, with careful assessment of clinical response before each additional dose. If the patient’s clinical response necessitates a change from the calculated loading dose of digoxin, then calculation of the maintenance dose should be based upon the amount actually given.
IV Digitalizinga Dose (mcg/kg)
Daily IV Maintenance Doseb
15 to 25
20% to 30% of the IV digitalizing dosec
20 to 30
1 to 24 Months
30 to 50
2 to 5 Years
25 to 35
25% to 35% of the IV digitalizing dosec
5 to 10 Years
15 to 30
Over 10 Years
8 to 12
aIV digitalizing doses are 80% of oral digitalizing doses.
bDivided daily dosing is recommended for children under 10 years of age.
cProjected or actual digitalizing dose providing clinical response.
In children with renal disease, digoxin dosing must be carefully titrated based on clinical response.
Gradual Digitalization With A Maintenance Dose
More gradual digitalization can also be accomplished by beginning an appropriate maintenance dose. The range of percentages provided in Table 5 can be used in calculating this dose for patients with normal renal function.
It cannot be overemphasized that these pediatric dosage guidelines are based upon average patient response and substantial individual variation can be expected. Accordingly, ultimate dosage selection must be based upon clinical assessment of the patient.
Peak digoxin body stores larger than the 8 to 12 mcg/kg required for most patients with heart failure and normal sinus rhythm have been used for control of ventricular rate in patients with atrial fibrillation. Doses of digoxin used for the treatment of chronic atrial fibrillation should be titrated to the minimum dose that achieves the desired ventricular rate control without causing undesirable side effects. Data are not available to establish the appropriate resting or exercise target rates that should be achieved.
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