DOSAGE AND ADMINISTRATION 2.1 Important Dosing and Administration Information In selecting a digoxin dosing regimen, it is important to consider factors that affect digoxin blood levels (e.g., body weight, age, renal function, concomitant drugs) since toxic levels of digoxin are only slightlyhigher than therapeutic levels. Dosing can be either initiated with a loading dose followed by maintenance dosing if rapid titration is desired or initiated with maintenance dosing without a loading dose. Parenteral administration of digoxin should be used only when the need for rapid digitalization is urgent or when the drug cannot be taken orallly. 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. For adults, no more than 500 mcg of Digoxin Injection should be injected into a single site. For pediatric patients, see the full prescribing information for pediatric digoxin injection (not available from West-Ward) for specific recommendations. Administer the dose over a period of 5 minutes or longer and avoid bolus administration to prevent systemic and coronary vasoconstriction. Mixing of Digoxin Injection with other drugs in the same container or simultaneous administration in the same intravenous line is not recommended. Digoxin Injection 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 do not flush with the parenteral solution after its contents are expelled into an indwelling vascular catheter to avoid over administration of digoxin. Consider interruption or reduction in digoxin dose prior to electriclal cardioversion [see Warnings and Precautions (5.4)]. 2.2 Loading Dosing Regimen in Adult Patients 2.3 Maintenance Dosing in Adult Patients The maintenance dose is based on lead body weight, renal function, age, and concomitant products [ see Clinical Pharmacology (12.3)]. The recommended starting maintenance dose in adult patients with normal renal function is given in Table 2. Doses may be increased every 2 weeks according to clinical response, serum drug levels and toxicity. Table 3 provides the recommended (once daily) maintenance dose for adult patients according to lean body weight and renal function. The doses are based on studies in adult patients with heart failure. Alternatively, the maintenance dose may be estimated by the following formula (peak body stores lost each day through elimination): Total Maintenance Dose = Loading Dose (i.e., Peak Body Stores) x % Daily Loss/100 (%Daily Loss = 14 + Creatinine clearance/5) Reduce the dose of digoxin in patients whose lean weight is an abnormally small fraction of their total body mass because of obesity or edema. 2.4 Monitoring to Assess Safety, Efficacy, and Therapeutic Blood Levels Monitor for signs and symptoms of digoxin toxicity and clinical response. Adjust dose based on toxicity, efficacy, and blood vessels. Serum digoxin levels less than 0.5 ng/nL have been associated with diminished efficacy, while levels above 2 ng/mL have been associated with increased toxicity without increased benefit. Interpret the serum digoxin concentration in the overall clinical context, and do not use an isolated measurement of serum digoxin concentration as the basis for increasing or decreasing the digoxin dose. Serum digoxin concentrations may be falsely elevated by endogenous digoxin-like substances [ see Drug Interactions (7.4)]. If the assay is sensitive to these substances, consider obtaining a baseline digoxin level before starting digoxin and correct post-treatment values by the reported baseline level. Obtain serum digoxin concentrations just before the next scheduled digoxin dose or at least 6 hours after the last dose. The digoxin concentration is likely to be 10-25% lower when sampled right before the next dose (24 hours after dosing) compared to sampling 8 hours after dosing (using once-daily dosing). However, there will be only minor differences in digoxin concentrations using twice daily dosing whether sampling is done at 8 or 12 hours after a dose. 2.5 Switching from Intravenous Digoxin to Oral Digoxin When switching from intravenous to oral digoxin formulations, make allowances for differences in bioavailability when calculating maintenance dosages (see Table 4). Digoxin dose is based on patient-specific factors (age, lean body weight, renal function, etc.). See full prescribing information. Monitor for toxicity and therapeutic effect. (2) Intravenous administration is preferable to intramuscular. Avoid bolus administration. (2) Image1.jpg Image2.jpg Image3.jpg Image4.jpg