Digoxin , also known as digitalis, is a purified cardiacglycoside extracted from the foxglove plant, Digitalis lanata .Its corresponding aglycone is digoxigenin, and its acetyl derivative is acetyldigoxin. Digoxin is widely used in the treatment of various heart conditions, namely atrial fibrillation, atrial flutter and sometimes heart failure that cannot be controlled by other medication. Digoxin preparations are commonly marketed under the trade names Lanoxin, Digitek, and Lanoxicaps.
36 to 48 hours(patients with normal renal function)3.5 to 5 days(patients with impaired renal function)
Patients with more severe heart failure, a third heart sound gallop, left ventricular enlargement and a depressed left ventricular ejection fraction are more likely to respond to digoxin therapy.
Atrial flutter refers to rapid and regular contractions (usually in the range of 120 to 350 times each minute) that is characterised on the ECG by a saw-tooth appearance. Not all atrial contractions are necessarily conducted to the ventricles due to a variable block within the atrioventricularnode. When conduction to the ventricles does occur, the QRScomplex morphology is regular but RR intervals may be random or follow a specific pattern.
The ECG trace shows regular flutter waves (arrowed) at a rate of five per second. Ventricular conduction is occurring after every two (shaded RR intervals) or three (unshaded RR intervals) atrial contractions.
Digitalis toxicity is one of the most frequently encountered drug-related causes of hospitalization. Conversely, the effect of serum digoxin concentrations below 0.8 ng/ml is clinically unimportant in most patients.
The program first calculates an ideal loading dose, enter a practical dose and the desired dosage form of the loading dose. Enter 0 if no loading dose is desired. The program calculates an ideal maintenance dose, the user enters a practical maintenance dose and interval. The program then displays an estimated steady-state serum level.
Vd = 226 + [(298 x CrCl) / (29.1 + CrCl)] x (BSA / 1.73)where
CrCl = normalized creatinine clearance (ml/min)BSA = Body surface area (square meters)
LD = Vd x Cp/F where Vd = Volume of distribution (liters)Cp = target serum level (mcg/l)F = bioavailability factor
Cl =[(A x CrCl) +B] x C
A =0.88 for aute CHF ,otherwise =1
B=23 for acute CHF ,otherwise=40
C=corrective factor for interacting drugs:
Cpss = (MD x F) / (Cl x tau)where
MD = Maintenance dose (mcg)F = bioavailability factorCl = Clearance (liters/hour)tau = dosing interval (hours)
MD = (Cl x Cp x tau) / Fwhere Cl = Digoxin clearance (l/hr)Cp = target serum level (mcg/l)tau = dosing interval (hours)F = bioavailability factor
2.In some cases of Wolff-Parkinson-White syndrome with atrial fibrillation, digitalization may accelerate anterograde conduction over the bypass tract to precipitate ventricular tachycardia or ventricular fibrillation.
3.Significant AV nodal heart block. Intermittent complete heart block or second-degree AV block or sick sinus syndrome may be worsened by digitalis, especially if there is a history of Stokes-Adams attacks or when conduction is likely to be unstable, as in AMI or acute.
The main causes of digitalis toxicity in the pediatric population include the following: