Question

TJ is a 50yo male, 70kg, 5’10”, being treated for NYHA Class III moderate heart failure. His current serum creatinine is 3.5mg/dL, and it has been stable over the last three months.
Meds: aspirin 81mg daily, enalapril 10mg twice a day, metoprolol XL 100mg daily, simvastatin 20mg at bedtime. BP 127/76 mmHg, Pulse 65bpm, RR 21rpm, Temp 37.5C,
Pain 0/10. Labs: CBC within normal ranges, Glu 83mg/dL, K 4.1mmol/L, Cl 96mmol/L, Ca 9.5mg/dL, AST 20IU/L, ALT 24 IU/L. The physician asks for your advice to begin digoxin.
Compute and oral digoxin tablet maintenance dose for this patient (Include calculations).

a. 74.23mcg daily
b. 125mcg every 48 hours
c. 125mcg daily
d. 250mcg every other day

Answer 1

There is no firm place for any inotropic agent in patients with chronic heart failure. Digoxin has vagomimetic effects, slowing sinus rate and prolonging atrioventricular conduction and therefore ventricular rate in patients with sinus rhythm or atrial fibrillation.

- It does not drop or increase blood pressure due to diuretic property,

- for digoxin native patients with severe heart failure , an initial loading dose that doesn't need to be adjusted for renal dysfunction is appropriate.

- maintenance doses should be adjusted according to renal function, erring on side of caution in older people,

- The contemporary fashion is to use lower maintenance doses of digoxin, typically 125mcg/day for a standardised-sized , middle aged patient with good renal function and 62.5 mcg/day for older, frailer patients,

- hence above given case study answer is 'b' 125 mcg/48 hrs is right answer.

Two formulas are widely to estimate kidney function from serum creatinine.

1) Cockcroft - Gault and

2) Four variable MDRD ( modification of Diet in Renal Disease)

Cockcroft formula : (140- age)*weight(kg)/72* sr.creatinine

= (140-50)*50/72*3.5 = 25ml/min

hence dose titaration is 125mcg/48hrs