Updated: 10/1/2019

Digoxin

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Snapshot
  • A 50-year-old man with a past medical history of renal failure and dilated cardiomyopathy presents to the emergency room for nausea, vomiting, and blurry vision. He noticed that previously white objects now look yellow. He was recently started on digoxin. An echocardiogram reveals an atrioventricular block. He is found to be hyperkalemic. He is given an antidote for suspected digoxin toxicity. 
Introduction
  • Drug
    • a cardiac glycoside derived from the foxglove plant, digitalis purpurea
  • Mechanism of action
    • direct reversible inhibition of Na+/K+-ATPase
      • causing ↑ in intracellular Na+ and ↓ in intracellular K+
    • indirectly inhibits Na+/Ca2+-exchanger
      • the increased intracellular Na+ prevents expulsion of Ca2+ from the cell and increases intracellular Ca2+
    • this results in
      • ↑ free Ca2+ ions 
      • ↑ inotropy and contractility 
      • ↑ vagal tone 
        • ↓ conduction through sinoatrial and atrioventricular nodes
        • ↓ heart rate
  • Clinical use
    • heart failure
    • left ventricular dysfunction
    • atrial fibrillation
Toxicity
  • Toxicity can be fatal
  • Clinical manifestations
    • gastrointestinal symptoms (most common)
      • nausea
      • vomiting
      • abdominal pain
      • diarrhea
    • vision changes 
      • yellow halos around objects
      • blurry vision
    • hyperkalemia
    • arrhythmias
  • Risk factors for severe toxicity
    • renal failure 
    • hypokalemia 
      • K+ competes with digoxin for binding sites and excretion
      • low K+ allows digoxin to bind at K+ binding sites on Na+/K+ ATPase 
  • Evaluation
    • serum digoxin concentration
    • serum potassium
    • serial electrocardiograms
  • Treatment
    • digoxin antibodies (anti-digoxin Fab fragments) 
    • Mg2+
    • activated charcoal
      • for those who present within 1-2 hours of ingestion
 

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Questions (2)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(M2.CV.27) A 67-year old male with congestive heart failure with systolic dysfunction presents to the emergency department with several days of nausea, vomiting, and decreased appetite. He denies fever, chest pain, abdominal pain, or sick contacts. He reports shortness of breath at baseline. His heart rate is 84 beats/min and his blood pressure is 118/87. Physical exam is remarkable for +1 pitting edema in his bilateral lower extremities. His current medications include furosemide, lisinopril, carvedilol, and digoxin. At a recent cardiologist visit, his furosemide dose was increased due to worsening lower extremity edema. His EKG is shown below (Figure A). His lab values are below.

Serum:
Na+: 135 mEq/L
K+: 3.7 mEq/L
Cl-: 94 mEq/L
HCO3-: 25 mEq/L

Management of this patient will likely entail which of the following?
Review Topic

QID: 106100
FIGURES:
1

Atropine administration

3%

(1/29)

2

Potassium and magnesium repletion

59%

(17/29)

3

Hemodialysis

10%

(3/29)

4

Cardiac catheterization

3%

(1/29)

5

Cardiac pacemaker implantation

21%

(6/29)

M2

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