DIGITALIS


I. Indications

  1. Controlling ventr. rate in AFib with rapid ventr. response
  2. CHF with low LVEF not responsive to diuretics + ACEIs

II. Pharmacology

  1. Dig levels should be checked 6-8h after last dose
  2. Therapeutic levels 0.7- ng/ml

III. Dig toxicity

  1. Very common; dig has low therapeutic ratio
  2. Predisposing factors to high Dig levels:
  1. Reduced renal function (n.b. Elderly pts may have nl serum Cr because of lean body mass but low Cr clearance and thus increased Dig levels)
  2. Lean body mass (e.g. elderly)
  3. Myxedema
  4. Drugs (interfering with bioavail. or elimination):
Quinidine Erythromycin Spironolactone
Amiodarone Tetracycline Triamterene
Propafenone Verapamil Captopril
Propantheline
(only affects slow
release dig)
   
  1. Predisposing factors to Dig tox with nl levels:
  1. Hypokalemia, e.g. with diuretics
  2. Hypercalcemia
  3. Hypomagnesemia
  4. Lung disease (acute & chronic)
  5. Hypoxia
  6. Acidosis
  7. Hypothyroidism
  8. Myocardial ischemia
  9. Myocarditis--danger of cond. block
  10. Drugs which block AV node:
  1. Ca++ blockers, esp. Verapamil
  2. Beta-blockers
  3. Clonidine and Aldomet
  1. Predisposing to low dig absorption:
  1. Metoclopramide (Reglan)--with slow release Dig only; 2? to gastric emptying
  2. Antacids
  3. Kaopectate
  4. Sulfasalazine
  5. Neomycin
  6. Questran
  1. Clinical features
  1. Fatigue
  2. GI sx: nau/vom, diarrh, anorex, abd pain
  3. Change in MS, abnl dreams
  4. Neuro sx: HA, dizziness, vis. probs, weakness
  5. Cardiac effects:
    1. Atrial and junctional premature beats; PAT with block, sinus and AV block, ventricular ectopy, ventricular tachycardia, ventricular fibrillation
  1. Tx:
  1. Stop the drug, stupid, and put on cardiac monitor
  2. Check for hypokalemia & tx if nec. (see under "Fluid and Electrolytes")
  3. Atropine 0.5-2.0mg IV if bradyarrhythmic, temporary pacing if no responds
  4. For Ventr. Arrhythmias, Lidocaine, Phenytoin, or Propanolol IV
  5. For PAT with Block, Phenytoin or Propanolol IV (if not hypokalemic)
  6. To reduce Dig levels, Dig-specific FAb-fragments ("DIGIBIND")--90% response rate
  7. Contraindicated measures: Electric cardioversion (can cause VFib), Quinidine (increases Dig levels)