I. Indications
- Controlling ventr. rate in AFib with rapid ventr. response
- CHF with low LVEF not responsive to diuretics + ACEIs
II. Pharmacology
- Dig levels should be checked 6-8h after last dose
- Therapeutic levels 0.7- ng/ml
III. Dig toxicity
- Very common; dig has low therapeutic ratio
- Predisposing factors to high Dig levels:
- 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)
- Lean body mass (e.g. elderly)
- Myxedema
- Drugs (interfering with bioavail. or elimination):
| Quinidine | Erythromycin | Spironolactone |
| Amiodarone | Tetracycline | Triamterene |
| Propafenone | Verapamil | Captopril |
| Propantheline (only affects slow release dig) |
- Predisposing factors to Dig tox with nl levels:
- Hypokalemia, e.g. with diuretics
- Hypercalcemia
- Hypomagnesemia
- Lung disease (acute & chronic)
- Hypoxia
- Acidosis
- Hypothyroidism
- Myocardial ischemia
- Myocarditis--danger of cond. block
- Drugs which block AV node:
- Ca++ blockers, esp. Verapamil
- Beta-blockers
- Clonidine and Aldomet
- Predisposing to low dig absorption:
- Metoclopramide (Reglan)--with slow release Dig only; 2? to gastric emptying
- Antacids
- Kaopectate
- Sulfasalazine
- Neomycin
- Questran
- Clinical features
- Fatigue
- GI sx: nau/vom, diarrh, anorex, abd pain
- Change in MS, abnl dreams
- Neuro sx: HA, dizziness, vis. probs, weakness
- Cardiac effects:
- Atrial and junctional premature beats; PAT with block, sinus and AV block, ventricular ectopy, ventricular tachycardia, ventricular fibrillation
- Tx:
- Stop the drug, stupid, and put on cardiac monitor
- Check for hypokalemia & tx if nec. (see under "Fluid and Electrolytes")
- Atropine 0.5-2.0mg IV if bradyarrhythmic, temporary pacing if no responds
- For Ventr. Arrhythmias, Lidocaine, Phenytoin, or Propanolol IV
- For PAT with Block, Phenytoin or Propanolol IV (if not hypokalemic)
- To reduce Dig levels, Dig-specific FAb-fragments ("DIGIBIND")--90% response rate
- Contraindicated measures: Electric cardioversion (can cause VFib), Quinidine (increases Dig levels)