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Digoxin
a cradiac glycoside used to increase cardiac contractility
- uses
- mechanism
- dose and half-life
- adverse drug reactions
- counter-indications and drug interactions
- metabolism and excretion
- dependency
Uses
DIG trial (NEJM, 1997): no benefit for mortality; lower hospitalization rates. However, may be high levels of mortality in women.
Mechanism
- inhibits the cardiac Na-K ATPase
- increase [Na] inside
- the Na/Ca exchanger increase intracellular [Ca], leading to increased contraction
- increased contractility increases cardiac output
Dose and Half Life
Digoxin is one of the few drugs whose levels can be monitored
Adverse Drug Reactions
- can lead to increased ACh release in the AV node, leading to increased refractory period and potentially to AV block and cardiac arrest
- can cause arrhythmias
- can cause hypokalemia
Digoxin Toxicity
- visual changes in 10-25%: changes in colour vision yellow/green, red/blue, hazy vision halos
- neuropsychiatric: 5-10%
- narrow therapeutic index - 2-3 x of a therapeutic dose can be toxic
Counter-Indications and Drug Interactions
Metabolism and Excretion
Dependency
Dig withdrawal: PROVED study, RADIANCE study
- people do worse if more congestive symptoms, worse ventricular function, not on ACEi