Digoxin Toxicity
What is a medication's half life? what is the half-life of digoxin? If Mrs. Kidway takes her digoxin at 8 am on a Monday, when will 75% of it be cleared from her body?
A medications "half-life" is the amount of time it takes for half of the medication to be eliminated from the bloodstream. The half-life of digoxin is 1.5-2 days. If Mrs. Kidway took her digoxin at 8:00am on a Monday then the medication would be 75% cleared around 8:00am on Thursday in an elderly woman because of the prolonged half-life, in a regular adult it would be around 2:00pm on Wednesday
Why is Mrs. Kidway taking digoxin?
Digoxin is usually used to treat certain abnormal heart rhythms such as a-fib. When used in combination with a diuretic and ACE inhibitor, it can also be used to treat heart failure. Digoxin slows the heart rate.
The onset, peak, and duration times of oral Digoxin are as follows:
Onset: 30 minutes - 2 hours Peak: 2 - 6 hours Duration: 2-4 days
Two highest priority nursing diagnoses:
1. Decreased Cardiac Output r/t drug toxicity affecting cardiac rate AEB heart rate of 50 BPM. 2. Decreased tissue perfusion r/t decreased cardiac output 2. Ineffective Self-Health Management r/t deficient knowledge regarding action and appropriate administration of digitalis AEB digitalis serum level above therapeutic level (3.8 ng/mL, therapeutic levels are 0.8-2.0 ng/mL).
How does Digoxin work in the body?
By inhibiting Na-K ATPase, digoxin causes increased availability of intracellular calcium in the myocardium and conduction system indirectly causes parasympathetic stimulation of the autonomic nervous system, which has effects on the SA and AV nodes reduces catecholamine reuptake at nerve terminals, making blood vessels more sensitive to catecholamines increases baroreceptor sensitization increases sympathetic outflow from the CNS to cardiac and peripheral sympathetic nerves allows progressive outflow of intracellular potassium, which increases serum potassium levels All of these actions cause an increase in the force and speed of myocardial systolic contraction, a slowing of the heart rate, decreased conduction speed through the AV node, and a decrease in the degree of activation of the SNS and renin-angiotensin system.
What symptoms may be noted when digoxin levels are at toxic levels?
Confusion, irregular pulse, loss of appetite, nausea, vomiting, diarrhea, palpitations, vision changes, decreased consciousness, decreased urine output, difficulty breathing, overall swelling.
Discuss how her digoxin toxicity will be treated.
Digibind/digifab and Atropine: Digoxin toxicity treatment is mainly guided by the signs and symptoms, not the digoxin level alone. Digoxin immune fab (Digibind) is the antidote for digitalis toxicity and is the first line treatment. Supportive treatment would consist of rehydration with IV fluids, oxygenation and possible ventilator support, discontinuation of the drug, and correction of any electrolyte imbalances. GI decontamination would be necessary for an acute overdose. Since Mrs. Kidway has been regularly taking digoxin, her toxicity is most likely chronic due to the long half-life. Correcting any electrolyte imbalances: correcting her hypokalemia (2.1 mEq/L, normal potassium level is 3.5-5 mEq/L) would be necessary since it can cause arrhythmias and impacts the cardiac system. Also, measurement of her creatinine level would be necessary since her kidney's function would need to be assessed. Continuous hemodynamic assessment would be necessary given Mrs. Kidway's age, and preexisting heart failure.
If Mrs. Kidway switches from a pill to an elixir preparation of digoxin, will she still receive 0.125mg?
If Mrs. Kidway's digoxin prescription was changed to the elixir form, she would not receive the full 0.125 mg because there is no way to be sure that she received every last drop of medication that was provided. Bioavailability of elixir is different than the capsule or tablet form. Elixir is 60-80%, capsule is 90-100%
At what serum digoxin range do cardiac dysrhythmias appear and what is the critical value for adults?
Levels greater than 2ng/mL can cause cardiac dysrhythmias to appear. The critical value for adults is greater than 2.5ng/mL.
Does licorice interact with digoxin? If so, explain.
Yes, licorice reduces the amount of potassium in the body. The lack of potassium will increase the amount of circulating Digoxin in the system and increase the serum levels, causing toxicity and increasing the side effects of the medication. This may have contributed to her digoxin toxicity.
What is the normal therapeutic range of serum digoxin?
The normal therapeutic range of serum digoxin for a client is 0.5-2 ng/ml
What do the terms leading dose and steady state indicate?
The term loading dose is defined as a large initial dose of a medication to rapidly achieve the therapeutic concentration in the body. When a fixed dose is administered at regular intervals, a drug will accumulate in the body during the absorption phase until it reaches steady state, during which the rate of drug intake equals the rate of drug elimination.
Given Mrs. Kidway's digoxin level, briefly explain what electrolyte balance is of concern.
The therapeutic range of digoxin is 0.5-2.0 ng/mL while Mrs. Kidway's digoxin level is 3.8 ng/mL- almost double the high end of the safe range. This has an effect on her electrolyte balance, specifically sodium and potassium beause digoxin blocks the sodium/ potassium ATPase pump. This pump normally causes sodium to leave cells and potassium to enter cells. Blocking this mechanism results in higher serum potassium levels because the potassium does not enter cells and is therefore left in the interstitial space. Hyperkalemia can be a potentially life threatening state causing muscle fatigue, weakness, paralysis, arrhythmias, nausea, and vomiting.
