Digoxin above 2.0 ng/mL, or bradycardia or a new arrhythmia on digoxin — hold the dose and notify the provider now.
Before you read
Test yourself first: 5 questions
Question 1 of 5
A client taking warfarin has an INR of 1.2 while the prescribed therapeutic range is 2.0 to 3.0. How should the nurse interpret this result?
Answer: C. An INR of 1.2 is below the therapeutic range of 2.0 to 3.0, meaning the client is not adequately anticoagulated and remains at risk for clot formation. A subtherapeutic INR does not indicate bleeding risk; that concern arises when the INR is above range. The dose will likely need to be increased, not held.
Question 2 of 5
A client taking warfarin has an INR of 5.2 and reports gum bleeding. What is the nurse's priority concern?
Answer: A. An INR of 5.2 is well above the therapeutic range (2.0 to 3.0) and the gum bleeding signals over-anticoagulation with active bleeding risk; the priority is the risk of hemorrhage and the need to hold the dose and notify the provider. The value is not therapeutic, subtherapeutic, or a sign of clot formation.
Question 3 of 5
A client recovering from surgery refuses opioid pain medication, stating a fear of becoming addicted. What is the nurse's most therapeutic response?
Answer: A. Therapeutic communication addresses the concern with accurate information: when opioids are used appropriately for acute pain under medical supervision, the risk of addiction is low, and untreated pain impairs recovery. Dismissing, shaming, or simply documenting the refusal without education are not therapeutic.
Question 4 of 5
A client taking a theophylline (xanthine bronchodilator) preparation has a serum theophylline level drawn. Which result is within the therapeutic range?
Answer: B. The therapeutic range for serum theophylline is 10 to 20 mcg/mL. A level of 15 mcg/mL is therapeutic. Levels above 20 mcg/mL increase the risk of toxicity, which manifests as nausea, vomiting, tachycardia, seizures, and dysrhythmias. Levels below 10 mcg/mL are subtherapeutic.
Question 5 of 5
A client is to begin warfarin while still receiving a therapeutic heparin infusion. Which statement best explains why both anticoagulants are given together initially?
Answer: A. Warfarin takes several days to achieve a therapeutic effect because circulating clotting factors must be depleted, so heparin provides immediate anticoagulation during this bridging period. The overlap is intentional, not a medication error, and continues until the INR reaches the therapeutic range.
Keep the streak going with more questions like these, each with a full rationale.
What is therapeutic drug levels?
With these narrow-therapeutic-index drugs, a small rise in level can move a client from benefit to harm. A trough is drawn just before the next dose to show the lowest level; a peak is drawn after absorption to show the highest. The nurse times the draw, reads the result before giving the next dose, and watches for each drug's own signs of toxicity.
Key points to remember
- Trough = drawn immediately before the next scheduled dose (lowest level). Peak = drawn after the drug is absorbed (highest level).
- Digoxin 0.5–2.0 ng/mL. Toxicity: nausea, visual changes, and arrhythmias. Check potassium with every digoxin level.
- Lithium 0.6–1.2 mEq/L; above 1.5 mEq/L is toxic. Watch for tremor, vomiting, and confusion.
- Phenytoin (Dilantin) 10–20 mcg/mL. Toxicity shows as nystagmus and ataxia.
- Vancomycin trough 10–20 mcg/mL. Troughs guide dosing and protect against kidney and ear toxicity.
- Theophylline 10–20 mcg/mL.
- The NCLEX-RN test plan expects you to compare a client's lab values with normal values and review lab results before giving a medication, so know these ranges well enough to spot a toxic level on sight.
Nursing priorities
- Time the draw to the dose (trough immediately before the next dose, peak after absorption), because a mistimed sample cannot be interpreted.
- Check the latest level before giving a narrow-index drug, because a dose given on top of a toxic level adds to the toxicity.
- Assess for drug-specific toxicity signs (digoxin: nausea, visual changes, arrhythmia; lithium: tremor, vomiting, confusion; phenytoin: nystagmus, ataxia), because these signs call for action even between scheduled levels.
- Hold the dose and notify the provider when a level is in the toxic range, because the dose must be changed before more drug is given.
- Monitor renal function for kidney-cleared drugs such as digoxin and vancomycin, because declining kidney function lets the level climb.
Labs & values
Worked example
- Cue: Before the morning dose, a client on digoxin reports nausea and visual changes; the morning level is above 2.0 ng/mL.
- Meaning: The level is above the 0.5–2.0 ng/mL range, and the symptoms match digoxin toxicity.
- Action: Hold the dose, check heart rate and rhythm, review potassium and renal function, and notify the provider.
- Evaluation: The dose stays held until a new order; symptoms and the repeat level are documented.
Patient teaching
- Take your medicine exactly as prescribed, and keep every scheduled blood test.
- On the day of a trough test, ask whether to wait and take your dose after the blood draw.
- If you take lithium, keep your fluid and salt intake steady. Call if you have shaking, vomiting, or confusion.
- If you take digoxin, report nausea or changes in your vision.
Memory tricks
- Three drugs share 10–20 mcg/mL: phenytoin, theophylline, and the vancomycin trough.
Common mistakes
- Drawing a 'trough' after the dose. A trough is drawn immediately before the next dose.
- Ignoring units. A digoxin level of 1.5 ng/mL is in range; a lithium level of 1.5 mEq/L is above the 0.6–1.2 range and at the toxic threshold.
- Giving a scheduled dose when the last level was above range.
- Overlooking worsening kidney function in a client on digoxin or vancomycin.
Red flags: report now
- Digoxin above 2.0 ng/mL, or bradycardia or a new arrhythmia on digoxin — hold the dose and notify the provider now.
- Lithium above 1.5 mEq/L, or confusion, tremor, or seizures — hold the dose and notify the provider urgently.
- New nystagmus or an unsteady gait on phenytoin — hold the dose, notify the provider, and expect a level to be drawn.
- Any monitored drug above its range — do not give the next dose until the provider responds.
References
Clinical references for this topic
