Abnormal drug levels: digoxin and lithium
at the bedside
- is the timing right → digoxin at least 6–8 h after the dose; lithium 12 h after the dose; an early sample reads falsely high
- then the patient → airway, breathing, circulation; full vitals; cardiac monitor; 12-lead ECG
- the number → compare with the lab range and the last level; a level in range does not exclude toxicity if the patient is unwell
- hold the next dose → until the level and the patient are reviewed
escalate now if
- digoxin with ventricular arrhythmia, progressive bradycardia, or 2nd or 3rd degree block not responding to atropine → digoxin Fab, senior, ICU; unstable → pads on, pacing and cardiology per bradycardia, do not wait for Fab
- digoxin toxicity with K⁺ > 5.5 → digoxin Fab; potassium
- lithium with confusion, falling consciousness, seizures or arrhythmia → dialysis criteria, ICU and nephrology
- any toxic level → call KPCC, Kuwait Poison Control Center, 2477 1779 → overdose or poisoning
differentials
digoxin high, or toxic in range
- kidneys → AKI or CKD is the usual cause on the ward
- interacting drugs → amiodarone, verapamil, diltiazem, clarithromycin
- makes it toxic at a lower level → low K⁺, low Mg, high Ca²⁺, hypothyroidism, older age
- units → ng/mL × 1.28 = nmol/L; heart failure aims low, about 0.5–0.8 ng/mL
lithium high
- kidneys and volume → AKI, vomiting, diarrhea, poor intake, fever
- interacting drugs → ACE inhibitor, ARB, thiazide, NSAID, a recent dose increase
- usual range → 0.6–0.8 mmol/L, up to 1.0; older adults lower; chronic toxicity can occur near the range
focused check
- digoxin → nausea, vomiting, confusion, visual change; ECG: bradycardia, AV block, ectopics, bidirectional VT
- lithium → coarse tremor, ataxia, slurred speech, myoclonus, confusion; vomiting and diarrhea; polyuria
- volume → JVP, mucous membranes, urine output, fluid balance
send now
- both → RFT with K⁺, Na⁺, Mg, Ca²⁺; 12-lead ECG; glucose
- digoxin → a level before any Fab; after Fab the usual assay is no longer reliable
- lithium → TSH and calcium if on long-term lithium; serum osmolality and urine osmolality if passing large volumes
treat
digoxin
- high level, well → hold digoxin; correct low K⁺ and Mg; review interacting drugs and renal dosing; recheck level and ECG
- bradycardia with poor perfusion → atropine 1 mg IV, repeat every 3–5 min, maximum 3 mg → bradycardia; not responding → Fab
- digoxin Fab → for ventricular arrhythmia, progressive bradycardia or 2nd or 3rd degree block not responding to atropine, K⁺ > 5.5 with worsening toxicity, or a steady-state level > 6 ng/mL
- chronic toxicity, level unknown → 6 vials IV over at least 30 min; bolus only if arrest is imminent
- level known → vials = level (ng/mL) × weight (kg) / 100, rounded up
- with senior and KPCC; pharmacy for supply
- K⁺ can fall fast after Fab → recheck K⁺ over the next hours
- high K⁺ → Fab treats it; the rest per potassium (calcium given more slowly with digoxin)
lithium
- stop → hold lithium; stop ACE inhibitor, ARB, thiazide, NSAID; tell psychiatry before any restart
- dry → 0.9% saline to restore volume, reassess lungs and urine output; not if overloaded
- large dilute urine → nephrogenic diabetes insipidus, Na⁺ can rise fast → sodium
- charcoal → does not bind lithium
- dialysis → nephrology now if falling consciousness, seizures or life-threatening arrhythmia at any level; level > 4.0 mmol/L with impaired kidneys; consider if > 5.0 mmol/L, significant confusion, or the expected time to reach < 1.0 mmol/L with optimal treatment is > 36 h
- recheck → level, RFT and ECG as KPCC advises, at least until clearly falling; modified-release lithium can peak late; after dialysis, serial lithium levels over 12 h for rebound and the need for another session
- hand over → drug, level and time sampled, doses held, ECG, K⁺ and creatinine, next level due, KPCC advice
evidence
| source | type |
|---|---|
| DigiFab prescribing information (DailyMed 2026) ↗︎ | drug label |
| JAMA 2003 · Serum digoxin concentration in heart failure ↗︎ | trial analysis |
| EXTRIP 2015 · Lithium poisoning ↗︎ | consensus recommendations |
| ISBD/IGSLi 2019 · Optimal lithium level ↗︎ | consensus |
| J Intensive Care Med 2017 · Lithium poisoning ↗︎ | review |
Verify indication, dose, allergies, interactions, renal/hepatic function and local protocols before prescribing.
go deeper the full MOC+ Acute Medicine set covers the on-call essentials.
free the on-call checklist covers the whole shift on one printable page.
studying for the IM exam? the IM Rapid Review covers this in the same format. see the sample chapter.
updated Oct 2026file lab/drug-levels-digoxin-lithium