Which of the following would be expected if a patient prescribed lithium was commenced on an ACE inhibitor?
Exam Question Dec 2014
Serotonin syndrome18%Increased clearance and decreased lithium levels20%Lithium clearance unchanged15%Reduced renal clearance and increased lithium levels23%Neurotoxicity23%
Exam Question Dec 2014
Lithium (toxicity)
The desired serum level of lithium is 0.6-1.0 mEq/L.
Lithium clearance is predominantly through the kidneys so things that interfere here such as diuretics, ACE inhibitors, and NSAIDS can have profound effects on serum levels. Also, individuals with chronic renal insufficiency must be closely monitored if placed on lithium therapy.
Risk factors for lithium toxicity include:
- Drugs altering renal function (see below)
- Decreased circulating volume (great heat, sauna)
- Infections (viral infections, gastroenteritis with diarrhoea and vomiting)
- Fever
- Decreased oral intake of water
- Renal insufficiency
- Nephrogenic diabetes insipidus
| Drug class | Examples | Effect on lithium levels |
|---|---|---|
| NSAIDS (and COX-2 inhibitors) | Aspirin, celecoxib | Increase |
| Thiazide diretics | Bendroflumethiazide | Increase |
| Loop diuretics | Furosemide | Generally have no effect on lithium levels |
| ACE inhibitors | Captopril, ramipril | Increase |
Features of lithium toxicity include:-
- GI symptoms (nausea, vomiting, diarrhea, and cramping abdominal pains)
- Neuro symptoms (coarse tremor, confusion, seizures, dystonia, hyperreflexia, nystagmus and ataxia)
The severity of toxicity can be assessed using the AMDISEN rating scale (see below).
| AMDISEN Rating | Description |
|---|---|
| 0 | No clinical signs or symptoms |
| 1 | Mild (nausea, vomiting, tremor, hyperreflexia, agitation, weakness, and ataxia) |
| 2 | Moderate (stupor, rigidity, hypertonia and hypotension) |
| 3 | Severe (myoclonus, cardiovascular collapse, seizure and coma) |
