What labs can indicate a Crestor (rosuvastatin) overdose?

Laboratory Tests to Identify Crestor (Rosuvastatin) Overdose

Creatine kinase (CK), liver function tests (ALT, AST), and renal function tests (creatinine, GFR) are the most important laboratory tests to identify a Crestor (rosuvastatin) overdose.

Primary Laboratory Tests

Muscle-Related Tests

• Creatine Kinase (CK):
  • Most critical test for statin toxicity
  • Significant elevation (>10 times upper limit of normal) suggests severe myopathy or rhabdomyolysis 1
  • May indicate statin-induced muscle damage, especially when accompanied by muscle symptoms

Liver Function Tests

• Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST):
  • Elevation >3 times upper limit of normal indicates potential hepatotoxicity 1
  • Severe statin-associated hepatotoxicity is rare but should be monitored in suspected overdose

Renal Function Tests

• Serum creatinine and estimated Glomerular Filtration Rate (eGFR):
  • Important to assess because:
    • Rosuvastatin is primarily excreted unchanged via the kidneys 2
    • Rhabdomyolysis can lead to acute kidney injury
    • Higher doses of rosuvastatin have been associated with cases of renal failure 3

Secondary Laboratory Tests

Urinalysis

• Urine myoglobin: Positive in cases of rhabdomyolysis
• Proteinuria: Rosuvastatin can cause tubular proteinuria 3

Additional Tests

• Blood glucose levels: Statins may affect glucose metabolism 1
• Complete Blood Count: To assess for other systemic effects
• Electrolytes: Particularly potassium, as rhabdomyolysis can lead to hyperkalemia

Clinical Correlation

Laboratory findings should be interpreted in the context of clinical symptoms:

1. Muscle symptoms: Myalgia, muscle weakness, or tenderness suggest statin-induced myopathy
2. Gastrointestinal symptoms: Nausea, vomiting, abdominal pain
3. Neurological symptoms: Headache, confusion
4. Renal symptoms: Decreased urine output, dark urine

Monitoring Protocol

For suspected Crestor overdose, implement the following monitoring schedule:

1. Obtain baseline CK, ALT, AST, creatinine, and eGFR immediately
2. Repeat measurements every 24 hours until values normalize
3. If CK >10 times upper limit of normal or if ALT/AST >3 times upper limit of normal, discontinue Crestor and provide supportive care 1

Important Considerations

• Rosuvastatin has minimal metabolism via the cytochrome P450 system, making it less prone to certain drug interactions but still susceptible to transporter-mediated interactions 3
• Patients taking medications that increase rosuvastatin blood levels (cyclosporine, gemfibrozil, certain antiretrovirals) may be at higher risk of toxicity 3
• Elderly patients, those with renal impairment, and patients with hypothyroidism are at increased risk for statin-induced myopathy

Pitfalls to Avoid

1. Don't rely solely on CK levels: Some patients may have significant myopathy with normal or minimally elevated CK
2. Don't ignore mild to moderate elevations: Even moderate elevations may indicate developing toxicity
3. Don't forget to assess renal function: Kidney injury can be both a cause and consequence of statin toxicity
4. Don't miss statin-associated autoimmune myopathy: Characterized by persistent CK elevation, muscle weakness, and presence of HMG CoA reductase antibodies 1

Early identification and management of Crestor overdose can prevent progression to more severe complications such as rhabdomyolysis and acute kidney injury.