Yes, Creatine Kinase (CK) and Creatine Phosphokinase (CPK) Are the Same Enzyme
Creatine kinase (CK) and creatine phosphokinase (CPK) refer to the identical enzyme—CK is simply the modern, preferred nomenclature for what was historically called CPK. 1, 2
Nomenclature and Clinical Use
CK and CPK are interchangeable terms for the enzyme (EC 2.7.3.2) that regulates high-energy phosphate production in contractile tissues, with CK being the currently accepted terminology in modern medical practice. 1
Serum CK activity is measured routinely as a sensitive indicator of injuries to skeletal muscle and myocardium, making it the essential test for suspected rhabdomyolysis regardless of which name is used. 1
Application to Your Clinical Scenario
In your patient with reddish urine after three days of rosuvastatin and fenofibrate, you should immediately order serum creatine kinase (CK) to assess for rhabdomyolysis—the test name doesn't matter since CK and CPK are identical. 3
Critical Actions for This Patient:
Obtain a CK measurement immediately when the patient reports suggestive muscle symptoms (implied by the reddish urine suggesting myoglobinuria) and compare to any baseline CK level prior to beginning therapy. 3
Discontinue both rosuvastatin and fenofibrate immediately if myositis is present or strongly suspected, as the combination of statin plus fenofibrate carries significantly increased risk of rhabdomyolysis. 3, 4
The combination of statin and fenofibrate is associated with marked elevation of rhabdomyolysis risk, with case reports documenting CK levels exceeding 90,000 IU/L and acute renal failure requiring hemodialysis. 4
Additional Essential Testing:
Check serum creatinine and urinalysis for myoglobinuria (brown urine positive for blood without RBCs), as myoglobin-induced renal tubular obstruction represents the most serious systemic complication. 5
Obtain thyroid-stimulating hormone (TSH) level, because hypothyroidism predisposes to myopathy and can exacerbate statin-induced muscle toxicity. 3, 5
Monitor serum potassium closely, as hyperkalemia from muscle breakdown can precipitate life-threatening cardiac arrhythmias. 5
Common Pitfall to Avoid:
Do not wait for symptoms to worsen or CK to peak before discontinuing the medications—rhabdomyolysis from statin-fibrate combinations can progress rapidly to acute kidney injury requiring dialysis, and early cessation with aggressive fluid resuscitation is critical for preventing renal failure. 4