This is an enzyme from the muscles of the heart, skeletal muscles and the brain. It is released to blood after damage, after which serum level rises in 6 hours, peaks in 18 hours, returns to normal in 2 to 3 days. It is often measured to confirm the clinical diagnosis of myocardial infarction. The isoenzymes can be fractionated by electrophoresis as CPK1 also known as CPK-BB from the brain; CPK 2 also known as CPK-MB originated from myocardial (heart muscle) damage; and CPK3 also known as CPK-MM from the skeletal muscles. CPK is elevated in: myocardial damage from infarction, defibrillation (cardioversion), and myocarditis skeletal muscle damage including convulsion, intramuscular injection, malignant hyperthermia, and radomyolysis brain trauma, cardiovascular accidents, electroconvulsive therapy, and tumors Normal range of CPK is 30 - 300 IU/ml with an MB fraction less than 4%