The major sources of amylase are the pancreas and the salivary glands. The most common cause of elevation of serum amylase is inflammation of the pancreas (pancreatitis). In acute pancreatitis, serum amylase begins to rise within 6-24 hours, remains elevated for a few days and returns to normal in 3-7 days. Other causes of elevated serum amylase are inflammation of salivary glands (mumps), biliary tract disease and bowel obstruction. Elevated serum amylase can also be seen with drugs (e.g., morphine) which constrict the pancreatic duct sphincter preventing excretion of amylase into the intestine.