Zetia blocks absorption of cholesterol in the intestine, while pravachol blocks the formation of cholesterol by your own body. While Zetia is a newer medication, Pravachol has been extensively studied and verified for efficacy and safety. Zetia is most often used in addition to Pravachol because the combination of the two medications is more effective than using pravachol alone. Your doctor may be choosing Pravachol now to use something that is likely to work without adding second agent, especially since your levels are increasing.