This phase 1 clinical trial is to evaluate the effects of the environmental change in intestine by antibiotics on the pharmacokinetic characteristics of simvastatin in healthy male volunteers. For change of intestine environment, especially the gut microbiota, investigators will administer PO vancomycin for 7 days, tid.

Inclusion Criteria:

• Age between 19 Y to 50 Y at the screening
• Body weight over 55 kg and BMI should be between 18.0 to 25.0 kg/m2
• Informed consent will be taken before all the procedures from volunteers
• SLCO1B1 genotype is *1/*1 when screening

Exclusion Criteria:

• No significant disease history or ongoing disease
• Allergic to simvastatin and vancomycin, or similar affiliation drug for simvastatin or vancomycin
• MDRD eGFR less than 60 mL/min/1.73m2
• Total cholesterol, LDL, TG is higher than 1.5 times more than upper normal limit at the screening
• HDL less than 35 mg/dL at the screening
• Positive HBV or HIV or HCV
• Who is administering or going to administer CYP3A4 inihibitor drug
• Other clinically significant situation under doctor's opinion

Investigators have no plan to share individual participant data.