Simvastatin is a cholesterol lowering drug whose mechanism of action is the inhi

Question

Simvastatin is a cholesterol lowering drug whose mechanism of action is the inhibition of HMG-CoA reductase. If a patient takes a 20.0 mg dose of simvastatin, what is the concentration of simvastatin in the blood? Assume the patient has 5.0 L of blood. The molecular weight of simvastatin is 435.

___________ ?M

Simvastatin is a competitive inhibitor of HMG-CoA reductase with a Ki of 1.2 10-4 ?M. What fraction of the enzyme will have a bound substrate under the conditions described above? Assume the concentration of HMG-CoA is 15 ?M, and the KM for HMG-CoA reductase is 1.4 ?M.

fes=__________

After a period of time, all but 0.10% of the simvastatin in the blood is metabolized. What fraction of the enzyme will have bound substrate under these conditions?

fes=____________

Please explain

Explanation / Answer

Mass of dose of simvastatin = 20.0 mg

= 0.02 g

Molar mass of simvastatin = 435 g / mol

Moles of simvastatin = 0.02 / 435

= 4.59x10-5 moles

Volume of blood = 5.0 L

Concentration of simvastatin in the blood = 4.59x10-5 moles / 5.0 L

= 9.18x10-6 M

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