Quiz 1 Drugs Flashcards
Mechanism of Atorvastatin
Competitive inhibitor for active site on HMG CoA reductase (rate limiting step of cholest. synth); [structural analogs of HMG CoA intermediate] -> decr plasma cholesterol by INCREASING gene expression of LDL RECEPTOR
Indications of Atorvastatin
First line use for hypercholesterolemia when at risk for MI
Side Effects of Atorvastatin
Elevated serum levels of hepatic enzymes; hepatitis; and myalgia, rhabdomyolysis, and other myopathies (muscle pain, weakness). Teratogen
Pharmakokinetics of Atorvastatin
Extensive 1st pass eff (liver) -> limits syst bioavail, targets liver (site of action); high plasma prot binding; half-life: 20 hrs
Contraindications of Atorvastatin
Metabolized by CYP3A4; incr risk myopathy w/ erythromycin, gemfibrozil, or naicin; those hypersensit, active liver dis, & pregnant
First line use for hypercholesterolemia when at risk for MI
Atorvastatin, Lorvastatin, Simvastatin
Statins have greater effect on LDL or HDL?
Lorvastatin, Atorvastatin, Simvistatin
Greater effect on LDL; higher the baseline TG level = greater lowering effect
Mech of Lorvastatin
Competitive inhibitor for active site on HMG CoA reductase (rate limiting step of cholest. synth);> decr plasma cholesterol by INCREASING gene expression of LDL RECEPTOR
**prodrugs, administered as lactones (transformed in liver to active form)
Difference in mechanism of Lorvastatin and Atorvastatin
Lorvastatin is a PROdrug and activated in liver
Toxicity of Lorvastatin:
All Statins same: Elevated serum levels of hepatic enzymes; hepatitis; and myalgia, rhabdomyolysis, and other myopathies (muscle pain, weakness). Teratogen
PharmK of Lorvastatin
Extensive 1st pass eff (liver) -> limits syst bioavail, targets liver (site of action); high plasma prot binding; half-life: 1-4 hours
Contraindications of All Statins
Metabolized by CYP3A4; incr risk myopathy w/ erythromycin, gemfibrozil, or naicin; those hypersensit, active liver dis, & pregnant
Simvastatin and Lorvastatin are the same except:
Simvustatin half life = 1-2 hours
Lorvastatin = 1-4 hours
What are the HMG CoA Reductase Inhibitors
Statins?
Atorvastatin
Lovastatin
Simvastatin
Rate limiting step in cholesterol biosynthesis
HMG CoA reductase
How do statins prevent substrate binding?
• statins inhibit HMGR by binding to the active site of
the enzyme, thus stericallypreventing substrate from
binding
How are statins similar and different from HMGR
• statins inhibit HMGR by binding to the active site of
the enzyme, thus sterically preventing substrate from
binding
All differ from HMG-CoA by being more bulky and more hydrophobic
DOMINANT MECHANISM FOR
CONTROLLING LDL PLASMA CONCENTRATIONS
REGULATION OF HEPATIC LDL RECEPTOR PATHWAY IS
characteristic Side effect of statins
characterized by intense myalgia, first in arms/thighs then in entire body
along with fatigue
serum creatine kinase levels increased 10-fold (rare)
MYOPATHY RISK FACTORS are greater when taking statins with
gemfibrozil
associated with increased risk of myopathy in
Chinese population
Simvastatin plus niacin
are statins safe to take when pregnant?
no
first line therapy in patients who are at high risk for MI
due to hypercholesterolemia
Statins
What pts should not use statins even though they have elevated cholesterol
The exception is patients with homozygous familial hypercholesterolemia, who have very attenuated responses to the usual doses of statins because both alleles of the LDL receptor gene code for dysfunctional LDL receptors; the partial response in these patients is due to a reduction in hepatic VLDL synthesis associated with the inhibition of HMG-CoA reductase–mediated cholesterol synthesis
Cholestyramine is what type of medication?
Bile Acid-Binding Resins
What is the only way cholesterol is excreated from body?
amount of bile salts (not reabsorbed) excreted (0.8 g/day) accounts for only mechanism for cholesterol excretion
How does cholestryramine increase bile acid excretion in feces
anion-exchange resins that readily exchange chloride ions
for bile salts in the small intestine and increase bile acid
excretion in the feces
What is the rate limiting step of bile acid conversion? What effect does cholesteryamine have on it
7 alpha hydroxylase; the increased excretion of bile acids lowers feedback inhibition thus increase breakdown of hepatic cholesterol
Increased catabolism of cholesterol from cholesteryamine will increase activity of?
hepatic HMG CoA reductase
How does cholestyramine lower plasma LDL-cholesterol?
Two mechanisms
increasing rate of removal of cholesterol through receptor-mediated catabolism
- liver responds to lowering of its cholesterol content by
forming more LDL receptors (similar to statins)
PharmK of cholestyramine:
- quaternary amine; hygroscopic powder administered as
chloride salt and insoluble in water - not absorbed but can interfere with absorption of other agents
- time delay before effects seen (1-2 weeks)