4.1.1 Hyperlipidaemia and Statins Flashcards
Where does cholesterol come from?
Most synthesised in body
25% from diet
What is cholesterol used for?
Membrane integrity
Precursor of steroid hormones (lipophilic)
Bile acids
Vitamin D
Why is LDL more susceptible to oxidation?
Longer half life than other cholesterol
Why is LDL particularly bad?
Susceptible to oxidation at damaged endothelium ROS contributes to endothelial dysfunction, increasing adherence of lipid rich deposits and foam cells formed, leads to atheromatous plaques
Why is HDL good cholesterol?
HDL carrier of cholesterol away from circulation to tissues that need it and to the liver for bile production
Why is raised cholesterol bad?
Associated with increased risk of CHD
How is cholesterol measured?
Measured as
Non-HDL cholesterol
and HDL cholesterol in mmol/L
Why is reducing cholesterol important?
Modiable risk factor for CVD
10% reduction affords 15% reduction in 10 year CHD mortality and 11% reduction in total mortality
How is treatment determined?
Total CVD risk
Adherence
Lifestyle changes
Why are high cholesterol levels not treated in the same way?
Different forms of hypercholesterolaemia, e.g. familial hyperlipidaemia has a different target focus
What other risk factors increase the risk of suffering from a significant CV event?
(Typically measured of happening within the next 10 years)
Raised SBP
Raised HDL-C
Smoking
Diabtes
LVH
When can fatty streak onset begin?
Can have very early onset
What is the mechanism of action of statins?
Competitive inhibition of HMG-CoA reductase
Reduced concentration of cholesterol in the cell, stimulates synthesis of LDL receptors
Increased LDL receptors on the apical membrane, promoting LDL uptake from blood
Low intracellular cholesterol decreases VLDL secretion
What additional benefits do statins have?
- Improved vascular endothelial function - ↑NO, VEGF, ↓endothelin
- Stabilisation of atherosclerotic plaque - ↓SMC proliferation ↑collagen
- Improved haemostasis - ↓plasma fibrinogen, platelet aggregation, ↑fibrinolysis
- Anti-inflammatory - ↓proliferation of inflammatory cells into plaque, plasma CRP, adhesion
molecules and cytokines - Antioxidant - ↓superoxide formation
All contribute to reduction in CVD risk
What are two examples of statins?
Atorvastatin
Simvastatin
How are statins activated?
Simvastain and atorvastatin are both prodrugs, activated by first pass metabolism
Simvastatin- t1/2 2h
Atorvastatin- t1/2 24h
Adverse effects of statins
GI disruption
Nausea and headache
Myalgia-diffuse muscle pain, dose related
Rare- rhabdomyolysis
Increased liver enzymes
Why do statins cause rhabdomyolysis?
Increases creatine kinase x5
When should you not take statins?
Renal or hepatic impairment
Pregnancy
Breastfeeding
Important drug interactions of statins
CYP 3A4 important for statin metabolism
Amiodarone
Diltiazem
Macrolides- increase [statin] plasma
Amlodipine also increases [plasma] statin
What should be considered while taking other drugs with statins?
May be appropriate to withhold statins short-term while taking other agents
Why can grapefruit and citrus fruits inhibit CYP3A4?
Furanocoumarins which inhibit CYP3A4 activity
Are all statins equal?
No, dose dependant reduction in LDL-C
Why was cerivastatin withdrawn?
Caused deaths due to rhabdomyolysis and renal failure
What are the NICE guidelines for offering statins?
Primary prevention- 20mg atorvastatin once daily if 10 year CVD risk is >10% using QRISK
Secondary prevention- 80mg atorvastatin once daily, if major CV event, amended according to adverse reactions in CKD-20mg
What is done before prescribing statins?
Full lipid profile, HDL and non-HDL + trigylcerides
What is the aim of statin treatment?
Broadly >40% reduction in non HDL-C at three months
Why is simivastatin taken at night?
Short half life, so taken at night as circadian rhythm of LDL receptor synthesis/activity increases at night, so statin will be more effective
What is the nocebo effect?
If you are told about potential adverse effects of a drug you are more likely to report experiencing them
What statin nocebo effect had an increased number of reports?
Myalgia, people getting placebo reported myalgia
