7. Hyperlipidaemia Flashcards
where does most of cholesterol in body come from?
Most cholesterol synthesised in body with contribution (~25%) from diet
role of cholesterol?
Essential for membrane integrity, precursor in production of steroid hormones, bile acids and
vitamin D
association of LDL with atheromatous plaques?
LDL susceptible to oxidation at damaged endothelium, ROS contributes to endothelial dysfunction increasing adherence of lipid rich deposits and foam cells formed – precursor to atheromatous plaques
function of HDL?
HDL carrier of cholesterol away from circulation to tissues that require it and the liver for
disposal in bile – so called “good cholesterol”
what does cholesterol increase risk of?
Risk of suffering from a significant cardiovascular event
What drugs are used to treat hyperlipidaemia?
- Statins
- Fibrates (PPAR activators - increase LDL transcription)
- Cholesterol absorption inhibitors
- PCSK9 inhibitors
What are 2 statins?
Atorvastatin, simvastatin
How do statins work?
- Competitive inhibition of HMG-CoA reductase(rate controlling enzyme in HMGCoA to mevalonate pathway) leading to reduced conc of cholesterol within cell
- low conc of cholesterol stimulates upregulation of hepatic LDL receptors - increased clearance of circulating LDL
- low intracellular cholesterol also decreases secretion of VLDL
What are the additional effects of statins?
- 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
Describe activity of the statins and their derivatives.
- Simvastatin is a pro-drug activated by first pass metabolism t1/2 2hrs
- Atrovastatin is active and also has active metabolites after first pass metabolism t1/2 >30hrs
What are the adverse affects of statins?
- GI disruption, nausea and headache
- myalgia - diffuse muscle pain (↑CPK >10 X normal limit) dose related
- Rarely - rhabdomyolysis - OAT differences?
Increased liver enzymes
What are the warnings, contraindications for statins?
- Renal or hepatic impairment,
- pregnancy and breastfeeding
Δ important drug interactions for statins?
- CYP 3A4 inhibitors- increases [plasma] statin
- Remember amlodipine (CCB) also increases [plasma] statin
Give examples of drugs that inhibit CYP 3A4.
amiodarone, diltiazem, macrolides
What must be done before prescribing statins?
Full lipid profile inc. HDL, and non-HDL + TGs before prescribing
What are the nice guidelines for prescribing statins for primary and secondary prevention?
- Primary prevention 20 mg atorvastatin once daily (10 year CVD risk of >10% using QRISK) inc. patient considerations and risk/benefit
- Secondary prevention 80 mg atorvastatin once daily (amended according to adverse reactions/drug interactions, CKD - 20 mg)
What is the target reduction when prescribing statins?
> 40% reduction in non HDL-C at three months
When is it better to take statins?
q. h.s (every night at bedtime)
- due to circadian rhythms, increased LDL synthesis/activity at night
- especially for simvastatin, short half life