1. Lipid Lowering Drugs
Dr. Hiwa K. Saaed, Ph.D.

2. Drugs used to lower lipid levels
 HMG-CoA reductase inhibitors (HMGs or statins)
 Fibric acid derivatives
 Niacin (nicotinic acid)
 Bile acid sequestrants
 Cholesterol absorption inhibitors

4. Atherosclerosis and lipoprotein metabolism
Major plasma lipids
Cholesterol ‘Chol’ (free & esterified), Phospholipids (pl), Triacylglycerols (TG), and
Free fatty acids (FFA)
LIPIDS, (Chol) and (TG), are transported in the plasma as
lipoproteins, of which there are four classes:
- chylomicrons
 transport TG and Chol from the GIT to the tissues,
 Where they are split by lipase, releasing FFAs
 FFAs are taken up in muscle and adipose tissue.
 Chylomicron remnants are taken up in the liver

5. - very low density lipoproteins (VLDL), which
transport Chol and newly synthetised TG to the
tissues, where TGs are removed as before,
leaving LDL:
- low density lipoproteins (LDL) with a large
component of Chol, some of which is taken up
by the tissues and some by the liver, by
endocytosis via specific LDL receptors
- high density lipoproteins (HDL), which absorb
Chol derived from cell breakdown in tissues and
transfer it to VLDL and LDL
Atherosclerosis and lipoprotein metabolism

6. Atherosclerosis and lipoprotein metabolism
There are two different pathways for exogenous and
endogenous lipids:
THE EXOGENOUS PATHWAY:
Chol + TG absorbed from the GIT are transported in the
lymph and than in the plasma as CHYLOMICRONS to
capillaries in muscle and adipose tissues. Here the core TG
are hydrolysed by lipoprotein lipase, and the tissues take
up the resulting FREE FATTY ACIDS (FFA)
 Chol is liberated within the liver cells and may be stored,
oxidised to bile aids or secreted in the bile unaltered
 Alternatively it may enter the endogenous pathway of lipid
transport in VLDL

7. Atherosclerosis and lipoprotein metabolism
cholesterol
may be
stored
oxidised
to
bile acids
secreted
in
the bile
unaltered
ENDOGENOUS
PATHWAY
EXOGENOUS
PATHWAY

8. Atherosclerosis and lipoprotein metabolism
THE ENDOGENOUS PATHWAY
Chol and newly synthetised TG are transported
from the liver as VLDL to muscle and adipose
tissue, there TG are hydrolysed and the
resulting FATTY ACIDS enter the tissues
The lipoprotein particles become smaller and
ultimetaly become LDL ,which provides the
source of Chol for incorporation into cell
membranes, for synthesis of steroids, and bile
acids

9.  Cells take up LDL by endocytosis via LDL
receptors that recognise LDL apolipoproteins
 Chol can return to plasma from the tissues in
HDL particles and the resulting cholesteryl
esters are subsequently transferred to VLDL or
LDL
 One species of LDL – lipoprotein - is associated
with atherosclerosis (localised in atherosclerotic
lesions). LDL can also activate platelets,
constituting a further thrombogenic effect
Atherosclerosis and lipoprotein metabolism

10. LIPID + PROTEIN (LIPOPROTEIN)
 Lipids are insoluble in plasma, combine with specific
proteins (apolipoproteins):
Soluble lipoproteins are classified:
1. Chylomicrons (CM): v rich in TG, v low APOL
2. Very low density lipoproteins (VLDL): same as CM
3. Low density lipoproteins (LDL): v rich in cholesterol-
atherosclerosis-CHD-CVA
4. High density lipoproteins (HDL): good cholesterol
5. Intermediate density lipoproteins (IDL)

11. Types of Lipoproteins
Lipid Protein
Content Lipoprotein Classification Content
Most chylomicron Least
 very-low density lipoprotein
(VLDL) 
 Intermediate-density lipoprotein
(IDL) 
Least High-density lipoprotein (HDL) Most

13. Clinical squelae of the hyperlipoproteinemia
The 2 major clinical squelae of the hyperlipoproteinemia are:
 Acute pancreatitis: occurs in pts w marked hyperlipidemia
 Atherosclerosis: certain plasma lipoptns play an essential
role in atherogenesis “LDL, IDL, HDL” those that contain
lipoptn (apo) B100
The characteristic cellular components in atherosclerotic
plaques are foam cells which are transformed
macrophages & smooth muscle cells that has become filled
with cholesterol esters “endocytosis”.

14. Coronary Heart Disease (CHD)
 CHD is the cause of about half of all deaths in
the United States.
 The incidence of CHD is correlated with:
1. elevated levels of LDL cholesterol and TGs
2. low levels of HDL cholesterol.
The risk of CHD in patients with cholesterol levels of 300
mg/dL is 3 to 4 times greater than that in patients with
levels less than 300 mg/dL
Other risk factors: smoking, HTN, obesity and DM

19. HMG-CoA REDUCTASE INHIBITORS ("statins")
 block cholesterol synthesis at the rate-limiting
step; Inhibit HMG-CoA reductase, which is used
by the liver to produce cholesterol
 increase uptake of LDL from circulation by
inducing LDL receptor expression
 most effective drugs at reducing circulating LDL
 most significant side effects are myopathies,
changes in liver enzymes and drug-drug
interactions

20. Hepatic Cholesterol Synthesis
Rate Limiting
Only pathway
for cholesterol
degradation
Energetically expensive; prefer to
conserve what is already
made/acquired – LDL receptor
pathway

21. Inhibition of HMG CoA reductase by the statin drugs.

22. Summary of 3-hydroxy-3-methylglutaryl
coenzyme (HMG CoA) reductase inhibitors.

23. Adverse effects of statins
 Mild, transient GI disturbances
 Rash
 Headache
 Myopathy (muscle pain)
 Elevations in liver enzymes

24. LIPID-LOWERING DRUGS-
StatinsPromising pharmacodynamic actions:
improved endothelial function
reduced vascular inflammation and platelet aggregability
antithrombotic action
stabilisation of atherosclerotic plaques
increased neovascularisation of ischaemic tissue
enhanced fibrinolysis
immune suppression
osteoclast apoptosis and increased synthetic activity in
osteoblasts

25. Activation of lipoprotein lipase by fibrates:
Clofibrate, gemfibrozil, (Lopid), fenofibrate
• Ligand for peroxisome proliferator activated
receptors (PPARs) increase expression of Lipase
 activating lipase, hence increasing hydrolysis of
TG in chylomicrons and VLDL particles.
 reduce hepatic VLDL production
 increase hepatic LDL uptake.
 Also suppress release of FFA from the adipose
tissue,
 inhibit synthesis of TGs in the liver,
 and increase the secretion of cholesterol in the
bile
Produce a modest decrease in LDL (~ 10%) and
increase in HDL (~ 10%).But, a marked decrease
in TGs (~ 30%).

26. Fibrates-Side Effects
 Abdominal discomfort
 Diarrhea
 Nausea
 Blurred vision
 Increased risk of gallstones, because?
 Prolonged prothrombin time
 Liver studies may show increased function

27. CHOLESTEROL ABSORPTION
INHIBITOR (EZETIMIBE)
 selectively inhibits the cholesterol transporter in
the intestine - reduces absorption by ~50%
 induces LDL receptor expression a synergistic
with statins
 potentiates side effects of statins (including
myopathies)

28. Bile acid binding resins (Anion-exchange resins)
cholestyramine, colestipol, colesevelam
sequester bile acids in the GIT
prevent their reabsorption and enterohepatic recirculation
The result is: decreased absorption of exogenous CHO
and increased metabolism of endogenous CHO into bile acid acids
increased expression of LDL receptors on liver cells
increased removal of LDL from the blood
reduced concentration of LDL CHO in plasm
(while an unwanted increase in TG)

30.  Bile acids are necessary for absorption
of cholesterol
 decreases absorption of fat-soluble vitamins and
other drugs
Therapeutic Uses
 Type II hyperlipoproteinemia
 Relief of pruritus associated with partial biliary
obstruction (cholestyramine)
Side Effects:
Constipation, Heartburn, nausea, belching, bloating

31. NIACIN (NICOTINIC ACID)/VIT B3
 Vitamin B3
 Lipid-lowering properties require much higher
doses than when used as a vitamin
 vitamin dose ~15-35 mg/day;
 antihyperlipidemic activity 1-2 g, 3x day
 Effective, inexpensive, often used in
combination with other lipid-lowering agents

32. Niacin- mechanism of action:
 stimulation of a nicotinic acid receptor
(discovered in 2003) that is found on
adipocytes decreases the release of FFAs
from adipocytes
 a decreased synthesis of TG and VLDL in
the liver à decrease in circulating VLDL
and LDL levels
 nicotinic acid is the most potent drug for
increasing HDL levels

33. Niacin inhibits lipolysis
in adipose tissue,
resulting in decreased
hepatic VLDL synthesis
and production of LDLs
in the plasma.

34. adverse effects of Niacin
 Flushing (due to histamine release)
 Pruritus
an intense cutaneous flush and pruritus, which
decreases after several days but is severe
enough to decrease compliance
 GI distress

35. Niacin
 To minimize side effects of niacin, start on
low initial dose and gradually increase it,
and take with meals.
 Small doses of aspirin or NSAIDs may be
taken 30 minutes before niacin to minimize
cutaneous flushing.

37. Thank you