MEDICINAL CHEMISTRY

moderate reduction in cholesterol level. Its low efficacy and high cost decrease its
popularity as lipid lowering agent.
HO
CH 3
H 3C
CH 3
β−Sitosterol (197)
(c) Acipimox: Acipimox is a synthetic derivative of nicotinic acid and like nicotinic acid;
it acts by inhibiting adipose tissue lipolysis (hydrolysis of lipid esters). It appears to
produce less flushing and GI-intolerance than nicotinic acid. It is about 20 times more
active than nicotinic acid.
(d) Neomycin: It is an amino glycoside antibiotic. It exerts hypolipidemic activity only
in oral administration while if given parenterally, neomycin does not reduce the plasma
level of LDL. The poor absorption upon oral administration of neomycin indicates that
its site of action is in GIT. The adverse effects like, ototoxicity, nephrotoxicity seen
during parenteral administration of neomycin, are not reported to occur with oral use of
the drug.
(e) Metformin: Chemically it is N, N-dimethyl biguanidine. It has no effect on
cholesterol biosynthesis but it affects the lipoprotein composition. It produces about 50%
reduction in the serum triglyceride level. It is also a hypoglycemic agent and lowers
blood glucose level.
(f) Dextrothyroxine: There exist an inversely proportional relationship between plasma
levels of cholesterol and thyroxine (198). It increases the hepatic catabolism of LDL and
thus lowers the plasma concentration of LDL particles.
I
I
HO O
I
D-Thyroxine (198)
I
CH 3
CH 3
NH 2
CH COOH
(g) Other agents having hypolipidemic activity include sucrose polymers,
eicosapentaenoic acid, propranolol and pindolol. Similarly estrogens also interfere in the
fat metabolism resulting into a decrease in plasma LDL concentration and an increase in
plasma HDL concentration. These metabolic effects of estrogens are partly opposed by
progestin.