medicinal chemistry, SAR, and synthesis

1. Antinicotinics
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2. Classification of Antinicotinics
Antinicotinics
Neuromuscular
Junction
blockers (NMJ)
Ganglionic
blockers
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3. Neuro Muscular Junction blockers (NMJ)
These are the drugs that prevent interaction of
Ach at Nicotinic receptor at Neuro muscular
Junction NMJ.
So there is temporary paralysis of skeletal muscle
Uses
Intubation of trachea and other endoscopic procedures
Induce muscle relaxation
Make orthopedic surgery easy and bone setting
Reduce dose of anesthesia
 Used as adjuvant drug in surgical anesthesia
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4. Types of Neuromuscular Blocking Drugs
Nondepolarizing drugs (competitive)
Depolarizing drugs (non-competitive)
Centrally acting drugs
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5. 1) Nondepolarizing (competitive) blocking
agents
Long acting: d-Tubocurarine,
Pancuronium (steroidal nucleus)
Doxacurium,
Pipecuronium
Intermediate acting: Atracurium,
cis atracurium
Vecuronium,
Rocuronium
Short acting: Mivacurium
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6. 2) Depolarizing agents (Non competitive)
Suxamethonium (Succinylcholine)
Decamethonium
3) Centrally acting
Beclofenac
Chlorzoxazone
Diazepam
cariosoprodol
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7. Non-depolarizing/
Competitive
(curare-like)
Blocking agents
N+ (14 Å) N+
GI resorption
BBB
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8. Curareis plant extract from
Chondrodendron tomentosum,
Strychnos toxifera etc. It is
used by South America tribals
as arrow poison for game
hunting. The animals got pa-
ralysed but not killed by
the arrow. Muscle paralyzing
active principles of curare
are alkaloids tubocurarine,
toxiferine etc. 8

9. N+:
quarter-
nary
N-atom
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10. Competitive (non-depolarizing) block
Most of the competitive blockers have two or
more quaternary N+ atoms which provide the
necessary attraction to the same site at N
receptor
And have long, flexible, bulky molecules and
were termed Pachycurare by Bovet (1951)
The bulk groups of the drug molecule does not
allow conformational changes in the subunits
needed for opening the channel.
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11. Mechanism of Action of Nondepolarizing/ competitive
Neuromuscular Blocking Drugs
Ach released from motor nerve endings is not able to
combine with its N-receptors to generate end-plate
potential (EPP). So contraction of muscle
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12. Intravenous injection of competitive blockers rapidly
produces skeletal muscle weakness, followed by flaccid
paralysis.
Small rapidly moving muscle fibers of eyes , ears toes are
affected first making it impossible to perform delicate
motor task and producing diplopia, slurred speech, and
difficult in swallowing
spreads to hands, feet, arm, leg, neck, face, trunk, finally
diapharm paralysed death due to hypoxia
Recovery occurs in the reverse sequence: diaphragmatic
contractions resume first.
Increased histamine release from mast cells
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13. Depolarizing drugs (non-competitive)
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14. Depolarizing agents also have two
quaternary N+ atoms but their molecule is
long, slender, and flexible. They are termed
Leptocurare by Bovet (1951)
Succinylcholine differ from Ach only in
duration action, that is longer duration of
action and more stable depolarization.
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15. Depolarizing agents (Non competitive)
MOA:
They depolarize muscle end-plates by
opening Na+ channels (just as ACh does) and
initially produce twitching and fascilations.
 These drugs do not dissociate rapidly from
the receptor, induce prolonged partial
depolarization of the region around muscle
end-plate, and inactivation of Na+ channels.
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16. Synthesis of Succinyl Choline
Dimer of Acetylcholine
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17. Ganglion
blocking
agents
- many side effecs
- out of date
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18. Ganglionic blockers
Ganglionic blockers inhibit autonomic activity by
interfering with neurotransmission within autonomic
ganglia.
This reduces sympathetic outflow to the heart
thereby decreasing cardiac output by decreasing
heart rate and contractility.
 Reduced sympathetic output to the vasculature
decreases sympathetic vascular tone, which causes
vasodilation and reduced systemic vascular
resistance, which decreases arterial pressure.
Parasympathetic outflow is also reduced by
ganglionic blockers.
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19. Therapeutic Indications
Ganglionic blockers are not used in the
treatment of in large part because of their side
effects and because there are numerous, more
effective, and safer antihypertensive drugs that
can be used. They are, however, occasionally
used for hypertensive emergencies.
Specific Drugs
Several different ganglionic blockers are available for
clinical use; however, only one (trimethaphan) is
very occasionally used in hypertensive emergencies
or for producing controlled hypotension during
surgery.
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20. Side Effects and Contraindications
Side effects of trimethaphan include prolonged
neuromuscular blockade
potentiation of neuromuscular blocking agents.
It can produce excessive hypotension and
impotence due to its sympatholytic effect,
and constipation, urinary retention, dry
mouth due to it parasympatholytic effect. It
also stimulates histamine release.
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