Nitric oxide regulates many physiological and pathological modalities in a human body. Manipulation of this characteristic for advancement in Pharmacotherapy of various diseases is the aim of ongoing NO trials.

1. NITRIC OXIDE
AND ITS ROLE IN
THERAPEUTICS
Dr. Prerana Manik Kadam – JR3
Guide : Dr. Smita Anand Tiwari
Dr. Prerana Manik Kadam 1

2. Introduction
Synthesis of Nitric oxide (NO)
OVERVIEW
Role in Physiology and Disease
NO synthesis inhibitors and donors
Therapeutic uses
Other drugs
Conclusion
Dr. Prerana Manik Kadam 2

3. Gaseous signaling
molecule
Nitric oxide
(NO)
INTRODUCTION
Readily diffuses across
cell membranes
Produced endogenously
- enzyme Nitric oxide
synthase (NOS)
Rapid and short
acting
Regulates
- cardiovascular
- inflammatory
- neuronal functions
Dr. Prerana Manik Kadam 3

4. History
KEYS
Ascanio
Sobrero
(1846)
- Synthesized nitroglycerin
- Cerebral vasodilation
- Treat angina
- Unstable and explosive
Studies of
macrophages
Release by products of
NO breakdown
Injection of endotoxin
Elevated urinary
nitrites and nitrates
NO
Dr. Prerana Manik Kadam 4

5. History
KEYS
Ferid Nurad
(1977)
Studied release of NO from
NTG
Louis Ignarro and
Salvador Moncada
(1987)
Recognized NO
as “EDRF”
Robert Furchgott
(1998)
Nobel prize in
medicine – NOS pathway
NO
MOLECULE OF
THE YEAR
Dr. Prerana Manik Kadam 5

6. SYNTHESIS OF NITRIC OXIDE
𝑪𝒂𝟐+
Calmodulin
𝑪𝒂𝟐+/Calmodulin
NOS
L-arginine Citrulline
NO
NO
Activation of 𝑪𝒂𝟐+ channels
Endothelial cell
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7. TYPES OF NOS
Property nNOS iNOS eNOS
Other names NOS-1 NOS-2 NOS-3
Tissues
Neurons
Skeletal muscle
Macrophages
Smooth muscle
cells
Endothelial cells
Neurons
Expression Constitutive Inducible Constitutive
Calcium regulation Yes No Yes
Function
Regulatory
Synaptic plasticity
Independent
Inflammatory and
neurodegenerative
disorders
Regulatory
Vascular
compliance
Skeletal muscle
relaxation
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8. METALLOPROTEINS
NO
SIGNALING
MECHANISMS
THIOLS (-SH GROUP)
TYROSINE NITRATION
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9. 9
NOS
NO
GTP PKG
Protein
Protein
P
cGMP 𝑪𝒂𝟐+
Vascular Smooth Muscle relaxation
Endothelial cell
Phosphorylation
METALLOPROTEINS
Dr. Prerana Manik Kadam

10. (AA cysteine)
THIOLS (-SH Group)
NO
Alter :-
Function
Stability
Localization
of target proteins
Major targets:
H-ras – regulator of cell
proliferation (Stimulation)
THIOL
Nitroso-
thiols
S-nitrosylation
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11. (Immune cells)
NO
Nitation of tyrosine
causes :-
DNA damage
Oxidation of cysteine
Clinical significance :-
Irreversible modification  +/- of protein function
Tyrosine
Superoxide
TYROSINE NITRATION
Peroxynitrite
(ONOO-)
Glutathione
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12. INACTIVATORS
INACTIVATION OF NO
SUPEROXIDE
METALS
OXYGEN
HEME
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13. ROLE OF NO IN PHYSIOLOGY AND DISEASE
• Vascular Effects
• Infection and Inflammation
• Septic shock
• Central nervous system
• Peripheral nervous system
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14. Vasorelaxation
VASCULAR EFFECTS
Antithrombotic effect
Inhibits expression of
adhesion molecules
on endothelial cell
surface
Inhibits oxidation of LDL
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15. INFECTION AND INFLAMMATION
• Peroxynitrite is an important microbicide
• Activates COX-2 – synthesis of inflammatory
prostaglandins
• Increase in iNOS - in leukocytes, fibroblasts
and other cells
• In acute inflammation -
Erythema
Vascular permeability
Oedema
BENEFICIAL
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16. INFECTION AND INFLAMMATION
• Excessive NO - tissue injury
• Elevated levels of NO, iNOS
Psoriasis lesions,
Bronchial asthma,
Inflammatory bowel lesions show
DETRIMENTAL
iNOS inhibitors
Inhibition of NO pathway
Acute and chronic inflammatory diseases
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17. Endotoxins and cytokines
Macrophages, neutrophils, endothelial cells
Induce synthesis of iNOS
Excessive NO generation
Hypotension, Shock, in some cases death
SEPTIC SHOCK
sGC inhibitors NOS inhibitors
No improvement
NOS inhibitors in gram-negative sepsis
Improvement
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18. On demand – neurotransmitter
Activate nNOS - NMDA receptor activation
NO diffuse to presynaptic terminal
Enhance efficiency of NT release
Improves Synaptic plasticity and Synapse strengthening
CENTRAL NERVOUS SYSTEM
NORMAL
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19. CENTRAL NERVOUS SYSTEM
ABNORMAL
Aberrant NMDA activation
Excessive NO synthesis
Excitotoxic neuronal death
Several neurologic diseases
Eg: Stroke, ALS, Parkinson’s disease
Reduce neuronal damage NOS inhibitors
Challenge-
Non selectivity of
inhibitors
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20. PERIPHERAL NERVOUS SYSTEM
Nonadrenergic, noncholinergic (NANC) neurons
Release NO
Relaxation of smooth muscles in corpora cavernosa
Penile erection
Eg: PDE-5 inhibitors  enhance the effect of NO signaling
Treatment of Erectile dysfunction.
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21. Condition Diseases/Disorders
Therapeutic
strategy
Treatment
Hypofunctioning
L-arginine NO
system
Hypertension
Vasospastic diseases
Impotency
Hypoxic Pulmonary
Ventilation
Diabetes
(1)Preserving the
endothelial
Integrity
(2) Boosting the failing
L-arginine/NO pathway
(3) Pretreatment with
antioxidants
Use of precursors of
L-arginine or NO
donors or indirect
potentiators of NO
activity
NO BASED - PROPOSED THERAPY
Reference: [Katzung B. G. (2004). Basic & clinical pharmacology (14th ed.). Lange Medical Books/McGraw Hill)]
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22. Condition Diseases/Disorders
Therapeutic
strategy
Treatment
Hyperfunctioning
L-arginine/NO
system
Neurodegenerative
diseases
Epilepsy
Septic shock
Cerebral malaria
Curb excessive
production of NO
Use of NO antagonists
or
selective NOS inhibitors
or
indirect inhibitors of
NO activity
NO BASED - PROPOSED THERAPY
Reference: [Katzung B. G. (2004). Basic & clinical pharmacology (14th ed.). Lange Medical Books/McGraw Hill)]
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23. PHARMACOLOGICAL MANIPULATION
OF NITRIC OXIDE
NO INHIBITORS
&
NO DONORS
Dr. Prerana Manik Kadam
23

24. INHIBITORS OF NITRIC OXIDE SYNTHESIS
NOS inhibitors:
• N-Monomethyl-L-
Arginine
(L-NMMA)
• N-Nitro-L-Arginine
methyl ester
(L-NAME)
• 7-Nitroindazole
BBS- 2
• Being evaluated
• Efficacy
- Inflammatory
conditions
- Sepsis
- Neurodegenerative
disorders
• Challenge
- Non selectivity
- eNOS inhibition -
vasoconstriction
and ischemic
damage
NOS isoform selective inhibitors are being designed
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25. NO
Organic Nitrates-
Nitroglycerin,
Isosorbide dinitrate
Sodium
Nitroprusside
Inhaled NO
NITRIC OXIDE DONORS
Organic Nitrites-
Amyl Nitrite
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26. I) AMYL NITRITE
- Mixed arteriovenous dilator including coronaries
- Like nitrates - needs conversion to a NO species
Advantages
- Inhalation route - rapid
- Was used for angina pectoris
- Nitrate-like rapid tolerance – not observed with amyl
nitrite
Disadvantages
- Produces throbbing headache
- Abuse liability
CURRENT STATUS
Cyanide poisoning
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27. II) ORGANIC NITRATES
Mechanism of
action
Mixed arteriovenous
dilator – veins and
coronary arteries
Reference: [Tripathi, K. D. (2018). Essentials of medical pharmacology (8th ed.)]
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28. II) ORGANIC NITRATES
Antianginal effects of nitroglycerin 
Decrease in cardiac preload
Decreases in cardiac afterload
Redistribution of coronary blood flow
ANGINA PECTORIS
It is a pain syndrome due to induction of an
adverse oxygen supply/demand situation in a
portion of the myocardium.
Reference: [Tripathi, K. D. (2018). Essentials of medical
pharmacology (8th ed.)]
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29. PHARMACOKINETICS
- Route: sublingual and oral
- Extensive and variable first pass
metabolism
II) ORGANIC NITRATES
Prophylaxis
Acute attack
Reference: [Tripathi, K. D. (2018). Essentials of medical
pharmacology (8th ed.)]
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30. ADVERSE EFFECTS
Throbbing headache
Flushing, weakness,
sweating
Dizziness and fainting
Methemoglobinemia
Rashes Prolong bleeding time
Pulmonary oedema
II) ORGANIC NITRATES
Palpitation
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31. - Frequently repeated
- Intermittent use
II) ORGANIC NITRATES TRUE VASCULAR
TOLERANCE
Reduced capacity of
the vascular smooth
muscle to convert
nitroglycerin
PSEUDO TOLERANCE
activation of
mechanisms unrelated
to the vessel wall
PREVENT NITRATE
TOLERANCE
Provide nitrate free
intervals everyday
• Inhibition of enzymes
Mitochondrial aldehyde dehydrogenase and soluble
guanylyl cyclase
• Depletion of sulfhydryl groups
• Activation of compensatory mechanisms :-
Volume expansion
Neurohumoral activation
Generation of free radicals
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32. DRUG POTENTIATION
Sildenafil
PDE-5 inhibitors
Vasodilators
CAUTION
Dangerous in MI –
Carefully titrated i.v. infusion to avoid
hypotension and tachycardia
II) ORGANIC NITRATES
WHY SHOULD NITRATES BE
WITHDRAWN GRADUALLY?
-Loss of response /decrease angina
threshold
- Sudden withdrawal  spasm of
coronary and peripheral blood vessels
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33.  MECHANISM OF ACTION
- Dilates pulmonary vessels, better ventilated areas, reduces ventilation-perfusion
mismatch and improves gaseous exchange
- Elevated pulmonary artery pressure lowered and cardiopulmonary function
improved
USES :-
- Neonatal and Adult PAH
DOSE :-
- 0.1 to 40 ppm by inhalation - monitor
III) INHALED NITRIC OXIDE
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34. Dilates arterioles and venules
• Indications :
Hypertensive emergencies and severe heart failure
• Route:
IV, rapidly lowers blood pressure, short acting - 1–10 minutes
• Adverse effects –
- Breaks down to generate five cyanide molecules and a single NO
- Accumulation of cyanide; metabolic acidosis, arrhythmias, excessive
hypotension, and death.
IV) SODIUM NITROPRUSSIDE
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35. OTHER DRUGS
• Nitric Oxide releasing analogues of Amodiaquine - Antimalarial
• Nitric Oxide releasing esters of Timolol – IOP lowering activity
• NO- releasing NSAIDs – with paracetamol
• NO-donor as analogues of Tolbutamide - Diabetes mellitus
• NO releasing analogues as anti-platelet agents – under evaluation
Dr. Prerana Manik Kadam 35

36. CONCLUSION
• Nitric oxide is a double edged sword as it is an important regulator in various
physiological and pathological processes.
• Synthesized by 3 isoforms of NOS- nNOS, iNOS and eNOS. NO increases cGMP levels
and brings about vascular smooth muscle relaxation.
• Deleterious effects due to non selectivity of NO limit the use of its donors and
inhibitors.
• Vast potential - use of NO in inflammatory conditions and cancer treatment is being
investigated.
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37. REFERENCES
• Samie R. Jaffrey, nitric oxide, Bertram G. Katzung –basic & clinical pharmacology, p 339- 345.
• Hemal H.Patel et al, general anesthetics and therapeutic gases, Goodman & gillman’s 13th
edition, the pharmacological basis of therapeutics.
• Kumar, S., Singh, R. K., & Bhardwaj, T. R. (2017). Therapeutic role of nitric oxide as emerging
molecule. Biomedecine & Pharmacotherapie [Biomedicine & Pharmacotherapy], 85, 182–201.
• Vong, L. B., & Nagasaki, Y. (2020). Nitric oxide nano-delivery systems for cancer therapeutics:
Advances and challenges. Antioxidants (Basel, Switzerland), 9(9), 791.
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Dr. Prerana Manik Kadam

38. Drugs with additional property of NO production :-
Nitric Oxide releasing analogues of Beta blockers- Nebivolol
Nitric Oxide releasing analogues of Dihydropyridines Nitrendipine – CCB
Nitric Oxide releasing analogues of K+ channel opener- Nicorandil
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41. CORONARY STEAL PHENOMENON/ REVERSE
ROBINHOOD PHENOMENON
H – Hydralazine
I – Isoflurane
D – Dipyridamole
E – Enflurane
ROBINHOOD PHENOMENON
Beta blockers
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