The document provides a comprehensive overview of antihistaminic agents, detailing the physiological role of histamine, its receptors (H1 to H4), and the classification of various antihistamines based on their chemical structures and mechanisms of action. Key drugs discussed include diphenhydramine, dimenhydrinate, and clemastine, among others, each with specified uses, such as treating allergies and nausea. Additionally, the document elaborates on the implications of each receptor type in various physiological processes and their relevance in therapeutic contexts.

1. Antihistaminic agents
Dr Gopal Krishna PadhyDr. Gopal Krishna Padhy

2. Introduction
Histamine [4-(2-aminoethyl)imidazole]occurs in mast cell ,
blood basophiles and acid secreting parietal cells.p g p
H2C CH2
NH2
4
N
H
N
2
3
5
Antigens derived from food products, pollens, dust and human
H
1
hair releases histamine and causes serious allergic reaction.
Th h i l i l ti f hi t i i d t th i tiThe physiological action of histamine is due to their action on
histamine receptors (H1, H2, H3 & H4).

3. Definition
Antihistaminic agents:
These are drugs which competitively antagonise the
action of histamine at H1 receptor.
Classification of Histamine H1 receptor antagonist1 p g
Aminoalkyl ether derivatives:
CH O CH2 CH2 N
CH3
CH3
.HCl
12
Diphenhydramine Hydrochloridep y y
IUPAC: N,N-dimethyl-(2-diphenylmethoxy)ethylamine

4. Dimenhydrinate
Complex of N, N-dimethyl (2-diphenylmethoxy) ethylamine
and 8-chlorotheophylline
IUPAC: 2-[2-[1-(4-chlorophenyl)-1-
Clemastine Fumarate
: [ [ ( p y )
phenylethoxy]ethyl]-1-methylpyrrolidine

5. Diphenylpyraline hydrochloride
IUPAC: 4-(benzhydryloxy)-N-methylpiperidine
2 2
3
3 2 2
3
3
Doxylamines Scuccinate
IUPAC: N N-dimethyl-2-(1-phenyl-1-pyridin-2-ylethoxy)IUPAC: N,N-dimethyl-2-(1-phenyl-1-pyridin-2-ylethoxy)
ethanamine

6. Ethylenediamine derivatives
Tripelennamine
IUPAC: N-benzyl-N′,N′-dimethyl-N-2-pyridylethylenediaminey , y py y y

7. Piperazine derivatives:
Cl
2 3 56
2
34
5
2 3
Cl
CH N N CH2
CH3
1
2 3
4
56
1
2 3
4
561
6 .HCl
CH N N CH3
1 2 3 4
56
.HCl
CH3
Chlorcyclizine hydrochloride Meclizine hydrochloride
56
IUPAC: 1-[(4-chlorophenyl)-
phenylmethyl]-4-
IUPAC:1-[(4˝-chlorphenyl)
phenylmethyl]-4-[(3´-methylbenzyl)
h l
p y y
methylpiperazine phenyl]piperazine

8. Buclizine Hydrochloride
IUPAC: 1-[(4-chlorophenyl)-
h l th l] 4 [(4 t tphenylmethyl]-4-[(4-tert-
butylphenyl)methyl]piperazine

9. ClCl
CH N N CH2 CH2 O CH2COOH
Cetirizine
IUPAC: 2-[2-[4-[(4-chlorophenyl)-
phenylmethyl]piperazin-1-yl]ethoxy]acetic acidp y y ]p p y ] y]

10. ClCl
C N N CH2 CH2 O CH2COOHH
Levocetirizine
2-[2-[4-[(R)-(4-chlorophenyl)-
phenylmethyl]piperazin-1-yl]ethoxy]acetic acidphenylmethyl]piperazin-1-yl]ethoxy]acetic acid

11. Propylamine derivatives
Saturated analogs
Chlorpheniramine maleate
C 3 hl h l 3 2´ d l ld h lIUPAC: 3-(p-chlorophenyl)-3-(2´-pyridyl)propyldimethylamine

12. Unsaturated derivatives
Triprolidinep
Ph thi i d i ti
IUPAC: trans-1-(4˝-methylphenyl)-1-(2´-pyridyl)-3-
pyrrolidinoprop-1-ene
Phenothizine derivatives:
3
2
3
33
P th iPromethazine
10-(2´-dimethylaminopropyl)phenothiazine

13. S
1
8
9
N
S
CH3
2
3
4
5
6
7
8
10
CH2 CH CH2
CH3
N
CH3
CH3
4
5 10
1 2 3
Trimeprazine
IUPAC: 10 (3´ dimethylamino 2´IUPAC: 10-(3 -dimethylamino-2 -
methylpropyl) phenothiazine

14. Tricyclic derivatives:
1
28
9
10 11
Cyproheptadine
N 1
2
3
4
5
6
3
4
5
67
yp p
hydrochloride
N
CH3
1
IUPAC: 4-(dibenzo[a,d]cyclohepten-5-ylidene)-
1-methylpiperidine
Azatidine
maleate
IUPAC: 11 (1 Methyl 4 piperidinylidene) 5 6 dihydro 5HIUPAC: 11-(1-Methyl-4-piperidinylidene)-5,6-dihydro-5H-
benzo[1,2]cyclohepta[3,4-b]pyridine

15. Loratadine
IUPAC 1 Pi idi b li id 4 (8IUPAC: 1-Piperidinecarboxylic acid, 4-(8-
chloro-5,6-dihydro-11H-
b [5 6] l h t [1 2 b] idi 11benzo[5,6]cyclohepta[1,2-b]pyridin-11-
ylidene)-, etyl ester

16. Miscellaneous compounds
Astemizole
IUPAC: 1-[(4-fluorophenyl)methyl]-N-[1-[2-(4-
methoxyphenyl) ethyl]-4-piperidinyl]-benzimidazol-2-methoxyphenyl) ethyl]-4-piperidinyl]-benzimidazol-2-
amine

17. Cromolyn sodiumCromolyn sodium
IUPAC: disodium;5-[3-(2-carboxylato-4-
oxochromen 5 yl)oxy 2 hydroxypropoxy] 4oxochromen-5-yl)oxy-2-hydroxypropoxy]-4-
oxochromene-2-carboxylate

18. Hi t i t t i t i i t f th
Histamine receptors
Histamine receptors are proteins present in various parts of the
body that bind with histamine to produce a specific outcome.
There are four known receptors designated H1 H4There are four known receptors, designated H1 - H4.
H1 Receptor
This is one of the most important receptors for modulating yourThis is one of the most important receptors for modulating your
internal clock, and are target for many clinical drugs.
When histamine reacts with these receptors in your brain it makeWhen histamine reacts with these receptors in your brain it make
you more awake and alert.This is why antihistamines cause
drowsiness.
 In other areas of the body, stimulation of these receptors
causes skin rashes, broncho-constriction, motion sickness, and, , ,
smooth muscle relaxation (consequently vasodilation - the widening
of blood vessels leading to redness of the skin).g
Excess activation of these receptors triggers the symptoms of hay
fever and other seasonal allergies.

19. H2 Receptor
Th f d i l ll l d i h h li iThese are found on parietal cells located in the stomach lining.
Histamine action at these receptors stimulates the release of gastric
id f hi h lt i t t itiacid, excess of which can result in gastroenteritis.
These receptors are also found on heart, uterus and vascular
smooth muscle cells Histamine reacting with the receptor at thesesmooth muscle cells. Histamine reacting with the receptor at these
places encourages smooth muscle relaxation.
This also found on neutrophils (one type of white blood cell)This also found on neutrophils (one type of white blood cell).
Histamine inhibits antibody and cytokine production by reacting
with these receptorswith these receptors.
H3 Receptor
These are present throughout the nervous system, though mostThese are present throughout the nervous system, though most
notably in the central nervous system.
They regulate histamine in the body, by inhibiting the furthery g y, y g
synthesis of histamine.

20. H4 Receptor
Discovered in 2001, these receptors regulate the levels of
white blood cell release from bone marrow.
They are located in the thymus, small intestine, spleen, the
colon, bone marrow and basophils.

22. Diphenhydramine

23. o Diphenhydramine predominantly works via the antagonism
Mechanism of action
p y p y g
of H1 (Histamine 1) receptors . It reverses the effects of
histamine on blood capillaries, reducing allergic reactionp , g g
symptoms .
o Moreover, it readily crosses the blood-brain barrier and, y
inversely agonizes the H1 CNS receptors, resulting in
drowsiness, and suppress the medullary cough center.pp y g
o Furthermore, diphenhydramine also acts as an
antimuscarinic . It behave as a competitive antagonist ofp g
muscarinic acetylcholine receptors, resulting in its use as an
antiparkinson medication.
Uses: Indicated for use in treating sneezing, runny nose,
itchy/watery eyes, itching of nose or throat, insomnia,
p
pruritis, urticaria, insect bites/stings, allergic rashes, and
nausea

24. Dimenhydrinate
MOA: Dimenhydrinate is a competitive antagonist at theMOA: Dimenhydrinate is a competitive antagonist at the
histamine H1 receptor, which is widely distributed in the
human brain Dimenhydrinate's anti-emetic effect is probablyhuman brain. Dimenhydrinate s anti-emetic effect is probably
due to H1 antagonism in the vestibular system in the brain.
Uses: Dimenhydrinate is indicated for the prevention and
treatment of nausea, vomiting, or vertigo of motion sickness.

25. Doxylamines Scuccinate
3
2 2
3
3
3
IUPAC N N di th l 2 (1 h l 1 idi 2 l th )IUPAC: N,N-dimethyl-2-(1-phenyl-1-pyridin-2-ylethoxy)
ethanamine
MOA: Dimenhydrinate is a competitive antagonist at theMOA: Dimenhydrinate is a competitive antagonist at the
histamine H1 receptor. It has pronounced sedative properties.
Uses: It is used in allergies and as an antitussive antiemeticUses: It is used in allergies and as an antitussive, antiemetic,
and hypnotic.

26. Clemastine fumarate
MOA: It works via the antagonism of H1 (Histamine 1)
h ff f h bl dreceptors . It reverses the effects of histamine on blood
capillaries and reduces allergic reaction symptoms.
Uses: Used in hay fever, rhinitis, allergic skin conditions, and
I dpruritus. It causes drowsiness.

27. Diphenylpyraline hydrochloride
MOA: It works via the antagonism of H1 (Histamine 1)g 1 ( )
receptors . It reverses the effects of histamine on blood
capillaries and reduces allergic reaction symptoms.p g y p
Uses: allergic rhinitis, hay fever, and allergic skin disorders.g y g

28. Tripelennamine
MOA: Tripelennamine binds to the histamine H1
Th bl k h f d hreceptor. This blocks the action of endogenous histamine,
which subsequently leads to temporary relief of the
b h b hnegative symptoms brought on by histamine.
Uses: Used for the symptomatic relief of hypersensitivity
h d h ldreactions, coughs, and the common cold.

29. Chlorcyclizine hydrochloride
3
MOA: It works via the antagonism of H1 (Histamine 1): g 1 ( )
receptors . It reverses the effects of histamine on blood
capillaries and reduces allergic reaction symptoms.p g y p
Chlorcyclizine also has some local anesthetic,
anticholinergic, and antiserotonergic properties, and can beg , g p p ,
used as an antiemetic.
Uses: used to treat urticaria, rhinitis, pruritus, and other, , p ,
allergy symptoms.

30. Meclizine hydrochloride
MOA: Meclizine is a histamine H1 antagonist with antiemetic
d l h b h land antivertigo properties. It also exhibits anticholinergic,
central nervous system depressant, and local anesthetic effects.
Uses: It is used in the symptomatic treatment of motion
k d l f d h b lsickness and control of vertigo associated with vestibular
system diseases.

31. Buclizine Hydrochloride
MOA B li i i hi t i H t i t ith ti tiMOA: Buclizine is a histamine H1 antagonist with antiemetic
and antivertigo properties. It also exhibits anticholinergic,
t l t d t d l l th ti ff tcentral nervous system depressant, and local anesthetic effects.
U It i d i th t ti t t t f tiUses: It is used in the symptomatic treatment of motion
sickness and control of vertigo associated with vestibular
s stem diseasessystem diseases.

32. Chlorpheniramine maleate
MOA: Chlorpheniramine binds to the histamine H1 receptor.
Th bl k h f d h h hThis blocks the action of endogenous histamine, which
subsequently leads to temporary relief of the negative
b h b hsymptoms brought on by histamine.
Uses: Used for the symptomatic relief of hypersensitivity
h d h ldreactions, coughs, and the common cold.

33. Triprolidine
MOA: Triprolidine binds to the histamine H1 receptor. This: p p .
blocks the action of endogenous histamine, which
subsequently leads to temporary relief of the negativeq y p y g
symptoms brought on by histamine.
Uses: Used for the symptomatic relief of hypersensitivityy p yp y
reactions, coughs, and the common cold.

34. PhenindamineTartarate
3
MOA: Phenindamine blocks the effects histamine in the body. It appear
to compete with histamine for histamine H1- receptor sites on effectorp p
cells.The antihistamines antagonize those pharmacological effects of
histamine which are mediated through activation of H1- receptor sites
and thereby reduce the intensity of allergic reactions and tissue injury
response involving histamine release.
Uses: It is used to treat sneezing runny nose itching watery eyes hivesUses: It is used to treat sneezing, runny nose, itching, watery eyes, hives,
rashes, itching, and other symptoms of allergies and the common cold.

35. Promethazine Hydrochloride

36. MOA:
h f h 1oPromethazine is a an antagonist of histamine H1, post-
synaptic mesolimbic dopamine, alpha adrenergic, muscarinic,
d NMDAand NMDA receptors.
oThe antihistamine action is used to treat allergic reactions.
A f d NMDA bAntagonism of muscarinic and NMDA receptors contribute to
its use as a sleep aid, as well as for anxiety and tension.
A f h H1 d doAntagonism of histamine H1, muscarinic, and dopamine
receptors in the medullary vomiting center make
h i f l i h f d i ipromethazine useful in the treatment of nausea and vomiting.
Uses: to treat rhinitis, allergic conjunctivitis, allergic: , g j , g
reactions to blood or plasma, dermographism, anaphylactic
reactions, sedation, nausea, vomiting, pain, motion sickness,, , , g, p , ,
and allergic skin reactions.

37. Trimeprazine Tartarate
MOA: Trimeprazine binds to the histamine H1 receptor. This
blocks the action of endogenous histamine, whichg ,
subsequently leads to temporary relief of the negative
symptoms brought on by histamine.y p g y
Uses: Used for the symptomatic relief of hypersensitivity
reactions, pruritus (itching) and urticaria (some allergic skin, p ( g) ( g
reactions).

38. Cyproheptadine hydrochloride
NN
CH3
MOA C h di i h f hi i f bi di HAMOA: Cyproheptadine competes with free histamine for binding at HA-
receptor sites.This antagonizes the effects of histamine on HA-receptors,
leading to a reduction of the negative symptoms brought on by histamineleading to a reduction of the negative symptoms brought on by histamine
HA-receptor binding. Cyproheptadine also competes with serotonin at
receptor sites in smooth muscle in the intestines and other locations.
Antagonism of serotonin on the appetite center of the hypothalamus may
account for Cyproheptadine's ability to stimulate appetite.
U All i hi i i hi i i i i d i d dUses:Allergic rhinitis, rhinitis, urticaria and angioedema and
dermatographism.

39. Azatadine maleate
HO OH
.
N
N
O O
N
CH3
MOA: Antihistamines such as azatadine appear to compete withMOA: Antihistamines such as azatadine appear to compete with
histamine for histamine H1- receptor sites on effector cells. The
antihistamines antagonize those pharmacological effects of histamineg p g
which are mediated through activation of H1- receptor sites and
thereby reduce the intensity of allergic reactions and tissue injury
response involving histamine release.
Uses: For the relief of the symptoms of upper respiratory mucosal
congestion in perennial and allergic rhinitis and for the relief of nasalcongestion in perennial and allergic rhinitis, and for the relief of nasal
congestion.

40. Astemizole
MOA:Astemizole competes with histamine for binding at H1-
receptor sites in the GI tract, uterus, large blood vessels, andp , , g ,
bronchial muscle.This reversible binding of astemizole to H1-
receptors suppresses the formation of edema, flare, andp pp , ,
pruritus resulting from histaminic activity.
Uses:Astemizole was indicated for use in the relieving allergyg gy
symptoms, particularly rhinitis and conjunctivitis.

41. Loratadine
MOA: Antihistamines such as Loratadine appear to compete with
histamine for histamine H1- receptor sites on effector cells. The
tihi t i t i th h l i l ff t f hi t iantihistamines antagonize those pharmacological effects of histamine
which are mediated through activation of H1- receptor sites and
thereby reduce the intensity of allergic reactions and tissue injurythereby reduce the intensity of allergic reactions and tissue injury
response involving histamine release.
Uses: For the relief of the symptoms of upper respiratory mucosal
congestion in perennial and allergic rhinitis, and for the relief of nasal
congestion.

42. Cl
Cetirizine
Cl
CH N N CH2 CH2 O CH2COOH
MOA: Cetirizine, a metabolite of hydroxyzine, is an antihistamine drug.
I ff h d h h l h b f h lIts main effects are achieved through selective inhibition of peripheral
H1 receptors. It compete with histamine for histamine H1- receptor
sites on effector cells The antihistamines antagonize thosesites on effector cells. The antihistamines antagonize those
pharmacological effects of histamine which are mediated through
activation of H1- receptor sites and thereby reduce the intensity ofp y y
allergic reactions and tissue injury response involving histamine release.
Uses: For the relief of the symptoms of upper respiratory mucosal
i i i l d ll i hi i i d f h li f f lcongestion in perennial and allergic rhinitis, and for the relief of nasal
congestion, Chronic urticaria.

43. Cl
Levocetirizine
Cl
C N N CH2 CH2 O CH2COOHH
MOA: It compete with histamine for histamine H1- receptor sites onp p
effector cells. The antihistamines antagonize those pharmacological
effects of histamine which are mediated through activation of H1-
d h b d h f ll dreceptor sites and thereby reduce the intensity of allergic reactions and
tissue injury response involving histamine release.
Uses: For the relief of the symptoms of upper respiratory mucosalUses: For the relief of the symptoms of upper respiratory mucosal
congestion in perennial and allergic rhinitis, and for the relief of nasal
congestion, Chronic urticaria.g

44. Cromolyn sodium
O h b d l f ll b lMOA: It inhibits degranulation of mast cells, subsequently
preventing the release of histamine and slow-reacting substance
f h l S S A d f llof anaphylaxis (SRS-A), mediators of type I allergic reactions. It
also may reduce the release of inflammatory leukotrienes. It
b h b l flmay act by inhibiting calcium influx.
Uses: For the management of patients with bronchial asthma.
Al d h f l k lAlso used in the treatment of vernal keratoconjunctivitis, vernal
conjunctivitis, and vernal keratitis.

45. Ranitidine
H2 receptor antagonist
3
3
3
MOA
2
IUPAC: 1-N'-[2-[[5-[(dimethylamino)methyl]furan-2-
yl]methylsulfanyl]ethyl]-1-N-methyl-2-nitroethene-1,1-
diamine
MOA: It antagonise the action of histamine at its H2 receptor.
Ranitidine reduces the secretion of gastric acid by reversible
bi di hi i (H2) hi h f dbinding to histamine (H2) receptors, which are found on
gastric parietal cells. This process leads to the inhibition of
hi t i bi di t thi t i th d ti fhistamine binding to this receptor, causing the reduction of
gastric acid secretion.
Uses: It is used in the treatment of duodenal ulcer gastricUses: It is used in the treatment of duodenal ulcer, gastric
ulcer, gastroesophageal reflux disease (GERD) and acid
indigestion It is also used in multi drug treatment protocolindigestion. It is also used in multi drug treatment protocol
for eradication of H.pyroli in treatment of peptic ulcer.

46. Cimetidine
IUPAC: 1-cyano-2-methyl-3-[2-[(5-methyl-1H-
d l 4 l) h l lf l] h l] d
N
OH
HS CH2 CH2 NH2 N
S CH2 CH2 NH2
S
S
N CN
H3C
H3C
imidazol-4-yl)methylsulfanyl]ethyl]guanidine
N
H
CH3
N
N
H
CH3
SH3C
H2O
SHCH3
N
S CH2 CH2 NH C
N
S CH3
CN
N
S CH2 CH2 NH C
N
H
N CH3
CN
CH3NH2
3
N
H
CH3N
H
CH3
SHCH3

47. MOA: It antagonise the action of histamine at its H receptorMOA: It antagonise the action of histamine at its H2 receptor.
Cimetidine reduces the secretion of gastric acid by reversible
binding to histamine (H2) receptors which are found onbinding to histamine (H2) receptors, which are found on
gastric parietal cells. This process leads to the inhibition of
histamine binding to this receptor, causing the reduction ofhistamine binding to this receptor, causing the reduction of
gastric acid secretion.
Uses: It is used in the treatment of duodenal ulcer, gastric
ulcer, gastroesophageal reflux disease (GERD) and acid, g p g ( )
indigestion. It is also used in multi drug treatment protocol
for eradication of H.pyroli in treatment of peptic ulcer.py p p

48. Famotidine
IUPAC 3 [[2 (di i h lid i ) 1 3 hi l 4
MOA: It t i th ti f hi t i t it H t
IUPAC: 3-[[2-(diaminomethylideneamino)-1,3-thiazol-4-
yl]methylsulfanyl]-N'-sulfamoylpropanimidamide
MOA: It antagonise the action of histamine at its H2 receptor.
Famotidine reduces the secretion of gastric acid by reversible
binding to histamine (H2) receptors which are found onbinding to histamine (H2) receptors, which are found on
gastric parietal cells. This process leads to the inhibition of
histamine binding to this receptor causing the reduction ofhistamine binding to this receptor, causing the reduction of
gastric acid secretion.
Uses: It is used in the treatment of duodenal ulcer gastricUses: It is used in the treatment of duodenal ulcer, gastric
ulcer, gastroesophageal reflux disease (GERD) and acid
indigestion It is also used in multi drug treatment protocolindigestion. It is also used in multi drug treatment protocol
for eradication of H.pyroli in treatment of peptic ulcer.

49. Omeprazole
Proton pump inhibitors
N
H3CO 3
4
5
Omeprazole
N
H
S
N
CH2 CH3
OCHH CO1
2
5
6
7
OCH3H3CO1
IUPAC: 5-methoxy-2-{[(4-methoxy-3,5-dimethylpyridin-2-
Mode of action
y {[( y , y py
yl)methyl]sulfinyl}-1H-benzimidazole
Hydrochloric acid (HCl) secretion into the gastric lumen is a
process regulated mainly by the H(+)/K(+)-ATPase of thep g y y
proton pump. Omeprazole inhibits secretion of acid from the
gastric parietal cells by irreversibly inhibiting the enzyme H+-K+g p y y g y
ATPase.

50. UsesUses
Omeprazole is used in the treatment of duodenal ulcer, gastric
ulcer gastroesophageal reflux disease (GERD) and acidulcer, gastroesophageal reflux disease (GERD) and acid
indigestion. Omeprazole is also used in multi drug treatment
protocol for eradication of H pyroli in treatment of peptic ulcerprotocol for eradication of H.pyroli in treatment of peptic ulcer.

51. 1
Lansoprazole
S
O
H
N
N
N
1
25
6
7
1
2 5
6
F
F
O
N 2
34
5 2
3 4
5
F
F
IUPAC: 2-({[3-Methyl-4-(2,2,2-trifluoroethoxy)-2-
Mode of action
d hl d Cl h l
pyridinyl]methyl}sulfinyl)-1H-benzimidazole
Hydrochloric acid (HCl) secretion into the gastric lumen is a
process regulated mainly by the H(+)/K(+)-ATPase of the
L l h b f d f hproton pump. Lansoprazole inhibits secretion of acid from the
gastric parietal cells by irreversibly inhibiting the enzyme H+-K+
ATPATPase.

52. Uses: Lansoprazole is used to reduce gastric acid secretion
d d f h fand is approved for short term treatment of active gastric
ulcers, active duodenal ulcers and gastroesophageal reflux
d (GERD) d d ddisease (GERD) and acid indigestion.
Rabeprazolep
IUPAC: 2-[[4-(3-methoxypropoxy)-3-
h l idi 2 l] h l lfi l] 1Hmethylpyridin-2-yl]methylsulfinyl]-1H-
benzimidazole

53. Mode of action
Hydrochloric acid (HCl) secretion into the gastric lumen is a
process regulated mainly by the H(+)/K(+)-ATPase of thep g y y
proton pump. Rabeprazole inhibits secretion of acid from the
gastric parietal cells by irreversibly inhibiting the enzyme H+-
U R b l i d t d t i id ti d
g p y y g y
K+ ATPase.
Uses: Rabeprazole is used to reduce gastric acid secretion and
is approved for short term treatment of active gastric ulcers,
ti d d l l d t h l fl diactive duodenal ulcers and gastroesophageal reflux disease
(GERD) and acid indigestion.

54. Pantoprazole
F OO O O
H
N
1
7
S
F
F OO O ON
N
N
2
34
5
6
N3
IUPAC: 6-(difluoromethoxy)-2-[(3 4-dimethoxypyridin-2-
Mode of action
IUPAC: 6 (difluoromethoxy) 2 [(3,4 dimethoxypyridin 2
yl)methylsulfinyl]-1H-benzimidazole
Hydrochloric acid (HCl) secretion into the gastric lumen is a
process regulated mainly by the H(+)/K(+)-ATPase of thep g y y
proton pump. Pantoprazole inhibits secretion of acid from the
gastric parietal cells by irreversibly inhibiting the enzyme H+-K+g p y y g y
ATPase.

55. U P t l i d t d t i id tiUses: Pantoprazole is used to reduce gastric acid secretion
and is approved for short term treatment of active gastric
l ti d d l l d t h l flulcers, active duodenal ulcers and gastroesophageal reflux
disease (GERD) and acid indigestion.