Antacids

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'Knowledge is the key that unlocks all the doors’
Episode1

St. Wilfred’s Institute of Pharmacy, Panvel.
DTE CODE: 3485
TOPIC : Antacids
Presented by : Mr.Vijay Ikale(Ass.Professor Pharmacology)

Toh kaise hai aap log ?
Parietal cell

Vagus nerve
G cells Enterochromaffin cells

M3(Gq)
H2(Gs)
CCK Receptor(Gq)

Episode 2

1. Belching
2. Heartburn
3. Nausea
4. Regurgitation
5. Bitter taste
6. Discomfort in upper
abdomen

Antacids
These are basic substances which neutralize
gastric acid and raise pH of gastric contents

1. Sodium carbonate
2. Sodium bicarbonate
3. Citric acid

Antacids
Antacids do not decrease acid production;
they just neutralize the gastric acid
They raise the gastric pH
Disadvantage : If gastric pH goes above
4 it stimulates G - cells to release
gastrin which induces acid production
but this effect is short lasting.
( Not applicable in case of Peptic ulcers)
G - cell will help you to
re-establish normal gastric pH

Systemic Absorbable
Sodium bicarbonate
NaHCO₃
Sodium citrate
Na3C6H5O7

Sodium bicarbonate
NaHCO₃
1. Water soluble
2. Rapid onset of action
3. Short duration of action
4. Raise the pH above 7
Systemic Absorbable
Characteristics :

Sodium bicarbonate infusion to treat acidosis
To prevent retinal damage due to formic acid
Refer Pharmacology of methanol

7
5
6
4
3
2
1
Neutral
Acidic
Acidosis

Do not prescribe systemic antacids
to the patient, if he/she suffering
from Peptic ulcers

Mild acidity
Antacids do not decrease acid production; they just
neutralize the gastric acid
They raise the gastric pH above 7
Disadvantage : If gastric pH goes above 4 it
stimulates G - cells to release gastrin which
induces acid production but this effect is short
lasting.

G -CELL
Acid rebound in stomach
Dost ….Dost
na rahhaaa

Sodium citrate
Na3C6H5O7
Properties are similar to sodium
bicarbonate ; Being a salt it does
not evolve CO2

Sodium bicarbonate
NaHCO₃
1. Large dose may cause
alkalosis
2. Produces CO2 ; Belching
3. It may cause acid rebound
4. Na+ overload ; Increases
risk of CHF and edema
Systemic Absorbable
Demerits :

Episode 3

Nonsystemic Non - absorbable
Stay outside
OK

1. These are insoluble
2. Poorly absorbable
3. Basic compounds
4. Reacts with stomach acid
to form chloride salt.
Characteristics :
Nonsystemic Non - absorbable

Non systemic antacids
Magnesium Hydroxide
Mg(OH)2
Magnesium Trisilicate
Mg2O8Si3
Aluminium Hydroxide
Al(OH)3
Magaldrate Calcium carbonate
CaCO3

Non systemic antacids : Magnesium Compounds
Magnesium Hydroxide
Mg(OH)2
Magnesium Trisilicate
Mg2O8Si3
1. These are insoluble
2. Poorly absorbable
3. Basic compounds
4. Reacts with stomach acid to form chloride salt.(Insoluble complexes)
5. Laxative in action ( Increases Bowel movement)

Magnesium Hydroxide
Mg(OH)2
Aqueous Suspension of
Mg(OH)2
Milk of magnesia
Non systemic antacids : Magnesium salts

Mechanism of action : Neutralization reaction
Reacts with stomach acid
to form chloride salt.

Non systemic antacids : Aluminium Compound
Aluminium Hydroxide Gel
Al(OH)3
Relax……….
Feeling Constipated
● Smooth muscle relaxation
● Delayed gastric emptying

What to do now ????
Magnesium Compounds Aluminium Compounds
I am Laxative in action
I will cause you
Constipation
O bhaiiiiiii……. Maroo
Mujhe Maroo

Combination of Magnesium Compounds and Aluminium Compounds
Magnesium salts are laxative, while
aluminium salts are constipating BUT
combination of both will cancel out each
others effect and bowel movement least
affected.
Hence most of the time antacids given in
combination
Antagonistic effect

Non systemic antacids : Calcium Compound
Calcium carbonate
CaCO3
Speed…..
Potent and Rapidly
acting acid neutralizer
a. CO2 Liberation
b. HCL Secretion
Disadvantages

Proton Pump (H+ - K+ ATPase pump)
activation
Gastric Reflux
Parietal cell
Milk alkali syndrome :
Headache,Weakness,Calcium
deposits
Kidney stones

Drug interactions
1. Raise gastric pH
2. Forms insoluble
complexes
Decreases absorption of many drugs such as :
1. Tetracyclines (Antimicrobial agent)
2. Fluoroquinolones (Antimicrobial agent)
3. Ketoconazole (Antifungal)
4. Diazepam(Sedative Hypnotic)
5. H2 blockers (Antihistamines)
6. Phenytoin(Anticonvulsant)
7. Isoniazid and Ethambutol (Anti-TB)

Uses
Say No to antacids if you
are suffering from Peptic
ulcers
Treatment of acidity
and heartburn.

Open sores (Injuries) occurs when
stomach acid damages the lining of
the digestive tract
1. Burning stomach pain
2. Feeling of fullness
3. Bloating or belching
4. Heartburn
5. Nausea
6. Vomiting
Peptic ulcers

Aggressive factors Defensive Factors
Peptic ulcers
1. Acid
2. Pepsin
3. Bile
4. H.Pylori
1. Gastric Mucus
2. Bicarbonates
3. Prostaglandins
4. Nitric oxide
5. Mucosal blood flow

Aggressive factors Defensive Factors
Healthy Gastrointestinal tract

Imbalance between aggressive and defensive factors
Uthaalee re
deva

Episode 4

Treatment of Peptic ulcers
M3
H2
CCK
Ca++
ATP
Acetylcholine
Histamine
Gastrine
H+
K+
H+ - K+ ATPase Pump (Proton
Pump)
Parietal Cell
Somebody please turn
off this Proton pump
OR Block the
Receptor activation
Prostaglandin receptor

Treatment of Peptic ulcers
Proton Pump Inhibitors
H2-Antihistamines
Prostaglandin analogue Anticholinergics
Ulcer Protectives Anti H. Pylori drugs

Cimetidine
Ranitidine
Famotidine
Roxatidine
Histamine Recptor Blockers ( H2 antagonist )
H2
Blocks acid production at first step
------Tidine

Cimetidine
Histamine Receptor Blockers ( H2 antagonist )
H2
X Ca++
and Phosphorylation
Deactivation of
Pump)
H+
K+
• Absorption : 60-80 %
• Distribution : It can cross Placenta , Poor BBB penetration
• Metabolism : Liver ; Hepatic enzymes Cytochrome P - 450
• Excretion : Urine
• Duration of action : 24 hr
Happy
X

Mild : Headache, Dizziness, Dry mouth, Rashes,
Bowel upset
Long term use : Antiandrogenic Action
Gynaecomastia, Loss of libido, Impotency,
Temporary decrease in sperm count
Side effects : No major side effects

Cimetidine
( Imidazole ring )
Interactions
X
Cytochrome P - 450
Metabolism of many
drugs which will leads to
toxicity
1. Theophylline
2. Phenytoin
3. Carbamazepine
4. Metronidazole
Absorption of ketoconazole
due to reduced gastric acidity
Antacids decreases absorption of all H2 blockers

Ranitidine
( Furan ring )
• 5 times more potent than
Cimetidine
• No antiandrogenic action
• No effect on male sexual function or
gynaecomastia
• Less inhibition of Hepatic enzymes
• Mild side effects
Advantages over Cimetidine

Famotidine
( Thiazole ring )
• 5 to 8 times more potent than ranitidine
gynaecomastia
• Mild side effects
• 70 % ; Excreted through kidney
• Used to treat ZE syndrome
Zollinger-Ellison

Roxatidine
(Piperidine ring)
• Pharmacokinetics and Pharmacodynamics
is similar to that of ranitidine
• 2 times more potent than ranitidine and
long duration of action
gynaecomastia

USES
Treatment of :
1. Duodenal ulcers (Acid reflux )
2. Gastric ulcers (Acid reflux )
3. Stress ulcers
4. Gastritis
5. Zollinger Ellison syndrome (Tumor ; secreting gastrin)
6. GERD ( Gastroesophageal reflux disease)
7. Prophylaxis of aspiration pneumonia
8. Urticaria (A skin rash triggered by a reaction to food, medicine or other irritants.)
Peptic ulcers

Proton Pump inhibitors ( PPIs ) - Prodrugs
H+
K+
X
ATP
Pump)

Omeprazole
Esomeprazole
Lansoprazole
Rabeprazole Pantoprazole
Proton Pump inhibitors ( PPIs )
Blocks acid production at Last step

Omeprazole
(Benzimidazole ring)
Below pH 5
a. Sulphenic acid
b. Sulphenamide
H+
K+
X
Parietal cell
Deactivation of
H+ - K+ ATPase Pump
(Proton Pump)
Happy
Omeprazole

Omeprazole
• All Proton Pump Inhibitors are administered
orally in enteric coated form to protect them
from molecular transformation in the acidic
gastric juice
• Should be taken on empty stomach because its
absorption (BA) affected by food
• Metabolism : Liver
• Excretion : Urine
Inhibition of HCL secretion within 1hr

USES
Treatment of :
1. Duodenal ulcers (Acid reflux )
2. Gastric ulcers (Acid reflux )
3. Bleeding Peptic ulcers
4. Stress ulcers (Burns, Severe trauma)
5. Gastritis
6. Zollinger Ellison syndrome (Tumor ; secreting gastrin)
7. GERD ( Gastroesophageal reflux disease)
8. Prophylaxis of aspiration pneumonia
Peptic ulcers

Adverse Effects
Mild
1. Nausea
2. Headache
3. Abdominal pain
4. Muscle and joint pain
5. Dizziness
6. No harmful effects in Pregnancy
Prolong use of Omeprazole leads to
Gynaecomastia and Erectile dysfunction

Interactions
Omeprazole
Phenytoin (Anti convulsant)
Warfarin (Anti Coagulant)
Diazepam (Sedative Hypnotic)
Inhibit oxiation
Clarithromycin inhibits metabolism of Omeprazole

Esomeprazole
High Oral bioavailability
Lansoprazole
More potent than
Omeprazole
Rabeprazole
Fastest acid
suppressing agent
Pantoprazole
More acid stable
Omeprazole

Prostaglandin Analogue
Defensive factor
PGE2 and PGI2
ATP
K+
Parietal Cell
EP3 (Gi)
H+ X

Prostaglandin Analogue : It is a compound having a structure
similar to that of another compound, but differing from it in respect
to a certain component
Misoprostol (
Exogenous)
Prostaglandin
(Endogenous)

Prostaglandin Analogue
Misoprostol
ATP
K+
Parietal Cell
EP3 (Gi)
H+ X
cAMP
M3
(Gq)
H2
(Gs)
CCK
(Gq)

Anticholinergics : Atropinic drugs, Pirenzepine, Oxyphenonium, Propantheline
Banned in India and USA
Invariably produced intolerable
side effects
1. Dry mouth
2. Blurry vision
3. Constipation
4. Decreased sweating
5. Decreased saliva
6. Sedation
7. Confusion
8. Hallucinations
9. Memory problems
10. Drowsiness
11. Trouble urinating
12. Delirium

Episode 5

Ulcer Protectives : These are the substances which forms protective
coat on the surface of ulcers and prevents damage from acid, pepsin,
bile, H.Pylori bacteria
Hello …..it's Sucralfate Myself CBS

Sucralfate : Basic aluminium salt of sulfated sucrose (Prodrug)
Below pH 4 it polymerizes i.e forms cross links and transformed into gel like matrix which
forms protective coat over ulcer surface and prevents damage from acid, pepsin, bile,
H.Pylori bacteria
Description :
1. It does not neutralize acid
2. Not used now ; Due to effective action of H2 blockers and PPIs
3. Side effects : Constipation, Nausea, Dry mouth
4. Interactions : Affects absorption of Tetracycline, Fluoroquinolone, Phenytoin,
Digoxin and Cimetidine

Alternative Uses of Sucralfate :
1. Burns
2. Bedsores
3. Radiation ulcers

Colloidal bismuth subcitrate
1. Water soluble compound
2. Below pH 5 it gets precipitated
3. Forms protective coat but does not neutralize acid
4. Mechanism of action is not clear
a. May increase PGE2 , Bicarbonate ions secretion
b.May forms coat over ulcer surface
c. May detach or inhibit H.Pylori directly
Side effects : Diarrhoea,
Headache, Dizziness
Patient acceptance is
compromised :
Blackening of tongue

Anti H.Pylori drugs
H.Pylori ?
1. Amoxicillin
2. Clarithromycin
3. Metronidazole
4. Tinidazole
5. Tetracycline

Helicobacter pylori
Gram-negative, Helically-shaped ( Spiral ) Bacterium usually found in the stomach mucosa
The bacteria are believed to cause stomach problems when they penetrate the stomach’s mucous lining and this
makes the stomach cells more vulnerable to the harsh acids. Stomach acid and H. pylori together irritate the
stomach lining and may cause ulcers in your stomach or duodenum
The spiral shape of H. pylori allows them to penetrate your stomach lining, where they’re protected by mucus and
your body’s immune cells are not able to reach them.

Amoxicillin
Don’t angry me…
Inhibition of cell wall synthesis
Bhagoooooo…..

Mechanism of action
Tetracycline
Protein synthesis blocked which
leads to death of microorganism
50S
30S

Mechanism of action
Clarithromycin
Protein synthesis blocked which
leads to death of microorganism
50S
30S

Binds to DNA molecule ;
Disrupt DNA structure and
inhibit protein synthesis.
Mechanism of action
Metronidazole Tinidazole
Cell Death

Antacids

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