Antacids and Acidifying agents

Prepared and presented by
Shakeeb AKHTAR Nehal Ahmad
(M.Pharm, Pharmaceutics , HOD of Pharmaceutics)
GASTROINTESTINAL AGENTS
ROYAL COLLEGE OF PHARMACEUTICAL AND RESEARCH
SAYNE KHURD- MALEGAON

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Royal College of Pharmaceutical and Research,
Malegaon
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Introduction
Gastrointestinal tract (GIT):

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Hyperacidity (Hyper chlorhydria)

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ANTACIDS
These are the drugs which usually alkaline substances
and used for neutralizing excess acid in the stomach
of patients suffering from Hyper-chlorhydria
(hyperacidity).

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CLASSIFICATIONOF ANTACIDS
Systemic (absorbable) antacids: e.g. Sodium bicarbonate
Non systemic (Non absorbable) antacids: Further classified as
a.Aluminium containing antacids: e.g. Aluminium hydroxide, Aluminium
phosphate, Basic aluminium carbonate.
b.Calcium containing antacids: e.g. Calcium carbonate, tribasic calcium
phosphate.
c.Magnesium containing antacids: e.g. magnesium carbonate, magnesium
citrate , magnesium hydroxide.
d.Combination antacid preparation: e.g. Aluminium hydroxide gel and
magnesium hydroxide.

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Aluminium compound as antacids
Aluminium hydroxide gel
It is aqueous white viscous suspension of hydrated aluminium oxide having
varying amount of basic aluminium carbonate. Contain not less than 3.5% and not more
than 4.4 % w/w of aluminium oxide.
Preparation : Adding hot solution of potassium alum
slowly with constant stirring
Hot solution of sodium carbonate
CO2
PPt of Aluminium hydroxide
wash with hot H2O to free from sulphate ion
Suspended in DW to required strength

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Properties : White viscous suspension. A clear liquid gets separated when it is kept
standing for some time. Al (OH)3 gel gives astringent AlCl3 when react with gastric HCl.
Nausea, Vomiting and constipation.
Assay : 5 g of substance in flask
3 ml HCl
Warm and cool, transfer to 100 ml flask ,volume make 100 ml 20ml
of solution in conical flask and 40 ml 0f 0.05 disodium EDTA + 80 ml of water and
few drop of methyl red.
IN NaoH to neutralize reaction (red to yellow)
Warmed for ½ h
3 g of heaxmine + 0.5 ml of xylenol solution (Ind.)
Titrated with 0.05 M lead nitrate (violet colour )
1 m of Disodium EDTA equivalence to 0.002549 g of Al2O3

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Uses: very effective slow acting antacid. Not absorbed in
alimentary canal and not produce carbon dioxide. Widely used in
intestinal toxemia and hyperchlorhydria. Dos not cause gastric
alkalosis.
Storage : In well closed container and not allow to freeze.
Dose: It dose is 7.5 t0 15 ml. It causes constipation and given with
magnesium salt which is mild laxative.

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Aluminium phosphate: Consist of hydrated aluminium
orthophosphate. It is having not less than 80.0 % of AlPO4.
Preparation :
Aq. Solution of aluminium chloride + sodium phosphate
soluble salt form
Wash and decant with water or membrane dialysis. Particle size is imp
depending on factor like con of reactant, temperature, pH.
Properties:
White powder having some friable aggregates. Practically insoluble in
water and ethanol soluble in dilute mineral acid almost in soluble in solution
of alkali hydroxides.

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Assay: Disolve 100 ml of HCl (10 ml + 25 ml of 0.5 M disodium EDTA+
ammonia sol to make alkaline )
Boil 5 mints
Aq ammonium solution + 6 ml glacial acetic acid.
2 ml of 0.025 % w/v of dithizone in alcohol and titrated with 0.05 M ZnCl2
red colour is obtained.
Uses: Used as antacid in the dose range of 5-15 ml. It offers advantages
as it do not cause phosphate deficiency.
 Basic Aluminium carbonate : It occurs in the form of gel.
Similar to aluminium hydroxide, It cause phosphate deficiency by
promoting phosphate excretion in the feces as aluminium phosphate.

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 Magnesium carbonate
Magnesium carbonate Heavy : This is a basic carbonate having chemical
composition 3MgCo3. Mg (OH)2.5H2O.Differ from light due to density.
Magnesium carbonate Light : Hydrated basic carbonate which differ from
heavy in bulk density. Chemical composition 3MgCo3. Mg (OH)2.3H2O
Preparation : Obtained from double decomposition from magnesium
sulphate and sodium carbonate. Both are dissolve separately in water and
solution are mixed (1:1) and concentrated. Boiling for 30 mints. Insoluble
magnesium carbonate is filtered on calicon cloth, washed until free from
sulphate and dry in oven.
Properties : White granular powder, odourless and testless. Insoluble in
water and alcohol. When heated it gives magnesium oxide losing carbon
dioxide and water.

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Assay : Complexometric titration
sample dissolve in HCl and volume make 250 ml with water
50 ml of solution + 100 ml water+ 15 ml NaOH.
40 mg of murexide indicator +3 ml of naphthol green.
titrate with 0.05 M disodium EDTA (deep blue colour)
Uses: Used as antacid and laxative. Dose 500mg to 2.0 g four times a
day.
Storage : Store in tightly closed container.

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Milk of Magnesia : is a suspension having less than 7 % w/w and
not more than 8.5 % w/w of magnesium hydroxide in purified water. It
contain one or more suitable preservatives.
Preparation: Light magnesium oxide + NaOH sol.
Smooth cream
diluted with water susp. Is produced thin stream into magnesium sulphate ,
stirring continuously
ppt allowed to settle
Upper liquid remove by decantation and residue filter
Residue is washed with water until become free from sulphate ion .
Properties : It is white uniform susp from which varying proportion of
water may separate out on standing.

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Assay: Sample (5 ml) + 25 ml of 1 N sulphuric acid
Back titrated with 1 N sodium hydroxide using methyl red
Uses : It finds used as antacid and laxative. Popular antacid. It has alkaline
reaction, it is used as alkaline mouth wash.
Dose: 5 t0 10 ml as an antacid and 15 t0 30 ml as laxative.
 Magnesium hydroxide (B.P)
Magnesium trisilicate

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Magnesium Hydroxide Mixture
It is 8% oral suspension of hydrated magnesium oxide.
Ingredients
Magnesium sulphate 47.5g
Sodium Hydroxide 15g
Light Magnesium Hydroxide 52.2g
Chloroform 2.5 ml
Purified Water 1000ml
Method Of Preparation
Dissolve NoH in 150 ml water + Light Magnesium oxide,
It Forms Smooth cream
Pour this suspension in thin stream into a solution of magnesium sulphate with stirring
Allow to precipitate
Wash PPT with purified water until the sulphate are washed
Mixed PPT with purified water, dissolve chloroform and make the volume 1000 ml

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Physical Properties
White uniform suspension which does not separate easily on
standing.
Uses
Used As Antacid
Oral Suspension used to relief in heart burn
Also prescribed in case of stomach ulcer

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Sodium bicarbonate:
Mol.formula NaHCO3 Mol wt 84.01
It contain not less than 99% not more than 100.5% of NaHCO3.
Preparation: On small scale it is prepare by passing CO2 throuh the
solution of sodium hydroxide. The solution is concentrated to get product.
On industry prepared by Solvy process.
NaCl saturated with amonia to remove impurities like Mg, Fe. come contact
with current of carbondioxide and cooled to enhance ppt.
Properties : Occours as white crystaline or amorphous powder having
sline taste. Freely soluble in water bt practicaly insoluble in alcohol.
Assay : sample dissolve in 20 ml of water. Titrated with 0.5 N sulphuric acid
using methyl orange as indicator.
Each ml of o.5 N suphuric acid =0.042 g of NaHCO3

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Uses: In medicine it is used for acid neutralizing properties. If find used as
antacid and combine with systemic acidosis.also used for preparing buffer
solution.
 Combination antacids
Preparations:
 Aluminium hydroxide magnesium carbonate co dried gel: It is a co
precipitate of aluminium hydroxide and megnesium carbonate to contain
critical proportion of water for antacid activity.
 Simeco tablets: contain aluminium hydroxide magnesium carbonate co
dried gel(282mg), magnesium hydroxide (85 mg) and activated
dimethicone(25mg)
 Aluminium hydroxide gel Magnesium trisilicate combination: This is a one
of more common combination . It has laxative, constipative and protective.

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 Calcium carbonate containing antacid mixture: Calcium
carbonate with aluminium hydroxide gel yield product which
have apid onset with prolonged action.
Magaldrate
Alginic acid sodium Bicarbonate containing antacid Mixture

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ACIDIFYING REAGENTS OR ACIDIFIERS
These are the drug which are able to increase the acidity in GIT.
Gastric acidifiers
Urinary acidifiers
Systemic acidifiers
Acids

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Dilute Hydrochloric Acid
Hydrochloric acid ……………………………………….274.0 g
Purified water……………………………………………..726.0 g
Preparation : Hydrochloric acid is added gradually to water and mixed.
Properties : It is colour less liquid. It is strong acidic and has about
1.04- 1.05 specific gravity.
Test for purity : It has been tested for As heavy metals, bromide
Iodide, sulphate and free chlorine.

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Assay : It is strong acid which is assayed by titrating a weighed
sample against 1 N sodium hydroxide using methyl orange as an
indicator.
HCl + NaOH NaCl + H2O
Uses : used as acidifier.
Storage : It is stored in well closed container.
Dose : 0.6 – 8 ml

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Books:
G.R. Chatwal “ Pharmaceutical chemistry inorganic” vol I
Page No. 152.
Dr. H.P. Tipnis and Dr. A.S. Dhake “ Inoganic Pharmaceutical
Chemistry” (Theory) Page No. 112.
Dr. Jyoti Gupta, Mohit Sanduja, “ Pharmaceutical Inorganic
chemistry” P.No. 3.1

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