DEFINITION OF DRUG
A drug may be defined as an agent, intended for use
in the diagnosis, mitigation, treatment, cure or prevention of disease in man
or in animals.
DOSAGE FORM
Drugs are rarely administered in their original pure
state. They are converted into suitable formulation which are called dosage forms. Every dosage form is a
combination of the drug and other non-drug components.
The non-dug components are known as “additives”. The additives are used to
give a particular shape to the formulation, to increase its stability and also
to increase its palatability as well as to give more elegance to the
preparation.
Ques. Why the drug should be converted into dosage forms ?
Ans. Transformation of drug into
different dosage forms is done for the following reasons:
1.
To protect the drug from oxidation (e.g. Vitamin C, Ferrous sulfate),
hydrolysis (aspirin) and reduction. e.g. coated tablets, sealed ampoules.
2.
To protect the drug from destructive effect of gastric juice (HCl) of
the stomach after oral administration e.g. enteric coated tablets.
3.
To provide a safe and convenient delivery of accurate dosage.
4.
to conceal the bitter (e.g. chloramphenicol), salty or obnoxious taste
or odour of a drug substance e.g. capsules, coated tablets and flavoured syrups
etc.
5.
To provide for the optimum drug action through inhalation therapy. e.g.
inhalation aerosols and inhalants.
6.
To provide for the drug into one of the body-cavities e.g. rectal
suppositories.
7.
To provide for the maximum drug action from topical administration
sites. e.g. creams, ointments, ophthalmic preparations and E.N>T. (ear, nose
and throat) preparation.
8.
To provide sustained release action through controlled release
mechanism. e.g sustained release tablets, capsules and suspensions.
9.
To provide liquid dosage form of the drugs soluble in a suitable
vehicle e.g. solutions.
CLASSIFICATION OF DOSAGE FORMS
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DOSAGE FORM
Route of
administration
|
Dosage forms
|
Oral
|
Powders, tablets, capsules, solutions, emulsions,
syrups, elixirs, magmas, gels, cachets, pills.
|
Parenteral
|
Solutions, suspensions, emulsions.
|
Transdermal
|
Ointments, creams, powders, pastes, lotions,
plaster
|
Rectal
|
Suppositories, tablets, ointments, creams,
douches, foams.
|
Urethral
|
suppositories
|
Sublingual
|
Lozenges, tablets
|
Intranasal
|
Solutions, sprays, inhalations.
|
Conjunctival
|
Ointments
|
Intra-ocular
|
Solutions
|
Intra-respiratory
|
Aerosols
|
Classification according to
physical state:
DOSAGE FORM
SOLID
|
SEMISOLID
|
LIQUID
|
GAS
|
MISCELLANEOUS
|
Cachets
Capsules
Powders
Insufflations
Dentrifices
Effervescent granules
Lozenges
Pessaries
Tablets
Suppositories
|
Creams
Jellies
Ointments
Pastes
Ophthalmic ointments
|
Applications
Aromatic water
Collodion
Draught
Ear drops
eye drops
Nasal drops
Elixirs
Mixtures
Emulsions
Suspensions
Enemas
Gargles
Gels
injections
Irrigations
Linctuses
Liniments
Lotions
Mouthwashes
Spirits
Sprays
Syrups
Tinctures
Paints
|
Aerosols
inhalation
|
Transdermal drug delivery systems
Sustained release drug delivery system
Ophthalmic drug delivery systems.
Implants
|
CACHETS
Cachets consists of a dry powder enclosed in a
shell. The shell is prepared from a mixture of rice flour and water by moulding
into suitable shape and then dried.
Two types of cachets are there:
(i) Wet seal
cachets:
lower half of the cachet is filled with powdered
drug. Then the flange of the empty upper half of the cachet is moistened with water,
and pressed over the lower half. The cachet is dried for 15 minutes.
(ii)Dry seal
cachets:
Drug powder is filled in the lower half and the
upper half is pressed over it just like a capsule.
Use:
They are used for administering the drug with
unpleasant taste and a large dose. Before administration, a cachet should be
immersed in water for few seconds and
then placed on the tongue and swallowed with water.
e.g. Sodium
aminosalicylate cachets
Sodium
aminosalicylate and isoniazid cachtets.
CAPSULES
Capsule
are the solid unit dosage form of medicament in which the drug or drugs are
enclosed in a practically tasteless, hard or soft soluble container of shell
made up of gelatin.
Hard
gelatin capsules are made up of two cylindrical halves, one slightly larger in diameter
but shorter in length known as cap and the other slightly shorter in
diameter but longer in length known as base.
Soft
gelatin capsules are flexible in nature. They may be spherical, ovoid
cylindrical or tubes. The small spherical capsules are also known as ‘pearls’.
soft gelatin capsules are used to enclose solids, semisolids or liquids.
for
oral administration the capsule is placed on the tongue and swallowed with a
drink of water.
Examples
of hard gelatin capsules: Ampicillin capsules, multivitamin capsules.
Examples
of soft gelatin capsules: chloramphenicol soft gelatin capsules.
DUSTING POWDER
These
are meant for external application on to the skin and are generally applied in
a very fine state of subdivision to avoid local irritation.
Dusting
powders are of two types:
(i)
Medical
(ii)
Surgical
Medical
dusting powders are mainly used for superficial skin conditions and for antiseptics,
anti-pruritic, astringent, anti-perspirant, absorbent, protective and lubricant
purposes.
e.g. dicophane dusting powder
zinc and salicylic acid dusting
powder
zinc, starch and talc dusting
powder.
Surgical
dusting powders
are used in body cavities, and also on major wounds as a result of burns and
umbilical cords of infants. Surgical dusting powders must be sterilised before
their use.
Dusting
powders are generally prepared by mixing two or more ingredients on of which
must be either starch, kaolin or talc as one of the ingredients of the
formulations. Talc and kaolin are commonly used because they are chemically
inert. however, since these materials are usually contaminated with pathogenic
bacteria, these must be sterilised.
e.g.
Neosporin powder.
INSUFFLATIONS
These
are finely divided powders meant for introduction into the body cavities such
as ears, nose, tooth sockets and vagina with the help of an apparatus known as
‘insufflator’, without which it will be difficult to apply the powders
directly.
Insufflator
sprays the powder into stream of finely divided particles all over the site of
application. The following difficulties are generally faced while using the
insufflators:
(i)
It is difficult to obtain a measured quantity of the drug as a uniform dose.
(ii)
It gets blocked when it is slightly wet or the powder used is wet.
Use: The insufflations are used
to produce a local effect, as in the treatment of ear, nose and throat
infection with antibiotics or to produce a systemic effect from a drug that is
destroyed in the gastrointestinal tract.
DENTRIFICES (Tooth Powders)
Dentrifices
are preparations which are generally used with the help of tooth brush for
cleansing the surfaces of the teeth. They are available in the form of fine
powders and pastes.
They
contain
1. a suitable detergent or soap
2. some abrasive substance like
calcium sulfate, magnesium carbonate, sodium carbonate in fine powder.
3. sweetening agent e.g.
saccharin sodium
4. a suitable flavour e.g.
peppermint oil, clove oil.
EFFERVESCENT GRANULES
The
effervescent granules are specially prepared solid dosage form of medicament,
meant for oral intake. they contain a medicament mixed with citric acid,
tartaric acid and sodium bicarbonate. Sometimes saccharin or sucrose may be
added as a sweetening agent.
Ingredients used;
(i)
Sodium bicarbonate: It reacts with the acids when the preparation is
added to water. The evolved carbondioxide produces effervescence.
(ii)
Citric acid and tartaric acid: The quantity of these is slightly more
than is necessary to neutralise the sodium bicarbonate because effervescent
preparations are more palatable if slightly acidic.
Tartaric
acid is anhydrous but citric acid has one molecule of water of crystallization.
heating liberates this water and the moist condition thus produced allows
partial interaction between the acids and bicarbonates, during which more water
is formed -
The
water of crystallization of the citric acid and the water from the reactions
makes the material coherent.
(iii)
Medicaments: often inorganic salts containing water of crystallisation
are incorporated. e.g. magnesium and sodium sulphates, sodium phosphate and
lithium citrate.
Methods of preparation
There
are two methods of preparation : 1. Hot method and 2. Wet method
Hot
method: A
large evaporating dish is heated on water bath. All the powders are taken in
that hot dish to ensure rapid evaporation of water liberated from citric acid.
Thus a coherent damp mass is prepared.
The
water required for granulation is provided from two sources:
1. From one molecule of water
of crystallisation of citric acid which is liberated during heating.
2. The water produced from the
reactions of citric acid and tartaric acid with sodium bicarbonate.
Wet
method: in
this method the mixed ingredients are moistened with non-aqueous liquid (e.g.
Alcohol) to prepare a coherent mass.
The
coherent damp mass from both the methods is then passed through a No. 8 sieve
and dried in an oven at a temperature not exceeding 600C. The dried
granules are again passed through the sieve to break the lumps which may be
formed during drying. The dried granules are packed in an air tight container.
Use: Before administration, the
desired quantity is dissolved in water, the acid and bicarbonate react together
producing effervescence.
The
carbonated water produced from the release of carbondioxide serves to mask the
bitter and saline taste of drugs.
More
over carbondioxide stimulates the flow of gastric juice and helps absorption of
medicament.
LOZENGES
Lozenges
are solid dosage form of medicaments which are meant for slow dissolution in
the mouth. Along with medicament they contain a sweetening agent, flavouring
agent and a strong binding agent.
They
may be prepared either by moulding or by compression.
Examples
are compound bismuth lozenges, liquorice lozenges.
PESSARIES
Pessaries
are solid unit dosage form of medicament meant for introduction into vagina.
The bases used for the manufacture of pessaries are such that at room
temperature they retain the original shape but when inserted into the body
cavity either it melts or dissolve in the cavity fluids to release the
medicament.
They
may be prepared either by moulding or by compression.
e.g.
lactic acid pessaries, nystatin pessaries.
POWDERS
Powders
are solid dosage form of medicament meant for internal and external use. The
powders meant for internal use are known as oral powders whereas those meant
for external use are known as dusting powders.
The
powders may be simple or compound.
When
the powders are dispensed in large quantities in a container and the patient is
asked to measure a specified quantity as a dose then these powders are known as
bulk powders.
e.g.
1.
Bulk powder for internal use;
e.g. Compound sodium chloride and dextrose oral
powder.
Compound
rhubarb oral powder
2.
Bulk powder for external use;
e.g. Snuffs
Talc
dusting powders
Tooth
powder.
TABLETS
Tablets
are unit solid dosage form of medicament or medicament with or without suitable
diluents. They are prepared usually by compression.
Tablets
are generally meant for oral administration but may be used by other routes of
administration.
e.g. aminophylline tablets
paracetamol tablets
antacid tablets.
SUPPOSITORIES
Suppositories
are special shaped solid dosage form of medicament for insertion into body
cavities other than mouth. These products are so formulated that after
insertion, they will either melt of dissolve in the cavity fluids to release
the medicament.
Suppositories
vary in shapes, sizes and weights. General suppositories from 1 to 2 gm are
prepared with either cocoa-butter or glecero- gelatin base.
e.g. aminophylline suppositories
glycerol suppositories.
SEMISOLID
DOSAGE FORMS
CREAMS
Creams
are viscous liquid or semisolid
emulsions intended for application to the skin i.e. for external use.
Creams
are of two types, aqueous creams and oily creams. In case of
aqueous creams the emulsions are oil-in-water type and in case of oily creams
emulsions are of water-in-oil type.
Due
to the presence of water soluble bases they can be easily removed from the
skin.
The
aqueous creams have a tendency to grow
bacterial and mold growth, therefore a preservative must be added in their
formulation.
e.g.
cetomacrogol cream, cetrimide cream, hydrocortisone cream, zinc cream BPC.
Advantages
of creams:
1. Creams are more acceptable
to the patients because they are less greasy and are easier to apply.
2. They interfere less with
skin functions.
3. o/w type of creams (superior
to w/o type) can be rub onto the skin more readily and are easily removed by
washing. w/o can be spread more evenly.
4. o/w type of cream are less
likely to soil clothes.
5. Evaporation of water from
o/w type of cream causes cooling sensation.
6. o/w creams absorbs the
discharges from the wound (liquid exudate) very quickly.
7. w/o creams (e.g. cold
creams) restricts evaporation from the skin, it can be used on non-weeping
surfaces to prevent dehydration ( in dry season), restore suppleness (softness)
- this property is said to be ‘emollient’.
Disadvantages:
1. Since it is a semisolid
preparation and containing oil in large amount, some of which are inedible,
hence creams are not used for internal use. Basically creams are meant for
application onto the skin.
2. the aqueous phase is prone
to the growth of molds and bacteria hence preservatives should be used.
3. Sometimes rancidification of
oils take place.
JELLIES
Jellies
are transparent or non-greasy semisolid preparations meant for external
application to the skin or mucous membrane. They are used for medication or
lubrication purposes.
e.g.
contraceptive jellies (spermicidal
action)
ichthammol jelly etc.
they
are used for lubricating catheters, surgical gloves and rectal thermometers.
The
gelling agents may be gelatin, or a carbohydrate such as starch, tragacanth,
sodium alginate or cellulose derivative.
OINTMENTS
Ointments
are the soft semisolid, greasy preparations meant for external application onto
the skin or mucous membrane (rectum and nasal mucosa).
They
usually contain a medicament dissolved, suspended or emulsified in the base.
Ointments
are used for their emollient and protective action to the skin.
e.g. compound benzoic acid ointment, cetrimide
emulsifying ointment
PASTES
Pastes
are semisolid preparations meant for external application to the skin. they
generally contain large amount of finely powdered solids such as starch,
zinc oxide, calcium carbonate etc.
They
provide a protective coating over the areas to which they are applied.
The
base may be anhydrous (liquid or soft paraffin) or water-soluble (glycerol or a
mucilage). Their stiffness make them useful as protective coatings.
e.g. magnesium sulfate paste.,
zinc and coal tar paste
OPHTHALMIC OINTMENTS
Ophthalmic
ointments are meant for application to the eye. They should be sterile and free
from irritation. They should be packed in sterile containers which should keep
the preparation sterile until whole of it is used up.
e.g. atropine eye ointment
chloromycetin eye ointments
Difference between paste and
ointments;
Paste
|
Ointment
|
1.
Contains a large amount of (50%) of finely powdered solids. As a
result they are often very stiff.
2.
When applied on the skin the paste adhere well and remain confined in
the area of application.
3.
They are porous so the perspiration (sweat)can escape through it.
4.
They are less greasy than ointments.
|
1.
Ointments contain very less amount of powdered solids. They are soft.
2.
Ointments are less viscous, hence spread beyond the area of application.
3.
Non-porous - hence perspiration cannot escape through it.
4.
More greasy than pastes.
|
LIQUIDS
APPLICATIONS:
Applications
are liquid or viscous preparations intended for application to the skin.
usually, they are suspensions or emulsions.
Most
of the official preparations contain paraciticides and are intended for only a
limited number of applications.
They
should be dispensed in coloured fluted bottles in order to distinguish them
from preparations meant for internal use. The container should be labeled “FOR
EXTERNAL USE ONLY”.
Examples
of applications are calamine
application compound B.P.C.
dicophane
application B.P.C.
MONOPHASIC LIQUID DOSAGE
FORMS
Monophasic liquid dosage forms are
represented by true or colloidal solutions.
The
components of the solution which is present in a larger quantity is known as
“solvent”, whereas the component present in a smaller quantity is termed as
“solute”.
Classification
1.
Liquid for internal use e.g. syrups, elixirs, linctus, drops and draughts.
2.
Liquids for external use which are of two types:
(a) Liquids to be applied to the skin e.g. liniments
and lotions etc.
(b) Liquids meant for body
cavities e.g. gargles, throat paints, mouth washes, eye drops, eye lotions, ear
drops, nasal drops, sprays and inhalation.
1. AROMATIC WATERS
Aromatic
waters are also known as medicated waters. They are dilute , usually saturated,
aqueous solutions of volatile oils (e.g. peppermint oil, cinnamon oil) or
volatile substances (e.g. camphor).
Uses:
(i) Some of them have a mild
therapeutic action but
(ii) mainly they are used as
flavouring agents in preparations meant for internal use.
Name
|
Concentrated
|
Dilution
|
(by volume)
|
Use
|
|
preparation
|
Concentrated
|
Water
|
|
Anise
water
|
Conc. Anise Water
|
1
|
39
|
Flavour
Carminative
Mild
expectorant
|
Camphor
water
|
Conc Camphor Water
|
1
|
39
|
Flavour
Carminative
Mild
expectorant
|
Caraway
Water
|
Conc. Caraway Water
|
1
|
39
|
Flavour
Carminative
|
Chloroform
Water
|
Double Strength Chloroform Water
|
1
|
1
|
Preservative
Flavor
|
Dill
Water
|
Conc. Dill Water
|
1
|
39
|
Flavor
Carminative
(in
gripe water)
|
Peppermint
Water
|
Conc. Peppermint Water
|
1
|
39
|
Carminative
Weak
preservative
|
Aromatic
waters are prepared by two IP methods:
(1)
Solution
* Essential oil is shaken with 500 times
its volume of Purified Water.
The shaking is repeated several
times during a period of 30 minutes. The mixture
set aside for 12 hrs or overnight and then filtered.
* Alternatively, the oil may be
triturated with a sufficient quantity of powdered talc or of Keiselghur, or of pulped filter paper and 500
times its volume of purified
water and filtered.
(2)
Dilution from concentrated waters:
One part (by volume) of concentrated
water is diluted with 39 parts of Purified Water.
e.g. Preparation of Camphor
Water
Formula:
Camphor 1gm
Alcohol 90% 2 ml
Purified Water q.s. 1000 ml
Camphor
is dissolved in Alcohol (90%) and then the solution is added drop by drop to
the purified water.
After
each addition the mixture is shaken well until the camphor is dissolved. . If
required the excess camphor was filtered out.
e.g. Preparation of Cinnamon
Water Concentrated B.P.C.
Cinnamon
oil is dissolved in the alcohol and then sufficient purified water was added in
successive small portions, to produce 1000 ml. The mixture was shaken
vigorously after each addition. Small amount of purified talc was suspended in
water and a filter bed is prepared on the filter paper. The filter bed was
dried and then the solution was filtered through it.
SYRUPS
Syrups
are liquid oral preparations in which the vehicle is a concentrated aqueous
solution of sucrose or other sugar.
N.B.
Syrups generally are not issued directly to the patients when it is issued to
the patients:
(i)
if it is clear it is called elixir and
(ii)
if it is suspension it is called mixtures.
·
Simple syrup IP is a saturated solution of
sucrose in purified water. The concentration of sucrose is 66.7 % w/w.
·
Syrup containing medicinal substances are called medicated syrups and those containing aromatic or flavoured
substances are known as flavoured Syrup.
Advantages
of syrups
1. Syrups retards oxidation
because it is partly hydrolyzed into reducing sugar such as dextrose and
levulose.
2. It prevents decomposition of
many vegetable substances. Syrups have high osmotic pressure which prevents the
growth of bacteria, fungi and molds which are the chief causes of decomposition
in solutions of vegetable matter.
3. They are palatable. Due to
the sweetness of sugar it is a valuable vehicle for the administration of
unpalatable substances.
The syrups may be divided into two
categories:
(a)
Syrups prepared by simple solution or admixture
e.g. Simple Syrup IP Sucrose 667 g
Purified
water q.s. 1000
Method:
Sucrose is added to water and dissolved by heating. The solution is cooled and
the required volume is made up with the required amount of water.
e.g. Ginger Syrup IP
Strong Ginger Tincture 50 ml
Syrup, sufficient to
produce 1000 ml
Both
are mixed thoroughly.
(b)
Syrups made by a process of extraction
e.g. Tolu Syrup IP
Tolu balsam 12.5 g
Sucrose 660 g
Purified
Water q.s. 1000 g
Procedure: Boiling purified water is added to Tolu balsam contained in a
tared vessel. The vessel is covered lightly and the contents are boiled gently
for half an hour.
Purified
water is added to adjust the specified weight.
The
mixture is cooled, filtered and sucrose is added. Heated on a water bath to
dissolve the sucrose. Finally sufficient purified water is added to produce the
required weight.
ELIXIRS
Definition: Elixirs are clear, liquid,
oral preparations of potent or nauseous drugs. They are pleasantly flavoured
and usually attractively coloured and are very stable.
·
Elixirs usually contains potent drugs, such as antibiotics,
antihistamines and sedatives.
·
Vehicles used in elixirs are
alcohol, glycerol and propylene glycol.
They are used
(i) for the production of clear solution.
Essential oils from flavoring agents may produce faint opalescence, hence
alcohol 10 - 20% is useful for keeping
oils in solution.
(ii) When potent medicaments
of low solubility is required to be dispensed, a mixture of solvents that will
give complete solution is used.
e.g. Phenobarbitone is
virtually insoluble in water but a clear product can be made by dissolving it
in alcohol and then diluting with glycerol and water.
e.g. One part of paracetamol
is soluble in 70 parts of water, 7 parts of alcohol, 9 parts of propylene
glycol or 40 parts of glycerol. In paracetamol elixir a mixture of alcohol,
propylene glycol and glycerol is used as vehicle.
Other
adjuncts used are:
(i)
Chemical stabilizers
e.g. Neomycin Elixir B.P.C.
is adjusted to pH 4 to 5 with citric acid to minimize the darkening that occurs
on storage.
e.g. Disodium edetate should
be incorporated to sequester heavy metals that catalyse decomposition of
antibiotic.
(ii)
Colouring agents
e.g. Amaranth Magenta red
Tartrazine Saffron
Green S Green
(iii)
Sweetening agents
e.g. Sucrose syrups, glycerol,
sorbitol solution, invert syrup and saccharin sodium
are used.
(iv)
Flavours
e.g. Blackcurrant Syrup in Chloral
Elixir
Concentrated Raspberry Juice with
invert syrup
Lemon spirit with syrup and invert
syrup.
Compound Orange Syrup
(v)
Preservatives
·
20% alcohol, propylene glycol or glycerol are preservative
·
Syrup is self-preservative due to high osmotic pressure
·
The most common additional preservative in chloroform; it is used in
the form of double strength water.
·
Some times the preparations contain benzoic acid and methyl parahydroxy
benzoate.
LINCTUSES
Linctuses
are viscous, liquid, oral preparations that are usually prescribed for the
relief of cough.
·
They contain medicaments which have demulcent (which soothes the
inflammed mucous membrane preventing contact with air in the surroundings),
sedative or expectorant action. The viscous vehicle soothes the sore membrane of the throat.
·
The usual dose is 5 ml. Linctuses should be taken in small doses,
sipped and swallowed slowly without diluting it with water in order to have the
maximum and prolonged effect of medicaments.
·
Simple Syrup is generally used as a vehicle. For diabetic patients
Sorbitol solution is used instead of Simple Syrup.
GLYCERIN
OR GLYCERITES
Glycerites
are the viscous preparations in which the drug is dissolved in glycerin with or
without heating. They are generally used as antiseptic or anti-inflammatory
preparations.
e.g. icthammol
glycerin
tannic acid glycerin
phenol glycerin
COLLODION
Collodions
are liquid preparations meant for external application to the skin. They are
convenient for application on small cuts and abrasions and are also used when a
prolonged contact between the skin and the medicament is required.
·
The vehicle is volatile and evaporates on application to the skin,
leaving a flexible, protective film covering the site.
·
Preparations
Volatile solvents used are ether and
alcohol.
Film producing ingredient is
pyroxylin (nitrocellulose)
Plasticizer giving the flexibility
is castor oil.
Preparation
The
solution is made by shaking the ingredients in a closed container, allowing to
stand for few days while impurities settle and then decanting the supernatant
liquid, because the solution is too volatile for filtration.
Storage
Collodions
are stored in small light-resistant, well closed containers.
LINIMENT
Liniments
are liquid, semi-liquid or occasionally semi-solid preparations intended for
application on the skin.
They
may be alcoholic or oily solutions or emulsions.
Most
are massaged onto the skin e.g. counter-irritant type.
Some
are applied on warm dressing or with a brush. e.g. analgesic and soothing type.
Liniments
must not be applied to broken skin because they would be very irritating.
e.g.
Soap Liniment BPC
Camphor Liniment BP
Methyl salicylate liniment BPC
Alcohol
is the main vehicle. In increases the
penetration of counter-irritant molecules through skin.
LOTIONS
Lotions
are liquid preparations for external application without friction.
They
are either dabbed on the skin or applied on a suitable dressing and covered
with water proof material to reduce evaporation.
e.g. Copper and zinc sulfate lotion is used
for impetigo
Zinc sulfate and salicylic acid for
ulcer
Salicylic acid lotion for dandruff
Salicylic acid and mercuric chloride
lotion for follicular infection
N.B. Copper and Zinc sulfate have astringent
action.
Salicylic acid has keratolytic
action.
GELS
Gels
are aqueous colloidal suspensions of the hydrated forms of insoluble
medicaments e.g. aluminium hydroxide gel, used as antacid.
EXTRACTS
Extracts
are concentrated preparations containing the active principles of vegetable or
animal drugs. The drugs are extracted with suitable solvents and the product is
concentrated o one of three types of extract -
Liquid Extract of which 1 ml usually
contains the active constituents from 1 g of drug.
Dry Extract obtained by completely
removing the solvent under, reduced pressure.
Soft Extract obtained by evaporation to
a plastic mass.
TINCTURES
These
are alcoholic preparations containing the active principles of vegetable drugs.
They
are weaker than extracts.
They
are usually prepared by maceration and percolation, or may be prepared by dissolving
the corresponding liquid extract of chemical substances (e.g. iodine) in
alcohol or hydroalcohol solvent.
e.g. Belladonna tincture
Aromatic cardamom tincture
Iodine tincture
SPIRITS
Spirits
are alcoholic or hydroalcoholic solutions of volatile substances.
Most
are used as flavouring agents but a
few have medicinal value.
e.g.
Chloroform Spirit, Lemon Spirit, Compound Orange Spirit.
INFUSIONS
(i)
Fresh Infusions are made by
extracting vegetable drugs for a short time with cold or boiling water (cf.
making of tea). They quickly deteriorate as a result of microbial contamination
and therefore must be used within 12 hours.
(ii)
Concentrated infusions are made by
cold extraction with 25 % alcohol. The alcohol preserves the product for an
indefinite period.
Dilution
of 1 part of concentrated infusions with 10 parts of water gives a preparation
corresponding fresh infusion.
e.g. Concentrated Compound Gentian Infusion
concentrated
Senega Infusion
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