A
solution is a homogeneous mixture that is prepared by dissolving a solid,
liquid, or a gas, in another liquid and represent a group of preparation in
which the molecule of the solute or a dissolved substance are dispersed among
those of the solvent. Most solution are unsaturated with the solute, in other
words, the concentration of the solute in the solution is below its solubility
limit. The strength of the pharmaceutical solutions is usually expressed in the
terms of % strength, although for very dilute preparations, expression of ratio
strength is some time used. The term % when used without qualification (as with
w/v, v/v, or w/w) means % weight-in-volume for solutions or suspensions of
solids in liquids; % weight-in-volume for solution of gases in the liquid; %
volume-in-volume for solutions of liquids in liquids; and weight-in-weight for
mixture of solids and semisolids. Solutions are of following types
These
are the solutions in water. For example Aromatic Water, Aqueous Acids,
Solutions, Douches, Enemas, Gargles, Mouthwashes, Juices, Nasal Solutions, and
Irrigation Solutions.
(a) Aromatic
waters: The USP
defines the aromatic water as clear, saturated aqueous solution of volatile
oils or other aromatic or volatile substances. The odors and tastes are
similar, respectively, to those of the drugs or volatile substances from which
they are prepared. They are used principally as flavored or perfumed vehicles.
(b) Aqueous
acids: Inorganic
acids and certain organic acids, although of minor significance as therapeutic
agents, are of great importance in pharmaceutical manufacturing and analysis.
This is especially true for acetic, hydrochloric, and nitric acids. Many of the
more inorganic acids are available commercially in the form of concentrated
aqueous solutions. The %age of the strength varies from one acid to the other
and depends on the solubility and stability of the solute in water and on the
manufacturing processes.
(c) Diluted
acids: Diluted acids
in USP are aqueous solutions of acids of a suitable strength (usually 10%w/v
but diluted Acetic Acid is 6% w/v) for internal administration or for the
manufacturing of other preparations. The strength of the official undiluted
acids is expressed in %age in w/w, where as the strength of the official
diluted acids are expressed in % in volume (w/v).
(d) Douches: The douches are aqueous solutions
directed against a part or into the cavity of the body. It functions as a
cleansing or antiseptic agent. E.g., an eye douche, used to remove the foreign
particles and discharges from the eyes. Douches are often dispensed in the form
of powders with direction for dissolving in a specified quantity of water or
the solution may be prepared by the pharmacist. Douches are not official class
of preparations but several substances in the compendia frequently are employed
as such in weak solutions. Vaginal douche are common example and used for
cleansing and hygienic purpose.
(e) Enemas: Enema preparations are rectal
injections employed to evacuate the bowl, influencing the general system by the
absorption, or to affect a local disease. The latter two are called retention
enemas. They may posses’ anthelmentic, nutritive, sedative, or simulative
properties or they may contain radiopaque substances for roentgen graphic
examination of the lower bowel. Sodium chloride, Sodium bicarbonate, Sodium monohydrate
phosphate, Glycerin, Docusate Potassium, and light Mineral oil are used in
enemas to evacuate the bowel. Evacuation enemas are generally given at body
temperature in quantities of 1 to 2 pt injected slowly with an injection.
Retention enemas are to be retained in the intestine and should not be used in
larger quantities than 150 ml for an adult. Usually the volume is considered
smaller such as a few ml and the term used for these enemas is microenemas.
Valporic acid, Metronidazole and Endomethacin have been formulated as
microenemas for the purpose of absorption.
(f) Gargles: These are aqueous solutions
frequently containing antiseptic, antibiotics, and/or anesthetics used for
treating the pharynx and nasophyrynx by forcing air from the lungs through the
gargles that is held in the throat; subsequently, the gargle is expectorated.
Many gargles must be diluted before the use.
(g) Mouthwashes: Mouthwashes are aqueous solutions
often in concentrated form containing one or more active ingredients and
excipients. They are used by swishing the liquids in the mouth cavity.
Mouthwashes are used for two purposes, therapeutic (plaque, gingivitis, dental
caries, and stomatitis) and cosmetic (bad breath by adding antimicrobial and/or
flavoring agents) purposes.
(h) Juices: A juice is made from the freshly ripe
fruit, is aqueous in character, and is used in making syrups that are employed
as vehicles. The freshly expressed
juices is preserved in Benzoic acid and allow to stand in room temperature for
several days, until the pectin that naturally are present are destroyed by
enzymatic action, as indicated by the filtered juices yielding a clear solution
with alcohol
(i) Nasal
solutions: Nasal solutions
are usually aqueous solutions designed to be administered to the nasal passage
in the drops or sprays.
(j) Otic
solutions: These
solutions are occasionally are referred as ear or aural preparations. Other
oral preparation includes suspension and ointments for topical application in
the ear. Ear preparations are usually placed in the ear canals by drops or in
small amounts for the removal of excessive cerumen (ear wax) or for the
treatment of ear infections, inflammations or pain.
(k) Irrigation
solutions: Irrigation
solutions are sterile, non pyrogenic solutions used to wash or bath surgical
incisions, wounds, or body tissues. Because they come in contact with the
exposed tissues, they must meet the astringent USP requirements for sterility,
total solids, and bacterial endotoxins.
(l) Syrups:
Syrups are
concentrated, viscous, aqueous solutions of sugar or a sugar substituted with
or without flavors and medical substances. When purified water alone is used in
making the solution of sucrose, the preparation is known as syrup or simple
syrup if the sucrose concentration is 85 %. In addition to sucrose, certain other
polyols, such as Glycerin or Sorbitol, may be added to retard the
crystallization of sucrose or to increase the solubility of added
ingredients. Alcohol often is included
as a preservative and also as a solvent for flavors; further resistance to
microbial attack can be enhanced by incorporating antimicrobial agents. When
the aqueous preparation contains some additional medicinal substances, the
syrup is called medicated syrup. Flavored syrups are usually not medicated, but
rather contain some aromatic or pleasantly flavored substances and are intended
to be used as a vehicle or flavor for prescription, such as Acacia, Cherry,
Cocoa, Orange, and Raspberry.
Nonaqueous solutions:
Pharmaceutical
preparations, and, in particular, those intended for internal use, rarely
contain more than one minor quantities of the organic solvents that are common
to the manufacturing or the analytical operations. Products of commerce for
internal use may contain solvents such as ethanol, glycerin, propylene glycol,
certain oils, and liquid paraffin. Preparation intended for external use may
contain solvent in addition to those just mentioned, namely isopropyl alcohol,
polyethylene glycol, various others, and certain esters. The various types of
non aqueous solution are mentioned below.
(a) Collodions: These
are liquid preparations containing pyroxylin, partially nitrated cellulose, in
a mixture of ethyl ethers and ethanol. They are applied to the skin by mean of
a soft brush or other suitable applicator and, when the ether and ethanol have
evaporated, leave a film of pyroxylin on the surface. Salicylic acid collodion
USP, contain 10% w/v of salicylic acid in flexible collodion USP and use as a
keratolytic agent in the treatment of corn and warts.
(b) Elixirs: Elixirs are clear, pleasantly
flavored, sweetened hydro alcoholic liquids intended for oral use. The main
ingredients in elixirs are ethanol and water but glycerin, sorbitol,
polypropylene glycol, flavoring agents, preservatives, and syrups often are
used in the preparation of the final products. The solvents are often used to
increase the solubility of the drug in the dosage form. Elixirs are more fluid
than syrups, due to the use of less viscous ingredients such as alcohol and the
minimal use of viscosity improving agents such as sucrose.
(c) Glycerins: Glycerin’s or glycerites are
solutions are mixtures of medicinal substances in not less than 50% by weight
of glycerin. Most of the glycerins are
mostly viscous and some have jelly like consistency. Glycerin is suitable
pharmaceutical solvent forming permanent and concentrated not otherwise
obtainable. Glycerins are hygroscopic and should be stored in tightly closed
containers.
(d) Inhalations: Inhalation preparations are so used
or designed that the drug is carried to the respiratory tract of the patient.
The vapors or mist reaches the affected area and give prompt relieve from the symptoms
of bronchial nasal congestion. Another group of products, also known as
meter-dose-inhalers (MDIs) are propellant–driving drug suspension or solutions
in liquefied gas propellant with or without a co-solvent and are intending for
delivering meter dose of the drugs to the respiratory tract.
(e) Liniments:
Liniments are alcoholic or oil based solutions or emulsions containing
therapeutic agents intended for external use. These preparations may be liquids
or semisolids that are rubbed onto the affected area; because of this, they
were once called embrocations. These are usually applied with fractions and
rubbing of the skin, the oil or soap base for ease of the application and
massage. Alcoholic liniments are generally used for their rubefacient,
counterirritant, mildly astringent, and penetrating effects. Depending on their
ingredients liniments works solely as a protective coating. Other liniments
contain antipruritics, astringents, emollients, or analgesics and are
classified on the basis of their active ingredients.
(f) Oleovitamins: Oleovitamins are fish liver oils
diluted with edible vegetable oils or emulsions of the indicated vitamins or
vitamin concentrates (usually vitamin A and D) in the fish liver oil. These
vitamins are unstable in the presence of rancid oil; therefore these
preparations should be stored in small, tight containers, preferably under
vacuum or under the atmosphere of an inert gas, protected from light and air.
(g) Spiritis: Spirits are sometime called essences,
are alcoholic or hydro alcoholic solutions of volatile substances. Like the
aromatic water, the active ingredient in the spiritis may be the solid, liquid,
or gas. Generally the alcoholic concentration of spiritis is rather high,
usually over 65%. Because of the greater solubility of the aromatic or volatile
substances in alcohol than in water, spiritis can contain a greater
concentration of this material than the corresponding aromatic water. When mix
with water or aqueous preparation, the volatile substances generally separates
and form a milky preparation. Salts may be precipitated from aqueous solution
by the addition of spiritis. Spiritis may be used pharmaceutically as a
flavoring agent and medicinally for the therapeutic value of the aromatic
solutes. The spiritis still listed in the USP/NF are aromatic ammonia spirit,
camphor spirit, compound orange spirit and peppermint spirit.
No comments:
Post a Comment