Dosage forms are drug products in the form that they are
available in the market (1)
They are usually with an inactive components or excipients in a
particular way and configuration and together with the active ingredient formulated
into a particular dose. (1)
TYPES OF DOSAGE FORM
Depending on the method or route of administration, dosage forms come in
Types include the oral, ophthalmic, inhalation, parenteral, topical and suppository.
These types can come or be manufactured in liquid, solid, gas and semisolid dosage forms. (1)(16)
constitute a significant proportion of pharmaceutical dosage forms. They mostly
serve as a means for drugs to be delivered topically by way of the skin,
cornea, nasal mucosa, vagina, buccal tissue, rectal tissue, urethral membrane,
and external ear lining. (17)
semisolid dosage form has numerous advantages when it comes to easy
application, rapid formulation, and ability to topically deliver a wide variety
of drug molecules. (17) (18)
Semisolids are available as a wide range of dosage forms, each having unique
Semisolid dosage forms are normally presented in the form of
creams, gels, ointments, or pastes. (2)
(18) They contain one or more active ingredients dissolved or
uniformly dispersed in a suitable base and any suitable excipients such as
emulsifiers, viscosity increasing agents, antimicrobial agents, antioxidants,
or stabilizing agents. (2) (17) (18)
It comprises of a body of product which is applied to skin or accessible
mucous membrane to alleviate or treat a pathological condition or other
protection against harmful environment
SSPDF are required to be smooth in texture, elegant in appearance,
non-dehydrating, non-gritty and greasy, non-staining, non-hygroscopic product,
with a non-irritating effect on applied surface, good miscibility with surface
secretion and do not alter the membrane function of surface. (19)
Ointments, cream, pastes and gel products falls under the semi-solid
pharmaceutical dosage form (19)
Selecting an appropriate
base for semi-solid depends on a number of factors, the therapeutic effect to
be established, the nature of the active ingredient at the intended site of
action, the desired shelf-life of the semi-solid and the supposed conditions in
which the product will be exposed. In many cases, a compromise has to be made
in order to achieve the required stability. For example, drugs that hydrolyse
rapidly are more stable in hydrophobic bases than in water containing bases,
even though they may be more effective in later. (20)
The type of base required
should be considered and a non-irritating or bases capable of sensitizing the
skin should be avoided. It must also not cause injury or delay healing.
The base should neither
irritate nor sensitize the skin, nor should it delay wound healing. It should
be smooth, inert, odourless, physically and chemically stable, and compatible
with both the skin and active ingredient(s) to be incorporated. It should
normally be of such a consistency that it spread and softens easily when stress
A wide range of raw
materials is available for the preparation of a semisolid dosage form. Apart
from the usual pharmaceutical ingredients such as preservatives, antioxidants,
and solubilizers, the basic constituents of a semisolid dosage form are unique
to its composition. The choice of suitable raw materials for a formulation
development is made on the basis of the drug delivery requirements.
OF SEMI-SOLID DOSAGE FORM
are homogenous, semi-solid preparations intended for external application to
the skin or mucous membrane. They are used as emollients or for the application
of active ingredients to the skin for protective, therapeutic, or prophylactic
purpose and where a degree of occlusion is desired.
(lipophilic) ointments are usually anhydrous and can absorb only small amounts
of water. Typical bases used for their formulation are water-insoluble
hydrocarbons such as hard, soft and liquid paraffin, vegetable oil, animal
fats, waxes, synthetic glycerides and polyalkylsiloxanes.
ointments can absorb large amounts of water. They typically consist of a
hydrophobic fatty base in which a w/o agent, such as wool fat, wool alcohols,
sorbitan esters, mono glycerides, or fatty alcohols can be incorporated to
render them hydrophilic. They may also be w/o emulsions that allow additional
quantities of aqueous solutions to be incorporated. Such ointments are used
especially when formulating aqueous liquids or solutions.
ointments: Hydrophilic ointment
bases are miscible with water. The bases are usually mixture of liquid and solid polyethylene
glycols (macrogols) 1.
are homogeneous, semi-solid preparations consisting of opaque emulsion systems.
Their consistency and rheological properties depend on the type of emulsion,
either water-in-oil (w/o) or oil-in –water (o/w), and on the nature of the
solids in the internal phase. Creams are intended for the application to the
skin or certain mucous membranes for protective, therapeutic, or prophylactic
purposes, especially where an occlusive effect is not necessary.
Gels: Gels are usually homogeneous, clear,
semi-solid preparations consisting of a liquid phase within a three-dimensional
polymeric matrix with physical or sometimes chemical cross-linkage by means of
suitable gelling agents.
Hydrophobic gels: Hydrophobic
gel (oleogel) bases usually consist of liquid paraffin with polyethylene or
fatty oils gelled with colloidal silica or aluminium or zinc soaps.
Hydrophilic gels: Hydrophilic
gels (hydrogel) bases usually consist of water, glycerol, or propylene glycol
gelled with suitable agents such as tragacanth, starch, cellulose derivatives,
carboxyvinyl polymers, and magnesium aluminium silicates.
are homogeneous, semi-solid preparations containing high concentrations of
insoluble powdered substances (usually not less than 20%) dispersed in a
suitable base. The pastes are usually less greasy, more absorptive, and stiffer
in consistency than ointments because of the large quantity of powdered
ingredients present. Some pastes consist of a single phase, such as hydrated
pectin, and others consist of a thick, rigid material that does not flow at
body temperature. The pastes should adhere well to the skin. In many cases they
form a protective film that controls the evaporation of water.
Poultices: A poultice is an ancient form of topical
medication also known as a cataplasma. It is a soft mass of vegetable
constituents or clay, usually heated before application. Kaolin poultice BP is
prepared by mixing and heating dried, heavy kaolin and boric acid with
glycerin. After cooling, the aromatic substances are incorporated with
stirring. The product is spread on a dressing and applied hot to the skin.
Advantage of semi-solid dosage
It is used externally
Drastic reduction in the side effect probability
First pass gut and hepatic metabolism is avoided.
Patient compliance is increased, the drug
termination is problematic cases is facilitated as compared with other routes
of drug administration.
Disadvantages of semi-solid
There is no dosage accuracy in this type of dosage
The base which is used in the semi-solid dosage
form can be easily oxidized.
If we go out after using semi-solid dosage form
problems can occur.
In general, semisolid
dosage forms are complex formulations having complex structural elements which
consist of Excipients.
An excipient is a substance formulated alongside
the active ingredient in preparing a pharmaceutical product.
When it comes to drugs, most of the attention goes to the active
pharmaceutical ingredient. But typically the vast majority of what is in a
tablet, capsule, semi-solid or liquid is not the active ingredient. A drug is
formulated with many other compounds called excipients which play an essential
role in delivering the active ingredient to the patient.
Excipients are intended to impact specific property to the product.
Excipients are usually pharmacologically inactive and of reasonable
compatibility with final product and product container closure system.
Types of excipients
reduce the adhesion between the powder or granules and the punch surface thus preventing
sticking of the tablet to punches by offering a non-sticky surface. They
are also used to help protect drugs from sticking to each other and the package
or container. The most commonly used is magnesium stearate.