Pharmaceutical Semisolid dosage forms
Semisolid
dosage forms are dermatological products of semisolid consistency and applied
to skin for therapeutic or protective action or cosmetic function.
Semisolid
dosage forms usually are intended for localized drug delivery.
In the past
few years, however, these forms
also have been
explored for the
systemic delivery of
various drugs.
Semisolids
constitute a significant proportion of pharmaceutical dosage forms.
They can be
applied topically to the skin, cornea, rectal tissue, nasal mucosa, vagina,
buccal tissue, urethral membrane, and external ear lining. Eg: Ointments, creams, jellies and pastes
etc.
Advantages of
semi-solid dosage form:
·
It is used externally
·
The probability of side effects can be reduced
·
First, pass gut and hepatic metabolism is
avoided.
·
Local action and Site-specific action of the
drug on the affected area.
·
Convenient for unconscious patients or patients
to have difficulty in oral administration.
·
Suitable dosage form for bitter drugs.
·
More stable than a liquid dosage form.
Disadvantages of
semi-solid dosage form:
·
The accuracy can’t be measured, for the
semisolid dosage form.
·
May cause staining.
·
They are bulky to handle.
·
Application with a finger may cause
contamination.
·
Physico-chemical is less stable than a solid
dosage form.
·
May cause irritation or allergy to some patients
Ideal properties of
semisolid dosage forms:
·
Smooth texture
·
Elegant in appearance
·
Non-dehydrating
·
Non-gritty
·
Non-greasy and non-staining
·
Non-hygroscopic
Ingredients needed
for semisolid dosage form:
·
Bases
·
Preservative
·
Humectants
·
Antioxidants
·
Emulsifier
·
Gelling agent
·
Permeation enhancer
·
Buffers
Bases used in
semisolid dosage form:
It is one of the most important ingredients used in the
formulation of the semisolid dosage form. Ointment bases do not merely act as
the carriers of the medicaments, but they also control the extent of absorption
of medicaments incorporated in them.
Ideal
characterization of bases used in semisolid dosage form:
They should be:
·
Inert, non-irritating, and non-sensitizing.
·
Compatible with skin pH and the drug.
·
Good solvent and/or emulsifying agent.
·
Emollient, protective, non-greasy and easily
removable.
·
Release medicament readily at the site of
application.
·
Pharmaceutically elegant and possess good
stability
Classification of
Bases:
According to USP ointment bases are classified into four
general groups:
·
Hydrocarbon bases (oleaginous bases)
(Petrolatum, Paraffin, Lanolin, etc.)
·
Absorption bases (cold cream, anhydrous lanolin,
etc.)
·
Water-removable bases ( oil in water)
·
Water-soluble bases (polyethylene glycol)
Antioxidants used in
semisolid dosage form:
Oxygen has the capability to become a part of potentially
damaging molecules called “free radicals.” Free radicals can attack the healthy
cells of the body. It can break their structure and that’s why the function is
also affected.
Example: Butylated hydroxyanisole, Butylated hydroxytoluene
Ingredients that
increase permeation:
Skin can act as a barrier. There are various penetration
enhancers that can help the drug to penetrate through the skin.
Oleic acid
The emulsifier used
in semisolid dosage form:
Emulsifiers are used to improve the stability of an emulsion
by increasing its kinetic stability. It reduces surface tension and prevents
coalescence. It helps to increase the viscosity at low concentration.
Emulsifying agents
used in semisolid dosage form:
Sodium lauryl sulfate: Oil/Water emulsion – Sodium stearate
and calcium stearate.
Glyceryl monostearate: This is a weak Water/Oil emulsifying
agent and it is used as a stabilizer and emollient in the Oil/Water emulsion.
Humectant used in
semisolid dosage form:
The humectant is a hygroscopic substance used to increase
the solubility of the active ingredient to increase skin penetration. It’s also
used to improve the hydration of the skin.
Buffers used in
semisolid dosage form:
Buffers are added for various purposes. Such as
·
Compatibility with skin.
·
Drug solubility.
·
Drug stability.
·
Influence the ionization of drugs.
Preservatives used in
semisolid dosage form:
Preservatives are used to inhibit the growth of
contamination of microorganisms.
Example: Para-hydroxybenzoate (parabens), phenols, benzoic
acid, sorbic acid, etc.
Pastes:
·
Pastes
are basically ointments containing high percentage of insoluble solids (usually
20-50 % or higher). They are semisolid preparations intended for external
application. Pastes are generally very thick and stiff.
·
They
have good adhesion on skin and they form thick coat. They are used mainly as
antiseptic, protective or soothing dressing.
Ointments:
·
Ointments
are semisolid preparations with or without medicaments intended for application
to the skin.
·
Medicaments
used in the formulation is dissolved, suspended or emulsified in an ointment
base.
·
The
ointments are mainly used as protective or emollient for the skin.
·
Ointments
may be used as-
1.
Antibiotic
ointments. Drug used: Neomycin.
2.
Antifungal
ointment. Drug used: Benzoic acid, salicylic acid, nystatin.
3.
Anti-inflammatory
ointment. Drug used: hydrocortisone, etc
ENVIRONMENT Temperature: 20-300 C, Humidity: 30-60 %,
DOCUMENTS: 1. Standard Operating Procedure (SOP) 2. Batch
Manufacturing Record (BMR) 3. Batch Packaging Record (BPR) 4. In House
specification
Creams:
· These are viscous semisolid emulsions which are meant for external use. They usually contain a water soluble base due to which they can be easily removed from the skin.
· They are of softer consistency and have light weight in comparison to true ointments when applied to the skin. Cream leave no visible evidence of their presence on the skin.
· They are of mostly two types
- Aqueous cream, Eg: Cetrimide Cream B.P
- Oily cream, Eg: Proflavine cream BPC
Gels
and Jellies:
·
Gels and jellies are
transparent to opaque semisolid preparations meant for external application to
the skin or mucous membrane.
·
Considered to be more rigid
than jellies. Jellies contain more fluid and less cross-linking agent.
·
They are non-greasy and
prepared from
·
Natural gums, eg:
Tragacanth, Pectin, Sodium Alginate etc.
·
Synthetic derivatives of
natural substances, eg: Methyl cellulose, Sodium carboxymethyl
cellulose.
Poultices:
·
Poultices are viscous pasty
preparations applied hot to the skin to reduce inflammation and to act as
counter irritant.
·
Heavy kaolin is commonly
included in the formulation because it act as a carrier of heat. It is an
outdated preparation.
Suppository:
Suppository is another way to deliver drugs.
It’s a small, round or cone shaped object that put in body
orifice, often into bottom.
Once its inside, its melt and dissolves and releases the
medicine and exert local or systemic effects.
Type of suppository
There are three type of suppository
Rectal Suppository –
into the rectum.
Vaginal Suppository –
into the vagina.
Urethral Suppository
– into male urethra.
ADVANTAGES OF
SUPPOSITORIES
Over Oral Drug Administration:
·
Avoid first pass metabolism
·
Introduce drugs into the body
·
Does not cause nausea and vomiting due to
gastric irritation in case of oral therapy
·
Used before surgery since oral therapy is
restricted
·
Beneficial for patients suffering from severe
vomiting
·
Can be administered to unconscious patients
·
Can be used as targeted drug delivery system
·
Localized action with reduced systemic
distribution
·
Get to site of action with lower dose reducing
systemic toxicity
·
Highly beneficial in haemorrhoids or vaginal
infections
·
Prolonged drug action achieved
Over parenteral drug administration:
·
Self-medication
·
No systemic side effects
·
No pain or site of action related issues
Over Vaginal Tablets:
·
Suppositories dissolves faster
·
Total bioavailability achieved
·
No residue remains like tablet
·
No need of applicator
·
Non staining
·
Non itching
DISADVANTAGES OF
SUPPOSITORIES:
·
Mucosal irritation
·
Patient compliance
·
Erratic and undesired absorption
·
Placement too high into rectum may lead to first
pass metabolism
·
Installation may trigger defecation reaction
·
GI state affects absorption
·
Diarrhoea & disease states affect absorption
Pharmaceutical Semisolid dosage forms notes pdf
