Pharmaceutical Dosage Forms and Drug Delivery System
Overview
Most people think of swallowing tablets or capsules when taking a medication. Taking
tablets or capsules may be the most common way people take medication, other forms
of administration are also available to introduce medication in to the body by routes
other than the mouth. In this lesson, the student will learn types and characteristics of
different dosage forms used to administer or introduce medication to the body. This
will include advantages and disadvantages of each type of pharmaceutical dosage
forms.
DEFINITION
Pharmaceutical Dosage Form is defined as the physical form of a dose of a chemical
compound used as a drug or medication intended for administration or consumption.
Common dosage forms include pill, tablet, or capsule, drink or syrup, aerosol or
inhaler, liquid injection, pure powder or solid crystal (e.g., via oral ingestion or freebase
smoking), and natural or herbal form such as plant or food of sorts, among many
others.
Route of Administration is defined as the path by which a drug or other substance
enters the body.
Solubility is the ability of a substance to dissolve in a solution
Solute is a substance that is dispersed and dissolved in liquid
Solvent is a liquid in which the solid, gas, or another liquid substance is dispersed
PHARMACEUTICAL DOSAGE FORMS
Section 1.
Liquid Dosage Forms
Liquid medication dosage forms deliver medication in a fluid medium which serves as
a carrier or delivery system commonly referred to as the vehicle.
Common vehicles are water, alcohol and oil. The medication maybe dissolved in the
vehicle or maybe present as very fine solid particles suspended, or floating in the
vehicle. Liquid dosage forms may pour as freely as water or may have a thick
consistency as syrup. Liquid dosage forms may be used for oral consumption or for use
in other parts of the body.
ADVANTAGES AND DISADVANTAGES OF LIQUID DOSAGE
FORMS
Advantages
1.
Usually faster acting than the solid dosage forms

Medications are absorbed into the bloodstream in a dissolved state. Liquid
dosage form is already dissolved or is present in small particles
suspended in a vehicle so it can be readily absorbed.
2.
Maybe easier to take than an oral solid dosage form
 For patients having difficulty in swallowing tablets or capsules.
3.
More flexibility in dosage than some other dosage forms.
 Can be dispensed in bulk containers than other dosage units
4.
May be more practical to administer than solid dosage forms for specific patient
cases.
 For medications that need to be administer directly into the eye or earsmore practical to use liquid than solid dosage forms.
Disadvantages
1.
May have a shorter time of expiration than other dosage forms.
2.
May have an unpleasant taste or sensation on the tongue.
 Drug particles present in oral liquid medication can come in contact with
taste and sensory receptors of the tongue and can cause bitter or metallic
taste. Sweeteners and flavoring agents are usually added to mask the
taste. Tablets on the other hand are coated and are swallowed quickly to
avoid in contact with taste receptors.
May not be convenient to take due to spillage, requires careful measurement,
special storage and handling.
 Liquid suspension may require refrigeration after reconstitution or
mixing. Accuracy of dose measurement is important.
3.
CLASSIFICATION OF LIQUID MEDICATION DOSAGE FORMS
A.
SOLUTIONS
1.
Aqueous and viscous aqueous solutions use purified water as the vehicle.
Aqueous solutions maybe ingested orally, applied externally or injected into the
bloodstream.
2.
Viscous aqueous solutions can be thick, sticky and sweet. Uses purified water as
vehicle.
3.
Non aqueous solutions are those that use solvents or dissolving liquids in
addition to or instead of water as the vehicle. Examples of non-aqueous solvents are
alcohol, glycerin and propylene glycol.
a.
Hydroalcoholic solution is a mixture of alcohol and water.
b.
Alcoholic solutions are non-aqueous solutions that contain alcohol but no
water.
TYPES OF AQUEOUS SOLUTIONS
1.
Douches. Douches are aqueous solutions that are directed into a body cavity or
against a part of the body to clean or disinfect. They are used to remove debris or
particles from the eyes and to cleanse vaginal area.
2.
Irrigating Solutions. Irrigating solutions are used to wash or cleanse part of the
body such as the eyes, nose, open wounds or skin with debris. These solutions
often contain medications such as antibiotics or other antimicrobial agents.
Irrigating solutions may be used in surgical procedures to clear the surgical field
of blood and debris.
3.
Enemas. Enemas are solutions introduce into the rectum to empty the bowel
(Fleet enema) or to treat diseases of lower gastrointestinal tract (Cortenema).
Enemas are commonly used to relieve serious constipation or to cleanse bowel
before surgery.
4.
Gargles. Gargle is a solution that treats conditions of the throat. Although
gargles are admitted into the mouth, they should not be swallowed. Note that some
gargle preparations may also contain alcohol.
5.
Wash. Wash is a solution used to cleanse or bathe a body part, such as the eyes
or mouth. Mouthwash is a solution used to deodorize, refresh or disinfect the mouth
whereas gargles are used to treat throat conditions (sore throat). Mouthwash should not
be swallowed and may also contain alcohol. Eye wash is a solution used to cleanse the
eye from foreign particles or debris.
6.
Sprays. Sprays are solutions that are delivered as a mist to the area to be treated.
Sprays can be used to the mucous membrane such as nose or throat and can be directly
applied to the skin.
TYPES OF VISCOUS (THICK) AQUEOUS SOLUTIONS
1.
Syrups. Syrup is a concentrated mixture of water and sugar. Syrup may or may
not contain medication. Syrup without the medication is called a flavoring agent or
flavored syrup. Flavored syrups are used as vehicles for unpleasant or bad tasting
medications. The advantage of syrup is its ability to disguise the bad taste of
medications.
Because syrups are thicker than the aqueous solutions , only a portion of the medication
dissolved in the syrup comes in contact with the taste buds, the remainder of the
medication is held above the tongue by thick syrup so it is not tasted when swallowed.
This is the reason why syrups are commonly used for pediatric medications.
2.
Jellies. Jellies are semi solid solutions that contain a high proportion of water.
Jellies are used as lubricants for surgical gloves and rectal thermometers. It is also used
reduce friction during ultrasound procedures.
TYPES OF NON-AQUEOUS SOLUTIONS
HYDROALCOHOLIC SOLUTIONS
1.
Elixirs. Elixirs are sweet, flavored water and alcohol mixtures intended for oral
ingestion. The alcohol content in elixirs depends on the ability of the other ingredients
in the elixir to dissolve in water. Some drugs do not dissolve in pure water but will
dissolve in water-and-alcohol mixture. Because of the alcohol content of elixirs, it has to
be given in caution with pediatric, elderly and alcoholic patients. These patients may be
very sensitive to small amounts of alcohol.
2.
Spirits. Spirits or essences are alcoholic or hydroalcoholic solutions that contain
volatile or easily evaporated substances. Because of the high alcohol content of spirits,
caution should be taken when storing the product, keep away from heat or flame.
ALCOHOLIC SOLUTIONS
1.
Collodions. Collodion is a liquid preparation of pyroxylin dissolved in ethyl
ether and ethanol. After application to the skin, the ether and ethanol evaporate and
leave the pyroxylin film on the skin. Collodions contain medications that are used to
treat warts and corns/callous. Collodion is highly flammable, caution must be taken
when storing the product, avoid excessive heat and flame.
MISCELLANEOUS SOLUTION
1.
Liniments. Liniment is a medication dosage form that is applied to the skin
with friction and rubbing. Liniments can be a solution, or suspension. Liniment is
widely used to relieve minor aches and pain of muscles.
B. EMULSIONS
Emulsions are mixture of two liquids that normally do not mix. In an emulsion,
one liquid is broken into small particles and evenly scattered throughout the other.
Parts of an emulsion
1.
Internal Phase is the liquid present in small particles
2.
External or Continuous phase.
To keep the two liquids from separating, an emulsifying agent is added to the
formulation. The emulsifying agent prevents the small particles of the internal phase
from fusing together and eventually separating from the external phase to form two
distinct layers.
Types of emulsions
1.
Oil-in-water emulsion. O/W consists of small oil globules dispersed throughout
the water. O/W emulsions are commonly intended for oral use. Bad tasting oily
medications are broken into small particles and dispersed throughout a sweetened,
flavored aqueous vehicle.
2.
Water-in-Oil emulsion. W/O consists of water droplets distributed throughout
the oil. W/O emulsions are often used on unbroken or intact skin.
COMPARISON OF O/W AND W/O EMULSIONS
Oil-in-Water (O/W)
Advantages

Improves taste of oral medications

Better absorption of oral medications in the bloodstream

Light, non-greasy feel when used topically

Water washable
Disadvantages

May easily wash off with water or if patient sweats

Does not spread easily on the skin
Water-in–Oil (W/O)
Advantages

Spreads evenly on skin

Soften skins

Not easily washed off
Disadvantages


May stain clothing
Heavy and greasy feel
C.
SUSPENSIONS
Suspensions are mixtures of fine particles of an undissolved solid distributed through a
gas, liquid. Suspensions are useful for administering a large amount of solid medication
that is inconvenient to take as a tablet or capsule. Since drug particles are suspended in
liquid, it is important to shake the suspension really well before using as particles may
have settled in the bottom of the container during storage. Oral suspensions usually use
water as the vehicle. For parenteral suspension, oil is used as the vehicle.
TYPES OF SUSPENSIONS
1.
Lotions. Lotions are suspensions intended for external application. They contain
finely powdered medications to cool, soothe, dry or protect the skin. Lotions can be
worked easily to cover large areas of the skin. Shake well before using.
2.
Magmas and milks. Magmas and milks are thick, viscous suspensions of
undissolved drugs in water. They are usually intended for oral use and must be shaken
well before using.
3.
Gels. Gels are similar to magmas and milk except that the suspended particle
size in gels is smaller. Gels are mostly intended for oral administration. Shake well
before using.
D. EXTRACTIVES
Extractives are concentrated preparations of active components obtained from plant or
animal tissues. The crude drug is extracted from the dried plant or animal tissue by
soaking it in solvent. The solvent is then evaporated, leaving the active component
behind.
1.
Tinctures. Tinctures are alcoholic or hydroalcoholic solutions whose potency is
adjusted so that each milliliter of tincture contains the equivalent of 100mg of crude
drug. Tinctures have high alcohol content and evaporate quickly leaving active
ingredient on skin.
Example: Iodine tincture
2.
Fluidextracts. Fluidextracts are more potent than tinctures, each milliliter of
fluidextract contains the equivalent of 1000mg of crude drug.
Example: Cascara sagrada fluidextract and Senna Fluidextract.