Posology and dosage regimen

Department of Pharmacy
Pokhara University
School of Health and Allied Sciences

Pokhara University
1. Introduction
2. Need for dosage forms
3. Characteristics of dosage forms
4. Classification of dosage forms
• Solid dosage forms
• Liquid dosage forms
• Semi-solid dosage forms
• Gaseous dosage forms
• Other dosage forms
5. Factor affecting dosage forms
6. Conclusion
Presentation on Posology & Dosage
Regimen

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 Posology
The word Posology is derived from the Greek posos- how much, and logos- science. So
Posology is the scientific study of the dosages of drugs especially the determination of
appropriate dosages.
 Dose
Dose is the quantitative amount administered or taken by a patient for the intended
medicinal effect.
 Dosage forms
They are the means by which drug molecules are delivered in appropriate concentration to
the sites of action within the body in order to achieve maximum therapeutic benefit with
minimum toxicity.
Every dosage forms is a combination of the drug and different kinds of non–drug
components called as Excipients or additives. The additives are used to give a particular
shape to the formulation, to increase stability, palatability & more elegance to preparations.
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1. Accurate dose.
2. Protection e.g. coated tablets, sealed ampoules.
3. Protection from gastric juice, e.g. enteric coated tablets.
4. Masking unpleasant taste and odor.
5. Placement of drugs within body tissues , e.g. injection
6. Sustained release medication.
7. Facilitation of Insertion of drugs into body cavities
8. Provide optimum drug action through inhalation therapy.
9. Provide drug action through topical administration at local area of body. e.g. creams,
ointment, emulsion, lotions etc.
10. Use of desired vehicle for insoluble drugs
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1. They should be free from microbial contamination or sterile.
2. They should possess high standard of cleanliness.
3. They should have suitable flavored.
4. They should be free from physical and chemical Incompatibility.
5. They should be suitable for extemporaneous preparation of drug
6. They should be acceptable to patient with respect to aesthetic values such as sight, feel,
taste, small, color.
7. They should be compatible to physicochemical characteristics of drugs and intended to
therapeutic purposes.
8. They are adequately colored to mask unpleasant appearance of drug, to identify the drug and
to indicate warning during the administration of drug.
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• Oral - Powders ,Tablets ,Capsules, Pills etc
• Topical - Ointment ,Cream ,Lotion ,Paste etc
• Rectal – Suppository , Enema ,Ointment etc
• Parenteral – Solution , Suspension ,Emulsion etc
• Vaginal - Suppository ,Ointment ,Tablets , etc
• Inhalation –Inhaler ,Aerosol etc
• Ophthalmic – Eye lotion ,Eye drop etc
• Otic – Ear drop
• Nasal – Tinctures , Oxymels ,Spirits etc
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Regimen

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 Solid dosage forms one of the oldest dosage forms and most of the solid dosage forms are
available in Unit dose.
 Unit dose may be defined as a exact quantity of the drug administered at once. e.g. Tablets,
Capsule, pills, cachets, powders etc.
 When drugs are to be administered orally in dry state, then tablets, capsules are most
convenient dosage forms
 Some of the dosage forms of solids are shown below:
1. Tablets
2. Capsules
3. Pills
4. Lozenges
5. Implants
6. Powder and Granules
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1. Tablets
• A tablet is a hard and compressed
medication in round, oval or square
shape.
• It is prepared by moulding or by
compression with or without excipients.
• A coating may be applied to hide the
taste of the tablet components or to
make the tablet smoother and easier to
swallow.
 Sugar coated tablets: It contains sugar
coating on outer layer which protect
medication and improve both appearance
and flavor.
 Film coated tablets: It contain outer
layer of polymer that can either soluble or
insoluble on water. They are thinner,
lighter in weight and cheaper to
manufacture than sugar coating.
 Enteric coated tablets: Enteric coated
tablets are used for drugs that are used
that are destroyed by gastric acid which
might irritate esophageal tract or
stomach.
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2. Capsule
• Capsules are solid unit dosage forms in
which one or more medicaments enclosed
within a gelatin shell.
• Capsules mainly divided in to two parts
namely as –Body (Longest part of capsule
shell), Cap (Smallest part of capsule shell)
• The capsule are generally prepared by
gelatin. The gelatin of capsule may be
transparent, semi-transparent and may be
colored with code to facilitate indication.
• There are two types of are shells in
capsules namely as
• Hard-shelled capsules: They are
normally used for dry and powdered
ingredients.
Fig-Hard-shelled capsules Fig-soft-shelled capsules
• Soft-shelled capsules: They are
primarily used for oils and for active
ingredients that are dissolved or
suspended in oil.
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3. Pills:
• These are small, rounded solid dosage
forms containing medicaments intended
for oral use.
• The medicaments are mixed with
excipients to forms a firms plastic mass.
• The mass is rolled to uniform pill pipe,
which cut into numbers of uniform pills.
• The pills are spherical in shape &
produced by rolling them under wooden
pill rounder.
4. Lozenges:
• It is a solid preparation consisting of sugar
and gum.
• It is used to medicate the mouth and
throat for the slow administration of
indigestion or cough remedies.
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5. Implants:
• These are dose forms that are placed
under skin by mean of minor surgery.
• They are use as long term contraceptives.
• An example for implant is Norplant. It
contains of six small thin capsules each
consisting 38 mg of Levonorgestrel used
to prevent pregnancy.It is implanted
under the skin in the upper arm of women
by creating a small incision and inserting
the capsules in a fan-like shape.
6. Powder and Granules:
• They are the solid dosage form which is
intended for external use.
• Powders are milled and pulverized by
machines for large scale commercial
manufacture.
Fig-Powder Fig-Granules:
• Granules are larger than powders and are
formed by adding very small amounts of
liquid on powder and mixture is passed
through granular device for granulation.
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 Advantages of Solid Dosage Form
• These are more stable dosage forms.
• It can also be used externally
• Minimum side effect
• Local action
 Disadvantages of Solid Dosage Form
• Some patient particularly children and the seriously ill persons cannot be able to swallow the
solid dosage forms
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• Liquid dosage form may be defined as a liquid-preparation that contains one or more soluble
chemical substances dissolved in a specified solvent.
• The component of the solution which is present in a large quantity is known as “solvent”
where as the component present in small quantity is termed as“solute”
• Liquid dosage forms are intended for external, internal or parenteral use.
 They mainly classified in to two category namely as –
• Monophasic liquid dosage forms
• Biphasic liquid dosage forms
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• Monophasic liquid dosage forms are
represent by true or colloidal solution.
• A solution is homogenous because the
solute is an ionic or molecular forms of
subdivision.
• In case of colloidal solutions, the
solutes are present as aggregates
although they cannot be seen by
necked eye or ordinary microscope.
• It is sub classified as –
1. Internal Use,
2. External use
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1. Solution
• They are clear Liquid preparations for oral
use containing one or more active
ingredients dissolved in a suitable vehicle.
2. Syrup
• It is a concentrated aqueous solution of a
sugar usually sucrose[Concentration of
sugar is 66% (w/w)].
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3. Elixirs
• It is clear, sweetened, aromatic,
hydro-alcholic preparations meant for
oral use.
• The composition of elixirs contained
mainly as ethyl alcohol (active
ingredients), water, glycerin or propylene
glycol, colouring agent, flavouring agent &
reservative.
4. Linctuses
• These are viscous liquid preparations
that’s are used for the treatment of
cough.
• They contain medicament which have
demulcent, sedative or expectorant
action.
• Simple syrup is used a vehicle for most of
the linctuses.
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5. Gargles
• Gargles are aqueous solutions used for
treating throat infection (pharynx and
nasopharynx part).
• They are usually available in concentrated
form with direction for dilution with
warm water before use.
• They are brought in to contact with
mucous membrane of the throat and are
allowed to remain in contact with it for a
few seconds
6. Mouthwash
• These are aqueous solutions with
pleasant or acceptable taste & odor.
• These are used to make clean &
deodorize the buccal cavity or used
for oral hygiene and to treat
infections of the mouth.
• They mainly contain antibacterial
agent, alcohol, glycerin, sweetening
agent, flavoring agent & colouring
agent.
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1. Emulsion
• It a biphasic liquid preparations containing two
immiscible liquid (Continuous Phase & dispersed
phase) made missicible.
• The liquid which is converted into minute
globules is called as dispersed phase & the
liquid in which the globules are dispersed is
called the continuous phase.
 Emulsions are of two types
• Oil on water emulsion: Oil is disperse phase and
aqueous solution is continuous phase
• Water on oil emulsion: Aqueous solution is
disperse phase and oil is continuous phase
2. Suspension
• They are the biphasic liquid dosage forms
of medicament in which finely divided
solid particles ranging from 0.5 to 5
micron are dispersed in a liquid or
semisolid vehicle, with aid of single or
combination of suspending agent.
• The solid particles acts as disperse phase
where as liquid vehicle acts as continuous
phase
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 Advantages of Liquid Dosage Form
• Faster absorption than solids
• Liquid dosage form are used fairly commonly by young children , elders and
seriously ill person who have trouble swallowing the solid dosage form
• The products like adsorbents and antacids are more effective in liquid dosage form
 Disadvantages of Liquid Dosage Form
• Less dosage accuracy
• Problem occur in prevention
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1. Creams
• These are viscous semisolid emulsions
which are meant for external use.
• Cream is divided in to two types namely as
I. Aqueous creams (O/W)
II. Oily creams (W/O)
I. Aqueous creams (O/W)
• They are composed of small droplets of
oil dispersed in a continuous aqueous
phase.
• They are more comfortable and
cosmetically acceptable as they are less
greasy and more easily washed off using
water
II. Oily creams (W/O)
• They are composed of small droplets of water
dispersed in a continuous oily phase.
• They are hydrophobic in nature.
• They are also more moisturizing as they
provide an oily barrier which reduces water
loss from stratum corneum layer of skin.
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2. Ointments
• They are semi-solid and greasy
preparations dissolved, suspended or
emulsified in ointment base for
application to skin, rectum or nasal
mucosa .
• The base is usually anhydrous and
immiscible with skin secretions.
• The ointments are mainly used for their
protective or emollient properties
3. Pastes
• They are basically ointments into which a
high percentage of insoluble solid has
been added.
• Pastes are semisolid preparations
intended for external application to skin
• The pastes are generally very thick & stiff.
• They do not melt at ordinary temperature
& thus forms a protective coating over the
area where they are applied.
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4. Gels
• Gels are semisolid system in which a liquid
phase is constrained within a 3-D
polymeric matrix (consisting of natural or
synthetic gum) having a high degree of
physical or chemical cross-linking.
• They are used for medication, lubrication
and some miscellaneous applications like
carrier for spermicidal agents to be used
intra vaginally.
5. Lotions
• They are usually aqueous, alcoholic or oily
liquid preparations.
• They are intended for external application
without friction or rubbing to the affected
area
• They are use on the skin or applied on a
suitable dressing and covered with a
waterproof dressing to reduce
evaporation.
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 Advantages of Semi-Solid Dosage Form
• It can be used externally
• Local action
• Probability of side effects is reduced
 Disadvantages of Semi-Solid Dosage Form
• There is no dosage accuracy
• The base which is used in the semi-solid dosage form can be easily oxidized
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1. Inhaler
• Inhalers are solutions, suspensions or
emulsion of drugs in a mixture of inert
propellants held under pressure in an
aerosol dispenser.
• It is a medical device used for delivering
medication into the body through the
lungs.
• It is mainly used in the treatment of
asthma and Chronic Obstructive
Pulmonary Disease [COPD].
2. Aerosol
• It is spray in pressurized container that
contain propellant and inert gases which
helps to carry active ingredients to its
location of application.
Regimen

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 Rectal Dosage Forms
1. Suppository
• It is a small solid medicated mass, usually
cone-shaped.
• It is inserted either into the rectum (rectal
suppository), vagina (vaginal suppository
or pessaries) where it melts at body
temperature.
2. Enema
• An enema is the procedure of introducing
liquids into the rectum and colon through
the anus.
Regimen

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 Parenteral Dosage Forms
• Parenteral Dosage Forms or injection is
an infusion method of putting liquid into
the body, usually with a hollow needle
and a syringe which is pierced through the
skin to a sufficient depth for the material
to be forced into the body.
• There are several methods of injection,
including:
1. Intravenous injection
• It is a liquid administered directly into the
blood stream via a vein.
• It is advantageous when a rapid onset of
action is needed.
2. Intramuscular injection
• It is the injection of a substance directly
into a muscle.
• Many vaccines are administered
intramuscularly.
• Intramuscular injections are often given in
the deltoid,vastus lateralis, ventrogluteal
and dorsogluteal muscles.
3. Subcutaneous injection
• Subcutaneous injections are given by
injecting a fluid into the subcutis, the layer
of skin directly below the dermis and
epidermis
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 Vaginal Dosage Forms:
1. Pessary
• Pessaries are solid medicated
preparations designed for insertion into
the vagina where they melt or dissolve.
• The capsules differing only in size and
shape.
2. Vaginal ring
• Vaginal rings are 'doughnut-shaped' polymeric
drug delivery devices designed to provide
controlled release of drugs to the vagina over
extended periods of time.
Fig -Vaginal ring
Fig Douche
3. Douche
• A douche is a device used to introduce a stream
of water into the body for medical or hygienic
reasons.
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 Ophthalmic Dosage Forms:
• Sterile, aqueous/oily solutions or suspensions
intended for instillation in eye sac.
1. Eye Drops:
• Eye drops are saline-containing drops used as a vehicle
to administer medication in the eye.
• Eye drops may contain buffers, stabilizing agents,
dispersing agents, solubilising agents, anti-oxidants &
agents required for tonicity/ viscosity adjustment
• Eye drops sometimes do not have medications in them
and are only lubricating and tear-replacing solution.
2. Eye lotions
• These are the aqueous solutions used for
washing the eyes.
• These are supplied in concentrated forms
& are required to diluted with warm water
immediately before use.
• They are required to prepared fresh &
should not be stored for more than two
days to avoid microbial contaminations.
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 Otic Dosage Forms
• Ear Drops
• These are the solutions of drugs that are
instilled into ear cavity with the help of dropper.
• These are generally used for cleaning the ear,
softening the wax & for treating the mild
infections.
• The solutions is generally prepared in
water, glycerin, propylene glycol & dilute
alcohol.
 Nasal Dosage Forms
• Drugs in solution may be instilled into the nose
from a dropper or from a plastic squeeze bottle.
1. Oxymels
• These are preparations in which the vehicle is a
mixture of acetic acid and honey.
2. Spirits
• They are alcoholic or aqueous alcoholic solutions of
volatile substances used as flavoring agents.
3. Tinctures
• These are alcoholic preparations containing the
active principals of vegetable drugs.
• They are relatively weak compared to extracts.
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1. Age
2. Body weight
3. Body surface area
4. Sex
5. Pathological condition
6. Drug physical state
7. Environmental factors
8. Psychological factors
9. Time of administration
10. Route of administration
11. Tolerance
12. Drug-drug interactions
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1. Age
 According to the age patient may be:
• Neonate –less than 6 months
• Infant -6 months- 2 years
• Child -2-12 years
• Adult -12-45 years
• Old - above 45 years
 Newborn Infants (Pediatric)
• Sensitive to certain drugs because of the
immature state of their hepatic and renal
function
• Failure to detoxify and eliminate drugs results in
their accumulation in the tissues to a toxic level.
 Elderly Patients (Geriatric)
• The decline in renal and hepatic function may
slow drug clearance and increases the possibility
of drug accumulation in the body and subsequent
toxicity.
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2. Body Weight
• The official usual doses for drugs are
considered suitable for 70 kg (150 pounds)
individuals.
• More the body weight have more volume
for drug distribution ,so required more
dose of the drug.
• Therefore, drug dosage may require
adjustment from the usual adult dose for
abnormally lean or obese patients.
 Clark’s Rule:
• Dose for child = Adult dose x Weight in pounds
150
3. Body Surface Area
• Average body surface area of a 70kg adult
is 1.7 to 1.8 sq.meters
• Larger the body surface area more volume
of the drug is needed for distribution, so
required more dose of the drug
• Dose for child dose = Adult x BSA of child
1.8 m2
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4. Sex
• Women are more susceptible to the
effects of certain drugs than are men.
• On the basis of body weight female adults
generally requires smaller doses than
males because percentage of adipose
tissue is greater and percentage of water
is lower in adult females as compared to
adult males.
• Pregnant women and nursing mothers
should use medications only with the
advise and under the guidance of their
physician.
5. Pathological State
• The effects of certain drugs may be
modified by the pathological condition of
the patient and must be considered in
determining the dose.
• Renal failure decreases drug elimination.
• Liver failure decreases drug metabolism
• In such a case the physician can prescribe
an alternate drug.
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6. Drug physical state
• Increasing the surface area of a drug by
the reduction of its particle size has a
significant effect on the rate of absorption
• Therefore the dose can be minimized by
reducing the particle size.
• Thus crystalline and amorphous forms of a
drug shows a significant difference in the
rate of absorption.
7. Environmental factors
• Exposure to insecticides , carcinogens,
tobacco smoke , charcoal , broiled meat
induce drug metabolism.
• Type of diet can alter drug absorption
8. Psychological factors
• Drug’s efficacy can be affected by Patient’s
expectations and attitude .
• Anxious patient requires more general
Anesthetic.
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9. Time of administration
• The time at which a drug is administered
sometimes influences dosage.
• Absorption of drug proceeds more rapidly
when the stomach and upper portions of
the intestinal tract are free of food.
• Similarly many drugs are effective to
administrate before a meal and are
ineffective to administare after the meal
which is based according to disease.
• Irritating drugs are better tolerated by the
patient when food is present in the
stomach to dilute the drug’s
concentration.
10. Route of administration
• Drugs administered intravenously enter
the blood stream directly and thus the full
amount administered is present in the
blood.
• In contrast, drugs administered orally are
rarely fully absorbed due to the various
physical, chemical and biologic barriers to
their absorption, including interactions
with the gastric and intestinal contents.
• Thus, a lesser parenteral dose of a drug is
required than the oral dose to achieve the
same blood levels of drug.
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11. Tolerance
• Tolerance is the resistance to the drugs
but no large dose produce normal
therapeutic action
• Tolerance is acquired by repeated use of
a drug in an Individual who was initially
responsive .
• A continuous presence of drug in the body
can also leads to tolerance
 For example
• The smokers are able to tolerate the
nicotine.
• An alcoholic person are also able to
tolerate a large amount of the alcohol.
• Some children can tolerate the relative
the large doses of arsenic , calomel and
belladonna.
12. Drug-drug interactions
• Drug-drug interactions are due to chemical or
physical interaction between drugs
• It can alter the absorption, distribution,
metabolism or excretion patterns of the drugs.
• The effects of drug-drug interactions may be:
 Beneficial: For example -Probenecid (used in
hyperuricemia) causes prolongation of penicillin
serum levels [as it decreases its renal excretion].
 Detrimental: For example -Tetracyclines (
antibiotic produced Streptomyces bacterium)
can combine with the metal ions such as
calcium, magnesium, aluminum and iron in the
gastrointestinal tract to form complexes that are
poorly absorbed.
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• Dosage forms are the means (or the form) by which drug molecules are
delivered to sites of action within the body.
• Basically there are three divisions of dosage forms: solid, semisolid, liquid.
• Posology is a branch of medical science which deals with dose quantity of
drug which can be administered to a patient to get the desirable
pharmacological action.
• Various factors can effect the absorption, distribution, metabolism or
excretion patterns of the drugs
• So these factors should be taken in consideration during the formulation
of different dosage forms.
Regimen

Posology and dosage regimen

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