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By the end of this lecture, the student should be able to
 Discuss the different routes of drug administration
 Identify the advantages and disadvantages of various routes
of drug administration
 Know the various mechanisms of drug absorption
 List different factors affecting drug absorption
 Define bioavailability
Pharmacokinetics

Pharmacokinetics of drugs
(ADME)
Are studies of
 Absorption
 Distribution
 Metabolism
 Excretion of drugs

Administration
Blood
Absorption
Distribution
Metabolism
Excretion
Different organs &
tissues
Drug
Site of action

Sites of
Administration
Absorption & distribution Elimination

 Enteral via gastrointestinal tract (GIT).
 Oral
 Sublingual
 Rectal
 Parenteral administration = injections.
 Topical application
 Inhalation

Disadvantages
Advantages
- Slow effect
-No complete absorption
- Destruction by pH and enzymes
- GIT irritation
- Food - Drug interactions
-Drug-Drug interactions
- First pass effect
- (low bioavailability).
Not suitable for
 vomiting & unconscious patient
 emergency
 bad taste drugs
- Easy
- Self use
- Safe
- Convenient
- cheap
- No need for
sterilization

First pass Metabolism
 Drugs taken orally are first taken to liver (via
portal circulation) where they are metabolized
before reaching to rest of body.
 so the amount reaching system circulation is
less than the amount absorbed
Results ?
Low bioavailability = low serum level of active
drug that can produce action

04 GENERAL PHARMACOLOGY (absorption).ppt

Oral Dosage Forms (oral formulations)
 Tablets (enteric coated tablets)
 Capsules (hard and soft gelatin capsules)
 Syrup
 Suspension
 Emulsion

Tablets
Hard- gelatin
capsule
Spansule
Soft- gelatin
capsule
Suspension
Emulsion

Disadvantages
Advantages
Not for
- irritant drugs
- Frequent use
 Rapid effect
 can be used in emergency
 High bioavailability
 No first pass effect.
 No GIT irritation
 No food drug - interaction
Dosage form: friable tablet

Disadvantages
Advantages
 Irregular
absorption &
bioavailability.
 Irritation of
rectal mucosa.
Suitable for
 children
 Vomiting or unconscious
patients
 Irritant & Bad taste drugs.
 less first pass metabolism
(50%)
Dosage form:
suppository or enema

Intradermal (I.D.) (into skin)
Subcutaneous (S.C.) (under skin)
Intramuscular (I.M.) (into muscles)
Intravenous (I.V.) (into veins)
Intra-arterial (I.A.) (into arteries)
Intrathecal (I.T.) (cerebrospinal fluids )
Intraperitoneal (I.P.) (peritoneal cavity)
Intra - articular (Synovial fluids)

Disadvantages
Advantages
 Only for water
soluble drugs
 Infection
 Sterilization.
 Pain
 Needs skill
 Anaphylaxis
 Expensive
Not suitable for oily
solutions or poorly
soluble substance
 Rapid action (emergency)
 High bioavailability
 No food-drug interaction
 No first pass metabolism
 No gastric irritation
Suitable for
 Vomiting &unconscious
 Irritant & Bad taste drugs.
Dosage form:
Vial or ampoule

Ampoule Vial
Single use Repeated use

Injection Special Utility Limitations
I.D. minute volume (0.1 ml)
suitable for vaccinations
& sensitivity test
not suitable for large volumes
S.C. 0.1 ml – 1 ml
suitable for poorly soluble
suspensions and for
instillation of slow-release
implants e.g. insulin zinc
preparation
not suitable for large volumes
I.M. larger volume 3-5 ml Suitable
for moderate volumes, for oily
solutions or poorly soluble
substances
not suitable for irritant drugs
Abscess- necrosis may happen
I.V. suitable for large volumes and
for irritating substances
not suitable for oily solutions
or poorly soluble substances
Must inject solutions slowly as
a rule

 Drugs are applied to skin, ear, eye, nose, vagina,
respiratory tract
 Usually used to provide local action.
 No first pass metabolism.
 Used for lipid soluble drugs

Disadvantages
Advantages
Not suitable for
irritant drugs
Only for some
drugs as
inhalation
anesthetics &
bronchodilators
 mucous membrane of respiratory
system
 rapid absorption (large surface
area)
 provide local action in
 limited systemic effect
 less side effects.
 no first pass effect
Dosage form: aerosol, nebulizer

Is the passage of drug from its site of
administration to its site of action through
cell membranes.
Sites of
Administration
Sites of
action
Cell membrane

 Is the fraction of unchanged drug that enters
systemic circulation after administration and
becomes available to produce an action
 I.V. provides 100% bioavailability.
 Oral usually has less than I.V.

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04 GENERAL PHARMACOLOGY (absorption).ppt

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