NTA Level 4 • Semester 1 • PST04104

Routes of Drug Administration

Pharmaceutical Dosage Forms • Source Session/Topic 7

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Session 7: Routes of Drug Administration

Total Session Time: 120 minutes

Prerequisites

• None

Students Learning Tasks

By the end of this session students are expected to be able to:

• Define Route of Drug Administration

• Explain the Major Routes of Drug Administration

• Explain Advantages and Disadvantages of Each Route of Drug Administration

Resources Needed:

• Flip charts, marker pens, and masking tape

• Black/white board, chalk and whiteboard markers

• Overhead projector (OHP)

• Computer

SESSION OVERVIEW

SESSION CONTENTS

STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)

READ or ASK students to read the learning tasks and clarify

ASK students if they have any questions before continuing

STEP 2: Definition of Route of Drug Administration (10 minutes)

|Activity: Brainstorming (5 minutes) |

| |

|Ask students to brainstorm on the following question: |

| |

|What is a route of drug administration? |

| |

|ALLOW few students to respond |

| |

|WRITE their responses on the flip chart/ board |

| |

|CLARIFY and SUMMARISE by using the content below |

• A route of drug administration is the path by which a drug is brought

into contact with the human body

• The choice of which route of drug administration to be used depends on

two factors which are:

o The existing preparations of the drug

o The state of the patient: Emergency or the impossibility of intake to

some routes

• When administering a drug, ensure that the pharmaceutical preparation is

appropriate for the route specified

STEP 3: Major Routes of Drug Administration (15 minutes)

|Activity: Buzzing (5 minutes) |

| |

|ASK students to pair up and buzz on the following question for 2 |

|minutes |

| |

|What are the major routes of drug administration? |

| |

|ALLOW few pairs to respond and let other pairs to add on points not |

|mentioned |

| |

|WRITE their response on the flip chart/board |

| |

|CLARIFY and SUMMARIZE by using the content below |

• There are four major routes of drug administration which are commonly

used:

o Enteral route

▪ This is the route which involves part of gastrointestinal tract

▪ Drugs are absorbed into the bloodstream and pass through the

liver on the way to their target organ/tissue

▪ Enteral route includes Oral route, Sublingual route, Buccal

route and Rectal route

o Parental route

▪ This involves injection via a hollow needle into the body at

various sites and to varying depth

▪ Parenteral routes includes Intradermal, Subcutaneous route

(S.C), Intramuscular route (I.M), Intravenous injections (I.V)

o Topical route

▪ Drugs are applied topically to the skin or mucous membranes,

mainly for local action

o Inhalation route

▪ Medication is sprayed or inhaled into nose, throat, and lungs

STEP 4: Advantages and Disadvantages of Each Route of Drug Administration

(80 minutes)

|Activity: Small Group Discussion ( 30 minutes) |

| |

|DIVIDE students into small manageable groups |

| |

|ASK students to discuss on the following question |

|What are the advantages and disadvantages of the different routes of |

|drug administration? |

| |

|ALLOW students to discuss for 15 minutes |

| |

|ALLOW few groups to present and the rest to add points not mentioned |

| |

|CLARIFY and SUMMARIZE by using the contents below |

Enteral Route

• Oral route: The mouth is commonly used route for administering drugs

o Advantage of oral route administration

▪ Most convenient to use

▪ Safe, does not break the skin barrier

▪ The gastrointestinal tract provides a huge surface area for

absorption

▪ The drug can be taken at home by a patient

▪ Portable

▪ No pain, easy to take

o Disadvantage of oral route administration

▪ Absorption can be variable and depends on the chemical

properties of a drug such as ionization, solubility and

stability

▪ Absorption can also depend on the stomach contents. For example

the absorption of tetracycline is inhibited in the presence of

milk

▪ Drugs may affect gastric emptying and this may affect absorption

▪ Inappropriate for patient with nausea and vomiting

▪ Drug may have unpleasant taste and odour

▪ Inappropriate if patient cannot swallow or is unconscious

▪ Drugs may irritate gastric mucosa

▪ Some of the drugs may be partially absorbed or destroyed by the

gastric juices example insulin

• Sublingual route

o The medication is placed under the tongue and allowed to dissolve

slowly

▪ Because of the rich blood supply in this region, there is

rapid onset of the action

▪ The patient is instructed not to move the drug with the tongue

not to eat or drink anything until the medication has completely

dissolved

o Advantage of sublingual route administration

▪ Same as oral route, plus

▪ Drug can be administered for the local effects

▪ More potent than oral because the drug directly enter the

circulation and bypasses the liver metabolism(first pass effect)

o Disadvantage of sublingual route administration

▪ If swallowed drug may be inactivated by gastric juice

▪ Drug must remain under the tongue until dissolved and absorbed

• Buccal route

o The tablet or capsule is placed in the oral cavity between the gum and

the cheek

o The client is instructed not to manipulate the medication with the

tongue; otherwise, it could get displaced to the lingual area where it

will be more rapidly absorbed or to the back of the throat where it

could be swallowed

o Advantage of buccal route administration

▪ Same as sublingual route

o Disadvantage of buccal route administration

▪ The same as sublingual plus

▪ Dose absorbed is unpredictable

• Rectal Route

o This means the drugs passed through the rectum

o Rectal drugs are normally in suppository form, although a few

laxatives and diagnostic agent are given via enema

o Advantage of rectal route

▪ Favours the drugs which has offensive taste or odour, or when it

can be changed by digestive enzymes

▪ Drug released at slow steady rate

▪ It avoids irritation of the upper gastrointestinal tract

▪ Is convenient and safe method of giving drugs when the oral

method is unsuitable particularly when the patient is unconscious

or vomiting severely

▪ Venous blood from the rectum does not pass to the liver thus no

first pass effect

o Disadvantage of rectal route

▪ Absorption is slower than other routes

▪ Irregular and uncompleted absorption

▪ Causes irritation to the rectum

▪ Inconvenience to administer

Inhalation route

• Inhalation is the breathing of air vapour or volatile drugs into the

lungs

• The gaseous drugs are inhaled and absorbed through epithelium of the

alveoli of the lungs

• Drug administered through this route may be for the local or systemic

effects

• Examples of the drug given by inhalation for systemic effects are

volatile anaesthetic agents such as ether and halothane

o Advantage of inhalation route

▪ Acts very quickly because the lungs have a larger surface area

for absorption and reach blood supply

▪ Drugs act at the site of action e.g. in asthmatic condition

▪ Introduces the drug throughout respiratory tract

▪ Can be used to unconscious patients

o Disadvantage of inhalation route

▪ Poor regulation of dosage

▪ Inconvenience in use

▪ Drug intended for localized effect can have systemic effects

▪ Limited to respiratory system only

Topical Route

• This means application of drug locally at an intended site such as skin,

eye, ear or nose

• Used for smoothing and softening the dry and rough areas of the skin

• May also be used to provide antiseptic or bacteriostatic effects in order

to inhibit the growth and multiplication of micro organism

• May also be used to provide a cleansing effects for the removal of dirt

dermis or infected tissue

o Advantage of topical applications

▪ Provide a local effect

▪ Few side effects

o Disadvantage of topical route

▪ Drug can enter body through abrasions and cause systemic effects

▪ May stain clothes

Parenteral route

• The term parenteral “refer to method of drug administration other than

oral and topical

• It is commonly used to indicate the administration of drugs by

“Injections”

• The common types of injections includes, intradermal, subcutaneous,

intramuscular and intravenous

• Drugs given parenterally must be sterile, readily soluble, absorbable,

and non-irritating

• Sterile aseptic technique must be used to avoid infection

• Accurate drug dosage, proper rate of injection and proper site of

injection are essential to avoid harm such as tissue injuries

• An injected drug is irretrievable

• An error in dosage or method or site of injection is not easy corrected

• Intradermal route

o Injection is made in the upper layer of the skin to the dermis

o The amount of drug given is small and absorption is slow

o Common method used for allergy testing

o The injections are best made with a fine, short needle (26 gauge) and

a small barrel syringe

o Advantage of intradermal route of administration

▪ Absorption is slow (this is an advantage in testing for

allergies)

o Disadvantage of intradermal route

▪ Amount of drug administered must be small

• Subcutaneous route

o Small amount of drug in solution are given subcutaneously

(hypodermically)

o The needle is inserted through the skin with quick movement, but the

injection is made slowly and steadily

o Advantage of subcutaneous route

▪ Onset of drug action is faster than oral route

o Disadvantage of subcutaneous route

▪ Involve sterile technique

▪ More expensive than oral

▪ Only small volume of drug can be administered

▪ Some drugs can irritate tissue and cause pain

• Intramuscular route

o Injections are made through the skin and subcutaneous tissue into the

muscular tissue

o Muscle tissue has a rich blood supply, medication moves quickly into

blood vessels to produce more rapid onset of action than the oral

route

o The anatomical structure of the muscle permits this tissue to receive

a larger volume of medication. e.g. deltoid and biceps muscle should

receive a maximum of 3ml

o Advantage of intramuscular injection

▪ Pain from irritating drug is minimized

▪ Can administer larger volume than subcutaneous

▪ This injection is technically easier than via I.V route

▪ The gastrointestinal tract and first pass metabolism are avoided

o Disadvantage intramuscular injections

▪ Break skin barrier

▪ Can produce anxiety

▪ Injections can be painful

▪ Self-administration is difficult

▪ Rarely, abscesses can form at the site of injection

▪ The needle may puncture a small blood vessel and cause bruising

of the skin

• Intravenous injections

o Medications and fluids are administered directly into the blood stream

and immediately available for use by the body

o The I.V route is used when a very rapid onset of action is desired

o It requires skill and sterile asepsis, and the drug must be highly

soluble and capable of withstanding sterilization

o I.V route is of great value in emergencies

o Advantage of I.V route

▪ A rapid onset of action

▪ The entire injected dose is almost instantly available, since it

bypasses the gastrointestinal tract and first pass metabolism

▪ A lower dose is administered than if the drug is given orally

▪ Administration is useful for drugs that are irritant when

administered intramuscularly

o Disadvantage of I.V routes

▪ Break skin barrier

▪ Limited to highly soluble drugs

▪ Drug distribution inhibited by poor circulations

▪ The drug has to be administered by trained person

▪ Involuntary injection into an artery can cause arterial spasm

with resulting tissue damage

▪ Accidental overdose can have serious consequences

STEP 5: Key Points (5 minutes)

• A route of drug administration is the path by which a drug is brought

into contact with the human body

• The choice of which route of drug administration to be used depends on

the existing preparations of the drug and the state of a patient

• There are four major routes of drug administration which are commonly

used. These are enteral, inhalation, parenteral and topical routes

STEP 6: Evaluation (5 minutes)

• What is the route of drug administration?

• What are the types of parenteral route?

• Which are factors to consider when selecting the route of drug

administration?

• What are the advantages of Intravenous route over oral route?

References

Aulton, M.E.,Taylor, M.K. (2001). Pharmaceutics: The Science of dosage form

design

(2nd ed.). USA: Churchill Livingstone

Cooper, J.W., Gunns, C., & Carter, S.J. (2008). Dispensing for

Pharmaceutical Students

(12th end). Delhi, India: CBS Publishers and Distributors.

Rawlins, E.A. (2001).Bentley’s Textbook of Pharmaceutics (8th ed.). London,

UK:

Bailliere Tindall.

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