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Routes of Administration of Drugs:

Learning Objectives:

At the end of the lecture, the student should be able to :

Describe the routes of administration of drugs.

Give the advantages of the each of the route of administration of drug.

Discuss the disadvantages of the drugs given by various routes.

ROUTES OF DRUG ADMINISTRATION:

A drug can be given systemically & Locally.

Systemic routes are divided into:

ENTERAL:

Oral, Sublingual, Rectal.

PARENTERAL:

Intravenous, Intramuscular, Subcutaneous.

Intra-arterial, Intra-articular, Intra-dermal.

INHALATIONAL.

TOPICAL & LOCAL APPLICATION

ROUTES OF DRUG ADMINISTRATION:

ORAL:

Both liquid and solid dosage forms of a drug are swallowed;

most commonly employed route of drug administration.

Advantages

Safe.

Convenient.

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Economical.

Drug absorption is good due to extensive surface area.

Disadvantages:

some drugs have slow absortion.

Onset of drug action is slow.

Irritable and unpalatable drugs can not be given.

Not utilized in unconscious and uncooperative

patients.

Cannot utilize in severe vomiting.

Some drugs are destroyed in stomach like insulin

etc.

Drugs after absorption are metabolized in liver

before reaching the systemic circulation, this is

called FIRST PASS EFFECT.

Drug absorption affected by intake of food.

Some drugs produce irritation to gastric mucosa.

SUBLINGUAL:Solid or liquid dosage form of drug is kept below the tongue for short

period of time to be absorbed through oral mucosa.

Advantages

economical ; specific apparatus or

sterilization is needed.

Quick termination of undesirable drugeffects by spitting remaining drug.

First pass effect is avoided.

Drug absorption and effects are quick.

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Disadvantages:

Bitter tasting and unpalatable drug.

Irritation of oral mucosa.

can not give to unconscious patient.

Large quantities can not be given.

can not be given in severe vomiting.

some drugs are absorbed through oral mucosa,like nitroglycerine.

RECTAL:

Solid and liquid forms of drugs can be given through

rectum.

solid drug given rectally is known as SUPPOSITORY.

Liquid drug given rectally is called ENEMA..

Drugs are used to produce local or systemic effects.

Advantages

used in children.

Little first pass effect.

Can be given in vomiting.

Can be given in unconscious patient.

Higher therapeutic concentrations of drug are

achieved rapidly in rectum.

for rapid evacuation of bowel, usually during gut

sterilization before any surgical or radiological

procedure.

Disadvantages

inconvenient.

Drug absorption is slow and erratic.

Irritation or inflammation of rectal mucosa can occur.

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PARENTERAL ROUTES:

Advantages

Rapid onset of action.

can be given to unconscious patients.

Accuracy of dosage is ensured.

Useful in emergency situations.


Drugs producing gastric irritation can be given.

Drugs that are not absorbed from G.I.T can be given.

Drugs destroyed by gastric acid can be given.

can be given in presence of vomiting and diarrhea.

Disadvantages:

Less safe.

side effects produced, are difficult to control.

Technical person needed

self-administration is difficult .

Expensive.

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Inconvenient and painful.

Chances of nerve and blood vessel damage.

Danger of infection, if proper sterilization techniques are not used.

INTRAVENOUS:

Advantages

No absorption required;

bioavailability is 100%.

Desired blood concentration of drug is achieved

quickly and can be maintained.

Large volume of drug can be given.


Drugs can be given in presence of vomiting and

diarrhea.

INTRAVENOUS:

Advantages:

Useful for unconscious patients.




Drugs that are not absorbed from G.I.T can be

given.


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Disadvantages:

Extravasation of drugs produces irritation and

cellulitis.

Chances of thrombophlebitis.

Repeated I/V administration requires patent veins,

sometimes that may not be possible.

Less safe, once the side effects produced, they are

difficult to control.

Disadvantages:

Technical person is needed, self-administration is difficult.

Expensive.

Inconvenient and painful.


INTRAMUSCULAR:

Drugs injected in deltoid muscle or gluteal region.

Intramuscular injections are given at:

deltoid, gluteus maximus and vastus lateralis.

Deep I/M injections are

less painful than I/M

injections on arm due to

high fat content.

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Absorption of drug from gluteal region is slow

especially in females due to high fat deposition.

Deep intramuscular injections are given at upper

outer quadrant of buttock to prevent the injury tomajor nerves.

Intramuscular injections are given at an angle of

90 degrees.

Advantages

Rate of absorption is uniform.


Irritant substances can be given.

Drugs can be given to unconscious patients.

Accuracy of dosage is ensured.




Drugs that are not absorbed from G.I.T can be given.


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Disadvantages

Small quantities up to 10 ml of the drug can be given at a time.

Local pain and abscess formation.

Technical person is needed, self-administration is difficult.

Expensive.


Chances of nerve damage.

SUBCUTANEOUS:

Drugs are injected below the skin.

Advantages:

Actions of the drugs are sustained and

uniform.

Drugs can be given in presence of vomiting

and diarrhea.

Drugs can be given to unconscious patients.


Drugs that are not absorbed from G.I.T can

be given.

Disadvantages:

Only non-irritant drugs can be given otherwise

severe irritation, pain and necrosis of

subcutaneous tissues can occur.

Absorption of the drugs is slow than I/M

injection.

Expensive.

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Large volumes of drug can not be given.

INHALATION:Gases, volatile liquids and solids (in the form of finely divided

powders) are inhaled for systemic and local effects. Inhalation

of solids is called insufflation.

Advantages

Rapid absorption of the drug due to large surface area.


Rapid local effects.

Disadvantages:

Only few drugs can be

administered.

may produce irritation of

pulmonary mucosa.

Inconvenient procedure.

Chances of cardiotoxicity.

Systemic side effects may be produced due to rapid absorption of drug.

Poor ability to regulate dose.

TOPICAL OR LOCAL APPLICATION:

Drugs may be applied to skin and mucous

membrane of eye, ear, nose, throat, mouth,

urinary bladder, vagina and rectum for local

effects, this is called topical or local

application.

Drugs are given in the form of ointments,

creams, lotions, and powders.

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TOPICAL OR LOCAL APPLICATION:

Some drugs like nitroglycerin and scopolamine are

absorbed through intact skin and are used to

produce systemic effects, in the form of transdermal

patches.

Absorption of the drug through skin can be increased

by suspending the drug in oily vehicle and rubbing the resultant preparation

on skin, this method is called innunction.

INTRAVESICULAR:

Agents used: Mitomycin, Doxorubicin,

Instilled into bladder via catheter

Side effects: excoriation, pain in bladder, hematuria

INTRA-ARTERIAL ROUTE:

Used for liver cancer treatment

Cannulate hepatic artery; continuous infusion of chemo; may use implanted

pump

High concentration directly to tumor bed

High rate of complication with arterial catheters

Chemotherapy agents: 5-FU

INTRAPERITONEAL ROUTE:

Indication: Colon and Ovarian

Peritoneal space has much surface area; may not be reached by IV chemo

Catheters used: implanted port

Chemotherapy agents used: Cisplatin, Taxol

Advantages: less systemic side effects

Disadvantages: infection, pain.

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INTRAPLEURAL:

Seeding of pleura

Used as sclerosing agent to stop pleural effusions

Injected by physician into chest tube and clamped. Patient changes position

15 min for 1 hour

Chemotherapy agents used: Bleomycin, Adriamycin, Talc slurry

Side effects: severe pain

INTRATHECAL ROUTE:

Meningeal spread of cancer

Prophylaxis in Acute Lymphocytic Leukemia

Lumbar Puncture

Chemotherapy drugs used: Methotrexate

Never used Vinca Alkaloids

(causes immediate death)

Side effects minimal;

mild headache or nausea

Notify physician for neck rigidity or change in level of consciousness

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Route for administration

-Time until effect-:

INTRAVENOUS 30-60 seconds

INTRAOSSEOUS 30-60 seconds

ENDOTRACHEAL 2-3 minutes

INHALATION 2-3 minutes

SUBLINGUAL 3-5 minutes

INTRAMUSCULAR 10-20 minutes

SUBCUTANEOUS 15-30 minutes

RECTAL 5-30 minutes

INGESTION 30-90 minutes

TRANSDERMAL (topical) variable (minutes to hours)

Time-release preparations:

Oral - controlled-release, timed-release, sustained-release designed

to produce slow, uniform absorption for 8 hours or longer better

compliance, maintain effect over night, eliminate extreme peaks and

troughs.

Depot or reservoir preparations - parental administration may be

prolonged by using insoluble salts or suspensions in non-aqueous

vehicles.

The ROA is determined by the physical characteristics of the

drug, the speed which the drug is absorbed and/ or released,

as well as the need to bypass hepatic metabolism and achieve

high conc. at particular sites

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THANK YOU!!

lec10-sem4-week1-20110625

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