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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

ORAL:

Both liquid and solid dosage forms of a drug are swallowed;most commonly employed route of drug administration.

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Advantages

Safe.

Convenient.

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 PASSEFFECT.

Drug absorption affected by intake of food.

Some drugs produce irritation to gastric mucosa.

First-pass Effect

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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 drug effects by spitting

remaining drug.

First pass effect is avoided.

Drug absorption and effects are quick.

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.

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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.

First pass effect is avoided.

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. Inconvenient and painful.

Chances of nerve and blood

vessel damage.

Danger of infection, if proper sterilization techniques are not

used.

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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.

Rapid onset of action.

Drugs can be given in presence of vomiting and diarrhea.

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INTRAVENOUS

Advantages:

Useful for unconscious patients.

Useful in emergency situations.

First pass effect is avoided.

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.

INTRAVENOUS:

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.

INTRAVENOUS:

Disadvantages:

Technical person is needed, self-administration is difficult.

Expensive.

Inconvenient and painful.

Danger of infection, if proper sterilization techniques are not

used.

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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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INTRAMUSCULAR:

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 to major nerves.

Intramuscular injections are given at an angle of 90 degrees.

Advantages

Rate of absorption is uniform.

Rapid onset of action.

Irritant substances can be given.

Drugs can be given to unconscious patients.

Accuracy of dosage is ensured.

Useful in emergency situations.

First pass effect is avoided. 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.

Disadvantages

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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.

Danger of infection, if proper sterilization techniques are not

used.

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.

First pass effect is avoided.

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 canoccur.

Absorption of the drugs is slow than I/M injection.

Expensive.

Danger of infection, if proper sterilization techniques are not

used.

Large volumes of drug can not be given.

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INHALATION:

Gases, volatile liquids and solids (in the form of finely dividedpowders) are inhaled for systemic and local effects.Inhalation of solids is called insufflation.

Advantages

Rapid absorption of the drug due to large surface area.

First pass effect is avoided.

Rapid local effects.

Disadvantages

Only few drugs can be administered.

may produce irritation of pulmonary mucosa.

Inconvenient procedure.

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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 rectumfor 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 resultantpreparation on skin, this method is called innunction.

INTRAVESICULAR

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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.

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

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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

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 orlonger 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 innon-aqueous vehicles.

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