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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

    Disadvanta