Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
Uploaded bydrarunsingh4
749 views

Routes of Drug Administration (Enteral & Parenteral).pptx

The document details various routes of drug administration, including enteral, parenteral, topical, and their respective advantages and disadvantages. Each route, such as oral, sublingual, intravenous, and inhalational, is discussed in terms of its application, onset of action, and suitability for various clinical scenarios. It highlights the importance of understanding these routes to optimize pharmacological effects and patient care.

Health & Medicine◦
Route of Drug Administratio n Dr Arun Singh MBBS, MD Assistant Professor
Learning Objectives Introduction Classification Enteral Route Parenteral Route Topical Route
Introduction For any drug to exert its pharmacological effects, it must reach its site of action. This usually necessitates its bio transportation across the cell membranes, which cannot be achieved unless the drug is purposely administered to produce its effects systemically or locally. Hence in this chapter the discussion will be centered around how drugs are administered, i.e., what are the different routes of their administration.
Classification • The major routes of drug administration are: I. Enteral Routes i) Oral ii) Sublingual iii) Rectal II. Parenteral Routes A) Injections i) Intravenous ii) Intramuscular iii) Intraperitoneal iv) Intrathecal v) Intramedullary vi) Intra-arterial vii) Intra-articular viii) Subcutaneous ix) Intracardiac x) Epidural B) Inhalational Administration C) Transdermal Administration III. Topical Routes i) Conjunctival, Nasal and Auditory mucosal ii) Vaginal and Urethral iii) Inunction and Dermal
Enteral Routes • Placement of a drug directly into any part of the gastrointestinal tract is called an ‘enteral’ mode of administration (Gk. enteron = intestine).
i) Oral Administratio n Site: • Swallowing a drug through mouth. Advantages: • Most commonly used method as it is safe, convenient and painless procedure. • Besides, it is economical as sterilization of drug is not essential.
Disadvantages: (i) Drugs have slower onset of action as their absorption is slow and erratic. • Many drugs being highly polar (e.g., aminoglycoside group of antibiotics— streptomycin) or being quaternary salts (e.g., d-tubocurarine) are not absorbed and hence cannot be given orally to provide systemic effects.
(ii) Drugs that are destroyed by digestive juices (e.g., penicillin-G, insulin, oxytocin and testosterone) cannot be administered by this route. (iii) Drugs having first-pass effect, i.e., those destroyed in liver before reaching systemic circulation (e.g., nitro glycerine morphine, isoprenaline) are not preferred to be given by this route.
(iv) Palatability of drugs is essential. • Drugs cannot be given by this route to an unconscious and uncooperative patient or to a patient having nausea, vomiting and diarrhoea. • Examples with Dosage Forms: Majority of drugs in solid dosage forms (e.g., tablets, capsules and powders) or in liquid dosage forms (syrups, elixirs and mixtures) are usually given orally.
• Majority of drugs given orally provide systemic effects, excepting a few which are administered orally to provide local effect, e.g., antacids and antidiarrheal drugs, such as norfloxacin, neomycin, pectin and kaolin, etc.
ii) Sublingual (and buccal) Administratio n Site: The drug is placed beneath the tongue or crushed in mouth and spread over the buccal mucosa. Advantages: (i) Quick onset of action because of rapid absorption taking place through buccal or sublingual mucosal membrane, (ii) After absorption, the drug passes directly into the systemic circulation, bypassing the portal circulation, thus avoiding first- pass degradation (iii) The drug can be spitted out if side effects are observed.
Disadvantages: (i) Distasteful, irritant drugs cannot be given. (ii) Unfortunately, drugs of higher molecular weights are not well absorbed by this route; otherwise, it could have been an extremely useful method for drugs like insulin or other peptides.
Examples with Dosage Forms: Isosorbide dinitrate and nitroglycerin tablets (for angina); and nifedipine in liquid form (after crushing the capsule, for hypertension). Drugs administered by this route mainly provide systemic effects except for the use of antiseptic lozenges which provide a local effect over buccal mucosa.
iii) Rectal Administratio n Site: Through rectum. Advantages: (i) Can be useful for patients having nausea and vomiting (ii) First-pass degradation is relatively less , as a major portion of the drug is absorbed from external hemorrhoidal veins (iii) Useful for gastric irritant drugs also.
Disadvantages: (i) Chances of rectal inflammation. (ii) Absorption is unreliable. (iii) Inconvenient and embarrassing to the patient. Examples with Dosage Forms: (i) For local effects: bisacodyl and glycerine suppositories, enemas and ointments. (ii) For systemic effects: aminophylline (bronchodilator) and indomethacin (anti-inflammatory agent) suppositories.
PARENTERAL ROUTES Routes other than “enteral” are called ‘parenteral’ routes of administration (Gk.por=aside from). Thus, the administration of drugs by injection, by topical application to skin or by inhalation through the lungs are all parenteral. However, for convenience and better understanding, topical routes will be discussed separately.
A) Injections • Majority of them provide fast systemic effects bypassing first-pass inactivation.
(i) Intravenous Administratio n Site: Through lumen of the veins, mainly the antecubital vein. Advantages: (i) The drug enters the systemic circulation directly, bypassing first-pass degradation (100% bioavailability). • There is a quick onset of action, and a lesser dose is required to achieve the desired plasma concentration (valuable in emergency). (ii) Can be employed even in unconscious, uncooperative patients and in those having nausea, vomiting and diarrhoea.
(III) Hypertonic solutions and GIT irritant drugs can also be infused by this route. (IV) Large volume of fluids can be infused at a uniform rate by this route. (V) Amount of the drug can be controlled with an accuracy not possible by any other route.
Disadvantages: (i)Strict aseptic conditions are needed and the patient has to depend on somebody forgiving an injection. (ii) Besides being painful, it is risky because once the drug is injected it cannot be recalled. (iii) Introduction of any particulate matter or air may produce embolism which may prove fatal.
(iv) Drugs in suspension or oily drugs cannot be administered by this route, as a result there are no depot injections’ available for this route. (v) Venous thrombosis, thrombophlebitis and necrosis around the site of injection can result if extravasation occurs.
Examples with Dosage Forms: Glucose (GDW), Glucose Normal Saline (GNS), dopamine and norepinephrinc drips for I.V. infusion. Many antibiotics, barbiturate anaesthetics, diazepam, heparin, etc. are injected by this route. The route provides mainly systemic effects of drugs.
ii) Intramuscular Injection Site: Deltoid muscle or gluteal mass of left or right buttock. Vastus muscle underlying the lateral surface of the thigh may also serve as an alternative area. Advantages: (i) Absorption is more predictable, less variable and rapid compared to oral and subcutaneous route. (ii) Depot injections can also be given by this route, for obtaining sustained drug effects.
• Disadvantages: (i) Perfect aseptic conditions are needed. (ii) Chances of abscess at the site of injection. (iii) Chances of nerve damage leading to paresis of muscle supplied by it . (iv) Large volumes cannot be administered (maximum of 5 ml).
Examples with Dosage Forms: • Various antibiotics, antiemetics and depot injection of testosterone, and neuroleptics (haloperidol and perphenazine depot injection). • The route provides mainly systemic effects of drugs.
iii) Intraperitone al Administratio n • Site : Into the peritoneal space. Advantages: Rapid absorption due to larger surface area. Disadvantages: • Painful, risky due to chances of adhesions and infections in peritoneal cavity (peritonitis). • Aseptic conditions are needed.
Examples with Dosage Forms: Less in use except for administering dialyzing fluids for peritoneal dialysis in cases of poisoning and renal failure. Most commonly used procedure for administering drugs in laboratory animals. The route provides mainly systemic effects.
iv) Intrathecal (intraspinal) Administration • Site: Into the subarachnoid space. Advantages: • The drug after diffusing from the lumbar sac passes into the subarachnoid space, bypassing the blood-brain barrier and blood-CSF barrier. • Thus, significant CSF levels are provided which otherwise are not possible by any other route. • The drug acts directly on meninges and the spinal cord. Disadvantages: Strict aseptic conditions and great expertise is needed to give such injections. Moreover, it is a painful and risky procedure.
• Examples with Dosage Forms: (i) Many radiopaque contrast media for myelography (to visualize spinal cord) (ii) Xylocaine injection for providing spinal anaesthesia. oMainly provide local effects but certain antibiotics used to treat infectious meningitis do provide systemic effects when given by this route.
v) Intramedullary Administration Site : Injection into the tibial or sternal bone marrow. Advantages: Onset of action very fast as the vascular spaces of bone marrow communicate directly with the large veins.
Disadvantages: • Risky, painful, strict aseptic conditions are needed and skill is also needed to give such injections. Examples with Dosage Forms: • Bone marrow transplantation. • Sometimes (but rarely) blood is also transfused by this route, specially in children, if veins are not available. • Mainly provide systemic effects.
vi) Intra- arterial Administrati on • Site: Into the lumen of the desired artery. Advantages: • Greater concentration of the drug can be delivered at the desired site of action. Disadvantages: Great expertise and aseptic conditions are required.
Examples with Dosage Forms: • Radiopaque contrast media for coronary angiography and cerebral angiography, and many anticancer drugs, are perfused through the artery to treat malignancy involving limbs. • The route mainly provides local effects, in the areas supplied by the injected artery.
vii) lntra-articular Administration • Site: Injection directly into the joint space. • Advantages: Ensures higher concentration of drug in a localized area. • Disadvantages: (i) Strict aseptic conditions are needed. (ii) Repeated administration into the joint space may further damage the joint. (iii) Painful procedure.
Examples with Dosage Forms: • Hydrocortisone or gold chloride injection for the treatment of rheumatoid arthritis. • The route provides local effects of the drug.
viii) Subcutaneous Administratio n Site: Injection into the subcutaneous tissue under the skin. Advantages: (i) Smooth but slower absorption for a longer period compared to intravenous or intramuscular route. (ii) Depot injections or implants can also be made.
• Disadvantages: (i) Suitable for only small volumes of drugs (maximum 1 ml). (ii) Irritant drugs cannot be administered as sloughing and necrosis may result. (iii) Not suitable in the states of shock as reduced peripheral circulation decreases the rate of absorption.
Examples with Dosage Forms: Subcutaneous injection of local anaesthetics (for local effects') and of insulin (for systemic effects). Vaccines are administered preferably by this route as the active protein reaches the lymphoid tissue directly, through lymphatics, without getting destroyed elsewhere in the body (e.g., by peptidases and esterases in the muscle mass).
• Other related (cutaneous) routes are as follows: a) Intradermal (intracutaneous) Route: • The drug is injected into the outer layers of skin. • The amount of drug given is small and absorption is slow. • A tuberculin syringe is used to give such an injection. • Example: Injection of BCG vaccine, diagnostic tests and allergic sensitization testing in patients.
b) Dermojet Injections: It is a subcutaneous needleless injection of a drug by means of a high-velocity jet projected through a microfined orifice. It is a painless procedure, useful for mass inoculation. c) Pellet and Biodegradable Implants: The drug as a solid pellet or packed in biodegradable tubes is implanted under the skin to provide a uniform but a slow release of the drug lasting over months, e.g., testosterone and contraceptive implants (for systemic effects).
ix) Epidural Injection • The drug is injected through a vertebral interspace between the dura of the spinal cord and the lining of the spinal canal, e.g., lidocaine injection to provide the epidural nerve block (local effect).
x) Intracardiac Injection • This injection is given by a long needle into the heart muscle through the left fourth intercostal space close to the sternum, e.g., injection of adrenaline to restart the heart beat in cases of sudden cardiac arrest (local effect).
B) Inhalational Administration Site: Inspiration through nose or mouth. Advantages: (i) Faster absorption and hence quick onset of action due to larger surface area of alveoli. (ii) Self administration is also possible. Disadvantages: Bronchial irritation leading to increased bronchial and salivary secretions.
• Examples with Dosage Forms: Oxygen and general anaesthetics inhalation (for systemic effects)-, metered aerosol preparations of salbutamol and isoprenaline for treatment of bronchial asthma and inhalation of sodium cromoglycate through spin inhaler as prophylaxis for bronchial asthma (local effect).
C) Transdermal Administration • Transdermal administration is considered under parenteral route because the patches, though applied topically, provide the systemic effects. Site: Adhesive matrix (patch) containing drug is applied to chest, upper abdomen, or mastoid region. • Advantages: Slow but sustained release of the drug for several days; bypasses first-pass hepatic inactivation. • Disadvantages: Nil; however, if irritation results, the site of application can be changed. Examples with Dosage Forms: Nitroglycerin (for angina), scopolamine (for motion sickness) and nicotine (for smoking cessation) transdermal patches for systemic effects.
TOPICAL ROUTES i) Conjunctival, Nasal and Auditory Mucosal: • Ointments or isotonic aqueous solutions of drugs, like sulfacetamide, chloramphenicol, gentamicin and ciprofloxacin are applied or instilled onto the conjunctiva for local effects. • Drugs can also be administered as nasal drops, nasal sprays and as ear drops. • However, absorption through mucous membrane can lead to systemic effects also.
ii) Vaginal and Urethral: • Solutions, ointments, emulsion, foams, tablets, suppositories and pessaries of various sulfa drugs, antifungal agents and metronidazole are used for local application into the vagina while various drug solutions and pencil-shaped bougies are available for urethral use.
iii) Inunction and Dermal Site: Rubbing the drug preparation onto the skin (Inunction) or can be dusted or sprayed over the surface of the skin (Dermal). Advantages: Safe and convenient.
• Disadvantages: (i) Difficulty in ascertaining the amount of the drug absorbed. (ii) Systemic absorption may take place if the skin has abrasions. Examples with Dosage Forms: Various antibiotic- -antifungal ointments, powders and solutions, various lotions, liniments, creams and ointments for their antiseptic, antipruritic and analgesic effects locally. • Similarly, antiseptic powders are dusted while analgesic preparations are sprayed to provide local effects.
Reference • HL Sharma , KK Sharma. Principles of Pharmacology 3rd edition
Routes of Drug Administration (Enteral & Parenteral).pptx