Shivangi Mistry, M.Pharm in Pharmacology, Assistant Professor in BMCP, Routes of administration, oral route, parentral routes

1. MS. SHIVANGI MISTRY
M.PHARM (PHARMACOLOGY)
ASSISTANT PROFESSOR
BHAGWAN MAHAVIR COLLEGE OF PHARMACY

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INDEX
SR.
NO.
CHAPTER PG.
NO.
1. Routes Of Administration Of Drugs 3
i. local route 3
ii. Enteral Or Oral Route 5
iii. Parenteral Or Injectional Route 6
iv. Novel drug delivery system 12

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 ROUTES OF ADMINISTRATION OF DRUGS:
 Drugs can be administered upon or into the body.
 On the skin and mucus membrane, drugs can be applied to produce localized effect.
 When drugs are given through mouth (oral route) or by injections (parenteral route) they
are absorbed into the blood stream and are distributed throughout the body fluids which
prevales all over the body. Such a effect produced by the drug is called systemic effect.
 There are three main routes of drug administration:
1. Local,
2. Oral or Enteral and
3. Injectional or Parenteral.
I. LOCAL ROUTE
 Drugs are locally administered on the skin and mucus and serous membranes. Powder,
paste, lotion, liniment, cream, ointment, plaster drops (nasal eye or ear) etc. are generally
used on the skin or mucus membranes.
 Application of drugs on the skin may be
(a) Enepidermic: Simple application of medicament on the skin.
(b) Innunction: Application of medicament by rubbing.
(c) Iontophoresis: Iontophoresis is a special method of applying drug to and pushing it
through the skin to reach the blood vessels and surrounding deeper tissues by electric
transmission.
 The drug is soaked in a wet pad and kept at the site of absorption. An electrode,
having the same polarity as the free drug, is kept above it. Since the polarity is same
in the electrode and the drug; the drug ions are repelled and thus the drug enters
through the skin.

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 In case of arthritis, i.e. an joint inflammation, methyl salicylates are administered by
iontophoresis.
(d) Irradiation: Rays are also applied to the skin both for local and systemic action, e.g. for
skin conditions local application of ultraviolet rays and deep as X-rays for systemic
action.
 drugs can be applied and smeared in Through lamellae (eyes), pessaries (vagina),
suppositories (rectum), bougie the (urethra) etc. drugs can be used locally for long time.
 Administration of drugs through nose:
 Drugs are either instilled to insufflated into the nose, applied, sprayed of inhaled in the
nasopharynx and tracheobronchial tree.
 In the nose, nasal drops are instilled or rarely pituitary snuff is insufflated whereas,
adrenaline is sprayed with an atomizer into the nasopharynx and tracheobronchi during
asthma carried attacks.
 In laryngitis For diagnostic or bronchitis purposes, tincture, benzoin iodine inhalations
are carried out. For diagnostic purpose, organic iodine in lipoidal form is tricked
through trachea for bronchography.
 Systemic use of drugs through lungs is inhalation of gas anaesthetics, e.g. chloroform,
ether etc. The gas being absorbed and carried through blood, all over is local the body,
viz. alveoli of lungs. Drugs like penicillin may also be introduced into route the
systemic circulation and locally in intractable places through lungs by inhalation of
drug-vapour clouds. This methods is however, hazardous.
 Enema: It is the administration of liquid medicament per rectum.
 Rectum has rich supply of blood and lymph which are useful for the absorption of the
drug so administration.

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 Evacuant enema: Soap water enema is a type of evacaunt enema. Amount of fluid is 600
ml. Water stimulates rectum by distension while soap acts as a lubricant. There is
increase in peristalsis and finally evacuation. It is usually given before surgical operation,
delivery or radiological investigation of gastro intestinal tract.
 Retention enema: In this type of enema drugs are given along with enema. Volume of
fluid administered is 150 ml. Examples of such enema are glycerine vegetable oil in
constipation, paraldehyde for basal anaesthesia, prednisolone in ulcerative colitis,
magnesium sulphate for cerebral edema.
II. ENTERAL OR ORAL ROUTE
 This is the most ancient convenient and commonly used route of administration of drug.
Drugs administered by oral route can have:
(a) Local Action: Kaolin as a local adsorbent; streptomycin for local antibiotic action in
intestine; glycerine tannic acid for astringent action on gums. Such an action is also
called ' topical action'.
(b) Reflex Action: Gentian as bitter reflex sialogogue, ammonium chloride as reflex
expectorant and as a reflex emetic in large doses.
(c) Systemic Action: Drugs like aspirin as analgesic and antipyretic; barbiturates as
hypnotics; anthracene group of drugs as purgative and other innumerable drugs can be
listed since most drugs are administered orally for their systemic action, i.e. after
absorption through the body fluids.
 Advantages of oral route:
(1) It is safe.
(2) It is convenient.
(3) It is economical.
(4) Self medication is possible.
(5) Absorption is selective as per need (e.g. iron in anemia).

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 Disadvantages of oral route:
(1) The absorption may be uneven and hence their blood levels can not be a predicted. Many
times this is inconsistent and erratic.
(2) The onset of action is slow.
(3) Drugs are either destroyed or sltered after absorption in the gaso-intestinal tract and also
in the liver (bitransformation). This is known as the “first pass effect”.
(4) Irritant and unpalatable drugs cannot be administered since they will be vomited out.
(5) A person who has severe diarrhoea or vomiting or is unconscious convulsive or non-co-
operative, cannot be given drugs safely by this route.
(6) Larger dose of drugs are required. Phenytoin is an exception where oral route requires
smaller dose as compared to parenteral route.
(7) Acid resistant drugs cannot be given.
(8) Some drugs may form complexes with food, e.g. tetracycline.
(9) Some drugs destroyed by acid or enzymes in the gut cannot be given e.g. insulin, benzyl
penicillin.
 Sublingual: The drug in the form of a tablet is put under the tongue. Only lipid soluble
and non-irritating drugs can be administered by this route. The drug is thus absorbed
straight into systemic circulation through the sublingual route without passing through
the liver.
 Hence, it does not undergo reduction in its potency. Another advantage is that if it is
found toxic, it can be spit out to safety. The drug most commonly used by this route is
glyceryl trinitrite in angina pectoris and isoprenaline in asthma. If the drug is to be used
in large amount and frequently, then this route becomes inconvenient.
III. PARENTERAL OR INJECTIONAL ROUTE
 Here, the drug does not enter gastrointestinal tract (thus called parenteral) but is passed
directly into the circulation.
 Following are the advantages of parenteral route:
1. There is quick onset of action.
2. Drug can be given to an unconscious or non-co-operative patients.

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3. Desired concentrations can be achieved.
4. Drug can be given to patients suffering from diarrhoea and vomiting.
5. Drugs that irritate the stomach or cannot be absorbed from the stomach or intestine, can
be given by this route.
6. Comparatively smaller doses are required for the effect.
7. The metabolism of drug prior to its entry into circulation (usually by liver) i.e. the " by-
pass" effect is avoided.
 But there are number of disadvantages:
(1) The “shot' is painful and expensive and needs surgical sterility and proper technique of
administration. It must therefore be resorted to, only when it is a must.
(2) It is inconvenient.
(3) Self medication is not possible.
(4) It is a risk factor for diseases like hepatitis, AIDS etc.
 There are many route for the parenteral or injectional method of drug administration such
as inoculation, intradermal, subcutaneous, intramuscular. intravenous, intracardiac,
intrapleural, intraperitoneal, intramedullary, intracisternal, intraspinal, intraarterial,
intraocular etc. Inhalation is also considered as parenteral route.
(a) Intradermal :
 Drug is given within the skin layers. (dermis).
 This route is used for testing sensitivity to drugs, e.g. penicillin, antitetanusserum
(ATS) etc.
 Highly diluted and a small quantity of drug is administered. Even this is painful.
 Absorption is through the lympathics.
 Intradermal sensitivity test gives a clue as to whther the drug (to be injected) would
be safe or allergic in nature for the concerned patient.
 Inoculation : small pox vaccine is administered by superficial puncturing or scaring
of epidermis. The vaccine drop is slowly absorbed by lymphatics. Administration of
vaccine by intradermal route is known as inoculation.

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(b) Subcutaneous :
 Drugs are injected under the skin. Their absorption is slow, hence the action is prolonged.
 Slow, hence, the action is prolonged.
 Sometime, very potent drugs are given by this route so that their effect is slow and
sustained, e.g. adrenaline.
 There are three methods :
(i) Hypodermoclysis : it is special process of infusing large amount of drugs like glucose
and saline though loose subcutaneous tissue of the body.
(ii) Hypospray : This is new needleless tech. for introducing drugs in subcutaneous tissue.
Drug is introduced under high pressure in the form of a fine jet. This hypospray
method is painless.
(iii) Implants: this is new tech. of implanting a tablet or porous capsule into loose tissue by
incision of skin, which is then stitched up. The tablet or porous capsule so introduced,
slowly liberates the drug and action continue for weeks or even months. Certain
hormonal drugs are implanted in this way.
(c) Intramuscular :
 It is commonest and choicest route of administering injectable drugs.
 The muscle has rich lymphatic supply and hence the absorption is very rapid.
 Irritant drugs and suspensions can be injected by this route.
 Drugs like iron dextran (imferon) and procaine penicillin are injected intramuscularly.
(d) Intravenous :
 This is the quickest route for fastest action of a drug. It goes directly into blood
circulation hence desired blood concentrations can be achieved. Irritant substances can
also be given by this route.
 Indications :
 Intravenous injection is indicated in following conditions:
1. In emergency (Indications for intravenous noradrenaline in shock or digoxin in cardiac
failure).
2. To maintain blood pH (sodium lactate in acidosis).

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3. To restore blood volume (blood transfusion).
4. To maintain normal blood coagulability. (heparin as anticoagulant and vitamin K to
promote coagulation).
5. Chemotherapeutic drugs (antibiotics and antitoxic sera in microbial toxaemia of the
blood).
6. Selective swift route to avoid decomposition and irritation (diluted quinine
in cerebral malaria).
7. For general anaesthesia (intravenous injection of pentothal sodium).
8. For sclerosing veins (quinine and urethane in varicose veins).
9. For diagnostic purposes (tetra-iodo-phenolphthalein in gall bladder investigation).
 Intravenous Injections in Infants : Drugs are injected through the umbilical vein in the
newborn and through the superior longitudinal sinus in infants under special
circumstances.
(e) Intra Arterial : This route is rarely used by the surgeon for tracing or relieving certain
arterial diseases. The procedure is very risky. Anticancer drugs are given by this route for
localized effects. Certain drugs are given by this route for the diagnosis of peripheral
vascular diseases.
(f) Serous Cavity Injections : For local concentration, drugs are injected in serous cavities,
peritoneal, pleural, pericardial and articular cavities. Of these, intrapertioneal injections
are quickly effective because of the rich lymphatic supply in that region.
 Injections of antibiotics and corticosteroids are administered in inflamed joint cavities
by experts, with precision. This is intra-articular Injection.
 Hydrocortisone is sometimes administered intra-articularly by surgeon in rheumatoid
arthritis.
(g) Intracardiac : It is given quickly and directly in the cardiac muscle in sudden stoppage
of a healthy heart (adrenaline in drowning). It is the last resort of a defeated physician to
revive a stand still heart. The method, rarely does succeed.
(h) Intramedullary : It is given in the medullary cavity of the bone when intravenous
injection is not possible. Glucose and saline solutions, plasma and blood transfusion etc.

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can be easily administered by this route, especially in children. This route is also rarely
used. Bone-marow transplantation is done by this method in case of blood-cancer.
(i) Intraspinal : These injections are administered in lower lumber region of the
subarachnoid spaces surrounding the spinal cord (lumbar puncture). Spinal anesthetics,
diagnostic agents and antibiotics are sometimes injected there.
 Most of the operations below the umbilicus are performed now-a-days under spinal
anaesthesia. The drug so introduced intrathecally, acts directly on the nervous
system.
(j) Intracerebral, Intracisteral, Intraventricular and Intraneural : These injections are
given in certain parts of the brain in rare conditions. These are surgical procedures and
are rarely used. Injection of coramine directly into the brain at the terminal stage is
 however, not uncommon.
 A drug may exert different effects if given by different routes. For example,
magnesium sulfate (MgSO4), if given orally acts as purgative, given parenterally it
produces depressant effect. If MgSO4 is given through enema, it decreases
intracranial tension.
 Similarly ethylalcohol is antiseptic if applied on skin, however, it is central nervous
system depressant if given orally. Mercurials (e.g. Calomel) are administered orally
as purgative, parenterally as diuretic and locally as antiseptic.

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 NOVEL DRUG DELIVERY SYSTEMS :