No single method of drug administration is ideal for all drugs in all circumstances .A knowledge of advantages and disadvantages of different routes of administration is essential.

1. Routes of drug administration
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LECTURER-
MANI GOEL

2. Route of administration
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4. First pass metabolism
1- The first pass effect is the term used for the hepatic metabolism
of a pharmacological agent when it is absorbed from the gut
and delivered to the liver via the portal circulation.
2- The greater the first pass effect, lower the bioavailability of
the drug (the rate and extent of the drug reaching systemic
circulation).
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7. No single method of drug
administration is ideal for all drugs in
all circumstances .
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A knowledge of advantages and disadvantages
of different routes of administration is
essential.

8. • Most drugs can be administered by a variety of routes
• Choice depends on:
– Drug factors
– Patient related factors
• So knowledge of merits and demerits of different routes of administration is
essential
Convenience of the patient
Condition of the patient
Factors governing choice of route
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Patient factor:
Disease Factor:
Site of desired action
Rapidity with which response is desired
Physical and chemical properties of drug
Effect of digestive juices , first pass metabolism on the
drug and bioavailability.
Drug Factor:

9. Routes can be broadly divided in to
Enteral route (oral)
Parentral route
Topical Route
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1. Systemic
2. Local

10. Routes of drug
administration
Local
1. CONJUCTIVAL, NASAL, AUDITORY
2. VAGINAL AND URETHRAL
3. INUNCTION AND DERMAL
Systemic
Parentral
1.Inhalational
2. Injections
3. Transdermal
Enteral
1.Oral
2.Sublingual
3.Rectal
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11. A. SYSTEMIC ROUTES:
1.Enteral:Placement of drug directly into any part of gastrointestinal
tract(Gk.enteron=intestine)
i.Oral
ii.Sublingual
iii.Rectal
USE:
• For systemic actions or effects
• Drugs absorbed in the blood stream and distributed all over/site of
action through blood stream
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12. Introduction:
• Oldest, commonest & most natural way.
• The large surface area of GIT ,facilitates mixing of its contents
& different PH at different sites facilitates effective absorption of
drug
Advantages
• Self administration
• Non invasive, often painless
• Safer, more convenient
• Most economical method
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i. Oral route

13. Limitations
• May cause nausea & vomitting
• Can’t be used in unconcious, uncooperative patient
• Irritant or unpalatable drugs are difficult to administer
• Action is slower, not suitable in emergencies
• Absorption of drugs may be variable & erratic, certain
drugs are not absorbed
• Some drugs are destroyed by digestive juices or in
liver,Some drugs undergo extensive first pass metabolism
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14. Forms of Drugs:
• Solid forms: Powder, tablets, capsules,spansules, dragees ,modulate tablets
• Liquid Forms: Syrups, emulsions, mixtures,elixirs
To overcome some of disadvantages:
• Irritants are given in capsules
• Bitter drugs are given Sugar coated tablets
• Coating with synthetic resins, gums, colouring and flavouring agents
• Most for systemic effect except ANTACIDS and ANITIDIARRHOEAL DRUGS like --
---norfloxacin, streptomycin, pectin, and kaolin.
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15. Tablet is placed under tongue Crosses buccal mucosa Enters into systemic circulation
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The tablets or pellet containing drug is placed
under tongue or crushed in the mouth
ii.Sublingual or buccal
.Merits:
• As liver is bypassed, directly enters in to systemic circulation, Rapid absorption -
Because of the good blood supply to the area, absorption is usually quite rapid.
• Self Administration
• Can be spitout drug after obtaining desired effect
• Drug stability - pH in mouth relatively neutral (stomach - acidic). Thus a drug may be
more stable.

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Demerits:
1. Holding the dose in the mouth is inconvenient, unpalatable, Small
doses only can be accommodated easily.
2-buccal ulceration can occur.
3-lipid insoluble drug ,drugs of high molecular weight, irritant and
unpalatable drugs cannot be given by this route.
Example of sublingual drugs
Forms of drug
Only lipid soluble drugs
Non-irritating drugs can be administerd
Eg:
Isosorbide dinitrate and nitroglycerin for angina
Nifedipine for hypertension
Isoprenaline : asthma

17. Upper rectal mucosa Superior hemorrhoidal vein Portal circulation
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Lower rectal mucosa
Middle and inferior
hemorrhoidal vein
Systemic circulation
Solid medicament called suppositeries can be
administered per rectum.
iii.Rectal route

18. Merits:
• First pass degradation is largly bypassed.(50%)
• In patients with reccurent vomitting or unconcious .
• Sometimes easier to use in childrens
• easy to terminate exposure
• good for drugs affecting the bowel such as laxatives.
Demerits:
• Absorption is slower, irregular(50%)
• Inconvenient & embarrassing
• Rectal inflammation can result from highly irritant drugs
(Diazepam, indomethacin, Paraldehyde, ergotamine)
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19. Forms of drugs:
• Unpleasant drugs
• Irritants
• For systemic effect---AMINOPHYLLINE and INDOMETHACIN
• For local effect---DULCOLAX and GLYCERINE suppositories,
enema and ointments.
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20. • Parenteral – giving a substance by any route other than
enteral
1.Inhalational
2. Injections
3. Transdermal
Use:
• Drugs injected under the skin are not absorbed in the GI
tract and are not initially metabolized in the liver, so this
route eliminates the factors of absorption
2 .Parentral route :
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21. • SITE-Inspiration through nose or mouth, Drugs act locally on the
pulmonary epithelium and mucous on respiratory tract and may be
absorbed through these membranes, Lungs offer a large surface area
for absorption.
ADVANTAGES :
• Self administration possible.
• Rapid onset of action
• Avoid hepatic first pass metabolism
• Blood levels of volatile anesthetics can be conveniently controlled
i.Inhalational route
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22. DISADVANTAGES:
• Requires proper training, Even with best efforts only 2% drug
reaches to lungs.
• Not useful during acute attack of asthma
• Bronchial irritation  increased bronchial and salivary secretion
EXAMPLE-
• Volatile liquids and gases are given by inhalation (GA)
Solid particles inhaled as aerosol (salbutamol)
(a)oxygen therapy.
(b)General anaesthetics inhalation.
(c)MDI for asthma(salbutamol and isoprenaline)
(d)Prophylaxis for asthma(sod. Chromoglycate)
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23. ii . INJECTIONS
Injections are given with the help of syringe and needle
• Intravenously – IV
• Intramuscular – IM
• Intradermal - ID
• Subcutaneously
• Intraperitoneal
• Intramedullary
• Intrathecal
• Intra- articular
• Intraarterial
• Intra- cardiac
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24. 1. Intravenous(IV)
• IV injected to one of superficial veins , Lumen of vein, mainly
cubital vein which directly reaches to the circulation.
Advantages
• This route is employed for unconcious or uncooperative patients
• Used in patients with vomitting or those unable to swallow.
• The action is almost immediate.
• Large volume of solutions can be infused through this route, Drugs
having short life can be infused continuously.
• Irritants can be given I.V.
• Avoids destruction of drugs by gastric and intestinal juices.
• Avoids destruction by liver enzymes, Avoids First pass metabolism
.(100% bioavailibility)
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25. Drawbacks for Parenteral Medication:
• Self medication is difficult, Painful.
• More expensive, less safe.
• Only aqueos solutions can be given, Suspensions & oily
preparations – not useful.
• Once the drug is under the skin, it cannot be retrieved.
• Thrombophlebitis
• Necrosis and sloughing
• Air embolism
• Sudden Fall in B.P. & arrythmic shocks
• Strict aseptic precautions needed
Can be given as:
Bolus : initial large dose is given, injected ,slowly. eg. Heparin
Rapid i.v. inj: E.g. adenosine
Slow inj. : over 15-20 min. eg Aminophylline
Slow infusion : 1-8 hrs or more, eg Dopamine, dobutamine ,oxytocin25