3. Factors Affecting Choice Of Route
• Physical & chemical properties of drug
• Site of desired action-
a. Local, b. Generalized
• Rate & extent of absorption from various routes
• Effect of digestive juices & first pass metabolism
• Rapidity of the desired response- emergency/routine
• Condition of the patient
• Accuracy of dosage
5. ORAL ROUTE
The most common and oldest route
Liquid or solid preparations are given
Drug is given through oral cavity.
ADVANTAGES
Safe
More Convenient- self-administered
Painless
Economical- compared to other parenteral routes
Usually good absorption
No need for sterilization
6. DISADVANTAGES
1. Slow action of drug - can not used in emergency
2. Irritable and unpalatable drugs- Difficult to administer
3. Cannot be used uncooperative, unconscious and vomiting patients
4. Causes- Nausea and vomiting
5. Some drugs destroyed- Digestive juice (Eg- Insulin, streptomycin)
6. First-pass effect (Liver)- Due to Biotransformation (Eg-
Testosterone, Lidocaine)
7. Food–Drug interactions and Drug-Drug interactions
8. SUBLINGUAL / BUCCAL ROUTE
Advantages
•Drug absorption is quick
•Rapid onset of action
•Quick termination
•First-pass avoided
•Can be self administered
•Overdose can be avoided
Disadvantages
•Unpalatable & bitter drugs
•Irritation of oral mucosa
•Large quantities not given
Tab or pellet containing the drug - under tongue
Crushed in mouth and
Absorbed by- Buccal mucous membrane
Ex- GTN, Isoprenaline
9. Advantages
Irritant or unpleasant drug can be given
Little or no first pass effect
Used in vomiting or unconscious
patients
Higher concentrations rapidly achieved
Disadvantages
Inconvenient
Absorption is slower, irregular,
unpredictable
Rectal inflammation can occur
RECTAL ROUTE
Administration of liquid or semisolid medicament- Suppositories or
Enema
10. Evacuant Enema Retention Enema
Used to remove fecal matter
Max.qty.- 600 ml
Used before
a. surgical operation
b. Delivery
c. GIT investigation by X ray
• Eg- Soap water enema
Used to retain drugs in rectum
Max.qty.- 120 ml
Used for producing anasthesia
Eg- Paraldehyde enema
Predinisolone enema
11. PARENTERAL ROUTES
Par= beyond, enteral= intestinal
Routes of drug administration other than oral/ alimentary tract
Administering drug directly into blood or tissue fluid
Ampoule iv infusion Vial
13. ADVANTAGES
1. Rapid onset of action
2. Useful in unconscious, unco-operative patients
3. Useful in patient suffering from vomiting, nausea
4. 100% drug absorption
5. No destruction or degradation of drug- Gastric juice
6. No gastric irritation
7. Accurate dosage of drug
8. No first pass metabolism (Liver is bypassed)
14. DISADVANTAGES
1. Costly route
2. Technique is invasive and painful
3. Inconvenient- assistance of other person is needed
4. Self medication is not possible
5. Skilled person- necessary- to avoid injury to nerves, blood vessels
6. Difficult to control or reverse effect of drug- RISKY
15. Introduced directly into Lumen of Vein
Drug is injected IV
1. As Bolus- Eg- Furosemide
2. Over 5-10 min- diluted in 10-20 ml of isotonic glucose or saline
3. In an infusion- Eg- NS, DNS
ADVANTAGES
1. Very rapid onset of action- Most effective in Emergency condition
2. Large qty of drug can be administered- Eg- Fluids in dehydration
3. Irritant and hypertonic solutions can be given
4. Required drug concentration in blood- obtained accurately
5. 100 % bioavailability
INTRAVENOUS ROUTE
16. DISADVANTAGES
1. Care should be taken- Inserting needle into vein
2. Drug should not leak out- site of administration
3. Speed of drug entering into vein- Must be controlled and
maintained
4. Chances of causing air embolism is risky
5. Local irritation – Phlebitis
6. Once drug administered- no retreat
7. Side effects are more quicker than any other route
17. ADVANTAGES
Uniform and slow absorption
of drug
Rapid onset of action
Mild irritants can be given
First pass avoided
Gastric factors can be avoided
DISADVANTAGES
Only up to 10ml drug given
Local pain and abscess
Expensive
Nerve damage
INTRAMUSULAR ROUTE
Large skeletal muscle- Deltoid, triceps, laterofemoral, gluteus maximus
Suitable for administration- soluble substances, Mild irritants,
suspensions and colloids
Eg- Sex hormones, Corticosteroids, Penicillin G
18. Drug injected- loose connective tissue- Subcutaneous tissue under
skin
Only soluble, non-irritant drugs are injected
Small vol.of drug injected- up to 2 ml
Slow absorption of drug as compared to I.V. and I.M. route
Self injection is possible
Eg -Insulin, Testosterone, Morphine
SUBCUTANEOUS ROUTE
20. Subcutaneous injections
Drug can be administered subcutaneously as ;
1. Dermojet- Needleless method, drug is injected
by means of high velocity jet produced through
micro fine orifice
2. Pellet implantation- a tablet or porous capsule
is inserted into the loose tissues by incision of
the skin, which is then stiched up.
21. Type of
Injection
Needle Dia. Needle length Needle Angle
Subcutaneous 25 to 30 guaze 3/8 to 5/8 inch 45 to 90
I.M. 18 to 25 guaze 5/8 to 1 ½ inch 90
0
0
0
22. Intradermal Route
Injected into skin raising bleb
Only small qty is injected (1ml)
Used for detecting allergy to drugs
Eg- Penicillin
Vaccines are also administered
Eg- BCG Vaccine, Small pox vaccine,
Local anaesthetic
Intrathecal
Injected into subarachnoid space
Useful for local and rapid effect- Spinal anaesthetics, antibiotics
Eg- Amphotericin B is used in treating Cryptococcal meningitis
23.
24. Rapid delivery of a drug across the large surface area of alveoli
Producing an effect almost as rapidly as with IV injection.
Used for drugs- Volatile liquids and gases
Effective and convenient - patients with respiratory problems
No first pass effect
Eg- Salbutamol,Albuterol
DISADVANTAGE-
Require special apparatus
Irritation of respiratory tract may takes place
INHALATION
26. INTRANASAL
Drug administered directly into the nose.
Digestive juice and liver is bypassed
Eg-
1. Nasal decongestants- anti-inflammatory corticosteroid.
2. Desmopressin - diabetes insipidus
3. Salmon calcitonin - osteoporosis
27. Route for administration
-Time until effect-
Route Time
Intravenous 30-60 seconds
Inhalation 2-3 minutes
Sublingual 3-5 minutes
Intramuscular 10-20 minutes
Subcutaneous 15-30 minutes
Rectal 5-30 minutes
Ingestion 30-90 min
Transdermal (topical) Variable (minutes to hours)
28. External application of drug
Dusting powders, lotions, paste, ointments, drops, spray
Site of drug action-
Skin, Eye, Ear, Nose, Rectum, Vagina, Throat
Simplest route
Useful - Prolonged effect of drug is required
Drug absorption- depends on lipid solubility of drug
Watery solution of drug- absorbed in blood- undesirable
toxic effect
Topical Route
29. No single method of drug
administration is ideal for all
drugs in all circumstances