2. Factors Governing The Route of
Administration
• Physical & chemical Properties
• Site of desired action
• Rate & extent of Drug absorption
• Effect of Digestive Enzymes & FPM
• Rapidity with which the response is required
• Condition of Patient :- Conscious & Vomiting
3. WHAT ARE THE ROUTES OF
ADMINISTRATION FOR DRUGS?
ENTERAL PARENTERAL LOCAL
Oral
Sublingual
Rectal
Intravenous (IV)
Intra-arterial (IA)
Subcutaneous (SC)
Intradermal (ID)
Intramuscular (IM)
Intraperitoneal (IP)
Lungs (Inhalation)
Skin (Topical)
Nose (Intranasal)
Eye (Ophthalmic)
Ear (Otic)
Vagina
Urethra
Urinary Bladder
Intrathecal
Epidural
Directly Into Target
Tissue
5. Oral
• Oldest & commonest
• Advantages:
• No need of assistance
• Convenient - portable, no pain, easy to take.
• Cheap - no need to sterilize , compact, multi-dose
bottles, automated machines produce tablets in large
quantities.
• Variety - fast release tablets, capsules, enteric coated,
layered tablets, slow release, suspensions, mixtures
6. Disadvantages:
• Slower action of drug , not suitable for emergencies
• Unpalatable drugs difficult to administer.
• May cause Nausea and vomiting
• Cannot be used for uncooperative / unconscious
/vomiting patients
• Varied and erratic drug absorption
• Destruction of drug by gastric juices
8. Sublingual
• Some drugs are taken as smaller tablets which
are held in the mouth or under the tongue.
These are buccal or sublingual dosage forms.
• Nitroglycerine,
• may be used for the rapid relief of angina..
9. Advantages:
• First pass - The liver is by-passed thus there is no
loss of drug by first pass effect
• Bioavailability is higher.
• Quick onset of action
• Rapid absorption - Because of the good blood supply
to the area, absorption is usually quite rapid.
• Drug stability - pH in mouth relatively neutral
(stomach - acidic). Thus a drug may be more stable.
10. Disadvantages:
• Holding the dose in the mouth is inconvenient.
If any is swallowed that portion must be
treated as an oral dose and subject to first pass
metabolism.
• Only small doses only can be accommodated
easily.
• Irritant drugs cannot be given
11. Rectal
• Most commonly by suppository or Retention
enema.
• Irritant drugs & Unpleasant Drugs - can be
given
• Some drugs given by this route include
Diazepam, Indomethacin, Ergometrine,
Chlorpromazine and some barbiturates
13. Advantages:
• By-pass liver - Some of the veins draining the
rectum lead directly to the general circulation,
thus by-passing the liver. Reduced first-pass
effect.
• Useful - This route may be most useful for
patients unable to take drugs orally ( vomiting
& unconsciousness) or with younger children
14. Disadvantages:
• Erratic absorption - Absorption is often
incomplete and erratic.
• Rectal Inflammation can be induced
• Inconvenient & embarassing
17. Subcutaneous
• This involves administration of the drug dose
just under the skin
• Richly supplied by Nerves
• Less vascular
• Only small volume of drug can be injected
• Self injection is possible
• Only nonirritant drugs
• Not practiced in shock patients.
• Suitable for insoluble suspension & solid pellet
implantation
18. • Pain, necrosis, tissue sloughing
• Absorption of solid pellets implanted under the
skin occurs slowly over weeks or months,
e.g.,testosterone
• Insulin, adrenaline, heparin, vaccines inj
24. • Advantages:
• Absorption slow but usually complete.
• Improved by massage or heat.
• Vasoconstrictor may be added to reduce the
absorption of a drug, thereby prolonging its
effect at the site of interest.
25. • Disadvantages:
• Can be painful
• Irritant drugs can cause local tissue damage
• Maximum of 2 ml injection thus often small
doses limit use.
26. Intramuscular
• Drug injected to one of the large Skeletal
Muscle
• Deltoid, Triceps, Gluteus, Rectus
• Advantages:
• Larger volume than sc, can be given by IM
• A depot or sustained release effect is possible
with IM injections, e.g. procaine penicillin
streptomycin , diazepam
28. Intramuscular Route
• Limitations
– Neurovascular damage
– Bleeding (eg anticoagulant therapy)
– Pain
– Infection
– Delayed absorption in shock
Avoided in Anticoagulant treated patients
- can cause Hematoma
29. Disadvantages:
• Trained personnel required for injections.
• The site of injection will influence the absorption,
generally the deltoid, Gluteus muscle is the best site
• Absorption is sometimes erratic, especially for
poorly soluble drugs, e.g. diazepam, phenytoin.
• The solvent may be absorbed faster than the drug
causing precipitation of the drug at the site of
injection.
31. Intravenous
• Drugs may be given into a peripheral vein over
1 to 2 minutes or longer by infusion. Rapid
injections are used to treat
epileptic seizures,
acute asthma, or
cardiac arrhythmias
32. Advantages:
• Rapid - A quick response is possible
• Total dose - The whole dose is delivered to the
blood stream. Large doses can be given by
extending the time of infusion.
• Veins (tunica intima) relatively insensitive - to
irritation by irritant drugs at higher
concentration in dosage forms.
33. Disadvantages:
• Suitable vein - It may be difficult to find a suitable
vein.
• Maybe toxic - Because of the rapid response, toxicity
can be a problem with rapid drug administrations,
could then give as an infusion, monitoring for
toxicity.
• Requires trained personnel - Trained personnel are
required to give intravenous injections.
• Expensive - Sterility, pyrogen testing and larger
volume of solvent means greater cost for preparation,
transport and storage.
34. Intraarterial
• Direct inj into artery
• Localization of effect in particular tissue or
organ
• Liver tumours, head & neck cancers
• Diagnostic agents
• Reserved route for experts
35. Intradermal
• Drug inj. into layers of skin to raise a bleb
• Multiple puncture of epidermis
• BCG, small pox vaccination
• Testing drug sensitivity- Penicillin’s and ATS
36. Intrathecal
• Blood Brain Barrier & Blood CSF Barrier
slows drug entry into CNS
• Used when local and rapid effects of drugs on
the meninges or cerebrospinal axis desired
• Spinal anaesthesia
• Acute CNS infections
• Into spinal subarachnoid space
• Direct intraventricular drug in brain tumours.
38. Topical Injection
• Intraarticular adm. of hydrocortisone
• Intrathecal into subarachnoid,d space of L2-3
or L3-4 – lignocaine, AMB
• Intramedullary into bone marrow
• Intraarterial-anticancer drugs in limbs cancer
• Retrobulbar,behind eyeball-hydrocortisone
hemisuccinate
• Intrapleural-anticancer agents
• Intraperitoneal-anticancer agents
39. The ROA is determined by the
physical characteristics of the
drug, the speed which the drug is
absorbed and/ or released, as well
as the need to bypass hepatic
metabolism and achieve high
conc. at particular sites
Important
Info
40. No single method of drug
administration is ideal for all
drugs in all circumstances
