Routes of Drug Administration
The drug are administered to have effect
on the whole body system or have
localized effect on certain region.
Besed on the purpose,there is systemic
administration or local application of drug
by various routes are-
1.Oral. 2.Sublingual. 3.Per Rectal.
4.Injectable(Parenteral). 5.Local(Topical)
Application. 6.Inhalation. 7.Other Method
and Devices of drug delivery.
ORAL ROUTE=
• Drug which are absorbable and stable in GIT are
given by this route.
• Though majority drugs are administrated by this
route but every drug cannot be given by this
route or disadvantages of this route=it take
some time before drug effect is seen and
intensity of effect may not predictable thus ,this
route will not be suitable for emergency
condition.
• Patient have vomiting and diarrhoea,this route
not prefered.
For majority of situation it serves the
purpose or advantage of this route=
• Dose adjustment is easy. Self administration is
possible,comparatively it is less costly and
possibility of injury or infection is not there so
it is most convenient to patient
Drug which are not absorbable;which
are destroyed in GIT;
• Which are destroyed during portal circulation
after absorption(having high first pass
metabolism)and drugs which are irritant
cannot given by this route.
• Patients who are appose non-cooperative
unconscious patients should not be given
drug by this route
SUBLINGUAL ROUTE=
• This is a peculiar route for the drugs undergoing
high first pass metabolism.
• The tablet is kept underneath the tongue and
drug is allowed to get absorbed.
• The drug rapidly absorbed and immediate
systemic effect is produced.
• Very few drugs are given by this route.In case of
angina pectoris glyceryl trinatrate and isosorbide
dinitrate are use sublingually.
• Buprenorphine is use sublingually for chronic
pain in malingnancy.
PER RECTAL(PR)=
• It is less preferred route ,being cumbersome.
• For the purpose of sysemic action ,very few
drugs are used in this route.
• Use of diazepam by this route for status
epilepticus or febrile convulsion is important
in children.
INJECTABLE(Parenteral)=
• As better and quicker absorption is expected
by this route,it is important route in case of
emergency situation and for the not
absorbable orally.
• This will be suitable in unconscious and
uncooperative patient.
• Accurate dose adjustment is possible by this
route
When drug cannot be given oral because of
irritation or patient has vomiting, diarrhea
and dehydration injection route is preferred.
There will no problem related to high first pass
metabolism in port circulation,because portal
circulation being bypassed.
It is not a convenient route for self
administration of drug.
• Some injection(particular with irritant
drugs)are pain ful.
• There is possibility of local damage(be care ful
to nerve at the site of injection,repeated
injection of insulin causes lipodystrophyin
diabetic patient).
• Aseptic precaution are needed in this route.
Various way of injection eg. sc,im,iv,
intra-thecal;intra-peritoneal;
• Intra-articular;intra- arterial;sub-
conjuctival;retro-bulbar;
INTRA-DERMAL(id)=
Vary small quantity of the drug is
administered(only0.1-0.2ml);the injection is
painfull;only test dose is administered(to
determine hypersensitivity reaction).
BCG vaccine is given by this route
Drug kept under the skin by this route.
INTRAVENOUS(IV)=
• There is very quick effect as drugs enters the
circulation(no process of absorption is involved).
• Rapid(bolus)administration into high
concentration reaching to the heart may causes
cardiac toxicity.
• Suspensions and oily preparation cannot be
injected(danger of embolism).
• Irritation of vein can lead to phlebitis and
thrombosis.
• It is easy to adjust the rate of administration with
accuracy by this route.
• By this route the drug is administered as
• (A)Bolus injection(diazepam for status
epilepticus,diazoxide for the hypertansive
emergency).
• (B) as slow intravenous administration after
adequate dilution of drug(adrenaline for
anaphylatic shock 1ml of adrenaline solution
diluted to 10ml saline and 5ml of it is injected
over a few minutes)
• (C)as intra venous infusion drug dilute in a large
volume of suitable vehicle is given over a period
of a few hours.insuline50 units added to 500ml
of saline and infused as 15 drops per min. in a
patient of 60kg for t/t of diabetic coma.Dopamine
10-12 drops per min for t/t of cardiogenic shock.
• Intra venous infusion needed when continuous
blood level of drug is to be maintained.Drug
having very short half life(like
insuline,dopamine,oxytocin,lignocaine etc.)are
preffered given by this route.
SUCUTANEOUS(SC)=
• About 1-5ml can be injected.
• Non-irritant drugs are injected.
• There is slow and steady absorption occur.
• If peripheral circulation is not maintained,absorption is
poor and drug is not effective.
• Insulin and adrenaline are usually administered by this
route.
• Lignocaine is given by this route for surgical procedure.
• In this route adrenaline retard the absorption of
lignocaine and local aneasthetic effect is prolonged.
• Irritation of vein can lead to phlebitis and thrombosis.
INTRAMUSCULAR(IM) =
• Deltoid,triceps and gluteus maximus muscles
are usual sites.
• Injection is less painful.
• Soluble drugs are quickly absorbed.
• In case of repository(depot) preparation like
oily solution and suspensions are absorbed
slow and steady.
• Exercise and blood flow in the area are
determinant of rate of absorption.
Some special routes of injection=
• Intra-thecal=for spinal anaesthesia
• Intra-peritoneal=large volume can be
given;used for peritoneal dialysis.
• Intra-arterial =Radio-opaque dyes are injected
for radiography.
• Intra-articular=Steroids can be given in joint
cavity.
• Sub –conjuctival,retro-bulbar are specialized
route in ophthalmology.
LOCAL (TROPICAL)APPLICATION=
• Application on the skin,mucous membrane or in
body cavities for localized action is local
application.
• Skin,mucous membrane including of the body
cavities like mouth,vagina and rectum are
common sites of local application.
• There is quick and localized action. As there is
minimal systemic absorption chances of systemic
unwanted effects are less.However,local irritaion
may occur.
INHALATION=
• By this route, the drug in the form of gas,volatile
liquit,aerosols or fine powder are inhaled.
• They get absorbed and produce systemic effecs(general
anaesthesia by halothane,isoflurane,oxygen correct
hypoxia and carbon di oxide stimulates respiration and
corrects pH balance).
• If drug is not absorbed it produces local effect in
respiration tract without producing
systemic(unwanted)effects.
• Action is expected to be quick.
• Anti-asthma drugs salbutamol,beclomethasone are
commenly used by this route.
OTHER METHODS AND DEVICES OF
DRUG DELIVERY=
• OCUSERT: Adevice place under eyelid,delivers
pilocarpine continuously over a long
time(seven days)for treatment of glaucoma.
• PROGESTASERT: It produce continuous release
of progesterone for long period(a year) useful
as intrauterine contraceptive.
• DRUG ELUTING STENTS:Metallic stents are
covered with polymer containing drug;used in
coronary angioplasty to reduce restenosis.
• SUBCUTANEOUS IMPLANTS:Solid pellets or drug packed in a capsule of
suitable material is implanted underneath the skin is one the new drug
delivery systems.
• PRO-DRUG:The drug is administered In an inactive form.Inside the body, it
is converted into an active compound.
• By use of pro-drug availability of the active drug is
increased(talampicillin,bacampicillin leads to better avaibility of
ampicillin)or its distribution to particular sites is increased(levodopa
reaches to brain and converted to dopamine to be effective in parkinsons
disease).
• TARGETED DELIVERY:It is a new advancement in drug delivery system.A
cytotoxic drug is atteched to the monoclonal antibodies specific to cancer
cell antigen;drug produces intense effect on cancer cells and general
toxicity is very much reduced.
• Anti-cancer drugs and amphotericin B for kala-azar are ued in this manner.
PATIENT RELATED ASPACTS=
• Whether pt requires rapid effect of the drug?
• Is pt in a position to comply with advavice
about administration?
• Is it emergency situation?
• Does pt suffer from vomiting, diarrhea?