Routes of
Administration
of drugs
By.
Dr.Abdul latif Mahesar
ROUTES OF
ADMINISTRATION
►Enteral (Alimentary)
► Par - enteral
( Other than Alimentary)
ROUTES OF
ADMINISTRATION
Enteral (Alimentary canal)




Oral
Buccal & Sublingual
Rectal
Nasogastric
Par - enteral ( Other than
Alimentary)

Par - enteral injections
Intravenous , intramuscular, intradermal,
Subcutaneous, intrarterial, intrarticular,
intraperitoneal, intrathecal


Inhalation
Topical
ORAL
MERITS
 Commonest, Safest
 Convenient ,
 No skill required, self medication
 Painless, & acceptable
 Cost effective

No maximal/strict sterilization required
ORAL
MERITS cont’d
 Due to slow rate of absorption adverse effects occurs less and
slowly as compared to
parenteral route


Large volume (doses) can be given

Systemic / local effects in G.I.T
For local effect
e.g.,
neomycin (an aminoglycoside),
anthelmintics
antiamoebic.
ORAL con’d
De-merits
 Absorption varies (delay, decrease, or
increase )
affected by ---- food or drugs that affect GI
motility
e.g. antimuscarinic, opioids )

(Dose may not accurately be delivered)

Irritation of gastric mucosa

Patient compliance not ensured
ORAL cont’d
Demerits
 First pass metabolism ( First pass effect,
Presystemic elimination)

Metabolism of drug (to inactive form)
after administration before it reaches the
systemic circulation Usually with orally
administered drugs
ORAL
De-merits cont’d

First pass metabolism
- Orally administered drugs
- First pass effect in GIT
- Hepatic first pass metabolism
during its first passage thru liver
 Greater the first pass effect, lesser will be
the bioavailability
BIOAVAILABILITY
is the fraction of administered drug that
gain access to the systemic circulation
(after absorption) in a chemically
unchanged form
ORAL cont’d
Demerits cont’d
- Drugs with high first pass effect needs
to be given in high doses
- Variation in first pass effect
among individuals cause variation in
drug response
ORAL cont’d
Demerits cont’d

Not suitable for :
Unconscious patients
Vomiting patients
Emergency --- (Slow onset of action)

GIT diseases or abnormality may
affect the absorption of drug
ORAL cont’d
Demerits
- Following drugs can not be given by oral route:
- Drugs destroyed by Stomach pH
(some Penicillins e.g., benzyl penicillin)
- Drugs destroyed by Intestinal enzymes
(e.g., Insulin, oxytocin)
- Hydrophilic drugs which can not absorbed
(e.g., Aminoglycosides, but can be given for
local effect such as neomycin)
ORAL cont;d
Demerits cont’d
Uneven distribution (for local effect),
in some diseases of gut whole thickness of wall is
affected (e.g. severe bacillary dysentery, typhoid)
& effective blood concentrations ( as well as
luminal concentrations ) may be needed.
Drug interaction:
one drug can affect the absorption of other
drug e.g., antacids decrease the absorption of
tetracyclines.
SUBLINGUAL &
BUCCAL
Merits
 Rapid onset of action
 useful in emergency
(glyceryl trinitrate, nifedipine & ergotamine),
especially if tablet is crushed, giving greater
surface area for solution

Effect can be terminated by spitting out tablet
SUBLINGUAL &
BUCCAL
Merits
 No sterilization required

No skill
 first pass hepatic metabolism is avoided
 Increase in bioavailability
 Not affected by gastric acidity or intestinal enzymes
SUBLINGUAL & BUCCal
Demerits

Inconvenient for frequent use

Irritation of oral mucosa & excessive
salivation

Promotes swallowing, so losing the advantage of
bypassing the first pass effect

Patient compliance not ensured

Not suitable for large doses and vomiting patients

Bitter, irritant can not be given
RECTAL

Dose requirement same or slightly greater than
oral route
RECTAL
Merits
 Can be used for producing both the systemic effects
and local effects


Drugs that are irritant to stomach can be given by
suppository (aminophylline, indomethacin)
Suitable in unconscious, vomiting , motion
sickness, migraine or when a patient can not swallow , &
when cooperation is lacking (sedation in children)
RECTAL
Merits

No sterilization

No skill

Avoid 50% first pass hepatic metabolism (from
lower rectum)

For local effect e.g. in proctitis or colitis
RECTAL
Demerits
 Psychological, patient may be embarrassed and dislike this
way

Irritation of mucosa & inflammation may occur
with repeated use

Emergency (slow onset of action)

Absorption unreliable, especially if rectum is full of
feces
PAR-ENTERAL
INJECTIONS
Dosage forms:
Solution,
Suspension
PAR-ENTERAL
INJECTIONS
Intravenous ( I / V ),
Intramuscular ( I / M ),
Subcutaneous ( S / C )
Intra dermal
Intra articular
Intrathecal
Intraperitoneal
I / V INJECTIONS &
INFUSIONS


Merits
Rapid onset of action
useful in emergency
 No first pass effect, 100% bioavailability,
 Dose more accurately delivered & give smooth
effective, & highly predictable blood
concentration
 Suitable in vomiting , motion sickness, migraine,
unconscious patients, or when a patient can not
swallow , & when cooperation is lacking
- Large volume (doses) of drug can be given
Intra venous and I.V
infusions cont’d
Merits
 Suitable in vomiting , motion sickness, migraine,
unconscious patients, or when a patient can not
swallow , & when cooperation is lacking

Large volume (doses) of drug can be given
Intra venous and I.V
infusions cont’d
 Following drugs which can not be given by
oral route, are given intravenously

Drugs destroyed by stomach pH
(some Penicillins e.g., benzyl penicillin)

Drugs destroyed by intestinal enzymes
(e.g., Insulin)

Hydrophilic drugs which can not absorbed
(e.g., Aminoglycosides)
Intra venous and I.V
infusions cont’d
Merits
- Drugs that are too irritant (anticancer agents) to be
given by other routes
- In I.V. infusion ----Rapid modification of dose and
immediate cessation of administration if unwanted
effects occur
I / V INJECTIONS &
INFUSIONS
De-merits

Costly

Inconvenient

More chances of adverse effects, most
dangerous

Maximal Sterilization, chances of infection
Skill, no self medication

Local irritation at site of administration
I / V INJECTIONS &
INFUSIONS
Demerits
 Local venous thrombosis with:
prolonged infusion
irritant formulations
microparticulate components of infusion
fluids, especially if small veins are used
Infection of intravenous catheter and small
thrombi on its tip during prolonged infusions
PARENTERAL : I / M
INJECTIONS
Merits
 Reliable and suitable for irritant drugs and
depot preparations (penicillins , neuroleptics,
medroxyprogesterone) can be used at monthly
or longer intervals

Absorption is more rapid than following
subcutaneous injection or oral route
(soluble preparations are absorbed within 10 – 30 mins.)
: I / M INJECTIONS
De-merits

Inconvenient

Painful especially for frequent use

More chances of adverse effects than oral
Sterilization,
 Chances of infection

Skill required

Local irritation at site of administration
I / M INJECTIONS
De-merits
Not acceptable for self administration
If any adverse effect occur tha can not be
removed.
S / C INJECTIONS
Merits

Can be used for local and systemic effects both
 Reliable and acceptable for self administration
(e.g. diabetic patients taking Insulin)
For local effect --- e.g. local anesthetics
S / C INJECTIONS
De-merits
 Poor absorption in peripheral circulatory
failure

repeated injections at one site can cause
lipodystrophy, resulting in erratic
absorption (insulin)
INHALATION

Can be used for local & systemic effects both
As a gas, --- e.g. ---- General anaesthetics
As an aerosol,--- e.g. ---- β2 –adrenoceptor agonist
bronchodilators
As a powder, e.g. sodium chromoglycate
INHALATION
Merits

Drugs as gases can be rapidly taken up or eliminated,
giving the close control that has marked the use of
this route in general anesthesia

Self administration is practicable

Aerosols & powders provide high local concentration
for action on bronchi, minimizing systemic effects

Aerosols can also be used for systemic effect, e.g
ergotamine for migraine
INHALATION
De-merits
 Special apparatus is needed


Drug must be nonirritant.
If the patient is unconscious
Obstructed bronchi (mucus plugs in asthma)
may
cause therapy to fail
TOPICAL application


For local effect
Skin
Mucous membrane (eye, nose , ear , lungs,
anal canal, rectum, urethra, vagina, etc. )
For systemic effect ----- Transdermal
TOPICAL APPLICATION:
FOR LOCAL EFFECT
Dosage forms
Ointment, lotion, cream, etc
Merits
usually high local concentration can be used
without systemic effect
TOPICAL APPLICATION:
FOR LOCAL EFFECT
Demerits
systemic effects can occur especially when there is
tissue destruction e.g.,
adrenal steroids & neomycin --- to ---- skin,
atropine & β-adrenoceptor blocker --- to --- eye
TOPICAL APPLICATION: FOR
SYSTEMIC EFFECT:
TRANSDERMAL DELIVERY
SYSTEM (TDS)

Dosage form:
Patches, ointment
as a sticking plaster (Patch) attached to skin or
as an ointment
glyceryl trinitrate
postmenopausal hormone replacement
TOPICAL APPLICATION: FOR
SYSTEMIC EFFECT
Merits:

Used for slow continuous administration for long
duration

Fluctuations in plasma concentration are largely
avoided

Usually No first pass effect

Drug can be removed if required
TOPICAL APPLICATION:
FOR SYSTEMIC EFFECT:
Demerits:

Only small number of drugs can be used by
this route

Slow onset of action

Local reactions