Transcript routes of adminstration

ROUTS OF ADMINSTRATION
Prepared by:
Prof. Abdulkader.H.El Daibani
A) Oral route
 Oral route most common route
(tablets,capsules ,syrup….)
Advantages:
 Convenient,safest,economicals,does'
t need sterilization.
A) Oral route
Disadvantages:
 Irritation of gastric mucosa may lead to nausea
,vomiting, and abdominal pain e.g. aspirine can be
minimized by given the drug in enteric coated
preparation which prevent dissolution of drug in
stomach .
 Polar drugs are not absorbed from G.I.T e.g.
gentamicin.
 Some drugs may stick to esophageal mucosal cause
ulceration e.g. (doxycycline taken with full glass of
water).
A) Oral route
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Destruction by digestive enzyme e.g. (insulin) and acid PH
(penicillin G).
Irregular absorption due to delay in gastric emptying
(anticholenergic and food) ,faster intestinal transit (infection and
diarrhea).
F.P.E(first pass effect) :Some drugs may be metabolized on 1st
entery before reaching the circulation ↓B.O(Bioavailability) by
mucosal enzyme- lungs (Tyramine,isoprenaline) or liver
(Lidocaine,morphine,glyceryl trinitrite ,propranolol).
F.P.E can be avoided by sublingual or parental routes and to some
extent by rectal route.
Lack of compliance of frequent admin.)and can't be given to
unconscious pt.(patient)
Oral route can be used for local effect Neomycin for sterilization of
G.I.T prior to surgery and anthelmithics.
Enteric coating : coating prevent dissolution of tablets in stomach
also prevent gastric irritation
Sustained (controlled) release
preparation
 slow and uniform absorption of drugs long
duration of action.
 Advantage:
 1)↓ frequent of admin. Also ↑ compliance.
 2)Maintance of therapeutic effect overnight
e.g theophylline to prevent nocturnal
asthma.
 3)less side effects due to elimination of
peaks plasma conc.
Enterohepatic circulation (E.H.C):
 Some drugs which conjugate with
glucuronic acid in liver are too polar
to be reabsorbed and excreted in bile
and hydrolyzed by bacterial flora in
small intestine to release the parent
drug which then reabsorbed from
G.I.T and then reconjugated in liver
and execrated in bile this leads to ↑
duration of action e.g estrogens and
sulidac.
Bioavailability
 Fraction of unchanged drug which
reaches systemic circulation following
admin.by any route.
 F=AUC after O.P dose/AUC after I/V
dose.
 Where:
 AUC is area under the curve.
Factors affecting Bioavailability
 formulation ( Particle size
,excipients…..etc) affect disintegration and
dissolution e.g digoxin.(No therapeutic
equivalence).
 PKa of drug Ka where Pka is a dissociation
constant
 pH of the medium.
 Conc. gradient.
 Blood flow.
 Surface area.
Factors affecting Bioavailability
 Route of admin.
 Content of G.I.T.
 e.g. milk contain Ca++ chelates with
tetracycline, cholestyramine form
complex with digoxin which can't be
absorbed.
 F.P.E
 Gastric motility.
B)Sublingual route Nitroglycerine)
Advantages:
 1)rapid action
 2)avoid F.P.E.
 3)Quick termination by spitting or
swallowing tablet.
Disadvantages:
 1)inconvenient.
 2)irritation of mucosa.
C) Rectal route: (Suppositories and
enemas)
 Indomethacine, aminophylline
Advantages:
 1)useful in case of vomiting due to motion sickness or
migraine.
 2)can be used in unconscious pts.
 3)partly avoids F.P.E.
 4)can be used for local effect e.g. colitis , proctites.
Disadvantages:
 1) slow, irregular and incomplete absorption.
 2)some drugs may cause irritation.
D)Parenteral routes (I/V ,I/M,S/C)
a) Intravenous route I/V
Quickly (bolus) or slowly (infusion).
I/V drip 100%bioavialability.
Advantages:
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rapid effect.
Accurate plasma conc.
Irritant drugs can be given.
Drugs not absorbed from G.I.T can be admin.
Large volume can be given.
Avoids F.P.E.
Routes of choice in emergency.
a)Intravenous route I/V
Disadvantages:
 Adverse effect if given quickly or in large
dose.
 If repeated admin. a cannula is inserted
into vein may cause infection.
 Local irritation or leakage outside vein may
cause tissue irritation and necrosis
 Need sterilization.
 Drug can't be returned back or recall.
b) Intramuscular route (I/M) :
Advantages:
 uniform and fast absorption
,absorption faster than from S/C.
 Irritant drug can be given.
 Delayed by given drug in oily soln.
(depot) ,depot inj.(pen.,neuroleptics
,haloperidol,medroxy progestron).
b) Intramuscular route (I/M) :
Disadvantages:
 volume to be injected is small
(<5ml).
 pain at site of inj.
 If inj near or in nerve may cause loss
of sensation or paralysis.
 If injected into vein cause toxicity.
c) Subcutaneous S/C:
Advantages:
 suitable for self admin. (insulin).
 S/C pellets or implants under skin
act as depot and have prolonged
duration (weeks or months e.g.
contraceptive).
 Vasoconstrictions delay absorption
e.g adrenaline.
c) Subcutaneous S/C:
Disadvantages:
 irritant drugs shouldn't be used
because it may cause sever pain and
tissue necrosis.
 Repeated inj. at same site result
( lipodystrophy) at site of inj.
 Volume given is limited (<1ml).
d) Parentral route for local effect.
I) Intradermal route:
 0.1 ml inj. between dermis and
epidermis used for sensitivity tests
of penicillin and vaccine +ve test
cause weal and flare.
d) Parentral route for local
effect.
II) Intra-articular route:
Inj. in a joint to (synovial fluid) for local
condition e.g. methyl prednisolone in
arthritis.
d) Parentral route for local
effect.
III) Intrathecal route:
 Drug inj. into spinal subarachnoid
between (L3 and L4) space to by pass
B.B.B. used for raid effect of drugs on
meningitis or cerebrospinal axes e.g.
antibiotics in infections.
 Opioid for anesthesia and cytotoxic
drugs for cancer of C.N.S.
d) Parentral route for local
effect.
IV) Intraperitoneal route (I/P):
 I/P→large surface from which drugs
given to partal circulation then to
liver in 100% F.P.E. this route is
commonly used in animals but rarely
in humans (peritoneal dialysis).
d) Parentral route for local
effect.
Disadvantages:
 tissue adhesion.
 Risk of infection.
 Drugs may be inj. into abdominal
cavity.
 Low bioavailability.
E) Pulmonary route
(inhalation):
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Gases and volatile liquids –general anesthetics
e.g.(NO2,halothane).
Aerosol-salbutamol,beclomethasone , ipratropium(bronchial
asthma).
Aerosol particle dispensed in gas liquid or solid).
Advantages:
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Rapid absorption.
Accurate dosing.
Suitable for self admin.
Avoid F.P.E.
Used for local (asthma)or systemic effect (general
anesthesia or migraine).
E) Pulmonary route
(inhalation):
Disadvantages:
 Special apparatus needed.
 Some drugs cause irritation.
 Obstruction of respiratory passage
(therapeutic failure).
 Inhalation of steroid for long time may
cause infection with candida albicans in
mouth and throat.
 Route of drug abuse.
F) Topical route:
 a) mucous membrane conjuctiva:
 nasopharynx
,vagina,urethera,colon,bladder mainly
for local but sometimes for systemic
effect e.g. sodium cromoglycate.
 ADH as nasal spray –rapid absorption
(nocturnal enuresis).
F) Topical route:
 absorption proportional to area and to lipid.
 Solubility of drug-epiderms act as lipid barrier- dermis
is freely permeable used for local effect
.cream,ointment,lotion and powder e.g.antimicrobials
and steroids but if large area is used steroid may
produce systemic effect.
Systemic effect:
 using transdermal adhesive patches of
glyceryltrinitrate for treatment of angina pectoris and
hyoscine for motion sickness adhesive patches act as
sustained release preparation.
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