Download route of administration

1-What
2-How
is the best drug to be used?
it is going to be given?
Important
Info!
The route of administration (ROA) that
is chosen may have a profound effect
upon the speed and efficiency with
which the drug acts
No single method of drug
administration is ideal for all
drugs in all circumstances
 1-Entral
route (i.e. through the gastrointestinal tract)
 2-Parentral (i.e. outside the gastrointestinal tract)
But in our daily practice the term parental is reserved for
injections; that is why we can add a third category
called:
 3-
Other routes of administration. (Topical,
Inhalation…..etc.)
A-Oral rout:
Advantages:
1-Convenient - portable, no pain, easy to take.
2-Cheap - no need to sterilize (but must be hygienic of
course).
3-Variety - fast release tablets, capsules, enteric coated,
layered tablets, slow release, suspensions,
mixtures…etc.
1-Sometimes inefficient - high dose or low solubility drugs
may suffer poor availability; only part of the dose may be
absorbed.
2- First-pass effect - drugs absorbed orally are transported to
the general circulation via the liver.
3- Food and G-I motility can effect drug absorption.
4-Local effect - Antibiotics may kill normal gut flora and
allow overgrowth of fungal varieties.
5-Unconscious patient - Patient must be able to swallow
solid dosage forms. Liquids may be given by tube.
Advantages:
1-First pass - The liver is by-passed thus there is no loss
of drug by first pass effect.
2-Rapid absorption - Because of the good blood supply
to the area absorption is usually quite rapid.
3-Drug stability - pH in mouth relatively neutral (cf.
stomach - acidic). Thus a drug may be more stable.
1-Holding the dose in the mouth is inconvenient.
2-If any is swallowed that portion must be treated as an
oral dose and subject to first pass metabolism.
3-Small doses only can be accommodated easily.
Advantages:
1-By-pass liver - Some of the veins draining the rectum
lead directly to the general circulation, thus by-passing
the liver.
2-This route may be most useful for patients unable to
take drugs orally or with younger children.
1-Erratic absorption - Absorption is often incomplete
and erratic.
2-Not well accepted
Subcutaneous (SC.)
This involves administration of the drug dose just
under the skin.
Advantages:
1-Can be given by patient, e.g. in the case of insulin
2-Absorption slow but usually complete.
1-Can be painful
2-Irritant drugs can cause local tissue
damage
3-Maximum of 2 ml injection thus often
small doses limit use.
Advantages:
1-Larger volume, than sc, can be given by IM
2-A depot or sustained release effect is possible with IM
injections, e.g. procaine penicillin
1-Trained personnel required for injections. The site of
injection will influence the absorption.
2-Absorption is sometimes erratic, especially for poorly
soluble drugs, e.g. diazepam, The solvent maybe
absorbed faster than the drug causing precipitation of
the drug at the site of injection.
Advantages:
1-Rapid - A quick response is possible
2-Total dose - The whole dose is delivered to the blood
stream. Large doses can be given.
3-Veins relatively insensitive to irritation by irritant
drugs at higher concentration in dosage forms.
1-Suitable vein - It may be difficult to find a suitable
vein.
2-Maybe toxic - Because of the rapid response, toxicity
can be a problem with rapid drug administrations.
3-Requires trained personnel - Trained personnel are
required to give intravenous injections.
4-Expensive - Sterility, pyrogen testing and larger volume
of solvent means greater cost for preparation,
transport and storage.
Inhalation:
Absorption of gases is relatively efficient, however solids
and liquids are excluded if larger than 20 micron
Particles larger than 20 micron impact in the mouth
and throat.
This route of administration can be used for:
1-Local effect - bronchodilators
2-Systemic effect - general anesthesia
1-Local effect - eye drops, creams, ointments,
etc.
2-Systemic effect - e.g., nitroglycerin
transdermal patch.
This means injecting the drug into the
synovial fluid to get a direct local action
of the drug into the joint space.
e.g. local steroid hormone injections.
This means injecting the drug into the cerebrospinal
fluid (CSF), through a special CSF needle by making a
puncture through L3-L4, or L4-L5, intervertebral
space.
This method is commonly used in the setting of
chemotherapy regimen in CNS prophylaxis or
treatment.
This technique is somewhat similar to the
intrathecal injection, except that the
injection is given in the epidural space.
It is commonly used to give local analgesia
during labor.
Means injecting the drug directly into the
pleural space to induce
pluerodesis(obliteration of the pleural
space),
or to give chemotherapy directly to the
pleural or peritoneal space
No single method of drug
administration is ideal for all
drugs in all circumstances