Routes of drug administration
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Transcript Routes of drug administration
ROUTES OF DRUG
ADMINISTRATION
Compiled by
Sarafadeen Adebayo, Ph.D.
Saturday, July 18, 2015
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Objectives
To describe the various routes of drug
administration
Relate dosage forms and route of
absorption to the potential rapidity of
absorption/therapeutic activity.
To understand the advantages and
disadvantages of the various routes of drug
administration
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Buccal/Sublingual
Buccal or sublingual dosage form enable drugs to be
taken as smaller tablets held in the mouth or under
the tongue.
Buccal tablets are often harder tablets [4 hour
disintegration time], designed to dissolve slowly.
Nitroglycerin, as a softer sublingual tablet [2 min
disintegration time] may be used for the rapid relief
of angina.
This ROA is also used for some steroids such as
testosterone and oxytocin while nicotine-containing
chewing gum may be used for cigarette smoking
replacement.
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Advantages of buccal sublingual
administration:
First pass - The liver is by-passed thus there is
no loss of drug by first pass effect for buccal
administration. Bioavailability thus is higher.
Rapid absorption - Because of the good blood
supply to the area absorption is usually quite
rapid.
Drug stability - pH in mouth relatively neutral
(cf. stomach - acidic). Thus a drug may be more
stable.
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Disadvantages
Holding the dose in the mouth may be
inconvenient.
If any is swallowed that portion must be
treated as an oral dose and subject to first
pass metabolism.
Small doses only can be accommodated
easily.
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Rectal
Most commonly used for suppository or
enema.
Some drugs given by this route include:
◦ aspirin,
◦ dipyrone,
◦ paracetamol
◦ theophylline
◦ Chlorpromazine
◦ some barbiturates
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Merits & Demerits of Rectal
Administration??
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Some Parenteral Routes of
Administration
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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
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Advantages of IV
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 relatively insensitive to irritation by
irritant drugs.
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Demerits of IV
Suitable vein may be difficult to locate.
May be toxic - Because of the rapid response,
toxicity can be a problem with rapid drug
administrations
◦ could then be given as an infusion while monitoring for
toxicity.
Requires trained personnel
Expensive - Sterility, pyrogen testing and larger
volume of solvent means greater cost for
preparation, transport and storage.
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Subcutaneous
This
involves administration of the
drug dose just under the skin.
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Advantages:
Can be given by patient, e.g. in the case of
insulin
Absorption slow but usually complete.
◦ Absorption rate can be improved by massage
or heat.
◦ Vasoconstrictor may be added to reduce the
absorption of a local anesthetic agent, thereby
prolonging its effect at the site of interest.
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Disadvantages:
Can
be painful
Irritant
drugs can cause local
tissue damage
Maximum
of 2 ml injection thus
often small doses limit use.
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Intramuscular
Injection
administered into the:
◦deltoid muscle of the buttock
or
◦gluteal muscle of the upper
arm.
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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
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Disadvantages:
Trained personnel required for injections.
◦ The site of injection will influence the absorption,
generally the deltoid muscle is the best site
Absorption is sometimes erratic, especially
for poorly soluble drugs, e.g. diazepam,
phenytoin.
The solvent maybe absorbed faster than the
drug causing precipitation of the drug at the
site of injection.
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Inhalation
Drugs
administered as fine particles of
liquids or solids or as aerosols or spray.
The
drug may be required for local or
systemic effects.
Local effect - bronchodilators
Systemic effect - general anesthesia
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Merits
Rapid
absorption, by-passing
the liver
Absorption
of gases is
relatively efficient, however
solids and liquids are excluded
if larger than 20 micron and
even then only 10 % of the
dose may be absorbed.
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Example of Drugs administered by
inhalation into the lungs
Drugs
Comments
Corticosteroids Beclomethasone dipropionate, betamethasone valerate &
triamcinolone acetonide used for relief of brochial asthma
Ergotamine
tartrate
Available as a pressurized aerosol preparation & provides
relief from migraine much faster than from oral preparations
Sympathomim
etics
Fenoterol, rimiterol, salbutamol, salmeterol, & terbutaline are
well absorbed from the lungs giving early relief from
asthmatic attack.
Sodium
cromoglycate
Well absorbed from the lungs when administered as a fine
powder or spray but poorly absorbed from the gastrointestinal tract. Inhalation of the powder may cause
bronchospasm; isoprenaline may be administered
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concurrently to minimize this effect.
Topical
Local effect - eye drops, antiseptic,
sunscreen, callous removal, etc.
Systemic effect - e.g., nitroglycerin
ointment.
Absorption through the skin, especially via
cuts and abrasions but also intact skin, can
be quite marked.
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Other Routes of Administration
Intra-nasal - some systemic absorption
has been demonstrated for propranolol
and some low dose hormones
Intra-arterial for cancer chemotherapy
to maximize drug concentrations at the
tumor site
Intrathecal directly into the
cerebrospinal fluid.
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***END OF PRESENTATION***
QUESTION/DISCUSSION SESSION
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