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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