Transcript AdministrationRoutes

Routes of Administration
&
Dosage Forms
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The oral route
The most frequently used route for local and systemic treatments…Why?
Advantages: Convenient , simple ,safe, cheap, variety of forms.
Disadvantages:
Slow onset of action.
Variable gastric emptying (factors).
Possibility of irregular or poor absorption ( low bioavailability).
Drug solubility may be altered by some substances in the GIT (e.g. Ca+2).
Destruction of certain drugs in the GIT (due to enzymes or secretions).
First pass effect (i.e. presystemic metabolism).
Not suitable for unconscious or vomiting patients and for pre- or postoperative use.
Examples: Tablets, suspensions, solutions, emulsions, powders, granules,
capsules, gels, elixirs.
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The buccal/sublingual route
Two sites are used for absorption from the buccal cavity:
1.For sublingual absorption, the area under the tongue is used: Very fast
onset of action but with short duration.
2. For buccal absorption, the buccal sulcus is used. This is the area between
the upper lip and the gum: Fast onset of action and longer duration than the
sublingual routes.
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.
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The buccal/sublingual route
Advantages:
• Quick onset of action.
• Rapid absorption - Because of the good blood supply to the area
absorption is usually quite rapid.
• Avoiding the first pass metabolism: As the liver is by-passed, there is no
loss of drug leading to higher bioavailability.
• Drug stability: pH in mouth relatively neutral (stomach - acidic). Thus a
drug may be more stable.
• Can be administered to unconscious and vomiting patients (e.g.
antiemetic drugs).
Disadvantages:
• Holding the dose in the mouth is 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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The parenteral route
This route describes drug administration by injection such as
•Intravenous route (i.v.): Very fast onset of action.
•Subcutaneous route (s.c.): The easiest and least painful type of
injection to administer.
•Intramuscular route (i.m.): The drug can be formulated in an
aqueous solution (fast onset), a suspension or in an oily vehicle
(slower onset and more prolonged action).
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The parenteral route
Advantages:
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Rapid - Total dose - Large doses can be given by
extending the time of infusion.
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GI stability
Disadvantages:
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Requires trained personnel .
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Suitable vein – Safety issue.
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Expensive - Sterility, pyrogen testing or preparation,
transport and storage.
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The rectal route
• More local than systemic.
• Examples: suppositories, ointment, creams, powders, enemas and tablets.
Advantages:
• Can be used when the oral route is unsuitable (vomiting, unconscious and
uncooperative patients). Can also be used when the drug causes GIT
irritation.
• Only some of the drug absorbed from the rectum will be subject to the
first pass effect (much less than the oral route).
Disadvantages:
• Erratic or irregular absorption : Absorption is often incomplete and may
give rise to a variable effect.
• Inconvenient.
P.S. Similar properties to the vaginal route.
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The topical route
• Applied to the skin:
 Mainly to local effect such as antifungals.
 But may also be systemic ( nitroglycerine cream): Avoids first pass
effect and provides close to zero-order kinetics over prolonged time
intervals.
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Also applied to other topical surfaces such as
Eye (ophthalmic preparations),
Ear (otic or aural preparations)
Nose (nasal dosage forms).
• Examples: Ointments, creams, pastes, lotions, gels, solutions,
topical aerosols.
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The inhalation (respiratory) route
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Drugs are administered usually by inhalation through the nose or
mouth.
Mainly for local effect such as bronchodilators (treatment of asthma)
And can be used to produce a systemic effect (such as general
anesthesia).
 The lungs provide an excellent surface for absorption (in the alveolar region)
when the drug is delivered in gaseous or aerosol.
 Rapid absorption, by-passing the liver.
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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.
Examples: Aerosols (solution, suspension, emulsion, powder forms),
inhalations, sprays, gases.
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Dosage Forms
• Drug substances (i.e. active pharmaceutical
ingredients) are seldom administered alone,
but rather as a part of a formulation in
combination with one or more non-medical
agents (i.e. excipients) that serve varied and
specialized pharmaceutical functions.
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Pharmaceutical Ingredients can serve
several functions
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solubilize
suspend
thicken
dilute
flavor
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color
emulsify
stabilize
preserve
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Types of Dosage Forms
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Solutions
Syrups
Elixirs
Suspensions
Emulsions
Creams
Ointment
Lotions
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Capsules
Tablets
Suppositories
Pessaries
Powders
Granules
Parenteral
Aerosols
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Why use dosage forms?
•Protection of a drug substance from destructive
influences of atmospheric oxygen or humidity
•Protection from influence of gastric acid after oral
administration
•To mask taste of offensive drugs.
•To provide liquid preparations of substances that
are either insoluble or unstable
•To provide clear liquid dosage forms
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Why use dosage forms?
• To provide time-controlled release of drugs
• To provide optimal topical administration
• To provide for the insertion of a drug into
one of the body’s orifices
• Provide for placement of drugs into the
blood stream
• Provide for lung inhalation of drugs
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Key points
*The route can be chosen to give local or
systemic effects, fast or slow
*The oral route is the most commonly used
route
*Gastric emptying, stability and other materials
present in the GIT may limit availability of drug
from the oral route
*Sublingual absorption gives a short, fast-onset
activity
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Key points
*Buccal absorption takes place between the
gum and lip. This route can be used with
unconscious patients and to avoid first pass
metabolism
*Rectal absorption partially avoids first pass
metabolism. It is useful for nil-by-mouth
patients and in cases of gastric irritation.
*Inhalation requires a much lower dose than the
oral route, with a rapid onset
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Key points
*Administration to the skin maybe used for both
local and systemic effects
*Injections can give the fastest onset of action
but prolonged action is also possible using oily
intramuscular injections.
*A wide range of different dosage forms have
been devised which have different properties
and uses.
*The same drug may usefully be used in different
formulations to assist different types of patients.
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