Chapter 7
Routes and Formulations
Routes and Formulations
• The way the body absorbs and distributes
drugs varies with the route of administration.
• Drugs are contained in formulations and the
route of administration is either enteral or
parenteral.
– Enteral – anything involving the alimentary canal
(from the mouth to the anus). Enteral routes are
oral, sublingual, buccal, and rectal.
– Parenteral - any route outside the alimentary
canal.
Formulations
• For each route of administration,
there are various formulations
used to deliver the drug.
• Different dosage forms affect
onset, duration of action, and
concentration of drug in the body.
• Review pages 142-143
Local or Systemic Effect
• A local effect occurs when the drug activity is
at the site of administration. (eyes, ears, nose,
skin).
• A systemic effect occurs when the drug is
introduced into the circulatory system by any
route and carried to the blood to the site of
activity.
Oral Formulations
• Oral administration is the most frequently
used route because they are easy to use,
carry, and administer.
• The term used to specify oral administration is
peroral or PO.
• Certain drugs are effected by the pH of the
stomach.
Oral formulations
• Liquid oral formulations generally reach the
circulatory system faster than solid dosage
forms.
– Disintegration and dissolution are not required
for when dosage is in a liquid form.
• Disintegration- the breaking apart of a tablet into
smaller pieces.
• Dissolution – when smaller pieces of disintegrated
tablet dissolve in a solution.
Solid Formulations
•
•
•
•
Tablets
Capsules
Bulk powders
Modified release
Liquid Formulations
• Solutions – a clear liquid dissolved in a solvent
(a liquid that dissolves another substance)
• Aqueous solutions are the most common type
of oral solution. Water is the solvent.
• Syrups – solution that is saturated with sugar.
• Nonaqueous solutions – contain solvent other
than water.
• Elixirs – alcohol or water based, sweetened.
Not as thick as a syrup
Liquid Formulations
• Spirits – alcoholic or hydroalcoholic solution that
are usually used for flavoring but some are
medicinal.
• Tinctures - alcoholic or hydroalcoholic solution.
• Suspensions – solution in which the drug does
not completely dissolve in the solvent.
Sweetened or flavored. Settle over time.
• Emulsions – oil and water based. An emulsifier is
used to make the drugs mix.
• Gels – gelling agents are used to increase
viscosity of the drug.
Sublingual Formulations
• Tablets are placed under the tongue in sublingual
administration.
• When the drug is released from the tablet, it is
quickly absorbed into the circulatory system since
the membranes in the mouth are very thin and
there is a good blood supply.
• Nitroglycerin is the best known.
• Limitations to sublingual
– Condition of the mouth
– The patient
– Unpleasant taste to hold in mouth
Buccal Formulations
• Buccal cavity are the insides
of the cheek.
• Tablets and lozenges are
placed in the pouch
between the cheeks and the
teeth to dissolve.
• Rapid absorption of drugs.
Rectal Formulations
• Drugs are administered via the rectum for a local effect
or to avoid degradation after oral administration.
• If oral administration is unavailable because the
patient is vomiting, unconscious, or unable to swallow
oral formulations, the rectal route is an option.
• Disadvantages:
– Pt’s don’t like it
– Absorption is unpredictable
• Most common rectal formulations are:
– Suppositories – melt when inserted
– Solutions – enemas or cleansing
– Ointments - local effect, hemorrhoids
Parenteral Routes of Administration
• Parenteral – a route of administration outside
the alimentary tract. Alimentary - the organs from the
mouth to the anus. The GI tract is a portion of the alimentary
tract.
• Parenteral routes include:
Intraocular Intranasal
Dermal Vaginal
Inhalation
Injections
Parenteral Routes
• Uses:
– Oral drug is poorly absorbed or degraded by
stomach acid
– Rapid drug response is desired
– Uncooperative patient
– Unconscious patient
Parenteral Routes of Administration
• Disadvantages:
– Cost
– Requires skill to administer
– Can’t take it back
– Risk of administration, ie. Blood clots, infection
Parenteral Routes of Administration
• Several parenteral routes require a needle
and syringe.
– Intravenous – injected directly into a vein
– Intradermal – administered into the top layer
of the skin
– Intramuscular – administered into a muscle
– Subcutaneous – administered into the
subcutaneous tissue of the skin
Injection types
Intravenous Formulations
• Intravenous dosage forms are administered
directly into a vein.
• It takes 20 seconds for the medication to
circulate throughout the body.
• Solutions are the most common IV
formulations and are aqueous (water).
Complications of IV therapy
•
•
•
•
Thrombus – clot formation
Phlebitis – inflammation of a vein
Air embolism – air introduced into a vein
Particulate matter – small pieces of glass from
a broken vial or ampule
Intramuscular
• Less hazardous than the IV route but many
people experience pain at the injection site.
– Risks include: hematoma, scar formation,
embolism, cyst.
• Injection site should be as far away from
major nerves to avoid nerve injury or damage.
• Only 2 – 5 mL of solution can be given,
amount depended on site. Larger muscle,
more medicine.
Subcutaneous
• Injection or insertion of a device beneath the
surface of the skin.
• Insulin is given by the SQ route
• Risks similar to IM
• Maximum amount of fluid is 2 mL.
Intradermal
• Small volumes that are injected into the top
layer of skin. TB test is only 0.1 mL of
solution.
• Intradermal injections forms a wheal, or
raised blister like area.
Ophthalmic Formulations
• Used for local treatment of the eye.
• Formulations are sterile and are either
suspensions or solutions. Ointments and
inserts are available.
• Disadvantages:
– Loss of dose due to spillage.
– Tears wash away medication
– Drug can get to systemic circulation
– Can be difficult to use
Intranasal
Formulations
• Nasal cavity can hold about 20
mL (or 4 tsp), which is a very
large surface area and has a rich
blood supply.
• Primarily used for decongestant
activity on the nasal mucosa.
• Blood concentrations are about
equal to IV formulations.
• Route being considered for
insulin delivery.
• Disadvantages
– Should not be used for prolonged
periods.
– Drug often swallowed because
often difficult to administer
Inhalation Formulations
• Drugs intended to reach the pulmonary
system.
• Large surface area and rich blood supply, but
due to inconsistencies in absorption the route
is not as good as IV.
• Gaseous and anesthetics are the most
important drugs given this route.
• Most dosage forms are aerosols.
Dermal Formulations
• For local effects on or with in the skin.
• Dosage formulations are lubricants, drying agents,
protectants, emollients, etc. and are used for a variety of
skins conditions.
• Some dermal dosage formulations promote percutaneous
absorption (through the skin) and used for birth control,
cardiac disease, depression, smoking cessation, etc. and
cause a systemic effect.
• Advantages:
– ease of administration
– easily removed if needed.
• Disadvantages:
• absorbed amount is limited.
Vaginal Formulations
• Used generally for localized effects.
• Formulations for this route are solutions,
ointments, creams, foams, suppositories,
tablets, and IUD (contraceptive device).
• Disadvantages:
– Variable absorption
– Toxic Shock Syndrome risk – TSS is a bacterial
infection in the blood.