The Dosage Form
To correctly process a written medication order, it is necessary to know some
basic terminology. When the drug is prescribed, it is usually prescribed in
a specifi c dosage form. The form in which the drug is used depends on
the condition of the patient. Most drugs are taken in tablet form orally (by
mouth), but others must be used in a suppository form (e.g., for a vomiting
patient), topically, in the eye, systemically, on the skin (for a rash or
skin condition), or in oral liquid form (for a child). Some drugs may also be
administered through the skin, via the transdermal patch.
Since different dosage forms are packaged and used differently, it is important
to know which dosage form the drug must be in. In addition, the instructions
written by the prescriber on the prescription form are abbreviated, and
the technician must be familiar with these abbreviations to accurately convey
the instructions to the patient. (See Table 2-1 and Appendix B.)
Solid Dosage Forms
Solid dosage forms are those that can be picked up and handled. These include
the oral dosage forms of tablet, capsule, and enteric-coated tablet
(Figure 2-1).
The Tablet
A tablet is made of pressed powder. How hard the powder is pressed determines
how the tablet can be used. For example, a sublingual tablet is made
to dissolve quickly, under the tongue, and therefore cannot be pressed hard
into a dense tablet. (Since the tablet is so soft, it must be handled very carefully
to avoid turning it into a pile of powder.) An example of a sublingual
tablet would be a nitroglycerin tablet, which is made to dissolve quickly so
that the drug may be rapidly absorbed into the system.
Most tablets are lightly coated with a protective coating (a “fi lm” coating)
to protect the drug. This is does not affect the absorption or dissolution of
the medication. An enteric tablet is coated with a hard-shell coating, designed
to protect the drug from acid in the stomach. The drugs contained in enteric
tablets are normally best absorbed in the basic pH of the duodenum. An
exception is enteric-coated aspirin, which is coated so that it will not dissolve
in the stomach and subject the stomach lining to its effects. Enteric-coated
tablets should not be split or crushed.
The Capsule
A capsule is a gelatin “container” fi lled with powdered drug, drug granules,
a liquid drug formulation, or an oil. Examples would be antibiotics capsules,
liquid vitamins (e.g., A, D, or E), and many over-the-counter cold remedies.
Other Solid Dosage Forms
Other dosage forms, which are less frequently prescribed and solid in nature,
include:
• The lozenge: a hard tablet or molded shape containing drug in a sweetened,
fl avored base. The lozenge is designed to be held in the mouth
while it slowly releases drug for oral absorption. This dosage form is
particularly useful for administration of pain medication for chronic pain
and for the relief of nausea during cancer chemotherapy. Drugs available
in lozenge form are listed in Table 2-2.
• Drug powders for inhalation: In this dosage form, a very fi ne crystalline
form of the drug (a microcrystalline powder) is mixed with an inert sugar
(e.g., lactose) and packaged into a single-dose “blister.” The blister is then
inserted into a special apparatus called a “diskhaler,” which pierces the blister,
aerosolizes the drug, and allows the patient to inhale the medication.
Table 2-2 Drugs Available in Lozenge Form
• morphine sulfate
• lorazepam
• haloperidol
• clotrimazole
• nystatin
• diphenhydramine
• metoclopramide
• dexamethasone
• benztropine mesylate
Liquid Dosage Forms
The liquid dosage forms for oral use include syrup, elixir, and extract.
• Syrup is a sweetened liquid that contains the drug, sugar, and fl avoring.
• Elixir is similar to a syrup but contains a relatively high percentage of
alcohol.
• Extract is the oil or active portion of a plant or herb that is usually
removed, or extracted, with alcohol (e.g., an oil of peppermint or
wintergreen).
Liquid dosage forms
include syrup, elixir,
extract, tincture, solution,
and suspension.
Solutions and Suspensions
If the drug dissolves completely into the liquid (e.g., syrup, elixir), it is called
a solution. Another oral dosage form is the drug suspension, which is composed
of water and drug particles that do not dissolve but remain suspended
in the water. Suspensions need to be handled carefully, as the drug particles
tend to sink to the bottom very quickly. Mixing and drawing the dose can be
tricky—the withdrawal of the drug dose must be done immediately after mixing,
before the drug particles have a chance to settle. If the suspension is not
properly mixed or the dose is not drawn immediately, the wrong dose of drug
may be dispensed. If the dose is taken from the top of the container, it may
contain too much water and not enough drug. If it is taken from the bottom,
the drug solution may be too concentrated because the drug particles tend
to sink. In addition to mixing the suspension thoroughly, how the dose is
withdrawn matters, as well. The dose must be drawn up quickly, as the drug
particles may settle while the dose is being drawn.
Tincture
Tincture is another liquid dosage form. In modern times, it is only used
topically. The tincture is an alcohol-based drug form, such as tincture of
merthiolate, and is normally dispensed in a dropper bottle. These drugs are
not to be taken internally.
Drugs in suspension
need to be handled
carefully, as drug
particles may settle to
the bottom of the container
while the dose
is being withdrawn!
Semisolid Dosage Forms
The semisolid dosage forms include creams, lotions, ointments, and
suppositories.
• Creams and lotions are nothing more than emulsions (oil droplets suspended
in water), where the drug is usually dissolved in the oil. Creams
are thicker, as they contain less water than lotions.
• Ointments may vary from a thick emulsion to a drug suspended in a
waxy base, like petrolatum (which is like petroleum jelly, only much
stiffer and thicker). These preparations are usually used topically (on the
skin or mucous membranes, such as those in the mouth, inside the nose,
or rectum) and are normally dispensed in a tube or jar.
• Suppositories are made of wax and oils, and contain the drug that is meant
to be released slowly, and in a particular place. They are normally inserted
into body cavities, such as the rectum or vagina, where they adhere to the
cavity wall and release medication to the immediate area. Rectal suppositories
are also used to medicate patients who cannot take medication orally
(e.g., a vomiting patient), as the medication, if properly prepared, can be
absorbed through the rectal wall into the bloodstream. Suppositories are
normally large, and, being primarily made of soft wax, will melt at body
temperature. They should be stored in a cool room or refrigerated
(depending on the drug), and handling should be kept to a minimum
Storing Emulsions
Care must be taken when storing emulsions. Freezing the emulsion or exposing
it to excessive heat (near a heat source, for example, or storage in a warm room
for a long time) will cause the cream to separate into oil and water. Emulsions
should not be stored in the refrigerator and especially should never be frozen,
as the rapid change in temperature will cause the product to separate faster.
Emulsions should
never be frozen or
exposed to heat!
Administering the Drug—The Route of Administration
The route of administration defi nes how the drug gets into the body. Drugs
to be administered by different routes are prepared in different ways. The
most common route of administration is by mouth (oral, or po). These drugs
are given as a tablet or oral solution. Sublingual tablets (SL) are made to
dissolve under the tongue; the underside of the tongue and the fl oor of the
mouth contain large amounts of blood vessels near the surface, which allow
the drug to be absorbed into the system very quickly. These tablets are very
soft and dissolve easily. Sublingual preparations are also marketed in a spray
formulation, which are sprayed under the tongue.
Routes of administration include the following:
• Intranasal: a drug in drop or spray form is used
• Transdermal: a drug “patch” is used, which slowly releases drug into
the skin, where it is picked up by surface blood vessels and absorbed
into the body
• Inhalants: drugs may be used in powder or liquid form, in combination
with an inhalant apparatus, to be taken directly into the lungs
(e.g., drugs used for asthma)
• Administration through body cavities: drugs may be used in cream or
suppository form. They are inserted into body cavities, such as the
vagina or rectum, and used for local administration (e.g., for a yeast
infection or a case of hemorrhoids, respectively). Rectal administration
is also very useful for administration of drugs to a patient who cannot
take medications orally, as the drug is absorbed through vessels in the
rectal wall.
Drugs may also be administered through the lining of the cheek. This is
termed buccal (bYOUcahl) administration. The dosage form, in a lozenge or
buccal tablet, is inserted between the cheek and the gum.
Medicating the Eye and Ear
Drugs for the eye (ophthalmics) or ear (otics) are administered by drop (gtt).
The dropper or dropper container is calibrated to give a drop of the particular
size needed to give an accurate dose of drug.
Ophthalmic ointments may also be used (e.g., antibiotic ointments) and
are applied to the inside of the eyelid (usually at the bottom of the eye). The
tip of the ointment tube should never touch the eye.
Figure 2-2: Sterile instillation of eye medication
Parenteral Drug Administration
Any drug that is not given through the digestive system is given parenterally
(para means “around” and enteral refers to the digestive system). In
normal medical terms, however, parenteral administration refers to drugs
administered by injection. The three most common types of injections
are the intravenous, intramuscular, and subcutaneous injections. Other
types of injections include the intra-arterial, intracardiac, intrathecal, and
intradermal injections.
Injectable Drugs
Injections vary according to type. Intravenous injections are prepared in
three ways:
• The bolus: a one-time single-dose injection
• The IV drip: a bag or bottle of liquid that allows drug to be infused
over a long period of time (Figure 2-3)
• The “piggyback” IV: a solution contained in a smaller IV bag that is
infused along with the primary intravenous drip, usually through the
same tubing (Figure 2-4)
Intravenous injections
are seen in three
forms—the IV bolus,
IV drip, and “piggyback”
IV.
Intramuscular Injections
Intramuscular injections are placed into skeletal muscle. This allows the drug
to enter the bloodstream more slowly. This type of injection must fi rst diffuse
through muscle tissue before entering the bloodstream, so it requires a largebore
needle in order to penetrate the muscle.
The advantage to this type of injection is that the slow release of drug
into the system minimizes shock to the system, allowing it to gradually acclimate
to the effects of the drug.
Subcutaneous and Intradermal Injections
Injections into or under the skin include subcutaneous and intradermal injections.
Subcutaneous injections are placed under the skin, which allows for a slow
Figure 2-3: The IV Drip
When preparing an
intramuscular injection,
a large-bore needle
should be attached,
as a small needle will
not easily penetrate
muscle tissue.
absorption of drug into the bloodstream. Intradermal (ID) injections, which
are less common, are placed within the skin layers. Both of these types of injections
must be dispensed with a very fi ne needle (25–31 gauge) on the syringe.
Specialized Injections
Intra-arterial Injections. Occasionally, drugs need to be administered directly
into an artery, in order to have the best eff ect. Th ese are called intra-arterial injections.
Arteries are very muscular and the blood within them is under very high
pressure, so these injections require a somewhat larger bore needle.
Intrathecal and Intracardiac Injections. Intrathecal and intracardiac injections
are specialized injection forms. Intrathecal injections are placed into the
space between the spinal cord and spinal meninges (e.g., an epidural anesthetic
during childbirth), and intracardiac injections are placed directly into
the heart. These types of injections allow fast action of a drug by placing the
drug at the site of the organ itself.
Primary IV
Secondary IV
Figure 2-4: The Piggyback IV
Intramuscular and
subcutaneous injections
provide for a
slow rate of delivery of
drug to the system.
Interpreting the Prescription Order
Before fi lling the prescription order, you must fi rst check the prescription
form to make sure that the order is genuine, legal, and complete. Certain
information must be on the prescription form when it is received, and other
information may be fi lled in by the technician, unless the prescription is for a
controlled substance. In this case, no information is to be added, deleted, or
corrected on the prescription form.
Table 2-1 lists abbreviations commonly used on the prescription form
by the prescriber. These abbreviations must be interpreted accurately to
ensure that the correct medication is dispensed and that accurate instructions
are provided to the patient for the use of the medication. Additional
abbreviations may be found in Appendix A. You may be asked about any
of these, even abbreviations seldom used, on the exam, so it is wise to be
familiar with them.
Figure 2-5 represents the prescription form that would be received at the
pharmacy window. Information required to correctly fi ll this order is found
in the body of the prescription. Review the information required to appear
on the prescription:
• The drug name: This can be generic (the actual name of the drug) or a
brand (proprietary) name. This prescription specifi es the exact drug to
select for dispensing. This prescription was written for a brand name,
Lasix, although the prescriber did sign on the “May Substitute” line, so
generic substitution is permissible.
• The strength and dosage form of the drug: Drugs come in different
strengths and forms for different needs. The strength and form must
be specifi ed, unless the drug comes in only one form or strength. For
example, some combination drugs such as trimethoprim with sulfamethoxazole
combination or acetaminophen with codeine (Tylenol
#3, etc.) are dispensed in a specifi c dosage and proportion. Mannitol is
dispensed only in a solution for injection. The proportions and forms
of these drugs do not need to be specifi ed on the prescription form. In
contrast, Lasix tablets come in 20 mg, 40 mg, and 80 mg strengths, as
well as in oral solution and solution for injection. The dosage strength
Drugs are dispensed in
diff erent dosage forms
for diff erent needs.
John Smith M.D.
201 Tablet Lane
Anywhere USA
DEA# AS274064
Name
Address
Dispense as Written
Refill 0 1 2 3 4 5
SIG:
T
Date
May Substitute
Sally Swollen
John Smith M.D.
2/1/XX
Lasix 40 mg tabs #60
BID PRN edema
Figure 2-5: Sample Completed Prescription Form
and form did need to be specifi ed in the sample prescription shown in
Figure 2-5.
• The amount of drug prescribed: A prescription for tablets, such as that
in Figure 2-1, must specify the number of tablets to be dispensed. For
other dosage forms, however, this may not be the case. For example, a
prescription for a liquid dosage form may be specifi ed in more than one
way. Either the volume may be specifi ed, or the drug dose may be specifi
ed in mg, g, and so on.
EXAMPLE
The prescription order is for 500 mL of 10% calcium gluconate solution.
Since the volume was given, the specifi ed amount of solution (500 mL)
would be dispensed.
EXAMPLE
The prescription order is for 200 mg of Minocin IV. Minocin comes in a
sterile solution of 20 mg/mL. In this case, the volume of solution to be
dispensed for a 200 mg dose would have to be calculated (e.g., 200 mg
divided by 20 mg 10 mL).
• Instructions for the patient (the SIG): This is where knowledge of the
abbreviations in Table 2-1 comes in. Since the instructions must be
written out for the patient, the technician must be able to accurately
read the SIG. The prescription in Figure 2-5 states that one tablet
(designated by a horizontal bar with one vertical bar and one dot) is to
be taken twice a day (bid, or bis in deum), as needed (prn) for edema.
The amount of medication to be taken, and limitations on when or how
often it is to be taken, must be included on the prescription form.
The spacing of the doses, or dosage interval, is extremely important, as
the space between doses is based on the half-life (T1/2) of the drug. The T1/2
is a measure of how rapidly a drug is cleared from the body, and gives an
estimate of how quickly the effects of the drug will be terminated. (There
are many ways in which the actions of a drug may be terminated, but the
half-life is generally considered to be the main index of the length of a
drug’s effects.)
The half-life can be used to predict the dosage interval for a drug. To keep
the serum levels of a drug relatively constant, the drug should be replaced as
it is cleared from the body. Thus, dosage intervals are very important, and
the instructions for taking the drug must be communicated effectively to the
patient. It is also important to communicate to the patient the proper use of
the drug (e.g., proper insertion of a suppository, instillation of an ophthalmic
preparation, etc.).
The half-life of a drug
is the amount of time
taken for half of the
serum concentration
of drug to be eliminated
from the body.
It is used to establish
accurate dosage
intervals.
A drug dose may be
specifi ed by volume or
by equivalent weight
of drug.
EXAMPLE
The time it takes a drug to be eliminated from the body is around 5–7
half-lifes. If a drug has a 6-hour half-life, then it would take 30–42 hours
to be eliminated. (6 hrs 5 30; 6 hrs 7 42.)
• Signature of the prescriber and authorization to substitute: The signature
must be handwritten in ink. The authorization to dispense a generic
drug may be indicated in a box on the prescription form, in which the
letters “DAW” (“dispense as written”) are written (indicating that the
exact proprietary label must be dispensed) or absent (indicating that a
substitution is permissible). Depending on the state, the prescription
form may contain this box or may have a duplicate set of signature lines
bearing a designation such as “may substitute” or “no substitution permissible.”
If the prescriber designates “no substitution permissible,” the
drug must be dispensed exactly as written, in the correct form, strength,
and under the specifi ed proprietary label.
Information is normally entered on the prescription form by the technician
and then transferred to the patient profi le. Information to be gathered
includes the following:
• The patient’s address and telephone number: This information identifi es
the patient (there may be more than one patient with the same name).
It also provides a means of contact with the patient, in case of a problem
with a prescription or drug recall.
• The age or date of birth of the patient: This information is very important,
as it serves to identify the patient (e.g., to distinguish between a
father and son with the same name) and assures that the drug dosage
prescribed is appropriate for the age of the patient (drug dosage may be
reduced in a child or elderly person, for example, as organ functions are
less effi cient).
• Drug allergies: Many drugs are very similar in chemical structure and action.
Thus, if a patient is allergic to one drug (e.g., penicillin), he or she
may well be allergic to similar drugs, such as amoxicillin or even cephalexin.
A history of drug allergies is critical to the care of the patient, as it
may help prevent an uncomfortable or even fatal allergic reaction.
• Concurrent medications: These are medications already being taken by
the patient. A history of concurrent medications should include not
only other prescription medications but also those purchased over the
counter (e.g., cold remedies), and herbal remedies as well. (The fi rst
drugs were little more than pulverized plants, or plant extracts, after
all. We have done little more than refi ne them, in many cases.) Herbal
preparations can have very potent drug actions and interactions and
must be recorded in the patient profi le.
The “may substitute”
option gives the
patient and pharmacy
the option to choose a
less expensive generic
brand or another proprietary
label, as long
as the drug, strength,
and form remain the
same.
Many drugs interact
with each other to produce
adverse eff ects.
A particular drug may
also greatly increase
the therapeutic effects
of another drug,
which would require
an adjustment to the
patient’s dosage.
Dispensing the Correct Medication
Once the drug, dosage form, and strength have been established, the correct
medication is selected. This medication should be exactly what appears on the
prescription form.
Verifying the Medication—Use of the Manufacturer’s Label
Many drug names look alike and sound alike, so the manufacturer labels must
be compared carefully to the prescription order.
EXAMPLE
Extra letters may be present in the drug name on the label (e.g., Adalat
CC instead of Adalat). This may mean the drug is a different formulation
of the brand-name drug (in this case an extended-release form) or
may be a different drug altogether (e.g., quinine and quinidine). Some
of those abbreviations can be found in Table 2-3. If the name of the
drug does not match exactly, the drug should not be dispensed.
Verifying the Proper Dosage Strength
The choice of dosage strength is less critical than other information. If the
dosage strength does not match, it may be possible to convert dosages
(see Chapters 4 and 14). If the dosage form is incorrect, however, the drug
cannot be dispensed by the technician without consulting the pharmacist.
Table 2-3 Extended-release Formulations
LA long acting
SA sustained acting
SR sustained release
TR timed release
ER extended release
EXAMPLE
The drug order is for 250 mg amoxicillin tablets. There are no tablets
in stock, but the pharmacy does have amoxicillin suspension in stock
for oral administration. Both dosage forms are for oral administration,
so the suspension could be substituted, with proper calculations and
patient instruction (this would require the approval of the pharmacist).
EXAMPLE
The drug order is for Compazine suppositories. You have Compazine
solution for oral administration in stock, but no suppositories. The
order cannot be fi lled, as the dosage forms do not match (suppositories
are normally prescribed for patients who cannot take medications
orally).
Automated Unit Dose Delivery Systems
There are several automated dispensing systems presently marketed for institutional
use. One popular and innovative automated unit dose delivery
system coming into widespread use in institutional pharmacy is the Pyxis Rx
System. The Pyxis system is essentially a computerized cabinet that is located
on a hospital fl oor (unit). The cabinet is stocked with drugs, which are appropriate
to the particular hospital unit where it is located. Like the med
cart, drugs are fi led in locked drawers within the cabinet, and the units are
maintained and stocked by pharmacy personnel. The computer within the
Pyxis unit is on a local area network, which interfaces with the main hospital
computer. Thus, the unit actually charts patient medications as they are withdrawn
from the cart by hospital personnel.
Processing of Medication Orders Using the Pyxis System
The Pyxis system streamlines the dispensing of medication. Medication orders
are received as usual from physicians in the pharmacy. The pharmacy technician
then enters the orders into the main hospital computer system. The orders are
then checked by the pharmacist to ensure that the medications and doses are
appropriate for the age, weight, and diagnosis of the patient, and that therapeutic
duplications and drug-drug interactions are not present. The order is
then sent to the Pyxis system. Once the order has been verifi ed and is present
in the system, the fl oor nurse can enter appropriate information into the system
when it is time for a patient’s medication. The system then allows the withdrawal
of the proper unit doses of medication for administration to the patient.
Identifi cation of the nurse, by thumbprint or code, must be received by the
unit for the medication drawers to unlock and the medication to be withdrawn.
Advantages to the Use of Automated Unit Dosing Systems
The advantages to this system are many: Medication errors are reduced, as
the medication dispensed comes directly from the original medication order
(i.e., not faxed, transcribed, or photocopied); drug-drug interactions are
reduced; and patients receive their medications in a more timely manner, allowing more effective dosing. In addition, input from the pharmacist is almost
instantaneous. Blood analysis of drug levels can also be included in the
computerized information, allowing dosages to be adjusted almost instantaneously.
This provides better control over patient medication. Also, as patients
are transferred from room to room and fl oor to fl oor, their information
remains centralized with less chance of record loss. Documentation of drug
dispensing and administration is generated automatically with the system,
and can be printed out at any time, should a hard copy be needed.
Comparison of Drug Dispensing in Retail and Institutional Settings
Dispensing a prescription in an institutional setting is similar to the retail
setting, with a few exceptions. Several drugs are usually prescribed at once
(see Chapter 1) using the hospital order; these doses may be sent up to the
patient individually (e.g., a medication needed quickly, for an emergency
[STAT], or a medication prescribed for pain, emesis, etc., which is not part
of the usual routine of drugs), or placed into a unit dose cart. Unit dose
carts contain the daily medications of the patients on a particular hospital
fl oor. They are prepared daily by technicians and then checked by pharmacists.
These computerized carts contain the individual medications of
patients on the fl oor, normally enough to last for one day. The carts are
fi lled daily, from the physician’s orders for the various patients on the fl oor,
making it easier for nurses to properly administer medications to patients.
Narcotics prescribed “as needed” may not be dispensed in a unit dose cart.