DOSAGE FORMS

In order to take advantage of this multitude of medication administration routes,
a similarly diverse number of dosage forms have been devised. Some, such as urethral bougies, are no longer in common use, while others, such as the transcutaneous
patch and metered dose inhalers (MDI), are becoming increasingly popular.

Pills and Powders
When the general public thinks of an oral dosage form, the word pill is commonly
used. The pill is actually an archaic dosage form. Pills consist of medication combined
with inactive ingredients to form a gelatinous (doughy) mass. This mass is
then divided, rolled into cylinders on a pill tile, and then cut into individual pills.
The pills are then dried prior to use. Currently, few medications are truly pills.
Carter’s Little Liver Pills® and Lydia Pinkham’s Pills® are among the last of a once
popular dosage form for both manufactured and extemporaneously prepared medications.
Powder papers (a small, precisely measured quantity of medication and
diluent inside a folded piece of paper) were once a popular method of drug delivery.
Two over-the-counter (OTC) popular medications are available in this form: BC
Powders® and Goody’s Powders®.

Tablets, Capsules, and High Tech

The most common dosage form is the tablet. It is prepared from a dry mixture
of active and inactive ingredients (excipients). The excipients include binders, lubricants,
diluents, and coloring agents. This mixture is mechanically compressed into
solid tablets in various shapes. The excipients are considered inert ingredients, but
can occasionally cause difficulty in individual patients. Lactose is commonly used
as a diluent. The quantity is usually too small to cause adverse effects, even in a
lactose intolerant individual. Tartrazine, commonly called FD&C yellow dye No. 5,
is a coloring agent. Serious allergic reactions are possible to this agent and to
medications colored with it. Capsules are the other most common oral dosing form.
Active ingredients, diluents, and lubricants (to improve the flow of the powder
through the equipment) are put into preformed, hard gelatin shells that are then
mated with a second gelatin shell. Liquid medication can also be sealed into a
capsular shell. Several variations on the manufacturing of tablets and capsules can
result in delayed or extended medication release into the gastrointestinal tract. The
absorption of the drug into the bloodstream and the pharmacological effect of the
drug will be affected by this alteration in the release of the medicine. The most
advanced oral dosage forms use semipermeable membranes or laser technology to
produce dosage forms that release medication into the gastrointestinal tract at a
controlled rate.
Some drugs may be absorbed from the capillary beds in the mouth. Nitroglycerin
tablets are designed to dissolve under the tongue and will be absorbed sublingually.
Recently, rapid dissolving tablets have been developed to deliver medications into
the gastrointestinal tract. The medication is released in the oral cavity but is absorbed
at numerous locations in the gastrointestinal tract. This results in a quicker onset of
action. Rapid disintegration (RD) is frequently associated with this type of dosage
form. Other medications may be designed for absorption from the inner aspect of
the cheek. These are referred to as buccal dosage forms. Lozenges may be used to
deliver medication into the oral cavity for both local and systemic action. Local
anesthetics for treating a sore throat can be put into a lozenge. A powerful pain
medication, fentanyl, is available in a lozenge on a stick form for transmucosal
absorption. Cough suppressants are also available as lozenges.

Liquids
Of course, oral liquids remain a popular dosage form. This category includes
solutions such as teas (infusions and decoctions), fluid extracts, syrups, drops, and
tinctures, as well as emulsions and powders ready for reconstitution with water. With
the popularity of “natural remedies,” the use of teas and homemade preparations has
increased. All oral liquids are relatively simple in comparison to oral liquid nutritional
supplements. The supplements are generally oil-based solutions emulsified within
water-based solutions with some of their ingredients suspended in a colloidal form.
Recently, the introduction of foods having desirable pharmacological properties
has further blurred the distinction among drugs, nutritional supplements, and foods.
Benecol® (contains plant stanol esters) and Take Control® (plant sterol-enriched
spread) are the best examples of this, but even the marketing of oatmeal and oat
bran ventures into this newly grayed area separating drugs and foods.

Rectal Dosage Forms
Other enteral dosage forms are designed for absorption in the sigmoid colon and
may be solid dosage forms (suppositories), liquids (enemas), or aerosols (foams).
Again, both local and systemically acting medications may be given via this route.
Hemorrhoid treatments, antiemetics, laxatives, and antipyretics (medications used
to treat fever) are all commonly given in these forms.

Topical Agents
Topical dosage forms are similarly diverse. Ointments (oil base) may deliver
topical medications. Creams (water-soluble base), gels, and mustards (pasty substance
spread on a cloth and wrapped around a body part) also do so. Shampoos,
soaps, solutions, and topical patches may also deliver medication in a useful manner.
Nasal, ophthalmic, and otic (for the ear) solutions and suspensions are available.
Aerosols, sprays, nebulized medications, metered dose inhalers, and powders for
inhalation are used to deliver medication to the respiratory tract. Intravaginal suppositories
(also called vaginal tablets), creams, douches, and sponges are used to
deliver medications.

Injections
Parenteral dosage forms are mainly water-based solutions, but a few novel
approaches are used. These include solutions in solvents other than water, oil-in- water emulsions, and even drug-impregnated solids used as subdermal implants.
Recently, drugs have even been delivered inside liposomes in a parenteral liquid.

Pharmaceutical Elegance: Coats to Disguise, Protect, and
Increase Duration
Coatings have been used on tablets to hide bad tastes (e.g., E-Mycin—erythromycin).
One liquid suspension (Biaxin®—clarithromycin) consists of film-coated
granules. The coating again hides the taste of the medicine. Interestingly, this is a
liquid medication that should not be given via a small-bore feeding tube. The
granules can “logjam” at the curves in the tube and occlude it. Other coatings,
referred to as enteric coatings, are used to prevent dissolution and inactivation of
the drug in the stomach by gastric secretions. Extensive efforts have been made to
engineer dosage forms that change the absorption of medications. The goal is usually
to extend the duration of action for a drug with a relatively short half-life. Repetabs®
provide an example of tablets designed to provide a quantity of quickly released
medication followed by a quantity of drug released slowly over time. Capsules can
contain pellets coated with varying thickness of slowly dissolving excipients to
achieve a timed-release bioavailability. Since medications are sometimes crushed
before administration, one needs to know why the coating was on the tablet, where
the drug will enter the gastrointestinal tract, and how removing the coating will
affect the bioavailability of the dosage form.