Navigating the Wide World of Dosage Forms

While there's nothing fun or interesting about learning the various dosage forms (and believe me, there's a lot), learning them will help you to avoid mistakes. There is nothing more confusing to a patient than when their label says capsule and there are tablets in the bottle and vice versa. And knowing the difference between forms makes you better at your job. The dosage form can tell you which auxiliary stickers to affix or alert you to medication errors. If the form and the route don't match according to the prescription, the doctor may have prescribed the wrong medication.

There are no shortage of dosage forms. I'm going to try to break it down as simply as possible by route of administration. This may result in some duplicate entries (there are rectal and vaginal suppositories and suspensions for just about every route of administration).

Oral Solid Forms

• Tablet - Consists of active ingredient with fillers compressed into a formed unit. Can take any shape and color, the most common dosage form
• Capsule - Consists of a shell, usually made of gelatin, encasing the active ingredients. Available in many sizes from 000 upward (000 being the largest size, NOT the smallest)
• Modified Release Capsules or Tablets - As above, but with alteration to the release mechanism. These cannot be crushed, chewed or split unless otherwise noted in the manufacturer's package insert. 

Oral Dispersable Forms

• Chewable - Consists of active ingredient with fillers compressed into a formed unit, binders easily allow chewing for those who have difficulty swallowing solid forms
• Orally Disintegrating Tablets - Consists of active ingredient with fillers compressed into a formed unit with disintegrators which are unstable in moisture, allowing the tablet to dissolve on the tongue. Also called solutabs and melts
• Sublingual - Consists of active ingredient with fillers compressed into a formed unit with disintegrators which are unstable in moisture where the active ingredient is intended to be absorbed from into the blood stream from under the tongue, bypasses first-pass metabolism 
• Buccal - Consists of active ingredient with fillers compressed into a formed unit with disintegrators which are unstable in moisture where the active ingredient is intended to be absorbed from into the blood stream from the vestibule (area between the cheeks and teeth), bypasses first-pass metabolism 

Oral Liquid Forms

• Solution - Active ingredient is completely dissolved in a liquid vehicle
• Suspension - Active ingredient is incompletely dissolved into a liquid vehicle, resulting in particles of the active ingredient visible in the liquid. May settle while sitting, requires shaking before administration. Most common dosage from for pediatric antibiotics when the patient is too young to take oral solids
• Elixir - Active ingredient is dissolved in water and alcohol, often used when the active ingredient is insoluble in water alone
• Effervescent Tablets - a tablet that is dissolved in water before administration; eg. Alka-Seltzer tablets

Oral Inhaled Forms

• Aerosol - Active ingredient is suspended in a liquid vehicle with a propellant, usually HFA (hydroflouroalkane), since CFCs were banned in the United States due to concerns about ozone damage
• Powder - Active ingredient is contained within a capsule or foil strip which is punctured or opened and the active ingredient is inhaled in powder form

Nasal Inhaled Forms

• Solution - Active ingredient is completely dissolved in a liquid vehicle, more common of nasal antihistamines, such as azelastine
• Suspension - Active ingredient is incompletely dissolved into a liquid vehicle, resulting in particles of the active ingredient visible in the liquid. May settle while sitting, requires shaking before administration. More common of nasal corticosteroids, such as fluticasone

Otic (For the Ear) Forms

• Solution - Active ingredient is completely dissolved in a liquid vehicle
• Suspension - Active ingredient is incompletely dissolved into a liquid vehicle, resulting in particles of the active ingredient visible in the liquid. May settle while sitting, requires shaking before administration.

Ophthalmic (For the Eye) Forms

• Solution - Active ingredient is completely dissolved in a liquid vehicle, ophthalmic formulations of medications are designed to be isotonic with fluids in the eye and can be used in the ear if needed (otic preparations cannot be used in the eye)
• Suspension - Active ingredient is incompletely dissolved into a liquid vehicle, resulting in particles of the active ingredient visible in the liquid. May settle while sitting, requires shaking before administration. Ophthalmic formulations of medications are designed to be isotonic with fluids in the eye and can be used in the ear if needed (otic preparations cannot be used in the eye)
• Ointment - A mixture of liquid and solid ingredients (semisolid) that is applied externally, usually of a petrolatum base. Ophthalmic formulations of medications are designed to be isotonic with fluids in the eye

Rectal Formulations

• Suppositories - A solid dosage form with the active ingredient mixed into a waxy vehicle which melts at body temperature and delivers the medication
• Suspension - Active ingredient is incompletely dissolved into a liquid vehicle, resulting in particles of the active ingredient visible in the liquid. May settle while sitting, requires shaking before administration. Eg. Rowasa (mesalamine) rectal suspension

Vaginal Formulations

• Suppositories - A solid dosage form with the active ingredient mixed into a waxy vehicle which melts at body temperature and delivers the medication
• Cream - A semisolid mixture with the active ingredient suspended in a cream base. Vaginal creams are specially formulated to match the pH of the vagina and non-vaginal creams should not be used internally

Topical Formulations

• Lotion - Active ingredient is incompletely dissolved into a liquid vehicle, resulting in particles of the active ingredient visible in the liquid. May settle while sitting, requires shaking before administration
• Ointment - A mixture of liquid and solid ingredients (semisolid) that is applied externally, usually of a petrolatum base
• Cream - A semisolid mixture with the active ingredient suspended in a cream 
• Aerosol/ Spray - Active ingredient is suspended in a liquid vehicle with a propellant, usually HFA (hydroflouroalkane), since CFCs were banned in the United States due to concerns about ozone damage
• Shampoo - sometimes a solution, gel or suspension mixed with soaps that causes a lather
• Solution - Active ingredient is completely dissolved in a liquid vehicle
• Suspension - Active ingredient is incompletely dissolved into a liquid vehicle, resulting in particles of the active ingredient visible in the liquid. May settle while sitting, requires shaking before administration. Often called lotions
• Transdermal Patch - Active ingredient is contained in a matrix held to the skin by adhesive and releases the medication into the blood stream over time