BMS 113 · Common Core (Tronc commun)Section 3.2 · Pharmaceutical dosage forms
Section 12 of 31
Solid dosage forms
Describe the main oral solid dosage forms with their advantages and disadvantages.
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Why this matters
Most medicines a patient meets in practice are solid, so this is the section you will use every day at the dispensing counter. If you cannot tell an enteric-coated tablet from an extended-release one, you may tell a patient to crush a tablet that must be swallowed whole. Then the dose arrives all at once or in the wrong place.
What you need to know first
You need only Unit 3.1, which explains what a dosage form is and why excipients are added. No other background is required before this section.
Words to know (5)
Tablet
A hard unit dose made by compressing a powder of active ingredient and excipients. A round white 500 mg paracetamol tablet.
Enteric-coated tablet
A tablet with a coat that stays intact in stomach acid and dissolves only in the small intestine. An enteric-coated ibuprofen tablet spares the stomach.
Extended release
A design that releases small amounts of drug continuously over a calculated period instead of all at once. One sustained-release tablet replaces three daily doses.
Capsule
A soluble hollow container, usually of gelatin, that encloses a powder, granule or liquid drug. A fish-oil supplement is a soft gelatin capsule.
Effervescent tablet
An uncoated tablet with an acid and a carbonate that react in water and release carbon dioxide. It fizzes and dissolves in a glass of water before drinking.
One idea at a timeIdea 1 / 7
In one sentence A tablet is a hard compressed unit dose, so each tablet already contains the exact amount that the patient must take.
Tablets are compressed unit doses
A tablet is a hard, compressed medication containing a unit dose of one or more active ingredients together with excipients. Tablets come in various sizes from a few millimetres to a centimetre, in various shapes such as round, oval or square, and in various colours. Their excipients each have a job: disintegrants ensure that the tablet breaks up in the digestive tract, sweeteners or flavours mask the taste of bad-tasting active ingredients, and binders, glidants and lubricants ensure efficient tableting. Because each tablet is a unit, the patient never has to measure anything.
For example
A round white 500 mg paracetamol tablet contains its active ingredient, a disintegrant, a binder, a lubricant and perhaps a colourant — all listed on the label.
Pause and check yourself
Why does a tablet need no measuring by the patient?
Show the answer
Because it is a unit dose: the manufacturer has already measured the active ingredient into each compressed tablet.
Read detailed explanations
Enteric coating: a decision about pH, not about strength
An enteric coating is a polymer film chosen because it stays intact in acid and dissolves in a less acidic environment. The stomach is strongly acidic; the small intestine is not. The coat therefore behaves like a timer set by chemistry rather than by minutes. Two different problems are solved by the same trick. When the drug irritates the gastric mucosa, the coat protects the stomach by keeping the drug away from it. When the drug itself is destroyed by acid, the coat protects the drug until it reaches an environment where it can be absorbed. The vocabulary matters here: gastro-resistant or enteric-coated describes the coat; delayed release describes the timing that results. A newcomer’s misconception is that an enteric coat is simply a stronger or slower version of an ordinary tablet. It is not slow in the sense of gradual: once the coat dissolves, an enteric-coated tablet usually releases its whole dose at once in the small intestine. That is why an enteric-coated tablet must not be crushed for a patient who cannot swallow, and why the note “do not chew” appears on labels. A second misconception is that an enteric coat protects a drug from being destroyed anywhere in the gut. It only changes the site of release; the drug is still exposed to everything that happens after that site.
Extended release: the arithmetic of fewer doses
An immediate-release tablet produces a rise and then a fall in drug concentration, which is why the dose must be repeated. An extended-release tablet tries to hold the concentration steadier by releasing small amounts continuously over a calculated period. The benefit is practical: fewer administrations per day, a more even effect and better compliance, which matters most for medicines taken for long periods. The names to recognise are sustained release, sustained action, prolonged action, long acting, controlled release and timed release; they are used loosely in practice, and the label is the reliable guide. The mechanism behind the release can differ — a slowly eroding matrix, a membrane that the drug diffuses through, or an osmotic pump — but the clinical consequence is the same and so is the rule: the tablet must be swallowed whole. A beginner’s misconception is that an extended-release tablet is merely a stronger tablet. It is not stronger; it contains the amount needed for the whole period, and that amount is only safe because it is released slowly. Chewing, crushing or dissolving it converts a day-long dose into a single dose, which is a potential overdose. A related practical point is that some extended-release tablets may appear in the stool apparently intact once the drug has been extracted; that is not necessarily a sign that the medicine failed.
Explore the diagram
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Oral solid dosage forms
Tablets, capsules, powders, granules and the older solids, with the coat types, the advantages and limitations of the group, and the rule that extended-release tablets must never be chewed.
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01 / 6Tablet types
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Tablet types
Immediate-release tablets dissolve and release the drug at once; chewable tablets are chewed to speed disintegration, for children and vitamin products; effervescent tablets contain an acid and a carbonate that bubble in water. Coated tablets carry a sugar, film or enteric coat, and extended-release tablets release small doses over hours.
Schematic; not to scale. Coating thickness is exaggerated so the coat and core can be seen; the absorption ranking is reproduced from the lecture notes.
Key points to remember
✓A tablet is a compressed unit dose, so the patient measures nothing.
✓Coatings mask taste, ease swallowing, improve stability and can delay release until the intestine.
✓Extended-release tablets spread one calculated dose over hours and must never be chewed.
✓Tablets are cheap, stable and measurable but difficult for children, the elderly and unconscious patients.
✓Powders, granules, lozenges, pastilles and dental cones are the remaining solid forms.
Go deeper
Worked example
Choosing a solid form for three patients. A clinic must give the same two medicines to three patients: a six-year-old child who needs a vitamin supplement, an adult taking an anti-inflammatory that irritates the stomach, and an elderly patient who finds tablets difficult to swallow. You are asked to choose a solid dosage form for each and to justify the choice.
The child: choose a chewable tablet or an effervescent tablet. Chewing enhances disintegration and dissolution, and chewable forms are designed for administration to children.
The adult with gastric irritation: choose an enteric-coated tablet, because the coating does not dissolve until the tablet reaches the small intestine, protecting the stomach from a drug such as ibuprofen.
The elderly patient: a capsule is easier to swallow than a tablet, and an effervescent tablet dissolved in water avoids swallowing a solid unit altogether.
Check the limits: none of these choices helps an unconscious or vomiting patient, and if the drug exists only as an extended-release tablet it must never be crushed or chewed to make it easier to swallow.
There is no single best solid form. The right choice depends on who is swallowing, what the drug does to the gut, and what the formulation is designed to release — and the instructions on the label must be respected.
Common misconception
A common beginner belief is that any solid form can be crushed, split or chewed to make swallowing easier. That is false for enteric-coated and extended-release tablets: crushing an enteric coat exposes the stomach to an irritant drug, and chewing a sustained-release tablet releases the whole calculated dose at once.
Check your reasoning
Explain, in terms of release, why an enteric-coated tablet and an extended-release tablet must not be treated in the same way as an ordinary tablet.
Reveal an answer
Both carry a design that controls when the drug is released. The enteric coat holds the drug back until the small intestine, so the stomach is spared; the extended-release matrix meters out small doses over hours. Crushing or chewing destroys that control: the drug is released at the wrong place or all at once, which can cause local injury or overdose.
Where this comes from
BMS 113 General Pharmacology I lecture notes · Unit 5, pp. 24–30
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About this course and its sources
Bilingual lessons organised from the supplied BMS 113 General Pharmacology I lecture notes. Diagrams are original educational schematics; pharmacology, nursing and French-language review are pending.