1. Tablets

2. Tablet Ingredients

3. Excipients determine:
In addition to active ingredients, tablet contains a number of inert materials known as additives or excipients.
The use of appropriate excipients is important in the development of the optimum tablets.
Excipients determine:
the bulk of the final product
the speed of disintegration
rate of dissolution
release of drug
protection against moisture
stability during storage, and
compatibility.

4. Excipients are classified according to the part they play in the finished tablet.
Different excipients are:
1. Diluent
2. Binder and adhesive
3. Disintegrants
4. Lubricants and glidants
5. Colouring agents
6. Flavoring agents
7. Sweetening agents

5. 1. Diluents (Fillers)
Diluents are inert substances that are added to make required bulk of the tablet when the drug dosage itself is inadequate to produce the bulk.
Filler is not necessary if the dose of the drug is high.
Tablets weigh normally at least 50 mg, therefore a low dose of a potent drugs requires addition of a filler to increase the bulk volume of the powder and hence the size of the tablet.
One or more diluents may be used in one tablet preparation.

6. A diluent should have following properties: 1. Non toxic. 2
A diluent should have following properties: Non toxic Commercially available Low cost They must be physiologically inert. 5. They must be physically & chemically stable by themselves & in combination with the drugs They must be free from all microbial contamination They do not alter the bioavailability of drug.

7. Commonly used tablet diluents
Carbohydrates
Celluloses
Inorganic salts

8. Commonly used tablet diluents
1.Lactose, Starch and directly compressed starch-Sta Rx 1500.
2.Sucrose- Sugartab, DiPac, Nutab
3.Dextrose.
4.Mannitol
5.Sorbitol
6. Microcrystalline cellulose-Avicel (PH 101and PH 102).
7.Dibasic calcium phosphate dehydrate. 8.Calcium sulphate dehydrate.

9. Binders promote the adhesion of particles of the formulation.
2. Binders and Adhesives
Binders promote the adhesion of particles of the formulation.
Such adhesion enables preparation of granules and maintains the integrity of the final tablet.
This insures that the tablet remains intact after compression.

10. These materials are added either dry or in wet form to form granules.
The quantity of binder used has great influence on the characteristics of the compressed tablets.
The use of too much binder or too strong binder will make a hard tablet which will not disintegrate easily and which will cause excessive wear of punches and dies.
The same amount of binder in solution will be more effective than if it were in a dry form and moistened with the solvent. So it is preferable to incorporate the binding agent in solution.
If the drug substance is adversely affected by an aqueous binder, a non aqueous binder can be used.

11. Examples Acacia, tragacanth- Solution for 10-25% Conc.
Cellulose derivatives- Methyl cellulose, Hydroxy propyl methyl cellulose, Hydroxy propyl cellulose.
Gelatin % solution
Sugars: Glucose 50% solution – sucrose - dextrose
Polyvinylpyrrolidone (PVP)- 2% conc.
Starch paste-10-20% solution.
Sodium alginate.

12. 3. Disintegrants
Disintegrants are added to a tablet formulation to facilitate its breaking or disintegration when it contact in water in the GIT.
The breakup of the tablets to smaller particles is important for dissolution of the drug and subsequent bioavailability.
Disintegrants promote such breakup into smaller fragments in an aqueous environment thereby:
increasing the available surface area and
promoting a more rapid release of the drug substance.

13. Primary drug particles Drug in solution in GIT fluids
Tablet disintegration may be critical to subsequent drug dissolution rate and to satisfactory bioavailability
Deaggregation
Disintegration
in the GIT
in the GIT
Intact tablet
Granules
Primary drug particles
Slow dissolution Intermediate dissol Rapid dissol.
Drug dissolution
Drug in solution in GIT fluids
Absorption
Drug in blood

14. Examples Starch: (5-20% of tablet weight).
Starch has a great affinity for water and swells when moistened, thus facilitating the rupture of the tablet matrix.
Usually disintegration time would decrease as the percentage of starch increased.

15. 4. Glidants, antiadherents and lubricants
They have overlapping functions:
A- Glidants
They promote the flow of the tablet granules or powder by reducing friction between particles.
A glidant is a substance that allows particles moving smoothly, continuously.
Examples:
Corn Starch (5-10% conc.)
Talc (5% conc.)

16. B- Antiadherents
They reduce sticking or adhesion of the tablet granules or powders to the faces of the punches or the die walls,
Examples:
Mg stearate
talc
starch.

17. C- Lubricants
They reduce the friction occuring between the walls of the tablets and the walls of the die cavity when the tablet is ejected.
It works by coating on the surface of particles, and thus preventing adhesion of the tablet material to the dies and punches.
Examples:
Stearic acid.
Magnesium stearate.
Talc.

18. Lubricants are thus intended to:
Prevent adhesion of the tablet materials to the surface of dies and punches.
Facilitate the ejection of the tablets from the die cavity.
Lubricants give a sheen to the finished tablets.

19. Problems due to lubricants
They may reduce tablet strength (HOW?) due to their interference with the bonding between the particles during compression (counteract the role of the binder).
They may retard tablet disintegration and dissolution such as magnesium stearate (WHY?) because most lubricants are hydrophobic (counteract the role of disintegrant)

20. How to avoid this negative effect?
1-Minimum amount of lubricant is to be used.
2-More hydrophilic substances are suggested as alternatives e.g. surfactants and polyethylene glycol (PEG).
3-Combination hydrophobic and hydrophilic substances may be also useful.
4-Lubricants are added to granules before compression in a finely divided form.

21. 5- Coloring agents
The use of colors and dyes in a tablet has three purposes:
(1) Masking of off color drugs.
(2) Product Identification.
(3)Production of more elegant product.
All coloring agents must be approved and certified by FDA.

22. 6- Flavoring agents
They are usually limited to chewable tablets or tablets that are intended to dissolve in mouth, to impart pleasant taste to mask unpleasant taste.
Water-soluble flavors usually have poor stability. For this reason flavor oils or dry powders are typically used.

23. 7- Sweetening agents
For chewable tablets: Sugar, mannitol.
Saccharine (artificial): 500 time’s sweeter than sucrose
Disadvantage: Bitter after taste and carcinogenic
Aspartame (artificial)
Disadvantage: Lack of stability in presence of moisture.