TABLET EXCIPIENTS

DILUENT:- Diluents  are  fillers used  to  make required bulk of  the  tablet  when the drug dosage itself is inadequate to produce the bulk. Secondary reason is to provide better tablet properties such as improve cohesion, to permit use of  direct compression manufacturing or to promote flow.

Commonly used tablet diluents:-

1. Lactose-anhydrous and spray dried lactose
2. Directly compressed starch-Sta Rx 1500
3. Hydrolyzed starch-Emdex  and Celutab 
4. Microcrystalline  cellulose-Avicel (PH 101and PH 102) 
5. Dibasic calcium  phosphate dehydrate
6. Calcium  sulphate dihydrate
7. Mannitol  
8. Sorbitol
9. Sucrose- Sugartab, DiPac, Nutab
10. Dextrose

BINDERS & AHESIVES:- These materials are added either dry or in wet- form  to form  granules or to form cohesive  compacts for directly compressed tablet.

Example:

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

DISINTEGRANTS:- Added to a tablet formulation  to facilitate its breaking or disintegration when it contact in water in the GIT.

Example:

Starch- 5-20% of tablet weight.                
Starch derivative – Primogel and Explotab (1-8%)                
Clays- Veegum  HV, bentonite 10% level in colored tablet only.         
Cellulose derivatives- Ac- Di-Sol (sodium  carboxy methyl cellulose)                
Alginate                
PVP (Polyvinylpyrrolidone), cross-linked

SUPERDISINTEGRANTS:- Swells up to ten fold within 30 seconds when contact water.

Example:

Crosscarmellose- cross-linked  cellulose, Crosspovidone- cross-linked povidone (polymer),
Sodium  starch glycolate- cross-linked starch. These cross-linked products swell upto 10n fold with in 30 seconds when in contact with water.

A portion of disintegrant  is added before granulation and a portion before compression, which serve as  glidants  or  lubricant. Evaluation of carbon dioxide in effervescent tablets is also one way of disintegration

LUBRICANTS AND GLIDANTS:-

Lubricants are intended to  prevent adhesion of the tablet materials to the surface of dies and punches, reduce  inter particle friction and may improve the rate of flow of the tablet granulation. Glidants are intended to promote flow of  granules or powder material by reducing the friction between the particles.

Example:

LUBRICANTS:- Stearic acid
Stearic acid salt - Stearic acid, Magnesium stearate, Talc, PEG (Polyethylene glycols), Surfactants

GLIDANTS:- Corn Starch – 5-10% conc., Talc-5% conc.
Silica derivative - Colloidal silicas such as Cab-O-Sil, Syloid, Aerosil in 0.25-3% conc.

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. Two forms of colors are used in tablet preparation – FD &C and D & C dyes. These dyes are applied as solution in the granulating agent or Lake form  of these dyes. Lakes are dyes absorbed on hydrous oxide and employed as dry powder coloring.

Example:

FD & C yellow 6-sunset yellow
FD & C yellow 5- Tartrazine                
FD & C green 3-   Fast Green                
FD & C blue 1- Brilliant Blue                
FD & C blue 2 - Indigo carmine  
D & C red 3- Erythrosine 
D & C red 22 – Eosin Y

FLAVOURING AGENTS:- For chewable tablet- flavor oil are used

SWEETENING AGENTS:- For chewable tablets: Sugar, mannitol. 
Saccharine (artificial): 500  time’s sweeter than sucrose.