Bioavailability of a drug depends in absorption of the drug, which is affected by solubility of the drug in gastrointestinal fluid and permeability of the drug across gastrointestinal membrane. The drugs solubility mainly depends on physical – chemical characteristics of the drug. However, the rate of drug dissolution is greatly influenced by disintegration of the tablet.

Disintegrants used to increase surface area of the tablet fragments and to overcome cohesive forces that keep particles together in a tablet. However, There are several factors affecting disintegration process in tablet, they are :
  1. Effect of Fillers
  2. Effect of Binder
  3. Effect of Lubricants
  4. Effect of Surfactant
Effect of fillers
The solubility and compression characteristics of fillers affect the rate and mechanism of disintegration of tablet. If soluble fillers are used then it may cause increase in viscosity of the penetrating fluid which tends to reduce effectiveness of strongly swelling disintegrating agents and as they are water soluble, they are likely to dissolve rather than disintegrate. Insoluble diluents produce rapid disintegration with adequate amount of disintegrants.

Effect of binder
As binding capacity of the binder increases, disintegrating time of tablet increases and this counteract the rapid disintegration. Even the concentration of the binder can also affect the disintegration time of tablet.

Effect of lubricants
Mostly lubricants are hydrophobic and they are usually used in smaller size than any other ingredient in the tablet formulation. When the mixture is mixed, lubricant particles may adhere to the surface of the other particles. This hydrophobic coating inhibits the wetting and consequently tablet disintegration.

Lubricant has a strong negative effect on the water uptake if tablet contains no disintegrants or even high concentration of slightly swelling disintegrants. The disintegration time is hardly affected if there is some strongly swelling disintegrants are present in the tablet. There is one exception, sodium starch glycolate effect remains unaffected in the presence of hydrophobic lubricant.

Effect of surfactants

Surfactant Remarks
Sodium lauryl sulfate
Good-various drugs
Poor - various drugs
Polysorbate 20 Good
Polysorbate 40 & 60 Poor
Polysorbate 80Good
Tweens Poor
Poly ethylene glycol Poor

(Good – decrease in disintegration time, Poor – increase in disintegration time)

Sodium lauryl sulphate increased absorption of water by starch or had a variable effect on water penetration in tablets. Surfactants are only effective within certain concentration ranges. Surfactants are recommended to decrease the hydrophobicity of the drugs because the more hydrophobic the tablet the greater the disintegration time.