Factors Which Affect Absorption

a. Water Solubility. All body fluids are water based. Therefore, a drug must be soluble in water in order to be absorbed. Dissolution of the drug in aqueous (water) solution is dependent 6n the pH of the solution and the disintegration of the drug.

(1) Disintegration. Disintegration (Figure 3-1) increases the surface area of a drug. The speed at which a dosage form disintegrates is dependent upon the type of solid dosage form and the manufacturing process used to make that dosage form. The solid dosage form could be a tablet, suppository, capsule, powder, or suspension. Take a tablet for example. The manufacturer may add starch to the tablet in order to make it swell when it is added to water. The tablet may be a sublingual tablet that is made to rapidly dissolve in the mouth. On the other hand, the manufacturer may compress the contents of the tablet under great pressure so that it will slowly dissolve. Further, an enteric coating may be applied to the tablet so that it will dissolve in the intestine. In the case of some capsules, "tiny time capsules" systematically dissolve during a period and prolong the effect of the drug.


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