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PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

 This rate of dispersion, in turn, influences the rate of dissolution and, therefore,

bioavailability.

 The overall rate of dissolution of drugs from capsules appears to be a complex
function of the rates of different processes, such as :

 the dissolution rate of the gelatin shell,
 the rate of penetration of the GI fluids into the encapsulated mass,

 the rate at which the mass deaggregates (i.e. disperses) in the GI fluids, and
 the rate of dissolution of the dispersed drug particles.

 It is, therefore, important to have suitable diluents and/or other excipients in a

capsule dosage form, particularly when the drug is hydrophobic.

 These diluents will work to

➢ disperse the powder,

➢ minimize aggregation and

➢ maximize the surface area of the powder.

 Tightly packed capsules may have reduced dissolution and bioavailability.

4. Tablets

Uncoated tablets.

 Whereas solutions represent a state of maximum dispersion, compressed tablets

have the closest proximity to particles.

 Since problems in dissolution and bioavailability are generally inversely

proportional to the degree of dispersion, compressed tablets are more prone to

bioavailability problems. This is primarily because of the small surface area

exposed for dissolution until the tablets have broken down into smaller particles;

(due to the more compaction and the low degree of dispersion).

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