The in Vivo Absorption Pathway Of Solid Formulations

The common absorption pathway for solid preparations is that after oral administration, solid preparations must undergo a dissolution process of the drug before they can be absorbed into the bloodstream through the gastric intestinal epithelial cell membrane and exert their therapeutic effects. Especially for some insoluble drugs, the dissolution process of drugs will become the rate limiting process of drug absorption. If the dissolution rate is small and the absorption is slow, the blood drug concentration will be difficult to reach the effective therapeutic concentration. Compare the absorption pathways of various formulations after oral administration here
Dosage form
Absorption during disintegration or dispersion dissolution process
Tablets
○○○
Capsules
Granules
Powder
×○○
Suspension agent
Solution agent
Note: ○ - This process is required; X -- No need for this process
After oral administration, tablets and capsules first disintegrate into fine particles, and then drug molecules dissolve from the particles. The drugs are absorbed into the bloodstream through the gastrointestinal mucosa. There is no disintegration process after oral administration of granules or powders, and they quickly disperse with a larger specific surface area, resulting in faster dissolution, absorption, and efficacy of the drug. The particles of the suspension are smaller, so the dissolution and absorption process of the drug is faster. However, after oral administration of the solution, there is no disintegration or dissolution process, and the drug can be directly absorbed into the bloodstream, resulting in a shorter onset time of the drug. The general order of absorption of oral preparations is: solution>suspension>powder>granule>capsule>tablet>pill.
The dispersion of solid preparations into fine particles in the body is one of the effective measures to improve dissolution rate and accelerate absorption rate.