📚 > Pharmacology > General Pharmacology > Pharmacokinetics_>

Factors Affecting Drug Absorption: General Factors

These are the general factors that affect drug absorption by all routes.

Aqueous Solubility of the Drug

• The drug must dissolve in aqueous biophase in order to be able to cross the biological membrane.

• The aqueous solubility depends on:

  • Disintegration: breaking down of solid dosage form into fine particles.

  • Dissolution: dissolution of active drug molecules from fine particles into the solution.

• The more the aqueous solubility → the faster the absorption. e.g.:

  • Tablets take time to disintegrate and dissolve → absorption from them is slower.

  • In syrup, the drug is already dissolved and ready to be absorbed → absorption from them is faster.

Concentration of the Drug

Diffusion of drug molecules is driven by concentration gradient

↓

The higher the concentration of drug

↓

The faster the absorption.

Area of Absorbing Surface

The more the absorbing surface area

↓

the more the absorption.

Blood Flow at the Absorbing Surface

Blood flow removes the absorbed drug from the site of absorption

↓

concentration gradient is maintained for absorption of more drugs

↓

so the more the blood flow

↓

the faster the absorption.

---

Next >>

▶️ Factors Affecting Drug Absorption: Route-Specific Factors