The document discusses factors that affect drug absorption, dividing them into three categories: drug-related factors, patient-related factors, and dosage form factors. Drug-related factors include a drug's solubility, ionization state, and molecular size - lipophilic, unionized, and smaller molecular size drugs are generally better absorbed. Patient-related factors that influence absorption include blood flow, intestinal surface area, gastrointestinal pH, and disease states. Absorption is typically better in areas with higher blood flow like the small intestine.

1. CHAPTER#01
Pharmacokinetics
Lecture #04
Factors Affecting
Absorption of Drugs

2. Which factors affecting absorption
of drugs
• Divided into three parts
• 1.Drug related
• 2.Patient related
• 3.Dosage form of drug

3. Drug related:
• Drug related factor the first thing is solubility
because drug move across the biological
membrane.If drug is Lipophilic than the absorption
is more as compared to hydrophilic drugs

4. Ionization:
• If drug is in ionization form than the chemical
structure and PH or environment affect on it .
• When a drug is in its unionized form, it means that
the molecule is not carrying a net electric charge. In
other words, it has not gained or lost charged
particles (ions). The unionized form of a drug is
often more lipophilic (soluble in lipids or fats),
which can affect its ability to pass through cell
membranes, including those in the gastrointestinal
tract during absorption.

5. Molecular size of drug
• If molecular size of drug is large than the
absorption is decrease or small molecular size can
contribute to better absorption

6. 2.Patient related factors:
• 1.Blood flow : if blood flow is high than the
absorption is better . small intestine the absorption
is high because of blood flow as compared to
stomach .
• 2.Surface area: The area of intestine is larger
because thete is present of villi microvilli.
• 3.GIT PH: acidic drugs are rapidly absorbed in GIT
as comapred basic drugs are better absorbed in
intestine.
• 4.Disease: Disease also affect the absorption of
drug