[LADME] Factors affecting Drug Absorption

Proverbs 16:3

● Degree of Dissociation / Ionization

● Partition Coefficient

● Dose

● Chemical Structure

● Particle Size

● Crystalline Form

● GI Motility

● Surface Area of the Absorption Environment

● Perfusion

● Gastric Emptying Time (GET)

Factors affecting Drug Absorption include:

Henderson-Hasselbach Equation

[DEGREE OF DISSOCIATION / IONIZATION]

The Degree of Dissociation / Ionization for weak acids and bases is determined by the _____ equation.

● pka of the drug (acidic or basic)

● pH of the medium in which the drug is dissolved.

[DEGREE OF DISSOCIATION / IONIZATION]

The Degree of Dissociation / Ionization depends on the ____ [2]

Partition coefficient

_______-

• This represents the drug's ability to partition between lipid (oil) and aqueous (water) phases

• It is often measured as octanol-water partition coefficient (K).

octanol-water partition coefficient (K)

[PARTITION COEFFICIENT]

Partition coefficient represents the drug's ability to partition between lipid (oil) and aqueous (water) phases, often measured as _________.

TRUE

[PARTITION COEFFICIENT]

TRUE OR FALSE:

Lipid-soluble drugs have a HIGH partition coefficient, leading to increased diffusion and absorption.

K = C oil / C water

where:

● C oil = drug concentration in lipid

● C water = concentration in aqueous phase

[PARTITION COEFFICIENT]

Formula for Partition Coefficient (K):

Pegfilgrastim

Random BEQ:

• This drug is a recombinant human granulocyte colony-stimulating factor (G-CSF).

• This is used in patients undergoing chemotherapy by stimulating the production of white blood cells (WBCs) to reduce the risk of infection.

TRUE

[DOSE]

TRUE OR FALSE:

The higher the dose, the higher the absorption.

TRUE

[DOSE]

TRUE OR FALSE:

There is an increasing amount of concentration from the site of administration, more likely there is a high extent of absorption going to the systemic circulation.

TRUE

[CHEMICAL STRUCTURE]

TRUE OR FALSE:

The chemical structure (functional groups) of a drug (acidic or basic) influence where it is best absorbed in the GI tract.

< 500 MW

[PARTICLE SIZE]

Drugs should ideally have a molecular weight of ______ for efficient absorption.

• The smaller particle size, the greater the absorption.

TRUE

[CRYSTALLINE FORM]

TRUE OR FALSE:

Amorphous drugs dissolve faster than crystalline.

TRUE

[CRYSTALLINE FORM]

TRUE OR FALSE:

Anhydrous drugs dissolve faster than hydrous drugs.

GI Motility

This refers to the rate of contraction and movement of contents in the alimentary canal.

TRUE

[GI MOTILITY]

TRUE OR FALSE:

Rapid motility can reduce absorption because the drug may not stay long enough at the absorption site.

anatomic absorption window

[GI MOTILITY]

For drugs given orally, an ______may exist within the GI tract in which the drug is efficiently absorbed.

duodenum

[GI MOTILITY]

For many oral drugs, the _______ is the main absorption window.

TRUE

[SURFACE AREA OF THE ABSORPTION ENVIRONMENT]

TRUE OR FALSE:

Small intestine has higher absorption efficiency than the stomach.

120 sq. m.

[SURFACE AREA OF THE ABSORPTION ENVIRONMENT]

The small intestine's surface area is ______ sq. m, making it the main site of drug absorption.

villi and microvilli

[SURFACE AREA OF THE ABSORPTION ENVIRONMENT]

The large surface area of the small intestine is due to the presence of valve-like folds in the mucous membrane on which are small projections known as______ and even smaller projections known as _____________.

TRUE

[PERFUSION]

TRUE OR FALSE:

The higher the perfusion, the better the absorption.

splanchnic circulation

[PERFUSION]

The ______ circulation receives about 28% of the cardiac output and is increased after meals.

28%

[PERFUSION]

The splanchnic circulation receives about ____% of the cardiac output and is increased after meals.

mesenteric vessels

[PERFUSION]

Once the drug is absorbed from the small intestine, it enters via the ______ to the hepatic-portal vein and goes to the liver prior to reaching the systemic circulation.

Gastric Emptying Time (GET)

This is the time it takes the stomach to empty its contents into the small intestine.

2 - 3 hours

[GASTRIC EMPTYING TIME]

The normal Gastric Emptying Time (GET) is ______ hours.

TRUE

[GASTRIC EMPTYING TIME]

TRUE OR FALSE:

Food generally delays the rate of absorption but it doesn't necessarily mean that the food will alter the extent of absorption.