[BIOAVAILABILITY] Factors Affecting Drug Bioavailability

Proverbs 16:3

● Molecular size

● Lipid solubility (partition coefficient)

● Degree of ionization

● Chemical stability

● Aqueous stability

● Salt form

● Polymorphism

● Particle size

● Drug concentration

● Drug ion trapping

Physicochemical factors affecting drug availability:
[wag na sa dami ba naman HAHAHAHA]

TRUE

[PHYSICOCHEMICAL FACTORS]

SMALLER molecules penetrate membranes FASTER.
A) TRUE
B) FALSE

TRUE

[PHYSICOCHEMICAL FACTORS]

LARGE molecules require SPECIALIZED transport.
A) TRUE
B) FALSE

Partition Coefficient

[PHYSICOCHEMICAL FACTORS]

Lipid solubility is also known as _______?

TRUE

[PHYSICOCHEMICAL FACTORS]

HIGHER lipid solubility → BETTER membrane permeability
A) TRUE
B) FALSE

Lipid solubility (partition coefficient)

[PHYSICOCHEMICAL FACTORS]

This factor determines PASSIVE DIFFUSION efficiency.

Degree of Ionization

[PHYSICOCHEMICAL FACTORS]

This factor is governed by the pKa of drug and pH of environment.

● pKa of the drug

● pH of the environment

[PHYSICOCHEMICAL FACTORS]

Degree of Ionization is governed by the ____ [2]

TRUE

📌CLUE: “LUNA”

[PHYSICOCHEMICAL FACTORS]

Unionized form is MORE absorbable.
A) TRUE
B) FALSE

TRUE

[PHYSICOCHEMICAL FACTORS]

Weak acids are better absorbed in acidic pH.
A) TRUE
B) FALSE

TRUE

[PHYSICOCHEMICAL FACTORS]

Weak bases are better absorbed in alkaline pH.
A) TRUE
B) FALSE

This helps prevent NSAID-induced ulcers by reducing direct gastric irritation and limiting the inhibition of protective prostaglandins in the stomach lining.

[PHYSICOCHEMICAL FACTORS]

Why are aspirin tablets enteric coated?

Salt + Water (making the product highly hydrophilic → increased excretion)

[PHYSICOCHEMICAL FACTORS]

Products of acid + base

Gastric acid

[PHYSICOCHEMICAL FACTORS]

Acid-labile drugs degrade in ____

GI tract

[PHYSICOCHEMICAL FACTORS]

Enzyme-sensitive drugs degrade in ______

TRUE

[PHYSICOCHEMICAL FACTORS]

Penicillin G is unstable in ACID.
A) TRUE
B) FALSE

TRUE

[PHYSICOCHEMICAL FACTORS]

Drug must be in solution before absorption.
A) TRUE
B) FALSE

TRUE

[PHYSICOCHEMICAL FACTORS]

Poor solubility → slow dissolution → poor absorption.
A) TRUE
B) FALSE

TRUE

[PHYSICOCHEMICAL FACTORS]

Salt forms IMPROVE dissolution rate.
A) TRUE
B) FALSE

Sodium/potassium salts

[PHYSICOCHEMICAL FACTORS]

These salts are absorbed FASTER.

TRUE

[PHYSICOCHEMICAL FACTORS]

Different crystal forms → different solubilities.
A) TRUE
B) FALSE

TRUE

[PHYSICOCHEMICAL FACTORS]

Amorphous forms absorb FASTER than crystalline.
A) TRUE
B) FALSE

Crystalline

[PHYSICOCHEMICAL FACTORS]

This type of polymorphism has a more stable molecular structure, which results in decreased solubility and absorption, thereby prolonging the duration of action.

TRUE

[PHYSICOCHEMICAL FACTORS]

Smaller particles → larger surface area → faster dissolution.
A) TRUE
B) FALSE

TRUE

[PHYSICOCHEMICAL FACTORS]

HIGHER concentration gradient → FASTER diffusion
A) TRUE
B) FALSE

TRUE

[PHYSICOCHEMICAL FACTORS]

Drug accumulates in compartments with different pH.
A) TRUE
B) FALSE

● Kidneys

● Breasts

[PHYSICOCHEMICAL FACTORS]

Drug accumulates in compartments with different pH. Examples of these compartments are _____ [2]

● Dosage Form

● Disintegration Time

● Dissolution Rate

● Excipients

Pharmaceutical formulation factors affecting drug bioavailability [4]

Chewable tablets

[PHARMACEUTICAL FORMULATION FACTORS]

These tablets do not require the addition of disintegrants.

Solution > Suspension > Capsule > Tablet

[PHARMACEUTICAL FORMULATION FACTORS]

Arrange the following dosage forms according to their rate of absorption.

Tablet → Suspension → Capsule → Solution

A) Tablet > Capsule > Suspension > Solution
B) Suspension > Solution > Tablet > Capsule
C) Solution > Suspension > Capsule > Tablet
D) Capsule > Tablet > Solution > Suspension

TRUE

[PHARMACEUTICAL FORMULATION FACTORS]

Enteric-coated and sustained-release dosage forms DELAY absorption.
A) TRUE
B) FALSE

TRUE

[PHARMACEUTICAL FORMULATION FACTORS]

Faster tablet breakup → faster dissolution.
A) TRUE
B) FALSE

Dissolution

[PHARMACEUTICAL FORMULATION FACTORS]

Most common rate-limiting step in absorption.

Dissolution Rate

[PHARMACEUTICAL FORMULATION FACTORS]

This factor is influenced by FORMULATION and AGITATION.

● Formulation

● Agitation

[PHARMACEUTICAL FORMULATION FACTORS]

Dissolution Rate is influenced by ____ and ____

● Binders

● Lubricants

● Surfactants

[PHARMACEUTICAL FORMULATION FACTORS]

The excipients affect absorption such as _____ [3]

TRUE

[PHARMACEUTICAL FORMULATION FACTORS]

Some excipients enhance permeability
A) TRUE
B) FALSE

● Gastric Emptying Time (GET)

● GI Motility

● Surface Area

● Blood Flow at Absorption Site

Physiologic factors/Patient-related factors affecting drug bioavailability [4]

TRUE

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

FASTER gastric emptying → FASTER intestinal absorption
A) TRUE
B) FALSE

TRUE

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

An INCREASE in gastric emptying TIME corresponds to a DECREASE in gastric emptying RATE.
A) TRUE
B) FALSE

TRUE

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

A DECREASE in gastric emptying TIME corresponds to an INCREASE in gastric emptying RATE.
A) TRUE
B) FALSE

● Fatty Meals

● Pregnancy

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

Gastric emptying time (GET) is delayed by _____ [2]

TRUE

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

Diarrhea DECREASES contact time, leading to REDUCED absorption.
A) TRUE
B) FALSE

TRUE

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

Constipation INCREASES contact time, ENHANCING absorption.
A) TRUE
B) FALSE

Small intestine

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

This part of the GI tract has the largest absorptive surface due to the presence of villi and microvilli which increases absorption.

Perfusion

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

This means the flow of blood through tissues or organs.

TRUE

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

Increased blood flow enhances absorption.
A) TRUE
B) FALSE

● Shock

● Heart failure

[PHYSIOLOGIC FACTORS/PATIENT-RELATED FACTORS]

Conditions that decrease blood flow at the absorption site [2]

● Presence of Food

● Age

● Disease States

● Enzymatic Activity

● Chelation

● Adsorption

● Alteration of GI pH

● Altered GI Motility

📌Mnemonic: “PADEC” “AAA”

Other factors that affect drug bioavailability [8]

Tetracycline + milk

[OTHER FACTORS]

Example of chelation, leading to decreased absorption of the drug.