Lecture 14- Biopharmaceutics I

Question 1

Biopharmaceutics

Answer 1

Pharmacokinetics = investigates the effect of the body on the dosage form (ADME)

Biopharmaceutics= stage prior to this- how the design + formulation of the dosage affects the drug once in the body

^is the relationship between the physical, chemical + biological science applied to drugs, dosage form + route of administration / drug action

Absorption, distribution, metabolism + excretion

Question 2

Biopharmaceutics + Pharmacokinetics

Answer 2

Slide 5

Question 3

Drug absorption

Answer 3

Process of movement of unchanged drug from its site of administration to systemic circulation

Effectiveness of a drug can only be assessed by = its concentration + site of action
-difficult to measure
-conc can be measured more accurately in plasma

Correlation between= plasma conc of a drug + therapeutic response

Question 4

Involved in Biopharmaceutics

Answer 4

Route of administration; oral, injection

Nature of the dosage form; solution + suspension

Physiological parameters; fed, fasted state

Nature of the drug; water solubility, lipophilicity, particle size + stability

Onset of action vs dosage form- slide 9

Question 5

Route of administration; oral delivery

Answer 5

Given a drug by mouth= most common route of administration- most variable + requires the most complicated pathway to the tissues

Question 6

Factors affecting GI absorption of a drug from its dosage form

Answer 6

Pharmaceutical factors;
- physiochemical properties of drug substances
- dosage form characterises and pharmaceutical ingredients

Patient related factors;
Factors relating to the anatomical, physiological + pathological characteristics of the patient

Question 7

Physiochemical properties of drug substances

Answer 7

Drug solubility + dissolution rate
Particle size + effective surface area
Polymorphism; stable/ metastable
Psueodpolymorphism - L-phenylalanine anhydrous
Salt form of the drug - hydrochloride/ sodium/ sulfate
Lipophilicity of the drug
pKa of the drug + pH
Drug stability

Question 8

Dosage form characteristics + pharmaceutical ingredients

Answer 8

Disintegration time
Dissolution time
Manufacturing variables; e.g. wet/ dry granulation
Pharmaceutical ingredients
Nature + type of dosage form
Product age + storage conditions

Question 9

Patient- related factors

Answer 9

Slide 14

Question 10

Oral delivery;
Advantages + disadvantages

Answer 10

Slide 15

Question 11

First pass effect

Answer 11

Greater the first-pass effect, less drug reaches systemic circulation > reduces bioavailabity when administered via GIT

Drugs subjected to first pass effect;
Lidocaine - anaesthetic
Propranolol- beta blocker
Nitroglycerin- nitrate

Larger oral dose / alternative doseage form = required to achieve required therapeutic effect

Question 12

Mechanisms of drug absorption

Answer 12

2 mechanisms of drug transport across the GI epithelium;

Transcellular= across the cells and is further divided into;
-lipid diffusion, carrier-mediated transport + facilitated diffusion and endocytosis

Paracellular= between the cells

Question 13

Principles mechanisms of drug permeation

Answer 13

Passive/aqueous diffusion= Fick’s Law

Lipid diffusion through lipid bilayer

Carrier mechanism

Endocytosis/exocytosis

Question 14

Passive diffusion

Answer 14

Known as non-ionic diffusion; absorption of 90% of drugs

Fick’s first law of diffusion;
The drug molecule diffuse from a region of higher concentration to one of lower concentration until equilibrium is attained & the rate of diffusion is directly proportional to the concentration gradient across the membrane

Equation- slide 20

Passive diffusion- energy independent but depends more/less on the square root of the molecular size of the drugs

Mol weight of most drugs lie between 100-400 Daltons- can be effectively absorbed passively