Introduction Biopharmaceutics history 2

Contents 2
Introduction
Biopharmaceutics history 2
Main terms 5
Mathematical Fundamentals in Pharmacokinetics
Mathematic expressions and units 33-34 1
Calculus 27-29 2
Graph 29-31 2
Expressing blood concentrations 34-35 1
Drug Elimination, Clearance, Methabolism
Drug Elimination 149-150 1
Drug Clearance 150-152 2
The Kidney 157-162 5
Renal Clearance 163-168 5
Drug Metabolism 309-311 2
Hepatic Clearance 311-312 1
Hepatic Enzymes 323-325 2
Pharmacogenetics and Drug Metabolism
Genetic Polymorphisms 358-361 3
Cytochrome P-450 Isozymes 361-366 5
Phase II Enzymes 366-368 2
Transporters 367-368 1
Physiologic Factors Related to Drug Absorption 373
Nature of Cell Membranes 377-378 1
Passage of Drugs Across Cell Membranes 378 -389 1
Drug Interactions in the Gastrointestinal Tract 389-390 1
Oral Drug Absorption 390-401 11
Effect of Disease States on Drug Absorption 405-407 2
In Vitro Drug Product Performance
Drug Product Performance, In Vitro: Dissolution and Drug Release Testing 425-429 4
Performance of Drug Products: In Vitro–In Vivo Correlation 437-441 4
Compendial Methods of Dissolution 429-431 2
Alternative Methods of Dissolution Testing 431-434 3
Dissolution Profile Comparisons 434-436 2
Meeting Dissolution Requirements 436-437 1
Drug Product Performance, In Vivo: Bioavailability and Bioequivalence
Drug Product Performance 469-471 2
Purpose of Bioavailability and Bioequivalence Studies 471-472 1
Relative and Absolute Availability 472-474 2
Methods for Assessing Bioavailability and Bioequivalence 475-478 3
In Vivo Measurement of Active Moiety or Moieties in Biological Fluids 475-478
Bioequivalence Studies Based on Pharmacodynamic Endpoints—In Vivo Pharmacodynamic (PD) Comparison 478-479 1
Bioequivalence Studies Based on Clinical Endpoints—Clinical Endpoint Study 479-481 2
In Vitro Studies 481 2
CONTENTS 2
INTRODUCTION
BIOPHARMACEUTICS HISTORY 2
MAIN TERMS 5
MATHEMATICAL FUNDAMENTALS IN PHARMACOKINETICS
MATHEMATIC EXPRESSIONS AND UNITS 33-34 1
Mathematics is a basic science that helps to explain relationships among variables. For an equation to be valid, the units or dimensions must be constant on both sides of the equation. Many different units are used in pharmacokinetics, as listed in Table 2-1. For an accurate equation, both the integers and the units must balance. For example, a common expression for total body clearance is 2.10

After insertion of the proper units for each term in the above equation from Table 2-1, 2.10

Thus, the above equation is valid, as shown by the equality mL/h = mL/h.

An important rule in using equations with different units is that the units may be added or subtracted as long as they are alike, but divided or multiplied if they are different. When in doubt, check the equation by inserting the proper units. For example, 2.11

Certain terms have no units. These terms include logarithms and ratios. Percent may have no units and is expressed mathematically as a decimal between 0 and 1 or as 0% to 100%, respectively. On occasion, percent may indicate mass/volume, volume/volume, or mass/mass. Table 2-1 lists common pharmacokinetic parameters with their symbols and units.
A constant is often inserted in an equation to quantify the relationship of the dependent variable to the independent variable. For example, Fick’s law of diffusion relates the rate of drug diffusion, dQ/dt, to the change in drug concentration, C, the surface area of the membrane, A, and the thickness of the membrane, h. In order to make this relationship an equation, a diffusion constant D is inserted: 2.12

To obtain the proper units for D, the units for each of the other terms must be inserted: D(cm )mmgmcm /h232×=

The diffusion constant D must have the units of area/time or cm2/h if the rate of diffusion is in mg/h.
TABLE 2-1 Common Units Used in Pharmacokinetics

Parameter	Symbol	Unit	Example
Rate	dD/dt	Mass/time	mg/h
Zero-order rate constant	K0	Concentration/Time	mg/mL/h
First-order rate constant	k	1/Time	1/h or h^–1
Drug dose	D0	Mass	mg
Concentration	C	Mass/Volume	mg/mL
Plasma drug concentration	Cp	Drug/Volume	mg/mL
Area under the curve	AUC	Constration × time	mg·h/mL
Fraction of drug absorbed	F	No units	0 to 1
Clearance	Cl	Volume/Time	mL/h
Half-life	t1/2	Time	H

CALCULUS 27-29 2

CALCULUS
Pharmacokinetic models consider drugs in the body to be in a dynamic state. Calculus is an important mathematic tool for analyzing drug movement quantitatively. Differential equations are used to relate the concentrations of drugs in various body organs over time. Integrated equations are frequently used to model the cumulative therapeutic or toxic responses of drugs in the body.