study design for bioavailability and bioequivalence

BABASAHEB BHIMRAO AMBEDKAR UNIVERSITY

PRESENTATION ON STUDY DESIGN AND STATISCAL CONCEPTS IN ESTIMATION OF BIOAVAILABILITY AND BIOEQUIVALENCE

Presented By: Priya SinghPresented To: Dr. Sonali Singh

Bioavailability

Bioavailability  is the fraction of an administered dose of unchanged drug that reaches the systemic circulation.

when a medication is administered intravenously, its bioavailability is 100%.

 when a medication is administered via other routes (such as orally), its bioavailability generally decreases (due to incomplete absorption and first-pass metabolism).

Types of Bioavailability

There are two types….1. Absolute bioavailability -  It is the fraction of

the drug absorbed through non-intravenous administration compared with the corresponding intravenous administration of the same drug.

1. Relative Bioavailability - Relative bioavailability measures the bioavailability (estimated as the AUC) of a formulation (A) of a certain drug when compared with another formulation (B) of the same drug.

Bioequivalence

Bioequivalence is a term in pharmacokinetics used to assess the expected in vivo biological equivalence of two proprietary preparations of a drug.

In order to determine that two medicines are bioequivalent there must be no more than a 20% difference between the AUC and Cmax.

Assessment of Bioavailability

In vivo bioequivalence studies are conducted in the usual manner as discussed for bioavailability studies, i.e. ……

1. Pharmacokinetic Methods A. Plasma level-time study B. Urinary Excretion studies 2. Pharmacodynamic MethodsA. Acute pharmacological responseB. Therapeutic response

Pharmacokinetic Methods

The parameter that are useful in determining the bioavailability of a drug from a drug product based on indirect methods…

Plasma data1. Time of peak plasma conc.( t max)2. Peak plasma conc.(Cmax)3. Area under the curve (AUC) Urine data1. Rate of drug excretion in the urine (dXu /dt)2. Cumulative amount of drug excreted in urine (Xu)3. Time for maximum urinary excretion (tu)

Pharmacodynamics Methods

In order to estimate the bioavailability of a drug product accurately by this method, the following criteria should be met….

1. An established dose- related response curve 2. An easily measurable pharmacological response

such as heart rate, ECG, blood pressure, pupil diameter etc.

Bioavailability Study Protocol

A. Study objectiveB. Study design Experimental design Wash out period Drug products (test and std) Route of drug administration Dosage regimen Frequency and duration of sampling Randomization of drug administration Single versus multiple dose study design

Subjectsi. Healthy versus patientsii. Subject selection Medical history Physical examination Laboratory testiii. Study conditions Analysis of biological fluidsC. Methods of assessment of bioavailabilityD. Analysis and presentation of data

PART 1

STUDY DESIGN FOR THE ASSESSMENT OF BIOAVAILABILITY AND BIOEQUIVALENCE

Study Design

A good experimental design enhances the power of study.

It depends upon the question to be answered, nature of reference drug/dosage form and risk benefit ratio.

The study should be of cross over design and suitably randomized.

Subject Selection

Healthy adult volunteers Age: 18-45 years Age/ sex representation corresponding to

therapeutic and safety profile. Women: pregnancy test prior to 1st and last dose

of study Teratogenic Drugs: male volunteers

Study Conditions

The selected subjects should be maintained on a uniform diet and none of them should taken any drug at least one week prior to the study.

Fasting period before the administration. Standard diet to given after fasting, fluid intake

and volume to be allowed.

Wash-out Period The time interval between two treatments is

called “wash-out period”. It is require for the elimination of the

administered dose of a drug so as to avoid carryover effect.

Washout period is a function of the half-life and the dose of the drug administered, the number of washout period in a study depends on type of cross-over design used and the number of formulations to be evaluated .

Study Design

There are various study designs….1. Two Period cross-over design2. Latin Square Design3. Balance incomplete Block Design4. Parallel Group Design5. Replicate Cross-over study design

Two Period Cross-over Design

For two formulations Even no. of subjects Randomly divided into 2 equal groups. First period, each member of one group receive a

single dose of the test formulation, each member of the other group receive the standard formulation.

Subjects Period 1 Period 2

1-8 T S

9-16 S T

Latin Square Design

For more than two Formulations. A group of volunteers will receive formulation in

sequence..Volunteer No.

Period 1 Period 2 Period 3

1 A B C

2 B C A

3 C A B

Balance Incomplete Block Design (BIBD)

More than 3 formulations, Latin square design will not be ethically advisable

Because each volunteer mat require drawing of too many blood samples.

If each volunteer expected to receive at least two formulation, then such a study can be carried out using BIBD.

Volunteer No. Period 1 Period 2

1 A B 2 A C 3 A D 4 B C 5 B D 6 C D 7 B A 8 C A 9 D A 10 C B 11 D B 12 D C

Parallel- Group Design

Even no. of subjects in two groups. Each subject receive a different formulation. No washout necessary For drugs with long half life. This is also called as non- crossover study.

Treatment A Treatment B

1 2 3 4 5 6 7 8 9 10 11 12

Replicate Cross-over Study Design

For highly variable drugs Allows comparisons of within- subject variance Reduce the number of subjects needed Four period, two sequence, two formulation

design( recommended) Three period, two sequence ( partially

replicated )

Period 1 2 3 4

Group A T R T R

Group B R T R T

Period 1 2 3

Group A T R T Group B R T R

PART 2

STATISTICAL CONCEPTS IN ESTIMATION OF BIOAVAILABILITY AND BIOEQUIVALENCE

Statistical Concepts

In our study statistical analysis will be performed on PK data of subjects by using SAS statistical software .

If they cannot be estimated, the subject will be excluded from the pertaining pharmacokinetic analysis. If necessary an unequal no. of subjects per sequence will be used

Analysis of Variance

The various pharmacokinetic parameters (AUC (AUC 0-t and AUC 0-∞), Cmax) derived from the plasma concentration-time curve are subjected to ANOVA in which the variance is partitioned into components due to subjects, periods and treatments.

The classical null hypothesis test is the hypothesis of equal means: μT=μR (i.e. products are bioequivalent),

where - μT and μR represent the expected mean bioavailabilities of the test and reference formulations, respectively.

The alternate hypothesis therefore is H: μT ≠ μR (i.e. products are bioinequivalent)

F - Test

An F test will be performed to determine the statistical significance of the effects involved in the model at a significance level of 5% (alpha=0.05).

Ratio Analysis

Ratio of least squares means for test and reference listed drugs (RLD) formulations will be computed and reported for Log-transformed pharmacokinetic parameters C max, AUC (0-t) and AUC (0-∞).