Types of equivalent and measurement of bioavailability
A SEMINAR ON TYPES OF EQUIVALENT AND MEASUREMENT OF BIOAVAILABILITYPRESENTED BY:GANDHI SONAM MUKESHCHANDRA1ST YR M.PHARMDEPT. OF INDUSTRIAL PHARMACY
CONTENTS Introduction & importance Types of equivalents Methods for assessing the bioavailability
Introduction & Importance There are several formulations of same drug, in the same dose, in a similar dosage form and given through same route. Substitution of one product for another can be made equally effective, therapeutically as per standards. In order to ensure clinical performance of such drug products bioequivalence studies should be performed.
EQUIVELENTS It is a term that compares one product is similar with respect to a specific characteristic or function to another, or to the defined set of the standards. There are four types of equivalences: 1. Chemical equivalence 2. Pharmaceutics equivalence 3. Therapeutic equivalence 4. Bioequivalence
Chemical equivalence: two or more formulations contain the same labelled chemical substance as an active ingredient in the same amount. Pharmaceutics equivalence: two or more formulations are identical in strength, quality, purity, content uniformity and disintegration and dissolution characteristics.
Therapeutic equivalence: It indicates that two or more drug products that contain the same therapeutic active ingredients elicit same pharmacologic effects and can control the disease to the same extent. Bio equivalence: It is a relative term which denotes that the drug substance in two or more identical dosage forms reaches systemic circulation at same relative rate and to the same relative extent i.e. their plasma concentration-time profiles will be identical without significant statistical differences.
Methods for assessing the bioavailability Pharmacokinetics methods This method reflects the therapeutic effectiveness of a drug. Thus these are indirect methods. Plasma-level time studies Urinary excretion studiesPharmacodynamic methods This method involves direct measurement of drug effect on a physiologic process as a function of time. acute pharmacologic response therapeutic response
Pharmacokinetic methods Cmax: it gives indication whether drug is sufficiently absorbed systematically to provide therapeutic response Tmax: the peak time that gives an indication of rate of absorption AUC: it gives a measure of the extent of absorption or amount of drug that reaches the systemic circulation.
Extent of bioavailability can be determined by following equations F=[AUC]oral Div/[AUC]iv Doral Fr=[AUC]test Dstd/ [AUC]std D test
Pharmacodynamic methods1.(dXu/dt)max: it is obtained from the peak of plot b/w rate of excretion v/s mid point time of urine collected period.2. (tu)max: it is analogues to the tmax of plasma level data, its value decrease as absorption rate increases.3. Xu: it is related to the AUC of plasma level data and increases as the extent of absorption increases.
Extent of bioavailability can be determined by following equations F = (Xu α)oral Div/ (Xu α)iv Doral Fr= (Xu α)test Dstd/ (Xu α) std Dtest
Acute pharmacological response In this method acute pharmacologic effect such as change in ECG or EEG readings, pupil diameter etc. is related to the time course of the given drug. Bioavailability can be determined by construction of pharmacological effect- time curve as well as dose response graph.
THERAPEUTIC RESPONSE This method is based on observing the clinical response to a drug formulation given to patients suffering from disease for which it is intended to be used.
References Dr. Shobha rani, R Hiremath, Textbook of Biopharmaceutics & Pharmacokinetics. Pg no.32-47. D.M. Brahmankar, Sunil B. Jaiswal. Biopharmaceutics & Pharmacokinetics A TRETISE.Pg.no.285-289. Milo Gibaldi. Biopharmaceutics & Clinical Pharmacokinetics. Fourth edition. Pg.15 Leon shargel, applied Biopharmaceutics and pharmacokinetics. Fifth edition.2005.Pg.no.460-465.