A REVIEW ON: BIOAVAILABILITY AND BIOEQUILANCE

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ABOUT AUTHORS:
1 Shashi Kant*,Satinder Kumar, Rajender Kumar,
Research scholar department of pharmacy.
2 Dr. Bharat Prashar
HOD & Associate professor  Department of Pharmaceutical Sciences, Manav Bharti University, Solan (H.P)

* shashi_ranaute@yahoo.in

ABSTRACT:-
In this review article, we discussed about Bioavailability and bioequilance study, bioavailability means rate and extent to which active ingredients absorbed from a drug product and become available at site of action. This article provides the information about important aspect involved in bioequivalence and regulatory requirement for bioequivalence study. The rate or rapidity at which drug is absorbed is important consideration in treatment of acute conditions such as asthma attack in pain. Extent of absorption is of special significance in treatment of chronic conditions like hypertension, epilepsy. In this review we discussed all the factors affecting bioavailability from its dosage form, objective/purpose of bioavailability study, design and evaluation of bioequilance study, methods of assessing of bioavailability and bioequilance etc.

REFERENCE ID: PHARMATUTOR-ART-1326

INTRODUCTION:-
Bioavailability means rate and extent to which active ingredients absorbed from a drug product and become available at site of action.
The rate or rapidity at which drug is absorbed is important consideration in treatment of acute conditions such as asthma attack in pain. Extent of absorption is of special significance in treatment of chronic conditions like hypertension, epilepsy etc.

There are some definitions from 2003 orange book, code of federal regulations, 21 CFR 320 and other source:-

Pharmaceutical alterative: drug products that contain same therapeutic moiety but as different salts, esters or complexes. For example tetracycline phosphate or tetracycline hydrochloride equivalent to 250mg tetracycline base are considered pharmaceutical alternative.

Pharmaceutical equivalent: drug product in identical dosage form that contain same active ingredients that is same salt or ester, are of same dosage form, use same route of consideration, identical in strength.

Pharmaceutical substitution: the process of dispensing a pharmaceutical alternative for prescribed refers to comparison of bioavailability of different formulations, drug product or batches of same drug product. drug product. Eg. Ampicillin suspension is dispensed in place of Ampicillin capsule.

Therapeutic alternative: drug product containing different active ingredients that are indicated for same therapeutic or clinical objective. Eg Ibuprofen is given instead of aspirin.

Therapeutic substitution: process of dispensing a therapeutic alternative in place of prescribed drug product eg amoxicillin is dispensed instead of ampicillin.[1][2][3][4]

FACTORS AFFECTING BIOAVAILABILITY OF DRUGS FROM ITS DOSAGE FORM

A.    DRUG SUBSTANCE PHYSICOCHEMICAL PROPERTIES

1.      Particle size
2.      Crystalline or amorphous form
3.      Salt form
4.      Hydration
5.      Lipid or water solubility
6.      PH and pKa
7.      Dissolution rate and drug solubility

B.     PHARMMACEUTICAL INGREDIENTS

1.      Fillers
2.      Binders
3.      Coating
4.      Disintegrating agent
5.      Lubricants
6.      Suspending agent
7.      Surface active agent
8.      Flavoring agent
9.      Coloring agent
10.  Preservative
11.  Stabilizing agent

C.     DOSAGE BFORM CHARECTERISTICS

1.      Disintegration rate
2.      Dissolution time of drug in dosage form
3.      Product age and storage condition

D.    PHYSIOLOGICAL FACTORS AND PATIENT CHARECTERISTICS

1.      Gastric emptying time
2.      Intestinal  transit time
3.      Pathological condition(gastrointestinal abnormality)
4.      Gastric contents
5.      Food
6.      Gastrointestinal PH

E.     ROUTE OF ADMINISTRATION
The influence of route of administration on drug bioavailability is generally following order: Parenteral > oral > rectal > topical

Within parenteral route, intravenous injection of drug results in 100% bioavailability.

The amount of drug that reaches systemic circulation called systemic bioavailability.

Bioavailable fraction (F) refers to fraction of administered dose that enters systemic circulation.

F = Bioavailable dose/ Administered dose

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