Drug bio-availability

1. DRUG BIO-AVAILABILITY
Submitted by Submitted to
Isha Gumber Dr. Amita Mittal
B.Tech(Biotechnology)
7th sem
2519093009

2. CONTENTS
• Introduction
• Types of bioavailability
• Dosage of drugs
• Methods of assessing the drug bioavailability

3. BIO-AVAILABILITY
 Bio-availability is defined as rate and extent of absorption of unchanged drug from its dosage
form and become availableat the site of action.
 Rate and extent at which therapeutically drug reaches systemiccirculation.
 A measure relative to some standard of rate & amount of drug, which reaches the systemic
circulation unchanged following the administrationof dosage form.

4. TYPES OF BIO-AVAILABILITY
 ■ Absolute Bioavailability :
 If the systemic availability of a drug administeredorally is determinedby doing its comparison
with I.V. administration,it is known as absolute bioavailability.
 F= AUC AUC extravascular nous int ravenous

5. Relative Bioavailability
 If the systemic availability of a drug administeredorally is determinedby doing its comparison
with that of an oral standard of the same drug, it is known as a relative bioavailability.
 It is used to characterize absorption of drug from its formulations.

6.  "Range of Bioavailability - 0 to 1.
 "It is usually expressed as percentages (%).
 "An absolute bioavailability of 1 (or 100%) indicates complete absorption.
 Relativebioavailability of 1 (or 100%) implies that the bioavailability of drug from both the
dosage forms is the same but does not indicate the completeness of the systemic drug
absorption.

7. Bioavailability of drug from dosage form depends
upon following:-
 Route of administration
 Patient related factors
 Physicochemical properties of the drug
 Characteristics of the dosage form

8.  The influence of route of administrationon drug's bioavailability is generally in the following
order
 Parenteral > Oral > Rectal > Topical
 Most drugs are administered orally, for reason of stability and convenience.
 The dose available to patient Bioavailable dose.

9. Methods of assessing bioavailability
 There are two methods to determine bio-availability:-
 Pharmacokinetic methods( indirect )
 1. Plasmalevel analysis
 2. Urinary excretion data
 Pharmacodynamicdata( direct )
 1. Acute pharmacological response
 2. Therapeutic response

10. Pharmacokinetic methods
 Widely used and based on assumptions that pharmacokineticprofile reflects the therapeutic
effectiveness of a drugs.
 PLASMA LEVEL TIME ANALYSIS
 It is the most common type of human bioavailability studies.
 Based on the assumptions that there is direct relationshipbetween the concentrationof
the drug in blood or plasmaand the concentration of drug in the plasma.
 Following the administration of a single dose of a medication, blood smaples are drawn at
specifictime intervals and analyzed for drug content.
 Bio-availability(the rate and extent of drug absorption) is generally
assessed by the determination of following three parameters.
 They are
 Cmax(plasmapeak concentration)
 Tmax(timeof peak)
 Area under curve

11. 2. Urinary excretion data
 The method of determination bioavailability providedthat the active ingredient is excreted
unchanged in the significant quantity of urine.
 The cumulativeamount of active drug excreted in urine is directly proportional to extent of
systemicdrug absorption.
 The rate of drug excretion is directly proportional to rate of systemic drug absorption.

12. 1. Acute pharamcological response
 Bioavailability can be determined by the acute pharmacological effect-time curve as well as
from dose response graph.

13. 2. Therapeutic response
 This methodis based on the observing the clinical response to a drug formulations given to a
patient suffering from disease for which it is intended to be used.
 Eg:- Anti inflammatory drugs, the reduction in inflammationis determined.

14. BIOEQUIVALENCE
 Bioequivalence studies are usually performedto compare the rate and/or extent of absorption
of a new drug product or a generic equivalent with that of a recognizedstandard.
 Bioequivalence means pharmaceutical equivalents or pharmaceutical alternatives whose rate
and extent of absorption do not show a significant difference when administeredat the same
molar dose of the therapeutic moiety under similar experimental conditions.