This document discusses factors that affect the bioavailability of drugs. It defines bioavailability as the rate and extent that the active concentration of a drug is available at the site of action. There are two types of bioavailability: relative, which compares systemic availability after oral administration to an oral standard, and absolute, which compares oral to intravenous administration. Factors that can influence bioavailability include pharmaceutical factors like particle size and excipients, pharmacological factors like metabolism and interactions, and route of administration with generally parenteral having the highest bioavailability and topical the lowest.

1. Factors Affecting
Bioavailability of drug
Ashutosh Gupta
M. Pharm (pharmaceutics)
From BIT Mesra Ranchi
Assistant Professor
at
Department of Pharmaceutics
College of Pharmacy
TMU Moradabad
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2. CONTENTS
 Introduction of Bioavailability
 Objective of bioavailability studies
 Types of bioavailability
 Factors Affecting Bioavailability
 Pharmaceutical factors
 Pharmacological factors
 Route of administration
 Bibliography
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3. Introduction of bioavailability
 The rate and extent at which the active concentration of a drug is available
at the desired site of action.
Bioavailability=
𝑨𝑼𝑪 𝒐𝒇 𝒐𝒓𝒂𝒍
𝑨𝑼𝑪 𝒐𝒇 𝑰𝑽
*
𝑰𝑽 𝒅𝒐𝒔𝒆
𝑶𝒓𝒂𝒍 𝒅𝒐𝒔𝒆
 In such cases, the dose available to the patient, called as bioavailable
dose. It often less than the administered dose.
 The amount of drug that reaches the systemic circulation is called as
systemic availability.
 The term bioavailable fraction F refers to the fraction of administered
dose that enters the systemic circulation.
𝐅 =
𝐁𝐢𝐨𝐚𝐯𝐚𝐢𝐥𝐚𝐛𝐥𝐞
𝐀𝐝𝐦𝐢𝐧𝐢𝐬𝐭𝐞𝐫𝐞𝐝 𝐝𝐨𝐬𝐞
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4.  Primary stages of development of a suitable dosage foam for a new drug
entity to obtain evidence of its therapeutic utility.
Objective of bioavailability studies
Bioavailability studies are important in the-
 Determination of influence of excipients, patient-related factors and
possible interaction with other drug on the efficiency of absorption.
 Development of new formulations of the existing drugs.
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5.  Control of quality of a drug product during the early stages of factors,
storages and stability on the drug absorption.
 Comparison of availability of a drug substance from different dosage
forms or from the same dosage from produced by different manufactures.
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6. Types of bioavailability
There are two types of bioavailability
- Relative bioavailability
- Absolute bioavailability
 Relative bioavailability
The relative bioavailability is the systemic availability of a drug after oral
administration is compared with that of oral standard of the same drug.
𝐅𝐫 =
𝐎𝐫𝐚𝐥 𝐝𝐨𝐬𝐞 (𝐝𝐫𝐮𝐠)
𝐎𝐫𝐚𝐥 𝐝𝐨𝐬𝐞 (𝐬𝐭𝐚𝐧𝐝𝐚𝐫𝐝)
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7.  Absolute bioavailability
when the systemic availability of a drug administered orally is comparison
to its intravenous administration, is called as absolute bioavailability .
𝐅 =
𝑶𝒓𝒂𝒍 𝒅𝒐𝒔𝒆
𝐈. 𝐕 𝐝𝐨𝐬𝐞
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8. Factors affecting Bioavailability
There are various factors which affect the bioavailability of drug-
 Pharmaceutical factors
 Pharmacological factors
 Route of administration
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9. Pharmaceutical Factors:
 It is expected that, bioavailability of drugs to be in this decreasing
order-
Solutions > Suspension > Capsule > Tablet > Coated Tablet
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10. The Pharmaceutical factors include:
 Particle Size
 Salt Form
 Crystal Forms
 Nature of Excipients
 Degree of Ionisation
 Partition coefficient
 The method of manufacturing
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11. Pharmacological Factors 11

12. The Pharmacological factors include:
 Gastric Emptying and Gastrointestinal Motility
 Gastrointestinal Diseases
 Food and Other Substances
 First Pass Metabolism
 Drug-Drug Interactions
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13. Route of administration
 Parenteral
 Oral
 Topical
 Rectal
 Inhalation
Parenteral > Oral > rectal > Topical
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14. Bibliography:
 Brahmankar D.M, biopharmaceutics and pharmacokinetics, New Delhi,
Vallabh Publications, 2012.
 Goodman L. S, Goodman & Gilman’s Pharmacological Basis of
Therapeutics, 13th Edition, New York; New Delhi, TataMcGraw-Hill
Education, 2017.
 Katzung B. G, Basic and Clinical Pharmacology, 14th Edition, New York;
New Delhi, TataMcGraw-Hill Education, 2017.
 Tripathi K.D, Essentials of Medical Pharmacology, 7th Edition, New
Delhi, Jaypee Brothers Publications, 2013.
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15. ThankYou!

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