BA & Absorption

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FACTORS AFFECTING DRUG ABSORPTION AND BIOAVAILABILITY PRESENTED BY:- KUSUM SINGH M.PHARM. (1st year) I.T.S. ( PARAMEDICAL) COLLEGE, MURADNAGAR

TABLE OF CONTENT : 

TABLE OF CONTENT INTRODUCTION GASTROINTESTINAL ABSORPTION OF DRUGS MECHANISM OF DRUG ABSORPTION FACTORS AFFECTING DRUG ABSORPTION & BIOAVAILABILITY PHARMACEUTICAL FACTORS PHYSICOCHEMICAL PROPERTIES OF DRUG SUBSTANCES DOSAGE FORM CHARACTERISTICS & PHARMACEUTICAL INGREDIENTS

INTRODUCTION : 

INTRODUCTION DRUG ABSORPTION – Movement of unchanged drug from site of administration to systemic circulation. Fig:- Plots showing significance of rate & extent of absorption in drug therapy

GASTROINTESTINAL ABSORPTION OF DRUGS : 

GASTROINTESTINAL ABSORPTION OF DRUGS Oral route is most common ROA for systemically acting drugs; so more emphasis is given to GI drug absorption. It includes all aspects of variability observed in drug absorption. CELL MEMBRANE :- Cell membrane structure & Physiology

MECHANISM OF DRUG ABSORPTION : 

MECHANISM OF DRUG ABSORPTION Passive diffusion Pore transport Facilitated diffusion Active transport Ionic or Electrochemical diffusion Ion-Pair transport Endocytosis

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Figures showing different types of transport Mechanisms.

FACTORS INFLUENCING DRUG ABSORPTION & BIOAVAILABILITY : 

FACTORS INFLUENCING DRUG ABSORPTION & BIOAVAILABILITY Biopharmaceutics Consideration in Dosage form design By proper biopharmacetic design, the rate & extent of drug absorption (BA) / systemic delivery of drug to the body can be varied from rapid & complete absorption to slow & sustained absorption depending upon desired therapeutic objective. Sequence of events that occur following administration of solid dosage form until its absorption in systemic circulation. The process consists of four steps:- Disintegration Deaggregation Dissolution Absorption Rate at which drug reaches systemic circulation is determined by slowest of the various steps involved in sequence. Such a step is called as Rate- determining/ Rate- limiting step (RDS)

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Solid dosage form Granules or aggregates Fine particles Drug in solution At absorption site Ionic drug Ionic drug Non-ionic drug Non-ionic drug 1 2 3 3 3 4 Blood GI Lumen GI Barrier 1- Disintegration 2- Deaggregation 3- Dissolution 4- Absorption Sequence of events in the absorption of drugs from orally administered solid dosage forms

FACTORS INFLENCING GI ABSORPTION OF A DRUG FROM ITS DOSAGE FORM : 

FACTORS INFLENCING GI ABSORPTION OF A DRUG FROM ITS DOSAGE FORM PHARMACEUTICAL FACTORS:- Physicochemical properties of drug substances:- Drug solubility & Dissolution rate Particle size & Effective surface area Polymorphism & Amorphism Pseudopolymorphism ( hydrates/ solvates) Salt form of the drug Lipophilicity of the drug pKa of the drug & p H Drug stability p H- Partition Hypothesis

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2. Dosage form characteristics & Pharmaceutical Ingredients Disintegration Time ( Tablets/ Capsules) Dissolution time Manufacturing variables Pharmaceutical ingrdients ( excipients / adjuvants) Nature & type of dosage forms Product age & storage condition

Physicochemical factors affecting drug absorption : 

Physicochemical factors affecting drug absorption Drug Solubility & Dissolution rates