Introduction to biopharmaceutics and pharmacokinetics


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بسم الله الرحمن الرحيم(وَقُل رَبّي زِدْني عِلماً) : 

بسم الله الرحمن الرحيم(وَقُل رَبّي زِدْني عِلماً) INTRODUCTION TO BIOPHARMACEUTICS AND PHARMACOKINETICS Dr. Issra Al-Ani Al-Ahliyya Amman University

Slide 2: 

Biopharmaceutics can be defined as the study of how the physicochemical properties of drugs, dosage forms and routes of administration affect the rate and extent of drug absorption. For a drug to be effective, enough of it needs to reach its site of action(s) and drug stays there long enough to be able to exert its pharmacological effect. This depends on route of administration, the form at which the drug is administered and the rate at which it is delivered.

Slide 3: 

Differences between I.V route and other routes. Drug in systemic circulation : RBC – plasma plasma : bound and free Distribution: is dynamic equilibrium between drug in blood and drug in site of action. The degree of distribution depends largely on the ph-ch properties of the drug. In particular “ partition coefficient” or “lipophilicity.

Slide 4: 

Assay of drug : site of action ? plasma ? free or bound? Total drug in plasma is measured for clinical purposes.

Slide 5: 

The concentration of drug in blood plasma depends on many factors: 1- Amount of administered dose that is absorbed and reach systemic circulation. 2- The extent of distribution of the drug between the systemic cir. And other tissues. 3- The rate of elimination (metabolites and unchanged).

Pharmacokinetic : 

Pharmacokinetic Pharmacokinetics is the study of movement of drug in the body or how the body deals with the drug. Or….Pharmacokinetics is the study and characterization of time course of drug Absorption, Distribution, Metabolism and Elimination (ADME). Or LADME (liberation) Pharmacok. Is used in the clinical setting to enhance the safe and effective therapeutic management of individual patient.

Bioavailability : 

Bioavailability Bioavailability is the relative amount of an administered dose of a particular drug that reaches systemic circ. Intact and the rate at which this occurs. Or It is the rate and extent of drug absorption. Bioavailability is extremely important in determining whether therapeutically effective conc. Will be achieved at the site of action.

Notes: : 

Notes: The definition is not valid unless the drug is in its active form.(not a prodrug) The systemic circ. Refers only to venous blood. To get high bioav. The drug should be: 1- completely released from the dosage form. 2- fully dissolved in GIT fluids. 3-stable in GIT fluids. Pass through GIT barrier without being metabolized. Pass trough liver to the circ. Unchanged.

Causes of different bioavailability: : 

Causes of different bioavailability: 1- Same type of dosage form but diff. route of administration. 2- Same route of administration but diff. types of dosage (oral tablets and oral solution) 3- Same dosage form and same route of administration but different formulation factors.

Generally, factors affecting absorption or bioav.: : 

Generally, factors affecting absorption or bioav.: Physiological factors (GIT content, enzymes,pH, motility) Physicochemical factors (hydrolipophilicity) Rate limiting step?