introduction of bp--pk (22-7-10)

INTRODUCTION TO BIOPHARMACEUTIC & PHARMACOKINETICS: 

INTRODUCTION TO BIOPHARMACEUTIC & PHARMACOKINETICS BY : SAI KISHAN . I DEPT OF INDUSTRIAL PHARMACY

BIOPHARMACEUTICS: 

BIOPHARMACEUTICS Study of influence of formulation on therapeutic activity of drug. It is the interdependence of biological aspects of the living organism ( the patient) and the physico – chemical principles that govern the preparation and behavior of the medicinal agent or drug product.

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Modern biopharmaceutics is the study of the relationship of the physico-chemical properties and in vitro behavior of the drug and drug product on the delivery of the drug to the body under normal or pathologic conditions . Drug : A chemical molecule which can diagnose, treat, cure or prevent of disease in living organisms. Generally, the drug is combined with other ingredients into a drug formulation, which may be a solution, tablet, capsule or suppository.

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Factors involved in biopharmaceutics protection of the activity of the drug within the drug product. Release of the drug from a drug product. Rate of dissolution of the drug at absorption site. Systemic absorption of the drug.

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Aim : To adjust the delivery dose of the drug and to provide optimal pharmacological & therapeutic activity in a suitable dosage form. Why we need biopharmaceutics ? To produce an effective dosage form having minimum dosage regimen with less side effects & cost effective for patients.

Scope of Biopharmaceutics: 

Scope of Biopharmaceutics 1. Encompasses all possible effects observed following the administration of the drug in the various dosage forms. 2. Encompasses all possible effects of various dosage forms on biological response 3. Encompasses all possible physiological factors which may affect the drug in various dosage forms.

Pharmacokinetics : 

Pharmacokinetics The study of the time course of the drug concentration in the body, i.e. “ What the body does to the drug”. Involves the kinetics of drug Absorption, Distribution, and Elimination (Excretion & Metabolism)

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Bioavailability : The fraction of the administered dose that reaches the systemic circulation. Bioavailability is 100% for intravenous injection. It varies for other routes depending on incomplete absorption, first pass hepatic metabolism etc. Thus one plots plasma concentration against time, and the bioavailability is the area under the curve.

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Factors affecting Bioavailability: IV administration: bioavailability = 1 Other routes of administration = < 1 Major factors that reduce bioavailability to less than 100%: Incomplete absorption First-pass metabolism (liver metabolizes drug before drug reaches systemic circulation). Extent of Absorption: hydrophilic drugs - not be well absorbed -cannot cross cell membrane lipid component. Excessively lipid-soluble (hydrophobic) drugs may not be soluble enough to cross a water layer near the cell membrane.

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Drug Distribution: When a drug enters into the body, where it ends up depends on number of factors: Blood flow, tissues with the highest blood flow receive the drug first. Protein binding, drugs stuck to plasma proteins are crippled, they can only go where the proteins go (and that's not very far!). Lipid solubility and the degree of ionisation, this describes the ability of drugs to enter tissues (highly lipid soluble / unionised drugs can basically go anywhere).

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Protein Binding: Most drugs bind to proteins, either albumin or alpha-1 acid glycoprotein (AAG), to a greater or lesser extent. Drug’s tends to bind to a protein to have longer duration of action because of reduced metabolism & also the clearance is strongly dependent on the amount of protein binding. Why we need to understand protein binding: To know the free drug available for action at receptor site and thus to adjust the dose to be given.

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Importance of Biopharmaceutics & Pharmacokinetics: The assessment of Bioavailability & Bioequivalence of new drugs and generic marketed drugs. Pk Characterization of new drugs and new drug delivery systems. Adjustment of kinetic profile of drugs in diseased state and dose adjustment there of. Adjustment of dose regimen.

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Thank you !