Knowledge of Pharma

INTRODUCTION:  Pharmacokinetics, sometimes abbreviated as PK, (from Ancient Greek pharmakon "drug" and kinetikos "to do with motion") is dedicated to the determination of the fate of substances administered externally to a living organism. Pharmacokinetics is the science of the kinetics of drug absorption, distribution, and elimination (ie, excretion and metabolism). The description of drug distribution and elimination is often termed drug disposition.  Pharmacokinetics is often studied in conjunction with pharmacodynamics.  Pharmacodynamics explores what a drug does to the body, whereas pharmacokinetics explores what the body does to the drug. Pharmacokinetics includes the study of the mechanisms of absorption and distribution of an administered drug, the rate at which a drug action begins and the duration of the effect, the chemical changes of the substance in the body (e.g. by enzymes) and the effects and routes of excretion of the metabolites of the dru...

BIOEQUIVALENCE: It‘s commonly observed that there are several formulations of the same drug, in the same dose, in similar dosage form and meant to be given by the same route. in order to ensure clinical performance of such drug products, bioequivalence studies should be performed. TYPES  OF  EQUIVALENCE Chemical Equivalence:  When 2 or more drug products contain the same labeled chemical substance as an active ingredient in the same amount.  Pharmaceutical Equivalence:  When two or more drug products are identical in strength, quality, purity, content uniformity, disintegration and dissolution characteristics; they may however differ in excipients.  Bioequivalence:  A relative term which denotes that the drug substance in two or more dosage forms, reaches the systemic circulation at the same relative rate and to the same relative extent i.e., their plasma concentration time profiles will be identical without significant statistic...

METHODS  FOR  ASSESSING  BIOAVAILABILITY: Direct and indirect methods may be used to assess drug bioavailability. The in-vivo bioavailability of a drug product is demonstrated by the rate and extent of drug absorption, as determined by comparison of measured parameters, eg, concentration of the active drug ingredient in the blood, cumulative urinary excretion rates, or pharmacological effects.  For drug products that are not intended to be absorbed into the bloodstream, bioavailability may be assessed by measurements intended to reflect the rate and extent to which the active ingredient or active moiety becomes available at the site of action. The design of the bioavailability study depends on the objectives of the study, the ability to analyze the drug (and metabolites) in biological fluids, the pharmacodynamics of the drug substance, the route of drug administration, and the nature of the drug product.  Pharmacokinetic and/or pharmacodynamic paramet...

INTRODUCTION A multisource drug product is a drug product that contains the same active drug substance in the same dosage form and is marketed by more than one pharmaceutical manufacturer.  Single-source drug products are drug products for which the patent has not yet expired or has certain exclusivities so that only one manufacturer can make it. Single-source drug products are usually brand-name (innovator) drug products. After the patent and other exclusivities for the brand-name drug expires, a pharmaceutical firm may manufacture a generic drug product that can be substituted for the branded drug product.   Since the formulation and method of manufacture of the drug product can affect the bioavailability and stability of the drug, the generic drug manufacturer must demonstrate that the generic drug product is bioequivalent and therapeutically equivalent to the brand-name drug product.   Drug product selection and generic drug product substitution are major respo...

Physiologic Factors Related to Drug Absorption:   The systemic absorption of a drug is dependent on   The physicochemical properties of the drug,   The nature of the drug product, and   The anatomy and physiology of the drug absorption site.  1. Membrane Physiology A. Nature of Cell Membrane  The fluid mosaic model, proposed by , explains the transcellular diffusion of polar molecules.   According to this model, the cell membrane consists of globular proteins embedded in a dynamic fluid, lipid bilayer matrix. These proteins provide a pathway for the selective transfer of certain polar molecules and charged ions through the lipid barrier.  As shown in , transmembrane proteins are interdispersed throughout the membrane. Two types of pores of about 10 nm and 50 to 70 nma were inferred to be present in membranes based on capillary membrane transport studies. These small pores provide a channel through which water, ions, and dissol...