Week 2 Pharmacokinetics Flashcards
What is pharmacokinetics
Study of what the body does to the drugs
What is pharmacodynamics
Study of what the drugs do to the body
What are the steps in a drugs journal through the body
Absorbtion, distribution, metabolism then excretion
During absorption where does the drug enter
Plasma
During distribution where does the drug leave to go to
Leaves the bloodstream and distribute into the interstitial and intracellular fluid
What part of the body metabolizes
Kidney and liver
Water soluble drugs penetrate the cell membrane through?
Aqueous channels or pores
What is the function of the carrier protein
Facilitate the passage of large molecules
What is facilitated diffusion
Movement of a molecule from a region on higher concentration to a lower concentration with the help of a transport molecule
What is active transport
Movement from a region on low drug conc to the one of higher conc
What is endocytosis
This involves engulfment of the drug molecule by the cell membrane and transport into the cell by pinching off the drug filled vesicles
Exocytosis
This is used by cells to secrete many substances by a similar vesicle formation process
Why can uncharged substance be passed easily
Because of it’s lipid solubility
What is bioavailability
This is the fraction of the administered drugs that gain access to the systemic circulation
What are the factors influencing bioavailability
First pass hepatic metabolism
Solubility of the drug
Chemical instability
Nature of the drug formulation
What part of the body is the first pass hepatic metabolism usually associated with
Liver
When is a drug bio equivalent
When two drugs show similar bioavailability and similar times to achieve peak blood conc
What is therapeutic equivalence
When two drugs show the same result(efficacy) and safety
What kind of plasma does acidic drug bind to
Albumin
What kind of drugs does basic drugs bind to
Lipoproteins and alpha-1 glycoprotein
Drugs are mostly eliminated by ?
Biotransformation and excretion
Metabolism does what
Transforms lipophilic drugs into more polar excretable drugs
What part of the body does biotransformation take place
Kidney and intestines
Phase 1 metabolism consist of
Reduction
Oxidation
Hydrolysis reaction
Drugs that must be metabolized to thier active form are what?
Prodrugs
The phase 1 reaction of metabolism is catalyzed by ?
The cytochrome p450 system
Another name for cytochrome p450 system
Microsomal mixed function oxidase
Function of p450 system
Metabolise endogenous drugs and biotransform exogenous substance
The most important route for elimination of drug is where?
Kidney
Renal elimination of a drug
Glomerular filtration, proximal tubular secretion and distal tubular reabsorption
What elimination kinetic do most drugs in clinical use demonstrate
First order kinetics
In first order kinetics the rate of elimination of drug is proportional to what
The drug concentration
What drug shows zero order elimination
Ethanol
At high toxic concentration what drug shows zero order elimination
Phenytoin and aspirin
Active transport is driven by what
Hydrolysis of atp
Which drug is transported through endocytosis
Vitamin b12
Which neurotransmitter is secreted by exocytosis
Norepinephrine
other places where the firt pass metabolism can occur
Lungs, gastrointestinal tract and vasculature
Drug distribution depends on?
Blood flow
Capillary permeability
Degree of binding of the drug to plasma and tissue proteins
Hydrophobicity of the drug
Function of phase 1 metabolism
Convert lipophilic molecules into more polar molecules by introducing a polar functional group like OH or NH2
Drugs that increase the synthesis of one or more cyp isozymes are
Phenobarbital, rifampin and carbamazepine
