Pharmacology: Pharmacokinetics

Pharmacokinetics

what the body does to the drug

Step 1: absorption

allow drugs to pass through these barriers

step 2: distribution

by systems as blood and lymphatic vessels, drugs ability to act on it target tissues is also limited by several processes within the patient

Step 3: metabolism

how body transforms drugs through enzymatic degradation

step 4: excrection

drug is eliminated from the body primarily by the kidneys and in the feces

biopharmaceutics

the study of physical and chemical properties of drugs and their proper dosage as related to the onset duration and intensity of drug action

drug liberation

releasing from its dosage form, a drug in the solid state mustt dissolve to it;s molecular form in body fluids

true or false: a drug in an aqueous suspention must dissolve into suspendd crystals in the body fluid

true

tablet

crystals in a compressed powder

capsule

powder filled, molecules crystals in vegetable oil

suppository

crystals in waxy water miscible or water immicible base

solution

molecules dissolved in fluid

suspension

crystals in lattice matrix held in a aqueous or nonaqueous liquid

ointment

crystals or molecules in a semisolid oily base

cream

crystals or molecules in a water miscible semisolid cream base

gel

crystals or molecules in a water miscile semisolid gel base

aerosol

crytals or molecules suspended in gas liquid or semisolid

solubility

solute concentration at equilibrium, medications are formulated to dissolve at an optimal rate, water with tablet helps swallowing and dissolving medication

drug absorption

drug molecules move from administration to bloodstream

rate of drug absorption

rate limiting step dictates speed of drug entering blood stream, ex dosage form, route of administration, plasma drug concentration, mechanism of absorption (transport of the drug molecules across cell membrane)

paracellular transport

drug difusses betweel cells

passive diffussion

drug passess through cell membrane lipid bilayers, favors lipophilic drugs

facilitated diffusion

the drug is passively moved with its concentration gradient

active transport

drug moves against concentration gradient

blood brain barrier

prevents drug passive diffusion from the system to cerebral circulation

which drugs are unable to target facilitated or active transport proteins in the blood brain barrier

hydrophilic it cannot penetrate the CNS

first pass metabolism

drug enters hepatic portal circulation as absorbed through GI tract to be metabolizedf

true or false: some drug are taken without food because fatty foods slow gastric emptying

true

bioavailability

fraction of drug administered that reaches systematic circulation, based on route of administration, chemical formulation, patient specific factors

plasma concentration

rate of drug in plasma and rate of elimination

true or false: drug must reach target in sufficent concentration to yeild a therapeutic affect

true

drug distribution

drugs that are distrubuted to the interstitial and intracellular fluids are well perfused organs (liver kidney and brain) receive most of the drug, delivery to muscle, most visceral and fat is slower

what are factors that indluence drugs entery into systematic circulation

physiochemical properties of the drug, cardiac output and blood flow, binding of the drug to proteins in the plasma and target tissues, capillary permeability and tissue volume, concentration of the drug between the central compartment and peripheral compartment