Unit 1 Flashcards
Pharmacology
Action of drugs on living organisms
Neuropharmacology
Drug-induced changes in functioning of nerve cells
Psychopharmacology
Drug-induced changes in behavioral responding
Neuropsychopharmacology
Drug-induced changes in function of select neurons that influence specific sets of behaviors produced by injury, disease, or other factors
Drug Action
Local
Molecular changes within cells produced by drug binding to a target site/receptor
Drug Effect
Communal
Molecular changes within or between cells that lead to alterations in physiological/psychological function
Liberation
Rate of drug release into a biological system from administered form
Formulation
Mix of drug and excipient (i.e. time released). Can only control rate of delivery only when liberation
Excipient
Chemicals always added to drugs to facilitate ability of drugs to exist in different forms
Bioequivalence
Idea that if two drugs formulations have equal bioavailability and rate of absorption then plasma levels will be similar. NOT ALWAYS TRUE b/c of differing liberation rates/gut acidity
Absorption
Movement of drug from site of admin to blood circulation. Influenced by route of admin and liberation factors
Oral Administration PO
Most popular for safety and economy. Pills, liquids, etc. Must dissolve in stomach and pass through stomach wall to reach capillaries, so must be resistant to strong acids and enzymes. Majority not absorbed until proximal small intestine. Bioavailability affected by food in gut (slow gut movement = slow absorption), first pass effect
Intravenous Administration IV
Most rapid and accurate method b/c it circumvents stomach wall/first pass. Hazardous because of quickness/inability to stop, sterility, and dissolution in toxic fillers
Intramuscular Administration IM
Slow and even delivery of drug in non-aqueous additives (lipophilic oils). Often painful
Subcutaneous Administration SC
Often slow and steady delivery of aqueous drugs depending on blood flow to site. Similar to IM in use of slow delivery through oils
Gaseous Administration
Rapid absorption due to large surface area of pulmonary capillary system
Topical Administration
Direct application to mucosal membranes with rapid absorption into mucosal capillary system and rapid effects
Transdermal Administration
Slow absoprtion through transdermal patches into skin. Use lipophilic substances often dissolved in alcohol that can penetrate skin (lipid bi-layers).
Transport Across Cell Membranes
Rate of drug passage across various cell layers between site of administration and blood is the single most important factor in determining plasma drug levels
Passive Diffusion
From high concentration to low concentration as drugs move down the concentration gradient. Lipophilic/lipid-soluble, non-ionic drugs
Carrier-Mediated Active Transport
From low concentration to high through movement by a transport protein against the concentration gradient. Requires ATP. Ionic/charged drugs
Lipid-soluble Drug
Move across membranes via passive diffusion depending on concentration gradient / lipid solubility. Diffuse into cell membrane and establish a concentration which is always greater than within the cytoplasm. Must be able to penetrate membrane through lipophility, but overly lipophilic drugs can get stuck within the membrane
Salt Forms of Drugs
Substitute HBr/SO4 for hydrogen which increases aqueous solubility, facilitating solution in stomach and into blood for great stability/shelf-life. Once in aqueous environment, salt dissociates, releases drug, and is replaced by H. Problems encountered with drug weight vs salt weight
Ionization of Drugs
Most drugs are weak acids/bases that ionize in water, but depends on pH level [easier to be absorbed when more neutral] and ionization characteristics (pKa) [pH of solution in which drug is 50/50 ionized]
Distribution
Circulation of drug to target sites within a biological system (most blood goes to the brain).
Apparent Volume (Vd)
Distribution of a drug to the body, defined as relative amount of drug that leaves circulation and enters organs. Heavily influenced by lipid solubility. Vd = 3: drug distributed to 3L of body fluid. If Vd is too high, will distribute to areas not meant to be affected (even lipid myelin)
Distribution Phases
First Phase: Blood concentration drops as drug enters brain. High brain:blood ratio
Second Phase: Drug becomes soluble in other body tissues/organs including target which reduces blood concentration. Flips brain:blood ratio as blood diffuses(redistributes) from high [brain] to low [blood]
Third Phase: Drug leaves blood to enter fat (hair, fat, brain. Reservoir for lipophilic drugs)
Blood Brain Barrier
Vascular endothelial cells connevt by tight junctions and secrete basement membrane which force molecules to diffuse through basement membrane matrix. Astrocytes project astrocytic feet around basement membrane which makes barrier to diffusion of polar molecules, must go through basement. Can be opened by osmotic diuretic stress (manitol). Not on vomiting center to allow quick reaction.
Plasma (Depot) Binding
Depots in blood reduce [drug] available for diffusion by non-selectively binding drug to plasma proteins. Bound drug is not free to be metabolized by liver = longer drug action, protected against degradation. Responsible for terminating drug action b/c of redistribution of highly lipid soluble drugs
Metabolism
Breakdown/inactivation of drugs as it goes from prodrug to active form to inactive form. Mostly occurs in the liver (p450 system)
Biotransformation
Phase 1: oxidation hydrolysis, reduction of parent structure to produce a polar metabolite (can dissolve in aqueous sol.) of the drug that can be excreted in urine. All oral drugs undergo this in the gut.
Phase 2: Conjugation with glucuronide, sulfate, acetate, or an amino acid to produce a highly ionized, biologically inactive molecule that can’t cross membranes.
Drug half-life
Amount of time required for removal of 50% of drug in blood
First Order Transformation (Kinetics)
Drug clearance rate proceeds exponentially as usually [conversion enzymes] > [drug to convert]. Rate depends on [drug].
Zero Order Transformation (Kinetics)
Drug clearance rate is fixed as usually [drug to convert] > [conversion enzymes] with drug saturating metabolizing enzymes. Rate depends on [conversion enzymes] (slow)
Enzyme Induction
Increase in [enzymes] available for biotransformation increases the biotransformation rate of all drugs in system. Chronic exposure leads to upregulation of enzymes, which can bloat the liver, influence blood levels
Enzyme Inhibition
Some drugs directly inhibit metabolizing action of enzymes which decreases the biotrans rate of all drugs/natural molecules in system
Drug Competition
Some drugs share metabolizing enzymes which decreases the biotrans rate of both drugs in system, which can produce potentially dangerous drug interactions (alcohol + barbituates)
Individual Characterisitics
INdividual genetic/environmental differences in drug metabolism which can decrease the biotrans rate of drugs in a system. i.e. Asian lack of alcohol dehydrogenase -> weakened alcohol metabolism
Pharmacodynamics
Study of physiological and biochemical interactions of a drug with a target tissue that is responisble for the drug’s effect