Pharmacokinetics Flashcards

Question

What are the 4 types of ways that drugs can cross the phospholipid bylayer

Answer 1

Passive diffusion Transporters Membranous Pores Vesicle mediated transport - Pinocytosis

Answer 2

The movement of a substance from an area of high concentration to an area of low concentration Ion channels may enable this down a concentration gradient

Answer 3

Molecules combine with the membrane bound carrier protein - still moving down the concentration gradiaent - Faster process

Answer 4

Using energy in the form of ATP moves molecules against the concentration gradient

Answer 5

Molecules engulfed by cell membrane and vesicle formed Vesicle moved into the cell Molecule may then be released within the cell

Answer 6

Functional basis of barrier is reduced capillary permeability owing to: tight junctions between endothelial cells decrease in size and number of pores in the endothelial cell membranes presence of surrounding layer of astrocytes

Answer 7

Activation of inactive drug Production of active drug with increased activity from active drug Inactivation of active drugs Change in the nature of the activity

Answer 8

Metabolism occurs prior to and during absorption Intestinal Lumen Digestive enzyme secreted by the mucosal cells and pancreas Certain enzymes break down proteins and stop them from being absorbed Intestinal Wall Rich in enzymes that further metabolise drugs Liver Major site of drug metabolism Lung Cells of the lung have high affinity for many drugs and are the site of metabolism for many local hormones

Answer 9

Phase I Reactions Oxidation, reduction and hydrolysis Usually form more reactive products, sometimes toxic Often involve mixed function oxidase system in which Cytochrome P450 plays a key role Phase II Reactions Conjugation Usually form inactive and readily excretable products

Answer 10

Lipophillic Drug - Phase 1 reaction causes the formation of a more active drug Phase 2 reaction causes conjugation and it to be transformed into a hydrophillic form - able to be excreted in the urine

Answer 11

Isoenzymes that can inhibit or induce an affect either inhibiting the action or potentiating the affect

Answer 12

Enhance the production of liver enzymes which break down drugs Faster rate of drug breakdown Larger dose of affected drug needed to get the same clinical effect

Answer 13

Inhibit the enzymes which break down drugs Decreased rate of drug breakdown Smaller dose of affected drug needed to produce the same clinical effect

Answer 14

First pass effect Hepatic blood flow Liver disease Genetic factors e.g. acetylation status Other drugs- hepatic enzyme inducers, hepatic enzyme inhibitors Age Impaired hepatic enzyme activity Elderly Children < 6 months (especially premature babies)

Answer 15

Bioavailability is the proportion of a dose which actually gets into the systemic circulation

Answer 16

1. Pharmaceutical Preparation Particle size, composition of formulation 2. Physicochemical Interactions Other drugs or food may interact with or inactivate the drug 3. Patient Factors Malabsorption syndromes, gastrointestinal motility 4. Pharmacokinetic interactions and first-pass metabolism

Answer 17

This is the measure of the removal of drug from the body or the volume of plasma completely emptied of drug per unit time

Answer 18

1 cFluids: Urine, bile, sweat, tears, milk Important for low-molecular weight polar compounds 2. Solids: Hair, faeces Faecal elimination important for high-molecular weight compounds that are excreted in bile Distribution of drug along hair shaft can be used to indicate the history of drug intake during the preceding weeks 3. Gases: Important only for volatile compounds

Answer 19

Reduced excretion Increased renal impairment active metabolytes may be nephrotoxic

Answer 20

Elderly - renal blood flow decreases after the age of 30 Neonates CKD AKI

Answer 21

Creatinine Clearance It is neither passively reabsorbed or actively secreted Estimation of Creatinine clearance estimates the clearance of drugs filtered at the glomerulus

Answer 22

Cockcroft-Gault equation (140-age) x weight x constant Serum Creatinine Constant - male 1.23 and female 1.04