Pharmacokinetics Course Materials

1. Pharmacokinetics include: Administration, absorption, distribution, metabolism and excretion 2. Routes of Admin- oral, rectal, skin(topical), lungs, eyes , ears, urethra istration Injections: intravenous, intramuscular, subcutaneous, intradermal, intraperitoneal, intrathecal and intraarterial 3. First pass metab- A drug is given enterally(oral or rectal), likely to be abolism sorbed into the small intestine to the liver, where it is likely to be metabolised. gets less effective 4. the transition of lipid solubility, area available for absorption, possible spedrugs through cific carriers, and the amount that reaches the target from the membrane first pass metabolism is determined by four factors: 5. advantages of using different routes of administration: oral: safer and more convenient buccal/sublingual: avoids presystemic metabolism rectal: good for patients who vomit intramuscular: emergencies subcutaneous: insulin intrathecal: directly into CNS but quite risky 6. difference between IV nod oral dosing shown by graph: can be shown from the elimination of the drug in plasma over time. With IV, it starts off high and then decays as the drug leaves the plasma to reach its target, after it is excreted and metabolised. With oral, the time to get a peak is longer because the drug has to go through the GI tract, and the liver for first pass metabolism 7. Bioavailability: How well the drug is absorbed to reach its target. 8. measuring drug half life= time it takes for plasma drug conc to reach half in the plasma or clearance: rate of elimination/ plasma drug conc 9. removal of drug first order kinetics- most drugs eliminated. T0.5 is confrom plasma stant, rate of removal depends on how much drug is present 1/3 10. Absorption membrane permeability- lipid water partition 11. Distribution drugs transferred in and out of various tissues, maintaining adequate conc around the body 12. Drugs and mem- membranes- small polar molecules branes muscle-large polar molecules 13. pH is important: Basic drugs in a high pH-lipis soluble, transported Acidic drugs in a low pH-lipid soluble, transported Basic drugs in low pH- less soluble and not easily transported 14. protein binding High molecular weight proteins(plasma proteins) cannot pass through membrane, so any drug bound to them is not available for distribution only unbound drug is free for distribution 15. measuring vol- amount of drug in body/conc of drug in blood ume of distribution 16. Metabolism and once drug is absorbed and distributed, has to removed Elimination from body in order to reach renal system, drug has to become less lipid soluble and more water soluble-metabolism phase1- oxidation, reduction , hydrolysis.makes drugs more water soluble and prepares drugs for phase 2- drug is coupled to a second, larger water soluble molecule eg: sugar or amino acid 17. Metabolism-induction and inhibition induction- induce drug metabolising enzymes, increasing amount of enzyme, metabolised quickly, half life is less inhibition- less enzymes, slower, half life is more 18. elimination-exit routes renal, faecal, respiratory, skin, mothers milk 19. 2/3 pharmacodynam- drug receptor interaction ics affinity, efficacy, specificity 20. affinity How well drug binds to receptor. electrostatic forces attract drug. shape of drug fits recrptor, will be held with weak bonds. number of bonds= affinity of drug 21. efficacy strength of agonist eliciting response. potent agonist-small amount for an effect. weak agonist-need more. antagonistblocks receptor 22. Specificity how selective lignad is. high specificity=only binds to certain receptors 3/3