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Chapter 2 Pharm
Pharmacolgy
| Term | Definition |
|---|---|
| Pharmacology | Study of drugs: Origin, properties, and how they work. Multiple factors determine drug's effects. Pharmacology can be subdivided into several divisions |
| Pharmacotherapy | therapy that uses a specific medication or drug to treat a specific disease |
| Pharmacodynamics | study of actions of drugs on living organisms |
| Pharmacokinetics | study of what the body does to the drug |
| Pharmacy | practice of compounding, preparing, and dispensing drugs |
| Toxicology | study of harmful effects of drugs |
| Routes of administration | oral or per os- most common and usually the safest route, onset usually 30 to 60 mins, multiple factors impact absorption/ Parenteral (by needle)- intradermal, subcutaneous, intramuscular, or intravenous |
| Drug doses | Dose-response curve: graphic representation of relationship between dose in milligrams and response to drug, dose and response increase together until ceiling effect: point when additional dosage stops increasing effect and increasing dose may have toxic |
| Drug doses: Potency and Therapeutic dose | Potency- drug that reaches effective level with smaller dose is more potent/ more potent drug reaches toxic effects at smaller dosage Therapeutic dose- recommended amount to obtain desired effect |
| Drug Doses: Median Lethal Dose(LD50) and Median effective dose(ED50) | Median lethal dose(LD50): dose at which 50% of test animals die Median effective dose(ED50): dose at which 50% of test animals show desired effect |
| Drug doses: Therapeutic index | Ratio of LD50 to ED50, gives relative safety indication, formula is TI= LD50/ED50. the higher the TI the safer the drug, the closer to zero the more toxic the drug is |
| Drug absorption | Oral route: drug must pass through GI tract membrane Transdermal: Drug must be absorbed through skin Considerations: transport mechanisms, lipid solubility, and drug ionization |
| Transport mechanisms of drugs across membranes | Passive diffusion: governed by concentration gradient Filtration Active transport: requires energy or another substance or transporter |
| Fluid mosaic model | Plasma cell membrane comprises two layers of lipids with integral proteins between them Also includes channels through which water and small water-soluble molecules can pass - membranes have larger channels/ substances pass through channels by filt |
| Lipid solubility | Cell membrane comprises significant amounts of lipid material Lipid-soluble drugs pass through rapidly Many drugs very lipid-soluble -Ex: general anesthetics |
| Drug ionization | Primarily water-soluble drug must be weak acid or weak base to be absorbed rapidly - mostly in un-ionized form Ionized drugs difficult to absorb -ionized molecules poorly soluble in lipids - highly charged particles repulsed by fixed charges |
| continued from last card | in channels and membrane surface |
| Drug ionization | Absorption rate strongly influenced by tissue fluid pH -the more neutral (un-ionized) the drug, the better its absorption Henderson-Hasselbalch equation: pH=pKa+log(ionized drug/un-ionized drug) |
| Drug Mechanisms | Mechanism of action -explains how drug produces effect -helps identify proper clinical application when known Site of action -location where drug exerts therapeutic effect -not completely identified for all drugs |
| Drug mechanisms | Receptor site -receptor is part of cell or organism that combines with drug and initiates series of events leading to drug's effect -usually located on cell membrane -specific drug usually combines with specific receptor |
| Agonists and Antagonists | Agonists- drugs that combine with specific receptors to cause drug action Antagonists (blocking agents)- combine with receptors and cause no action or block an effect |
| Drug distribution | Drug- gains access to blood plasma, carried by blood throughout body, combines with receptor sites Amount of drug that reaches receptor site influenced by plasma protein binding, tissue affinity, and blood flow |
| Plasma protein binding | Circulating proteins in plasma chemically attract and bind certain drugs -only free drug available for action Drugs with affinity for plasma proteins -equilibrium between free drug and bound drug -change in fraction of bound drug alter degree of drug |
| Tissue affinity and blood flow | Some drugs have strong affinity for certain tissues or organs -creates potential reserve for drug and ex: barbiturates Some tissues and organs receive more blood - Liver, kidneys, brains exposed to largest amount of drug |
| Drug metabolism | Process by which drugs are altered, changed, inactivated, and prepared for elimination Also called biotransformation Resulting substance called metabolite -may be able to exert some activity and may be inactive and excreted from body |
| Drug metabolism | Enzyme induction: occurs when drug stimulates rate of action of microsomal enzyme system in liver and decreases overall time of drug's activity Enzyme inhibition: occurs when drug slows metabolism by enzymes and leads increased activity or toxicity |
| First-pass effect | Loss of drug from metabolism before reaching its intended site of action Drugs with high first-pass effect: Increased oral dosages may be required to achieve therapeutic effect and effect reduced through aerosol, sublingual, or parenteral administration |
| Drug excretion | Sites of excretion: kidneys, respiratory system, and GI tract Majority of drugs excreted by kidneys Can alter pH of urine to either: enhance excretion and increase absorption |
| Factors that alter drug effects | Patient adherence to physician's instructions: necessary for maximum effectiveness Placebo effect: depends on patient's perception of drug Pathologic state: various disease states impact drug effects |
| Factors continued | Administration with meals: some drugs are less toxic when taken with meals, other drugs not well absorbed at mealtimes Gender: does not directly impact drug sensitivity, facts impacting sensitivity are body weight, size, muscle mass, and metabolic rate |
| Factors continued | Age: very young and elderly most sensitive to drugs Genetic variations: relevant at liver microsomal enzyme system Drug interaction: mechanisms such as enzyme induction and enzyme inhibition can impact drug effects |
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cassiemartin
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