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Pharmacology
Drugs and the Body
Question | Answer |
---|---|
Generic Name | Nonproprietary- not protected by trademark or patent. Ex. Acetominaphen |
Trade Name | Proprietary- manufactured and sold only by the owner of the patent, formula, brand name, or trademark associated with the product. Ex. Tylenol |
Pharmaceutic | Disintegration and dissolution of ORAL drugs. The drug becomes a solution so that it can cross biologic membrane. When a drug is administered parentally, subQ, IM, IV no pharmaceutic phase. |
Rate Limiting | Factors that speed up or slow down the pharmaceutic phase. Ex. enteric coated capsules. Generic may differ from original b/c of filler/binder. |
Pharmacodynamics | Interactions b/w chemical actions of body & chemical effect on drug. Drugs act by: replace or substitute missing chemical, increase cellular activity, depress cellular activity, interfere with functioning of foreign cells (microorganisms, cancer cells) |
Pharmacodynamics definition | the study of drug concentration and its effect on the body. |
Dose response | The relationship between the minimal vs the maximal amount of drug dose needed to produce the desired drug response. MTC: max therapeutic concentration. MEC: min therapeutic concentration |
Receptors | Specialized protein structures that are found on cell membranes. Drugs designed to target specific types of receptors to initiate, limit, or prevent biological response. |
Response to a drug depends on | Affinity or attraction to a receptor and the concentration of drug at the receptor site** |
Agonists vs Antagonist | Agonist: drugs that produce a response or prolong activity. Antagonist: drugs the block a response (can be competitive for receptor site) |
Nonspecific Drug effect | Drugs that affect receptors at various sites and have properties of nonspecificity** Produce response wherever a particular type of receptor exists. |
Selective toxicity | Ability of drug to only attack those systems in foreign cells. Ex. antibiotics interfere with enzyme system of bacteria and not normal human cells. Drugs for cancer have poor selective toxicity. |
Therapeutic index | Estimates the margin of safety of a drug. The higher the TI the wider the margin of safety***. No drug is completely safe. |
Therapeutic range | should be b/w the minimum effective concentration in plasma for obtaining desired drug action and the minimum toxic concentration, the toxic effect |
Drug monitoring** | Done to maintain safety, assure effective concentration of drug. |
Peak level | the highest plasma concentration of a drug at a specific time, indicates absorption. Blood sample would be taken shortly after dose administered. |
Trough levels | The lowest plasma concentration of a drug, indicate excretion. Blood sample taken immediately before next dose. |
Critical concentration | amount of drug needed to cause a therapeutic effect. between maximum effective concentration and minimum effective concentration. |
Loading dose | high dose given to rapidly obtain effective concentration. |
Dynamic equilibrium | Determines the actual concentration of drug reached. Depends on: absorption from site of entry, distribution to active site, biotransformation (metabolism) in liver, excretion from body |
Pharmokinetics | the process of drug movement to achieve drug action. Four processes: absorption, distribution, metabolism, excretion |
Absorption | drug moves from site of entry into circulating fluids. Drugs that are liquid soluble and nonionized are absorbed faster than water-soluble and ionized drugs**. Most oral drugs are best absorbed in small intestine |
Absorption of enteral | In GI tract. Altered by: GI motility, presence of food in stomach, pH of stomach, amount of bowel surface area. Can be influenced by pain, stress that could divert blood flow from stomach |
Absorption of parenteral | Includes IM, subQ, sublingual, rectal, topical, inhaled. Altered by blood flow to area** and tissue type (fatty, muscle). |
Absorption with Subq or IM | Muscle tissue has more blood vessels so faster absorption. Subcutaneous (fatty) tissue has less blood vessels so slower absorption**. |
Absorption: IVs | Intravenous administration not affected by absorption "rules"-- drug is immediately into circulation. Pt gets 100% of dose |
First Pass Effect | Affects enteral drugs. Drugs pass through portal vein to liver before entering systemic circulation**. Portion of drug "lost" due to liver process. Some drugs may be activated or partially inactivated. Some drugs not give orally b/c of high loss** |
Bioavailability | Percent of drug administered that reaches systemic circulation. Oral/enteral is always <100% due to first pass effect. Usually 60-70%. IV always 100%. |
Factors that affect bioavailability | Drug form, route of administration, GI mucosa, motility, presence of food or other drugs in GI tract. Liver function** |
distribution | the process by which the drug becomes available to body fluids and body tissues. |
Protein binding | drugs attach to protein molecules and travel to site of action (mostly bind to albumin) Acts as drug reservoir. When drug is bound to protein-inactive** Unbound drug is free, active drug***. Only unbound drug able to move thru capillaries |
Protein binding Potential | Need to monitor pt's plasma protein and albumin levels, elderly and pediatric differences related to decrease in protein levels. Low protein levels, hypoalbuminemia increase risk for drug toxicity. |
Free Drug | Drug not bound to protein, active and can cause a pharmacologic response. Drugs compete are protein-binding sites and can "knock" other drugs off protein to increase free drug. |
Drugs that are protein bound... | have a longer duration of action |
Drugs with high protein binding | Have more drug interactions and drug will be released more slowly (free drug becomes available over longer time. |
Pts with low protein levels | Have less protein binding sites and have more free drug available, more toxicity possible, shorter duration of action |
Blood brain barrier | Protective cellular activity to prevent chemicals from entering brain. Lipid soluble drugs can cross. Most antibiotics not lipid soluble. |
Placenta and breast milk | Many drugs can easily pass through placenta-fetal risk. Many drugs secreted in milk- neonate risk. |
Metabolism (biotransformation) | Drugs can be metabolized in both the GI tract and liver, however, liver primary site of metabolism***. Liver disease such as cirrhosis or hepatitis with decrease metabolic processes** |
Drugs are altered by enzyme activity to | Become active, form active metabolism, become inactivated, become water soluble for easier excretion. |
Metabolic pathways | Can be overloaded by particular drugs ie acetaminophen if large dosages over short time or if several drugs using same pathway. |
Half-life | the time it takes for one half of peak drug concentration to be eliminated** 50% of drug in system. Takes 3-5 half lives to achieve steady state** |
Drugs with longer half-lives | Longer duration of action. Means less frequent dosing times, increased risk of danger |
Excretion | Kidneys- main way med is eliminated***. Monitor creatinine clearance to avoid drug toxicity. Drugs must be water soluble to be excreted via kidney. Urine ph can affect excretion. Drugs that are still protein bound can't be excreted through kidneys. |
Creatinine clearance | Normal 85-135 ml/min. Dosages of drugs may be decreased due to renal clearance |
Pharmacogenetics | effect of drug action that varies from a predicted drug response b/c of a genetic or hereditary factor. Some BP meds more effective for particular ethnic groups Some persons lack liver enzymes to metabolize anesthetic drugs. Some metabolize drugs quickly. |
Placebo effect | Perceived effect even though given an inactive chemical |
Adverse effects/Side effects | Expected, predictable effects not related to desired affect. Usually related to nonspecificity of drug***. Occur b/c drug has effects besides therapeutic effect, pt may be sensitive to drug, drug action causes other responses in body |
Some adverse/side effects desirable | Diphenhydramine (Benadryl)- drug is antihistamine that produces drowsiness effects, therefore used in sleep meds. Opiates cause decreased GI motility- used as antidiarrheal. |
Adverse reactions | More severe, not predictable, occur at normal dose, always undesirable, must be reported** |
Toxic effect | Damaging to organs. Monitored by drug levels. Therapeutic range. Usually kidneys and liver most effected |
Drug induced Tissue and Organ Damage | Skin reactions, super infections, blood dyscrasias, toxicity, altered glucose metabolism, electrolyte imbalance, sensory effects, neuro effects |
TC has liver and kidney disease. He is given a med with a half life of 30 hours. You expect the duration of this med to: | Increase |
In the older adult and those with renal dysfunction, the creatinine clearance is usually | decreased |