* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Basic-Pharm-161-Presentation-pharmacokinetics1
Survey
Document related concepts
Polysubstance dependence wikipedia , lookup
Orphan drug wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Compounding wikipedia , lookup
Psychopharmacology wikipedia , lookup
Theralizumab wikipedia , lookup
Pharmacognosy wikipedia , lookup
Pharmacogenomics wikipedia , lookup
Drug design wikipedia , lookup
Neuropharmacology wikipedia , lookup
Pharmaceutical industry wikipedia , lookup
Drug discovery wikipedia , lookup
Prescription costs wikipedia , lookup
Transcript
Pharmacokinetics Study of process of drug absorption, metabolism and excretion, distribution, biotransformation, excretion and halflife Absorption o Process by which drug is made available for use in the body. Transfer drug from the body fluids to the tissue sites- Absorption (Cont) Factors that influence the rate of absorption: Route of administration o IV- most rapid- immediate onset o IM- short onset w/in minutes- about 20 min o SubQ- rapid- e.g. insulin o Oral- takes 30-60 minutes before absorption from GI tract… onset of drug action thus delayed Absorption (Cont) Solubility of drug o More soluble, more rapidly absorbed o Most drugs are Water-sol (most readily absorbed)- and partially lipid soluble Law of Diffusion- drug molecules pass from an area of high concentration to an area of low concentration – – Concentration of drug on each side differs… so will equal out with transport Absorption (Cont) Drugs pass through cell membranes through Filtration Passive transport- most pass this way Active transport Absorption (Cont) Presence of certain body conditions: o Development of lipodystrophy o Orally, food delays drug absorption o Some drugs irritate stomach Absorption (Cont) Factors that influence distribution: Systemic circulation distributes drugs to various body tissues or target sites (receptor sites) o Interact w/ specific receptors during distribution o Some bind to protein or albumin in the blood plasma Absorption (Cont) Blood levels must be maintained for drug to be effective… Therapeutic level Blood flow needs to be adequate Blood-brain barrier: lipid barrier Blood-brain barrier: lipid barrier o Drugs need to be lipid soluble to get into brain cells. Biotransformation o Metabolism Process by which drug is converted to a substance that can be eliminated Drug is converted by the liver to inactive compounds DMMS- drug microsomal metabolizing system Drugs such as barbiturates and sedatives stimulate the DMMS when taken frequently Excretion o Inactive compounds of drugs excreted by the kidneys- must be water- soluble o Some drugs excreted w/o being changed by the liver o Caution for pts w/ kidney disease o lower doses in infants and children as immature kidney function…. And in older age pts w/ diminished kidney function Half-life o Time required for body to eliminate 50% of drug or for the concentration in blood to fall to half of the original level. o Affects timing/frequency of drug dosage Drug w/ short half-life of 2-4 hours need freq adm Drug w/ long half-life (20-24 hrs) req less freq dosing. Rate of metabolism and excretion affects half-life. Drug Reactions / Interactions • Adverse drug reactions: o Undesirable drug effects which may be common or infrequently occurring o May be mild, severe or life threatening. o May occur after first dose, after several doses, or after many Drug Reactions / Interactions (Cont) • Reporting adverse drug reactions: o Drugs used, studied for many yrs… and may take that long for adv rxns to become known. o Reporting mechanisms to help ID adv rxns Allergic drug reactions o Allergic reaction Hypersensitivity reaction Allergy to drug begins to occur after more than one dose given. Occ may occur the first time a drug is given e.g. penicillin so need to monitor pt carefully w/ first dose. Allergic drug reactions (Cont) immune system views drug as an antigen or foreign body which then stimulates the antigen-antibody response that prompts body to produce antibodies and release histamine from the cell against the drug. • Allergy SXS: itching, skin rashes, hives (urticaria), incr nasal secretions, diff breathing and wheezing due to broncoconstriction, cyanosis, sudden loss of consciousness, swelling of eyes, lips or tongue. Allergic drug reactions (Cont) o Anaphylactic shock- extreme serious allergic drug rxn occurs shortly after adm of drug w sensitivity TX raise BP, improve breathing, restore cardiac function, tx symptoms as arise. Allergic drug reactions (Cont) Angioedema – angioneurotic edema… collection of fluid in subq tissue. Eyelids, mouth, lips, throat. Dangerous when mouth affected. Swelling may block airway and result in asphyxia or difficult breathing or inability to breath Drug idiosyncrasy o Any unusual or abnormal rxn to a drug different from the one expected. o Cause due to genetic deficiency making pt unable to tolerate certain drugs and chemicals. Drug tolerance/ dependence o Body adapts to presence of certain drugs o Also sign of drug dependence o Some users experience discomfort when drug w/drawn- with physical or psychological symptoms Drug Reactions / Interactions • Cumulative drug effect: o Seen most commonly w/ liver or kidney disease as organs are major sites of detox and excretion. o Body is unable to metabolize and excrete a normal dose of drug before next dose occurs. Serious as can lead to toxic effects. Drug Reactions / Interactions (Cont) • Toxic reactions: o Levels build up to toxic when lgr doses given. o Some drugs such as digoxin have very, very narrow margin of safety before toxic Drug Reactions / Interactions (Cont) o Can be reversible or irreversible Liver damage reversible as liver cells can regenerate. Hearing loss due to damage to 8th cranial nerve permanent- due to streptomycin or gentimicin. Can reverse w/ administration of antidote, digitalis toxicity can give Digibind, Narcan for narcotic overdose. • monitor blood level for certain drugs: gentimicin, theophylline, digitalis Drug Reactions / Interactions (Cont) • Drug Interactions o Drug-drug interactions and food-drug interactions. o Occurs when one drug interacts w/ action of another. antacids interact w drugs like tetracycline Know interactions: oral anticoagulants anti-infectives, antiarrhythmics, alcohol Drug Reactions / Interactions (Cont) Additive drug reaction= when combined effect of the two drugs equal to sum of each drug given alone • Synergistic drug reaction= drugs interact w/ each other and produce effect greater than sum of separate actions. • Antagonistic drug reaction= one drug interferes w/ action of another and neutralizes or decreases effects Drug Reactions / Interactions (Cont) Drug-food interaction= food impairs or enhances drug given orally. Some req food Some antibiotics Factors influencing drug response o Age Infants and children req smaller doses Dose varies for age and wt. Elderly also need lower doses o Polypharmacy- taking numerous drugs that can potentially react. Factors influencing drug response (Cont) o Weight= based on wt of 150 # average wt o Gender= women in general require smaller dose of some drugs as smaller ratio of body fat and water o Genetic variations- some inherit protein or enzyme patterns that influence absorption o Emotional state o Patient expectations… placebo affect Factors influencing drug response (Cont) o Disease = presence of disease may influence action Liver disease= alters ability to metabolize or detoxify drugs. Kidney disease = impairs excretion. Route of administration Local and systemic effects • LOCAL: topical application affects the skin, eye, ear, mucous membranes – creams, ointments, suppositories SYSTEMIC: absorbed and distributed throughout system via blood stream Route of administration (Cont) oOral- slowest, and most convenient oParenteral= any route that does not involve GI tract or inhalation oIV- most rapid drug absorption oIM- into muscles • SubQ- into the subcutaneous tissues of the skin Nursing Implications • Many factors influence drug action: Need to know routes, factors, dosages, other drugs, if oral can be give w/ or w/o food. Observe reactions, responses, adv rxns drug tolerance. Report and record observations. Know when to w/hold drug and notify MD. Drug legislation / regulations o Federal legislation- describes conditions under which certain meds may be given and distributed. o State legislation- describes who may prescribe, dispense and administer certain drugs and under what conditions. Drug legislation / regulations (Cont) o Pure Food and Drug Act (FDA)= first act passed in 1906, o Harrison Narcotic Act= 1914 o Pure Food, Drug and Cosmetic Act= 1938 o Comprehensive Drug Abuse Prevention and Control Act= 1970 o Drug Enforcement Agency (DEA) Pregnancy Categories Drugs carry risk of causing birth defects o Teratogen= any substance that causes abnormal development of the fetus leading to a severely deformed fetus. o Five categories of potential for causing birth defects. Drug Development o FDA approval required for use, monitoring for adverse or toxic reactions o Investigational new drugs/ release of drugs for use.