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Transcript
More Foundations (not in your book!) and Drug Therapy Across the Lifespan Lecture 2 Transcultural Considerations Racial, hereditary, and genetic factors affect the way clients metabolize drugs and experience and tolerate medications and their side effects Age, gender, dietary practices, living conditions, socio-economic status and high risk behaviors also affect drug metabolism, efficacy, and client compliance Client’s religious practices may prescribe what is acceptable in terms of diet (i.e. Jews & kashrut, Muslims & Ramadan) Ethnocultural perceptions and beliefs of illness and disease also affect the client’s compliance with medical treatment and drug therapy Drug Interaction An altered or modified action or effect of a drug as a result of interaction with one or more other drugs Do not confuse with: – Adverse drug reaction - an undesirable drug effect from mild to severe – Drug incompatibility - chemical or physical reaction that occurs among two or more drugs outside the body Pharmacokinetic Interaction Absorption When a person takes two drugs at the same time, the rate of absorption of one or both drugs can change - one drug can decrease, increase or block the absorption rate of another drug. It does this in 3 ways, by: – Decreasing or increasing GI emptying time – Changing the gastric pH – Forming drug complexes (such as antacids & tetracyline (which makes the tetracycline ineffective) (These are discussed on next slides) Pharmacokinetic Interaction Absorption-Cont. Drugs that increase the speed of gastric emptying - increase GI motility what happens? (decrease in drug absorption in turn lessens the pharmacological reaction) Drugs that decrease gastric emptying & decrease GI motility an increase in absorption rate inc. in amount of drug absorption (for those drugs absorbed in the stomach) What is result? Remember the longer the drug stays in the GI system the greater the absorption. Pharmacokinetic Interaction Distribution Drug distribution to tissues can be affected by its binding to plasma/serum protein Remember only drugs unbound are free and can enter body tissues Two highly bound protein drugs compete for protein in plasma a decrease in binding of one or both drugs more free drug in circulation leads to drug toxicity Pharmacokinetic Interaction Excretion Most drugs are excreted in the urine, some through the bile which passes into GI tract Drugs can increase or decrease renal excretion of other drugs -Drugs that decrease Cardiac output decrease renal blood flow and delay excretion (Result?) -Diuretics decrease reabsorption of water in the kidneys, and can lead to hypokalemia and Digoxin toxicity Pharmacodynamic Interactions Reactions that result in additive, synergistic (potentiation), or antagonistic drug effects Additive Drug Effect - when two drugs with similar action from the same “category” (NOT THE SAME CLASS) are administered together * Result is the sum of the effects of the two drugs * Desirable: diuretic and Beta Blocker to decrease B/P or Undesirable: alcohol & aspirin > GI bleeding Pharmacodynamic Interactions Two more examples: Desirable = Two analgesics (pain medications) Tylenol and codeine - together increase pain relief Undesirable = Apresoline for HTN & nitroglycerine for angina > hypotension. Pharmacodynamic Interactions Synergistic Drug Effect - When one drug potentiates or enhances the effect of the other drug * Greater than the effect of each alone * Can be desirable or undesirable Desirable: Demerol (a narcotic) + Phenergan (an antihistamine) = Phenergan potentiates the effect of Demerol – Desirable less Demerol is needed Undesirable: Alcohol + a sedative-hypnotic (valium) an increase in CNS depression Some antibacterials have an enzyme inhibitor added to potentiate the effect of the drug (Desirable!) Pharmacodynamic Interactions Antagonistic Drug Effect - Two drugs in opposing drug categories given to the same patient; they have opposite effects and cancel each other out – Usually undesirable Desirable example: naloxone (Narcan) is an antagonist given after a morphine overdose to reverse the narcotic Drug – Food Interactions Food can increase, decrease, or delay drug absorption Decrease - with food binding ex. tetracycline and dairy products = less plasma concentration of tetracycline * Take 1h before or 2 h after meals & no dairy The classic interaction is when an antidepressant of the MAO (monoamine oxidase) inhibitor class is taken with tyramine rich foods - Cheese, wine, beer, yogurt, bananas. - May result in hypertensive crisis - Clients must be educated to avoid these foods when taking MAO inhibitors OTC Drugs Cold and Cough Remedies - Most stimulate the sympathetic nervous system. Clients with heart disease, HTN, thyroid disease should not take these without approval Sleep Aids - Most contain antihistamine to cause drowsiness. Should not be taken with a CNS depressant due to additive effects. *Can cause CNS stimulation in small children and elderly OTC Drugs Weight-Control Drugs - Many on the market. Contraindicated for clients with heart disease, Hypertension, diabetes mellitus, thyroid disease Drug Abuse is the excessive self-administration of a drug that could result in addiction (physical dependence) and could be detrimental to one’s health. Pediatrics: What You Need to Know! Infants: Newborn – 1 year old – Drugs generally remain active longer • Drug levels decline more slowly • Drug effects are prolonged • Drug effects may even be more intense – Increased drug sensitivity due to immaturity of body systems Pediatrics Children 1-12 years – Most pharmacokinetic parameters similar to those of adults • Except they metabolize drugs faster than adults (especially age 1-2) • May need increased dose / more frequent dosing interval for drugs eliminated by liver – Adverse Reactions • Some drugs cause unique adverse reactions in children –should avoid if possible Pediatrics Dose Determination for Children – Established dosing • Somewhat according to age (for metabolism) • According to weight (mg / kg) – No established dosing • Extrapolated from adult dosing Geriatrics: What You Need to Know! Drug Therapy Geriatrics Geriatric population – Use more medications than any other age group • Elderly (65 or older) represent 13% of US population • They use 30% of all prescribed drugs • They also use 40% of the OTC drugs • Need for more medications related to – More diseases, and increased severity of disease – Excessive prescribing Geriatrics Problems with drug therapy – Elderly are more sensitive to drugs • Pharmacokinetic changes – especially decreased metabolism – Decline of hepatic metabolism – Half life of drugs may increase – Decline in “first pass effect” – Degree of decline varies among individuals – What is net result?: • Elderly experience more adverse drug reactions – Elderly experience more drug-drug interactions • Often related to compliance issues • Related to polypharmacy Geriatrics Adverse Drug Reactions (ADR) – Seven times more common in the elderly than in younger adults • Accounts for 16% of hospital admissions • Accounts for 50% of medication-related deaths • Most ADR are dose related Geriatrics Compliance – 40% of elderly do not take medications as prescribed • May never fill or refill prescriptions • Drugs may be cost prohibitive – Would rather put food on the table • May not have received good teaching about drugs – May take them erratically – May not understand complex regimens • May be forgetful / confused Geriatrics Compliance – Steps to improve medication adherence • Make the regimen simple • Explain treatment plan clearly and write it down • Ask about cost concerns; arrange for help • Inquire about whether patient can get to a pharmacy – are there friends / family to help • Use of labels, calendars, diary, pill box