Nursing - Pharmacology Across The Lifespan

Pharmacology Across the Lifespan    Individual Responses o Key factors can cause different reactions o Each patient responds to drugs different ways  Be prepared for different adverse effects of the drug o Factors:  Body weight and composition  Body surface area  Age  Infants and elderly patients especially sensitive to drugs  Infants: organ immaturity  Elderly: organ degeneration o Pathophysiology  Kidney disease: reduced excretion and increased toxicity  Liver disease: reduced metabolism and increased toxicity  Acid-base imbalance: pH changes that alter absorption, distribution, metabolism, and excretion of drugs  Altered electrolyte status: rare for electrolyte changes to have an impact on drug responses o Tolerance - 3 types  Pharmacodynamic tolerance  Associated with long-term administration of drugs such as morphine or heroin  Metabolic tolerance  Resulting from accelerated drug metabolism  Tachyphylaxis  Decreased response to drug brought on by repeated dosing over a short time o Decreased responsiveness to a drug as a result of repeated drug administration o Higher doses required Placebo Effect o Placebo effect: any response a patient has to a placebo is based solely on his or her psychologic reaction to the idea of taking a medication, and not to any direct physiologic or biochemical action of the placebo itself  Nurses need to prevent a positive but realistic assessment of the effects of therapy  Primary use is control group for clinical trials Absorption o Bioavailability  Ability of the drug to reach the systemic circulation from its site of administration Occurs primarily with oral, not parenteral Tablet disintegration time, enteric coatings, sustained-release formulations o Other causes of variable absorption Pharmacogenomics o Pharmacogenomics: study of how genes affect individual drug responses  Altered drug metabolism  May accelerate or retard the metabolism  Warfarin, succinylcholine, isoniazid, cytochrome P450 o Variations  Altered drug targets  Genetic variations alter the structure of drug receptors  Other ways genetics can influence drug responses:  Some genetically determined drug responses are based on factors other than changes in drug metabolism or drug targets  Gender  Alcohol is metabolized more slowly in women than men  Certain opioid analgesics are much more effective in women than in men  Race  Genetic variations  Psychosocial factors  Failure to take medications  Drug interactions  One drug alters the effects of another  Diet  Starvation reduces protein binding of drugs, which increases levels of free drugs Pediatrics o Consider communication, cooperation, and adherence o Adverse effects in children  Subject to dose-related effects, however some are related to immature state of organs and ongoing growth/development  Growth suppression (glucocorticoids)  Discoloration of developing teeth (tetracyclines)  Kernicterus (sulfonamides) o Pharmacodynamics  Genetic makeup  Immature organ systems  Involves drug actions on target cells  Body composition  Lose adipose tissue when they start moving o Pharmacokinetics      ADME - changes Assessments  Health status  Lifespan  Developmental stage affects appropriate drug administration methods, communication with child, and patient/family teaching  Infants  Toddlers  Preschooler  School-aged children  Adolescents  Lifestyle: diet, habits, ADLs  Environment n  Cultural and inherited traits o Pediatric Dosing  Dosing dependent on child's weight  [BSA of child x adult dose] / 1.73  1 mg = 1,000 mcg Maximizing Therapeutic Effects o Best route, administration site, technique o Interventions to reduce psychological stress and anxiety o Prevention of medication errors  Child's weight  Reliable information  Double check  Oral liquids given with syringes  Involve family  Communication drug plan clearly  Document appropriately Education o Generic and trade names o Rationale for drug therapy o Description of intended therapeutic effect o Dose and route o Schedule and duration of administration o Potential adverse effects o Special drug-related precautions or restrictions Drug Therapy During Pregnancy and Breast-Feeding o Shortage of reliable date on toxicity from drug use during pregnancy or breast-feeding o Two-thirds of pregnant women take at least one medication; most take more  Chronic disorders o    Infectious diseases or cancers Drugs of abuse: alcohol, cocaine, heroin o Physiologic changes during pregnancy and their impact on drug disposition and dosing  Third trimester: renal blood flow doubles and renal excretion accelerated  Dosing of standard medications should increase  Tone and mobility of bowel decrease  Prolonged transit: increase in absorption  Kidney, liver, and GI tract o Risk-benefit analysis o Placental drug transfer  All drugs can cross placenta  Some can cross more easily than others o Adverse reactions during pregnancy  Can affect both mom and fetus o Birth defects  Teratogenesis  Occurs in three stages  Conception (first 14 days)  Embryonic period (3-8 weeks)  Fetal period (9+ weeks)  Gross malformations  Cleft palate, club foot, hydrocephalus  Neurobehavioral and metabolic anomalies o Pregnancy Categories  Better labeling per the FDA  Clear for pregnancy or breast feeding Pharmacology in Older Adults o About one-third take 5 or more medications  50% take one or more medications that are not medically necessary o Older adults can experience:  Increased sensitivity to drugs  Wider variations in response to drugs  More adverse drug reactions  More drug-drug interactions o Causes:  Organ system degeneration  Multiple and severe illnesses  Multiple drug therapy  Poor adherence o Pharmacokinetics  Absorption    delayed gastric emptying decreased gastric acidity  Distribution  Increase body fat  Decrease lean body mass  Decrease TBW  Decrease serum albumin concentration  Metabolism  Hepatic drug metabolism:  Decreased hepatic blood flow  Decreased liver mass  Decreased activation of some hepatic enzymes  Result is increase half-life  Excretion  Progressive decrease in renal drug function SLOW AND LOW - obtain desired therapeutic effect Predisposing factors:  Polypharmacy  5 or more drugs  Drug accumulation due to decreased renal function  Increase in illness severity  Multiple pathologies  Increase in use of drugs with narrow therapeutic index  Increase individual variation due to altered pharmacokinetics Measures to decreased ADRS  Avoid drugs on Beers criteria list  Employ simplest regimen possible  Perform periodic reviews  Monitor clinical responses  Initiate drug therapy in low doses  Thorough drug history (OTC, herbals 75% of nonadherence is unintentional   o o o o