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Chapter 11

What can human variability in biopharmaceutics and disposition do Significantly alter blood concentration time profiles and drug efficacy
What are variables to be considered in the differences in disposition and response to medications Age, weight, height, genetics and gender
Age stages of humans Neonates + infants, Children, Adolescent, Adults, The elderly
Neonates and infants age birth-1yr
Children age 1yr-12yr
Adolescent age 13-19yrs
Adults age 20-70
Elderly age over 70
Why would you have variables in giving Neonates/Infants medicine Drug distribution, metabolism and excretion are quite different because the oragans haven't quite fully developed
Why would you have variables in giving Children medicine They metabolize certain drugs more rapidly than adults.
What age does the metabolism start to increase? between 1 yr and 12 yr
When do metabolism rates decline with age, to normal adult levels
Drugs eliminated faster in children Clindamycin, valproic acid, ethosuximide, and theophylline
Why would you have variables in giving adults medicine? They experience a gradual decrease in many physiological functions between 30 and 70 yrs
Which age range typically consumes more drugs than any other age group the elderly
Why do the elderly consume a greater amount of drugs Greater instance of chronic illness and multiple disease states
The elderly taking more drugs results in what a higher incidence of side effects/drug interactions in this age group
What are some of the physiological changes an elderly person has that significantly affects drug action Changes in gastric ph and emptying time, intestinal motility and gastrointestinal blood flow. Changes in Cardiovascular system. Decrease in liver production of enzymes, decline in kidney function
What will changes in intestinal motility and gastrointestinal blood flow do to an elderly body slow the rate of absorption
What do changes in the cardiovascular system, including lower cardiac output tend to do to an elderly body? Slows distribution of drug molecules to their sites of action, metabolism and excretion
What will a decline in kidney function do to an elderly body tends to slow urinary excretion of drugs
Why were woman excluded from clinical drug investigation? to avoid exposure to a fetus or potential fetus to unknown risks
What did the FDA and NIH issue guidelines in 1993-94 stating Woman will be included in clinical drug investigations unless some clear and compelling reason is known not to do so
Acetaminophen and clofibric acid are eliminated more rapidly in woman than men
What does some gender base difference in drug responses tend to be related to hormonal fluctuations in woman during menstrual cycle
An obvious reason men and woman may vary with some results of drug distribution Differences in body composition
What factors might A woman in late stages of pregnancy may have physiological changes that tend to change the rate of absorption: Delayed gastric emptying, delayed gastrointestinal tract motitlity
What happens to drug plasma protein binding in pregnant women? may be reduced and metabolism increased in a number of drugs
the rate of urinary excretion for a number of drugs is much greater in pregnant woman
During pregnancy, drugs can also readily transport from where from the maternal to the fetal circulation
Because the fetus has underdeveloped mechanisms to handle drug exposure,drug concentrations do what may be greater in the fetus than in the mother
Pharmacogenetics a field of study which defines the hereditary basis of individuals differences in absorption, distribution, metabolism and excretion
What does the human variability, genetics, determine the types and amounts of proteins produced in the body
Why do genetic differences result in differences in drug action drugs interact with proteins in plasma, tissues, receptor sites and elsewhere
Genetic differences can result in differences in drug action
What is the largest contributing factor to inherited variability metabolism
Dosage adjustments are not usually made for adults who are slightly overweight. Who are they made for? People really underweight/emaciated/anorexic or obese
What is the body fat considered to be obese body fat content greater than 30% of your total body weight
Why does the dose have to be changed for an obese patient? because of significant changes in the distribution and renal excretion of a number of drugs
one example of psychological factors influencing individual response to drug administration in clinical trials, where placebos are used, patients report therapeutic or adverse effects
The disposition of some drugs can be altered in one person but not in another due to the presence of what? diseases other than the one for which a drug is used
A pathological condition in any of these organs may have both, what a direct effect on the drug action or a secondary effect through the other organs
there are a variety of Liver diseases that affect what hepatic function
liver diseases that appear to decrease hepatic metabolism and diminish drug elimination Cirrhosis and obstructive jaundice
How does acute viral hepatitis change disposition changes are insignificant, and return to normal as soon as the condition clears
during absorption, when liver activity is decreased, what else is affected? first pass metabolism is also reduced
When liver activity is decreased, and first pass metabolism is also reduced, how does that effect bioavailibility results in increased bioavailability for drugs that are usually deverely degraded by first pass metabolism
What condition do patients with cirrhosis develop? a condition in which a significsnt amount of blood coming from the intestine, bypasses the liver cells and directly enters the circulatory system
When the condition of significant amounts of blood bypassing liver cells and entering the circulatory system directly, what happens to the bioavailability? the bioavailability of the drugs that would otherwise be degraded by first pass metabolism rises substantially
What can circulatory disorders at the extreme cause either a change in magnitude of blood flow to and through an organ, or a regional - redistribution of the cardiac output.
Changes in blood flow influence what drug absorption, distribution, and elimination and therefore have the potential to alter the effect of a drug
What can decreased blood flow from cardiovascular disorders can cause widespread effects on absorption, such as Edema in the large intestine, decreased splanchnic blood flow, delayed gastric emptying, decreased intestinal motility, changes in GI ph, and changes to bacterial flora of the intestine
Decreased blood flow in the liver can effect what metabolizing drugs that are hepatically eliminated
What would a diminished blood flow in the liver lead you to think diminished blood flow = decreased clearance
What physiological changes does the liver go through if the blood flow is decreased external and internal hepatic anastomoses are formed, which shunt the blood away from hepatic cells that contain metabolizing enzymes
What effect do changes in renal blood flow have on elimination less effect in elimination of drugs than blood flow changes in the liver
What changes for renal excretion? renal excretion can change significantly for those drugs that have a high renal clearance
What does reduced renal function, especially end stage renal disease affect the elimination of many drugs and affect the plasma protein binding of drugs
What should be done as renal function decreases the dosage of a drug that is eliminated by the kidney should be reduced to avoid accumulation of the drug in the body
how does reduced renal function affect plasma protein binding? the plasma protein binding of acidic drugs is reduced in severe renal insufficiency
Normally the kidneys do not allow elimination of albumin but in chronic renal disease, what happens excessive protein filtration may occur, which leads to loss of albumin in the body
What is albumin's role in protein binding Albumin is the major plasma and tissue protein that is responsible for acidic drug binding
What is Orosomucoid a plasma protein that is rapidly produced when the body is injured. Also a protein that many basic drugs bind to
How do orosomucoids come into play with chronic renal disease Orosomucoid blood concentrations are higher than normal and this results in increased basic drug binding
How can decreased renal function be measured? by monitoring the amount of creatine excreted in the urine
where is creatine created? produced in the muscles in the body
How is creatine excreted? at a constant rate primarily by glomerular filtration
What happens to creatine in diseased kidneys? the rate of creatine excretion decreases
Cirrhosis a chronic and potentially fatal liver disease causing loss of function and increased resistance to blood flow through the liver
Acute viral hepatitis an inflammatory condition of the liver caused by viruses; the effects are less than in cirrhosis but long term exposure can progress into chronic disease with the same characteristics
Obstructive jaundice An obstruction of the bile duct that causes hepatic waste products and bile to accumulate in the liver
Hypothyroidism a condition in which thyroid hormone secretions are below normal, often referred to as an underactive thyroid
hyperthyroidism a condition in which thyroid hormone secretions are above normal, often referred to as an overactive thyroid
what happens to the bioavailibility of drugs with hypothyroidism the bioavailability of a few drugs is increased
what happens to the bioavailability of drugs with hyperthyroidism the bioavailability is decreased because of the change in gastrointestinal motility
Changes that affected by thyroid conditions Renal blood flow is decreased in hypothyroidism and increased in hyperthyroidism, the activity of metabolizing enzymes in the liver is reduced in hypothyroidism and increased in hyperthyroidism
Because of human variabilility, adverse drug reaction can.... occur in one person but not another
adverse drug reaction any undesired symptom and can involve any organ. common or rare, localized or widespread, mild or severe depending on the drug and the patient
CNS Central nervous system
CNS side effects may result from stimulation (agitation,confusion, delirium, disorientation, hallucinations), or CNS depression (dizziness, drowsiness, sedation, coma, impaired respiration and circulation)
Hepatoxicities liver toxicities
types of hepatotoxicities hepatitis, hepatic necrosis, biliary tract inflammation or obstruction
what kind of drugs are used to fight hepatotoxicities hepatotoxic drugs like acetaminophen, halothane, isoniazid, chlorpromazine, methotrexate, nitrofurantoin, phenytoin and aspirin
any drud in any dose can cause an allergic reaction or hypersensitivity. why does this happen? patients develops antibodies while previously taking the drug or a drug with a similar chemical structure.the drug will interact with the antibodies, releasing histamine and other substances that produce reactions
most severe form of rash/hypersensitivity anaphylactic shock
how long does it take to see if you have an allergy or hypersensitivity between minutes and weeks
Symptoms of anaphylactic shock severe respiratory distress, and convulsions
How would you treat anaphylactic shock immediate emergency treatment with epinephrine, antihistamines or bronchodilator drugs are required
Signs of adverse reactions in the Gastrointestinal area anorexia, nausea, vomiting, constipation and diarrhea. more serious includes ulcerations and colitis/ IBS
Chronic usage of narcotic analgesics, sedative-hypnotic agents, antianxiety agents, and amphetamines can result in what kind of dependence physiological and phycological
What is involved with physiological drug dependence accompanied by unpleasant physical withdrawal symptoms when the dose is discontinued or reduced.
What is involved in psycological dependence involves an emotional or mental fixation on drug usage
teratogenicity the ability of a substance to cause abnormal fetal development when given to pregnant women
What drug groups are considered teratogenic analgesics, diuretics, antihistamines, antibiotics and antimetics
Carcinogenicity The ability of a substance to cause cancer
what kind of drugs are carcinogenic several kinds of drugs, including hormones and anticancer drugs
a drugs effort can be altered by what a drug-drug interaction
the probability of someone having a drug drug interaction increases with what the number of drugs a person takes, and in certain disease states
Many drug-drug interactions can affect disposition of one or both drugs and result in what increases or decreases in therapeutic or side effects
4 means in which one drug may be affected by the extent or rate of GI absorption of another drug Complexation, Gastric emptying, Gastric PH and intestinal metabolism
During absorption when complexation happens, what do drugs form by binding to other drugs nonabsorbable complexes
What do nonabsorbable complexes result in decreased absorption
What can affect the absorption of tetracyclines, methyldopa and levodopa by decreasing absorption iron salts
What decreases the absorption of norfloxacin and ciprofloxacin Antacids and sucralfate
How does propanthelene delay acetaminophen absorption by slowing the rate of gastric emptying
Why use metoclopramide to increase acetaminophen absorption it increases gastric emptying time
a problem with reducing gastric emptying time is drugs that are to degraded by gastric acid, have a longer time to degrade, resulting in a decreased amount of drug available for absorption from the intestine
Drugs that alter the GI ph can have some varied effects on other administered drugs like what the amount of unionized drug available for absorption, the rate of dissolution, intestinal motility and degradation
What drug-drug action is involved between birth control and oral antibiotic therapy alterations in metabolism- the antibiotic kills the normal GI tract flora, which disrupts the enterohepatic recycling of the oral contraceptives estrogens
during distribution how does one drug increase the amount of free drug available during protein binding? one drug displaces the other drug from a plasma protein binding it increases the pharmacological effect and its elimination because more of the drug is available for metabolism and excretion
when displacement issues happen during plasma protein binding, how long before the displacement interactions generally occur within a week or two of administration, could be self correcting after a few days
if displacement of one drug by another during plasma protein binding happen, and interactions occur but self correct, what happens to the concentration of the displaced drug it often returns to pre-interaction levels, even if the patient continues to take both drugs
What is the biggest consequence of displacement interactions changes in pharmacological effect
If drugs are higher protein bound what happens to the displacement displacement tends to have a greater effect than drugs that are not highly bound
how plasma bound is warfarin? 98% plasma bound 2% free or unbound
If drug interaction displaces only 2% of the 98% bound warfarin, what is the result 96% bound warfarin with 4% free or unbound
Complexation when two different molecules associate or attach to each other
displacement a drug that is bound to a plasma protein is removed when another drug of greater binding potential binds to the same protein
Enzyme induction the increase in hepatic enzyme activity that results in greater metabolism of drugs
Enzyme inhibition the decrease in hepatic enzyme activity that results in greater metabolism of drugs
What does enzyme induction do to the metabolism of drugs increases the metabolism of rugs that use the same enzyme system and usually results in a reduction in pharmacological effects
Examples of enzyme inducers phenobarbital, carbamazepine, phenytoin and rifampin
What two recreational activities can also induce metabolism cigarette smoking and alcohol consumption
What is the time course for enzyme induction slower than many other tpes of intractions
other than being dose related what else can affect enzyme induction age, genetics or liver disease
which alteration in metabolism which usually occurs when two drugs compete for binding sites on the same metabolizing enzyme enzyme inhibition
Enzyme inhibition generally has what effect on plasma concentration and pharmacological effect increases plasma inhibition and pharmacological effect of atleast one of the drugs
what is studied if a drug is known to be metabolized by the liver manufacturers often study its potential for enzyme inhibition early in the drug development process
examples of enzyme inhibitors allopurinol, cimetidine, erythromycin, disulfiram, isoniazid, ketoconazole and verapamil
Unlike enzyme induction that has a much slower time course, what is the time course with enzyme inhibition rapid onset, generally within 24hrs and tends to disappear quickly, once the inhibitor is discontinued
Why is enzyme inhibition easier to predict? it appears to be dose related
when drugs share a similar chemical structure, they often share the potential for what enzyme inhibition
Drug interactions that change filtration are rare, and filtration changes are usually more likely to occur in what specific drug- those that change systemic blood pressure
Changes in filtration rate will also change what change the rate of drug excretion
there are different secretion sytems in the kidneys based on what basic drugs and acidic drugs
Which form of drugs do not seem to compete for the acidic drug transport system basic drugs
what form of drugs do not seem to compete for the basic drug transport system acidic drugs
what does it take for basic and acidic drugs to fight over transport systems, and what does it cause 2 basics or 2 acidics will fight, which causes one or both of the drugs to accumulate in the blood
what is used as a passive transport system and is influenced by the ph of urine and the extent of ionization of a drug urinary reabsorption
in acidic urine what happens during urinary reabsorption acidic drugs tend not to be reabsorbed while basic drugs are not
As a result of acidic drugs not being reabsorbed, what happens to basic drugs? they are excreted in the urine
In alkaline urine, what happens to acidic drugs they will not be reabsorbed but will be excreted in the urine.
In alkaline urine what happens to basic drugs basic drugs will be reabsorbed
some drug interactions do not alter drug disposition, but interact where at the site of action
Sometimes the drugs compete for the same receptor, other times the interaction is more indirect and involves interfering with normal physiological processes. what are the interactions called additive, summative, synergistic or potentiation
Why are the definitions of the drug interactions basically used as synonyms its difficult to quantify the extent of altered drug activity
when do Additive Effects occur occur when two drugs with similar pharmacological actions result in an effect equal to the sum of the individual effect
Many drugs affect the electrical activity of the heart. Amiodarone + dofetilide two drugs that are used, why? they prolong repolarization of the heart as part of their therapeutic effect
When 2 drugs that prolong repolarization as part of their therapeutic effect are used together, what is the result repolarization may be delayed too long and arrythmias may occur
when does Synergism occur Occurs when two drugs with similar pharmacological actions produce greater effects than the sum of the individual effects
Example of synergistic drugs asprin + warfarin= Anticoagulation
What does asprin do to anticoagulaed patients? increases the risk of bleeding because it inhibits platlet function and causes gastric erosions
what is a large dose of asprin 3g/day or more
what does a large dose of asprin do can increase entire anticoagulation response
What dose a low dose of asprin do appear to primarily increase minor bleeding
Additive effects the summation in effect when two drugs of similar pharmacological actions are taken
potentiation occurs when one drug with no inherent activity of its own increases the activity of another drug that produces an effect
antidote a drug that antagonizes the toxic effect of another
if Amoxicillin+ Clavulanic Acid are used for increased duration of amoxicillins antibiotic effect, why is the clavulanic acid used? it inhibits the enzyme that degrades amoxicillin, and then allows amoxicillin to be more potent than if used alone
Naxalone+Morphine How does Naxalone act as an antidote to Morphine distress? displaces morphine from its receptor sites, preventing the morphine from causing further depressive effects
Ways to receive Vitamin K through a drug or by eating grees like spinach, brussel sprouts or broccoli, or liquid supplements
Why is protamine sulfate given as an antidote to heparin overdose Protamine combines with heparin to form a stable complex, which leads to the decrease in the anticoagulant activity of both drugs
How is Flumazenil an antidote for the sedative effects of Diazepam, Midazolam, and zolpidem Flumazenil is a benzodiazepine antagonist that reverses the side effect by competing for the same receptors as the benzodiazipines and displaces them
when does the time course of drug interaction occur varies substantially, sometimes almost immediately, or can be a week
What does knowing the time course of interaction allow quick identification and treatment of potential interactions, also allows clinicians to evaluate the relative importance of an interaction from 2 drugs compared to their therapeutic effects
How do differences in diet come into play with drug-diet interactions differences in the diet maybe attributed to various factors including food preferences and availability, diets designed for weight gain and loss, and variations for seasonal, religious, and therapeutic reasons
How does the physical presence of food effect absorption interacting chemically, improving the solubility of some drugs by increasing bile secretion, affecting the performance of the dosage form, altering gastric emptying/ intestinal motility and altering liver blood flow
When is the bioavailability of a drug generally decreased when the presence of food slows absorption
How does tetracycline interact with dairy products the calcium in the dairy and the tetracycline combine to form an insoluble drug-food complex
what is an insoluble drug-food complex and how is it eliminated it is an insoluble nonabsorbable compound that is excreted in the feces
what does dietary fiber do to the absorption of drugs decreases the absorption of drugs
How can high fat meals influence drug distribution high fat meals increase fatty acid levels in the blood. the fatty acids bind to the same plasma protein binding sites as many drugs and displaces the previously bound drug and increases the free concentration of that drug, leading the the increased effect
How can interactions that alter drug absorption be minimized by separating the administration of drugs and food intake by about 2 hours
Drug-diet interactions when elements of ingested nurtrients interact with a drug and this affects the disposition of the drug
What are high protein diets associated with accelerated metabolism
what are high carbohydrate diets associated with to decrease metabolism
what effect does the substitution of fat calories for carbohydrates have doesn't affect drug metabolism rates
What kind of metabolism do mild or moderately undernourished adults have normal or enhanced metabolisms
Severely malnourished adults have what kind of metabolism decreased
What effect does increasing protein in the diet have on distribution appears to increase glomerular filtration, decrease reabsorption and decrease secretion in the kidneys
Increased protein diet increased metabolism
increased carbohydrate diet decreased metabolism
increased fat diet no effect
decreased calories decreased metabolism
Created by: megancarter



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