factors affecting drug activity chapter 11 pages 252-264
TRANSCRIPT
Factors Affecting Drug Activity
Chapter 11
Pages 252-264
Bell work 4/27
Can you think of three things that might influence an individuals response to medication?
Human Variability
Differences in age, weight, genetics, and gender are factors that influence the differences in response to medication among people.
Age
Infants and Neonates Drug distribution is different in a neonate and
infant because their organ systems are not fully developed. They do not eliminate drugs as efficiently as adults.
Age
Children Children metabolize certain drugs more rapidly
than adults. Metabolism rates increases between 1 year and
12 years (depends on age and drug). After age 12 metabolism rates decline with age to
a normal adult level.
Age
Adult Adults experience a decrease in many
physiological function after age 30. Decreases in affects on drug activity are gradual.
Age
The elderly Elderly typically consume more drugs than any
other age group due to chronic illness and disease.
Gender
Women used to be excluded from drug studies. In 1993 the FDA stated that women will be included in clinical drug trials.
Since then many studies have been completed and show that men and women do show differences in absorption, distribution, metabolism, and excretion (ADME).
Gender based differences in drug response appear to be related to hormonal fluctuations.
Gender differences may also be due to differences in body composition.
Genetics
The field of study, pharmacogenetics, defines the hereditary basis of individual differences in absorption, distribution, metabolism, and excretion (ADME) processes.
The largest contributing factor to variability is metabolism.
Body Weight
Dosage adjustments based on weight are generally not made for adults who are slightly overweight.
Weight is a factor in determining drug dosage for infants, children, or obese patients.
Psychological Factors
Psychological factors can influence individual responses to drugs.
When placebo drugs are given patients receiving them can report therapeutic and adverse effects.
Another factor can be patient’s willingness to follow prescribed dosage regimens.
Bell work 4/30
Name two groups of people that need to have adjustments in drug dosages?
What group of people metabolism drugs the fastest?
Adverse Drug Reactions
Drugs generally produce a mixture of either therapeutic (desired) or adverse (undesired) effects.
An adverse effect is an unintended side effect of a medication that is negative or in some way injures a patient’s health.
Reactions may be rare or common, localized or wide-spread, mild or severe depending on the drug and the patient.
Common Adverse Reactions
Hypersensitivity or Allergy Almost any drug, in any dose, can produce an
allergic or hypersensitive reaction in a patient. The drug will interact with antibodies, releasing
histamine and other substances that produce reactions that can range from mild rashes to potentially fatal anaphylactic shock.
Allergic reactions can occur within minutes or weeks after drug administration
Adverse Drug Reactions Central nervous system (CNS):
Stimulation – agitation, confusion, disoriented Depression – dizziness, drowsiness, sedation
Hepatotoxicity: Hepititis Necrosis
Hepatotoxic drugs include: acetaminophen, aspirin.
Gastrointestinal effects: Anorexia, nausea, diarrhea Ulcers, colitis
Adverse Drug Reactions Nephrotoxicity:
Kidney failure - Gentamicin and ibuprofen Idiosyncrasy:
Unexpected reaction the first time a drug is given Hematological effects:
Coagulation, bleeding, bone marrow disorders Drug dependence:
Chronic use of analgesics, sedatives, hypnotics,etc Teratogenicity:
Ability of a substance to cause abnormal fetal development
Carcinogenicity: Ability of a substance to cause cancer
Bell Work 5/1, 5/2
What is a potentially fatal hypersensitivity reaction that produces respiratory distress and cardiovascular collapse?
What is an unexpected reaction the first time a drug is given?
Drug – Drug Interactions Taking more than one drug at a time can
cause a drug-drug interaction. Drug – drug interactions can affect the
disposition (all processes of the ADME) of any drug.
Therapeutic effects and side effects can be decreased or increased when more than one drug is taken.
Drug – Drug Interactions See examples of drug-drug interactions on page 256-257
Common drug-drug interactions Additive effects – when two drugs effects equal
to the sum of the individual effects Synergism – two drugs produce greater effect
than the sum of the individual effects Potentiation – one drug increases the activity of
another drug Antidote – a drug given to block or reduce toxic
effects
Drug – Drug Interactions Complex – decreased intestinal absorption of oral
drugs occurs when drugs complex to produce nonabsorbable compounds
Displacement – a drug bound to a plasma protein is removed when another drug of greater binding potential binds to the same protein.
Inhibition – one drug with the elimination of a second drug may intensify the effects of the second drug
Induction – a drug causes more metabolic enzymes to be produced, increasing metabolic activity
Urinary excretion – some drugs are altered by raising urinary pH and decrease renal absorption
Drug – Diet Interactions Dietary intake may affect disposition of drugs.
Absorption - increased or decreased when food is in the stomach. Generally absorption is decreased.
Distribution – a previously bound drug is displaced and this increases the concentration of the drug in the blood and this leads to an increased effect
Metabolism – high protein diets are associated with increased drug metabolism and high carbohydrate diets are associated with decreased metabolism. Malnourished adults have a decreased metabolism
Excretion – high protein diet increases kidney function.
Disease States The disposition (ADME process) and effect of some
drugs can be influenced by diseases other than the one that the drug is intended for.
Hepatic Cirrhosis and obstructive jaundice decrease hepatic
metabolism and will diminish drug elimination Viral hepatitis little change in disposition
Circulatory Changes in blood flow can influence ADME and therefore
will have the potential to alter the effect of the drug
Disease States
Renal Reduced renal function can effect the elimination of many
drugs and affect the plasma protein binding of drugs Thyroid
Changes in thyroid function can effect many aspects of absorption excretion and metabolism