Factors Affecting Drug Activity Chapter 11 Human Variability

Factors Affecting Drug Activity Chapter 11

Human Variability n Differences in age, weight, genetics and gender as well as pregnancy are among the significant factors that influence the differences in responses to medication among different people. n Drug distribution, metabolism, and excretion are quite different in the neonate and infant than in the adult because their organ

Human Variability n Children metabolize certain drugs more rapidly than adults. n The elderly typically consume more drugs than other age groups. n The elderly also experience more physiological change that significantly affects drug action. n Genetic differences can cause different types & amounts of proteins to be produced in the body, causing a difference in drug action.

Adverse Drug Reactions n Drugs generally produce a mixture of therapeutic (desired) and adverse (undesired) effects. n Adverse drug reaction can be any symptom in any disease process & involve any organ. n Almost any drug in any dose can produce an allergic or hypersensitive reaction in a patient. n Anaphylactic shock (example: bee sting) is a potentially fatal hypersensitive reaction.

Adverse Drug Reactions n Common GI tract adverse reactions include: n n n Nausea Vomiting Constipation Diarrhea Teratogenicity is the ability of a substance to cause abnormal fetal development when given to pregnant women.

Adverse Drug Reactions n Nephrotoxicity: the ability of a substance to cause harm to the kidneys. n Carcinogenicity: the ability of a substance to cause cancer.

Drug-Drug Interactions n The administration of more than one drug at a time to a patient can cause drug-drug interactions. n Drug-drug interactions can affect the disposition of one or more drugs and result in the increase or decrease of therapeutic effects or adverse effects.

Drug-Drug Interactions (Terms) n Additive effects: occur when two drugs with similar pharmacological actions result in an effect equal to the sum of the individual effects. n Synergism: two drugs with similar pharmacological actions produce greater effects than the sum of the individual effects. n Potentiation: when one drug with no inherent activity of its own increases the activity of another drug that produces an effect.

Drug-Drug Interactions (Terms) n Antidote : blocks or reduces toxic effects of a drug. n Displacement: a drug bound to a plasma protein is removed when another drug of greater binding potential binds to the same protein. n Inhibition: a drug blocks the activity of metabolic enzymes in the liver. n Induction: a drug that causes more metabolic enzymes to be produced, thus increasing

Time Course of Drug Interactions n The time it takes for drug-drug interactions to occur can vary substantially. n Some interactions occur immediately, others may take weeks. n Knowing the time-course of an interaction allows quick identification & treatment of potential interactions.

Drug-Diet Interactions n Dietary intakes and pattern vary widely among individuals and can contribute to variability in the disposition of drugs. n Some foods contain substances that react with certain drugs. n Example: foods containing tyramine can react with MAO ( monoamine oxidase) inhibitors.

Disease States n The disposition and effect of some drugs can be inhibited by the presence of diseases other than the one for which a drug is used. n Hepatic, cardiovascular, renal and endocrine disease all increase the variability in drug response. n Example: renal disease has been correlated with decreased renal excretion of many

Disease States n Acute Viral Hepatitis: an inflammatory condition of the liver caused by viruses. n The effects are less than cirrhosis, but long term exposure progresses into a chronic disease state. n The chronic disease has the same characteristics as cirrhosis; which eventually causes fatal liver damage.

Disease States n Hypothyroidism: a condition in which thyroid hormone secretions are below normal (under active thyroid). n Hyperthyroidism: a condition in which thyroid hormone secretions are above normal (over active thyroid).