Chapter 2: Basic Principles of Drug Action and Drug Interactions

Alterations in Absorption

-Most drug interactions that alter absorption take place in the GI tract -Many alterations in absorption can be managed by separating the times of administration

All drugs are processed in the body through pharmacokinetics. What is the correct order that drugs pass through the body?

Absorption, Distribution, Metabolism, Excretion

synergistic effect

combined effect of two or more drugs is greater than the effect of each drug alone 1+1=3

Onset of action

start of pharmacologic response

carcinogenic effect

the ability of certain medications and environmental chemicals to cause cancers

Absorption

the movement of a drug from its site of administration into the blood

paradoxical effect

the opposite of the intended drug response

Metabolism (biotransformation)

the process by which the body inactivates or biotransforms drugs -CYP450 enzymes

additive effect

two drugs with similar actions are taken for an increased effect 1+1=2

side effects

unavoidable secondary drug effect

idiosyncratic effect

uncommon drug response

receptors

usually the drug forms chemical bonds with specific sites

Pharmacodynamics

what drugs do to the body

Pharmacokinetics

what the body does to the drug

Antagonists

prevent receptor activation ex: antihistamine

Interference

1st drug inhibits the metabolism or excretion of a 2nd drug

Displacement

2nd drug displaces the 1st drug from binding site

When the nurse administers a 50-mg dose of a drug with a half-life of 6 hours, how many milligrams will remain in the body at 24 hours?

3.13 mg

pharmacokinetics

ADME Absorption Distribution Metabolism Excretion

Metabolism is affected by

Genetics Use of multiple drugs Concurrent illness Age( younger increases, older decreases)

allergic reaction

Sensitization of the immune system

Principles of Drug Action and Drug Interactions

Basic principles -An understanding of the human body's processes is important to grasp drug actions and drug interactions in the body

Excretion

Elimination of drug metabolites and some of the active drug from the body

A patient is being started on a new drug that has been used safely by many people for years. The patient has no known allergies, and the nurse administers the drug correctly. Suddenly the patient experiences cardiac arrest. What is this type of reaction called?

Idiosyncratic

alterations in metabolism

Inhibition or stimulation of the enzymes that metabolize a drug Medications that inhibit metabolism of another medication Medications that induce metabolism of another medication

Which route of administration has the fastest rate of distribution?

Intravenous (IV)

duration of action

Length of pharmacologic effect

Agonists

activate receptors ex: oxytocin

half-life

amount of time required for 50% of the drug to be eliminated from the body

A patient reports postoperative pain, and the nurse administers morphine (a narcotic analgesic) intravenously to ease the pain. Fifteen minutes later, the nurse notes that the patient is very drowsy, respirations are slow and shallow, and oxygen saturation is low. The nurse administers another drug that decreases the action of the morphine. What is this effect called?

antagonistic

drugs

chemicals that alter existing physiological capability

Tetratogenic effect

drug induced birth defect

latrogenic disease

drug induced disease

Distribution

drugs are transported by body fluids to the sites of action

partial agonists

drugs that interact with a receptor to stimulate a response but inhibit other responses ex: pentazocine

Routes of drug administration

enteral (via gi) parenteral (IV, subcutaneous, intramuscular IM, IV) percutaneous (inhalation, sublingual, topical)

desired effect

expected response

peak action

highest concentration

drug level

how much drug present

Bioavailability

is understood to be the extent and the rate to which substance or its active moiety is delivered from a pharmaceutical form and becomes available in the general circulation. (bloodstream)

Primary organ of excretion

kidneys

Primary organ of metabolism

liver

incompatibility

noted when 2 drugs are mixed in a solution

Adverse effects

noxious, unintended, and usually undesired effects that may occur with use of the drug

antagonistic effect

one drug interferes with the action of another 1+1=0