Pharm. chapter 2

Enteral route

drug is administered directly into the gastrointestinal (GI) tract by the oral, rectal, or nasogastric route

Distribution

the ways in which a drug is transported throughout the body by the circulating body fluids to the sites of action or to the receptors that the drug affects

Percutaneous route

involves drugs being absorbed through the skin and mucous membranes ex: inhalation, sublingual (under the tongue), and topical (on the skin) administration.

After they have been administered, all drugs go through five stages;

liberation, absorption, distribution, metabolism, and excretion (LADME)

Allergic reaction

occur among patients who have previously been exposed to a drug and whose immune systems have developed antibodies to the drug.

idiosyncratic reaction

occurs when something unusual or abnormal happens when a drug is first administered

Metabolism

process whereby the body inactivates drugs

Two factors that influence drug distribution

protein binding and lipid (fat) solubility.

A time-response curve demonstrates the;

relationship between the administration of a drug and the associated response

anaphylactic reaction

severe, life-threatening reaction that causes respiratory distress and cardiovascular collapse

Drug interaction

the action of one drug is altered or changed by the action of another drug

Onset of action

the concentration of a drug at the site of action is sufficient to start a physiologic (pharmacologic) response.

The rate at which absorption occurs depends on

the route of administration, the blood flow through the tissue where the drug is administered, and the solubility of the drug

Two primary routes of excretion;

through the GI tract into the feces and through the renal tubules into the urine. Other routes of excretion include evaporation through the skin, exhalation from the lungs, and secretion into saliva and breast milk.

Peak action

time at which the drug reaches the highest concentrations on the target receptor sites, thereby inducing the maximal pharmacologic response for the dose given.

All drugs are processed in the body through pharmacokinetics. What is the correct order that drugs pass through the body? a)Liberation, absorption, distribution, metabolism, excretion b)Distribution, metabolism, liberation, absorption, excretion c)Biotransformation, liberation, distribution, absorption, excretion d)Excretion, distribution, liberation, absorption, metabolism

•Answer: a •Rationale: All drugs go through five stages after administration, which can be remembered with the acronym LADME.

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? a)Displacement b)Antagonistic c)Interference d)Synergistic

•Answer: b •Rationale: The morphine had a greater-than-desired effect on the patient. Because the drug was given intravenously, it is impossible to remove the drug from the patient's bloodstream. Therefore, the nurse does the next best thing and administers another drug that interferes with the action of the first, otherwise known as an antagonistic effect. The result is a decrease in the action of the original drug. The second drug is sometimes referred to as the antidoteto the first.

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? a)Allergic b)Mutagenic c)Idiosyncratic d)Therapeutic

•Answer: c •Rationale: Because the drug was a known safe drug and the patient had no known reason not to receive it, the response to the drug in this case was totally unexpected, or idiosyncratic. An allergic response is typically preceded by such reactions as rash, hives, tingling, or swelling.

Which route of administration has the fastest rate of distribution? a)Subcutaneous b)Intramuscular c)Transcutaneous d)Intravenous

•Answer: d •Rationale: The IV route places the drug directly into the bloodstream and isn't slowed down by the need to first travel from the GI tract into the bloodstream.

Primary organ of metabolism

Liver, other sites are GI tract and lungs

antagonistic effect

One drug interferes with the action of another.

FYI

Organs with the most extensive blood supplies (e.g., heart, liver, kidneys, brain) receive the distributed drug most rapidly. Areas with less extensive blood supplies (e.g., muscle, skin, fat) receive the drug more slowly

Drug receptors

Specific sites where drugs form chemical bonds

synergistic effect

The combined effect of two drugs is greater than the sum of the effect of each drug given together.

Displacement

The displacement of the first drug from protein-binding sites (i.e., bound drugs are inactive) by a second drug increases the activity of the first drug because more unbound drug is available.

Excretion

The elimination of drug metabolites and, in some cases, of the active drug itself from the body

Interference

The first drug inhibits the metabolism or excretion of the second drug, thereby causing increased activity of the second drug.

incompatibility

The first drug is chemically incompatible with the second drug, thereby causing deterioration when the drugs are mixed in the same syringe or solution or are administered together at the same site. Signs include haziness, formation of a precipitate, or a change in the color of the solution when the drugs are mixed.

Pharmacokinetics

The study of the mathematical relationships among the ADME features of individual medicines over time

additive effect

Two drugs with similar actions are taken for an increased effect.

Parenteral route

bypasses the GI tract with the use of subcutaneous (subcut), intramuscular (IM), or intravenous (IV) injection.

The onset, peak, and duration of action of a drug are often illustrated by a time-response curve;

drug concentration-time profile

The most common routes of drug administration

enteral, parenteral, and percutaneous routes

Duration action

how long the drug has a pharmacologic effect

Antagonist

Drugs that attach to a receptor but do not stimulate a response

Agonists

Drugs that interact with a receptor to stimulate a response

Partial agonists

Drugs that interact with a receptor to stimulate a response but inhibit other responses

Pharmacodynamics

The study of the interactions between drugs and their receptors and the series of events that result in a pharmacologic response.

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? a)25 mg b)12.5 mg c)6.25 mg d)3.13 mg e)1.56 mg

•Answer: d •Rationale: The half-life of a drug is the time required for 50% of the drug to be eliminated from the body. In this example at 24 hours, 6.25% or 3.13 mg of the drug would remain in the body.

1. A nurse was reviewing the drug route for an order written to be given via nasogastric tube and understood that this meant the drug would be administered by which route? 1. Enteral 2. Parenteral 3. Percutaneous 4. Intramuscular

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5. After the nurse injects the patient with the morning insulin dose, when will the action of the drug reach its highest physiologic effect? 1. During peak action 2. During displacement 3. During the half-life 4. During onset of action

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10. Drugs known to bind to an enzyme that cause the metabolism of the drug to be increased are called what? 1. Enzyme inhibitors 2. Enzyme inducers 3. Enzyme enhancers 4. Enzyme metabolizers

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3. What is the portion of a drug that is pharmacologically active called? 1. Protein-bound drug 2. Unbound drug 3. Drug tolerance level 4. Incompatibility factor

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4. When an antihypertensive drug causes a drop in blood pressure to the normal range, what is this effect called? 1. Antagonistic effect 2. Desired effect 3. Side effect 4. Additive effect

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2. A patient takes 50 mg of a drug that has a half-life of 12 hours. What percentage of the dose remains in the body 36 hours after the drug is administered? 1. 50 mg (100%) 2. 25 mg (50%) 3. 12.5 mg (25%) 4. 6.25 mg (12.5%)

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6. When a patient has taken a drug and a rash appears along with severe itching, what is this reaction called? 1. Idiosyncratic reaction 2. Antagonistic effect 3. Allergic reaction 4. Displacement effect

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7. When a patient who was prescribed warfarin and valproic acid begins experiencing an increased effect of warfarin, what is this known as? 1. Synergistic effect 2. Antagonistic effect 3. Idiosyncratic effect 4. Displacement effect

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8. A person who has an increased metabolic rate (e.g., hyperthyroidism) generally requires what type of dosage? 1. Normal dosage 2. Lower-than-normal dosage 3. Higher-than-normal dosage 4. A dosage that is based on his or her thyroid function levels

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Half-life

A measure of the time required for elimination. amount of time required for 50% of the drug to be eliminated from the body

FYI

Because the kidneys are major organs of drug excretion, the nurse should review the patient's chart for the results of urinalysis and renal function tests. A patient with renal failure often has an increase in the action and duration of a drug if the dosage and frequency of administration are not adjusted to allow for the patient's reduced renal function.

Urticaria (hives)

acute allergic reaction in which red, round wheals develop on the skin