Patho and Pharm Foundations

What is pharmacokinetics (PK)?

What the body does to a drug; summarized as ADME: absorption, distribution, metabolism, and excretion.

What does ADME stand for?

Absorption, Distribution, Metabolism, and Excretion.

What is absorption?

The entry of a drug into the bloodstream.

What happens with IV administration?

IV administration bypasses absorption because the drug enters the bloodstream directly.

Why does IV administration have the fastest onset?

The drug enters the bloodstream directly, producing an onset of seconds to minutes.

What is the onset of IV medications?

Seconds to minutes.

What is the IM route?

Intramuscular administration; the drug is absorbed from muscle tissue into the bloodstream.

What affects the onset of an IM medication?

Blood flow and the drug formulation; onset is generally minutes to hours.

What is the SubQ route?

Subcutaneous administration; the drug is absorbed from fatty tissue into the bloodstream.

How does SubQ absorption compare with IM absorption?

SubQ absorption is slower and more sustained than IM absorption.

What is the PO route?

Oral administration; the drug is absorbed through the gastrointestinal tract.

What factors affect oral drug absorption?

Food, gastrointestinal function, and first-pass metabolism.

How does PO absorption compare with IV absorption?

PO absorption is slower, while IV bypasses absorption and enters the bloodstream directly.

What is the sublingual/buccal route?

Absorption through oral mucous membranes directly into the bloodstream.

What is an advantage of sublingual/buccal administration?

It has rapid onset and avoids first-pass metabolism.

What is the topical route?

Absorption through the skin into local tissues or the bloodstream; absorption is slow and variable.

What is the transdermal route?

Absorption through the skin into the bloodstream, providing slow, continuous drug delivery over time.

What is the inhalation route?

Absorption through the lung alveoli into the bloodstream.

Why can inhaled drugs have a rapid onset?

The lungs have a large surface area and rich blood supply.

What is the rectal route?

Absorption through the rectal mucosa; absorption is variable and may partially bypass first-pass metabolism.

What is the intranasal route?

Absorption through the nasal mucosa; it provides rapid onset and avoids GI absorption and first-pass metabolism.

What is the intradermal (ID) route?

Absorption through the dermis; it is slow and localized and is commonly used for testing such as a TB skin test.

Why is IV administration particularly useful in an unstable or unresponsive patient?

IV administration delivers the drug directly into the bloodstream, allowing rapid drug delivery when a slower route may not act quickly enough.

What is the purpose of the baroreflex?

A negative feedback mechanism that helps maintain homeostasis of blood pressure by detecting changes and activating responses to restore balance.

What is an initiating event in a feedback loop?

The event that first knocks the system out of its normal steady state.

What is a stimulus?

The physical change produced by the initiating event that the body can detect.

What is a receptor in a feedback loop?

A structure that senses the stimulus and generates a signal.

What is the control center?

The part of the system that receives the receptor's signal, compares it with the setpoint, and decides whether to activate the effector.

What is an effector?

The structure that carries out the correction commanded by the control center.

What is a response?

The observable or measurable result produced when the effector acts.

What is a negative feedback loop?

A feedback mechanism that shuts off the response once the system returns toward balance.

What is homeostasis?

The restored or maintained steady state that the feedback system protects.

What is drug distribution?

The movement of a drug from the blood into body tissues.

What factors affect drug distribution?

Blood flow, lipid solubility, tissue storage, and protein binding.

Which form of a drug can reach target tissues and be excreted?

Only the free (unbound) form.

How can fat and bone storage affect drugs?

They can store drugs and prolong their effects.

What barriers can limit drug distribution?

The blood-brain barrier and placental barrier.

What is drug metabolism?

The conversion of drugs into forms that are easier to eliminate, primarily occurring in the liver.

What usually happens to drugs after metabolism?

They are usually converted into inactive metabolites, although some prodrugs become active after metabolism.

What is the first-pass effect?

Orally administered drugs may be metabolized by the liver before reaching systemic circulation.

What are CYP450 enzymes?

A major enzyme system involved in drug metabolism and drug interactions.

What factors can change CYP450 activity?

Age, genetics, liver function, medications, supplements, and foods.

What is a CYP450 inhibitor?

A substance that decreases CYP450 activity, slowing drug metabolism.

What happens to drug levels when metabolism is inhibited?

Drug levels increase, increasing the risk of excessive effects and toxicity.

What is a CYP450 inducer?

A substance that increases CYP450 activity, speeding drug metabolism.

What happens to drug levels when metabolism is induced?

Drug levels decrease, potentially reducing effectiveness.

What are examples of CYP450 inhibitors?

Sodium valproate, isoniazid, ciprofloxacin, ketoconazole, fluconazole, amiodarone, cimetidine, erythromycin, sulfonamides, and grapefruit juice.

What are examples of CYP450 inducers?

Carbamazepine, rifampin, chronic alcohol use, phenytoin, griseofulvin, phenobarbital, and St. John's wort.

What memory aid can help remember CYP450 inhibitors?

SICKFACES + grapefruit.

What memory aid can help remember CYP450 inducers?

CRAP GPS.

What is drug excretion?

The removal of drugs from the body, primarily through the kidneys.

What happens to drug levels when renal function is impaired?

Drug excretion decreases, causing drug levels to increase and increasing toxicity risk.

What is drug clearance?

The process/rate by which a drug is removed from the body and therefore how long it remains active.

What organs primarily filter and eliminate drugs?

The kidneys.

Which drugs are most readily filtered by the kidneys?

Free (unbound), water-soluble drugs.

What are other routes of drug excretion?

Lungs, bile/feces, saliva, sweat, and breast milk.

What is enterohepatic recirculation?

When a drug is excreted into bile, reabsorbed from the intestine, and returned to circulation, potentially prolonging its half-life and duration of action.

What is the therapeutic range?

The drug concentration that produces the desired effect without causing toxicity.

What is half-life?

The time required for the drug concentration in the body to decrease by 50%.

What is the minimum effective concentration?

The lowest drug concentration needed to produce a therapeutic effect.

What is a toxic concentration?

A drug concentration associated with harmful effects.

What is therapeutic drug monitoring?

Measuring plasma drug levels for medications with narrow safety margins to help prevent toxicity.

Why are peak and trough levels monitored?

To avoid toxic drug concentrations at the peak and ineffective concentrations at the trough.

What is a loading dose?

A larger initial dose used to rapidly achieve a therapeutic drug level.

What is a maintenance dose?

Repeated doses used to maintain a therapeutic drug level.

How long does it usually take most drugs to reach steady state?

Approximately 4–5 half-lives.

How can renal or hepatic impairment affect drug therapy?

It can increase drug half-life and increase the risk of toxicity.

What is pharmacodynamics (PD)?

The study of how drugs produce effects in the body.

Why can two patients respond differently to the same medication dose?

Genetics, age, disease states, and receptor differences can affect drug response.

What should nurses assess instead of assuming a standard dose will work identically for everyone?

The patient's actual response, effectiveness, and adverse effects.

What is interpatient variability?

Differences in drug response among individuals.

Why don't standard medication doses work exactly the same for every patient?

Standard doses are based on average patient responses, but individuals may require lower or higher doses.

What is ED50?

The median effective dose—the dose that produces the desired response in 50% of patients.

What should nurses monitor because of interpatient variability?

Patient response, medication effectiveness, and adverse effects.

What is the dose-response relationship?

The relationship between the amount of drug given and the intensity of its effect.

What generally happens as drug dose increases?

The response usually increases until a maximum effect is reached.

What happens when the dose continues increasing after the maximum effect is reached?

Adverse effects may increase without additional therapeutic benefit.

What are the three phases of a dose-response curve?

Low-dose phase with minimal response; therapeutic range where increasing dose increases effect; plateau where maximum response has been reached.

What is the goal when selecting a medication dose?

Use the lowest dose that achieves the desired therapeutic response.

What is therapeutic index (TI)?

The margin between a drug's effective dose and toxic dose.

What does a high therapeutic index mean?

The drug has a wider safety margin.

What does a low therapeutic index mean?

The drug has a narrow safety margin and requires careful dosing and monitoring.

What drugs are examples of medications with narrow therapeutic indexes?

Lithium, vancomycin, and warfarin.

Why are narrow-therapeutic-index drugs closely monitored?

Small changes in dose, metabolism, or excretion can significantly affect safety.

What is potency?

The amount of drug needed to produce an effect.

What is efficacy?

The maximum effect a drug can produce.

Does greater potency mean a drug is more effective?

No. Potency and efficacy are different; a more potent drug requires less drug to produce an effect, while a more efficacious drug produces a greater maximum effect.

Which is often more clinically important: potency or efficacy?

Efficacy, because it determines the maximum therapeutic effect the drug can produce.

What is a drug receptor?

A cellular target where a drug binds to produce an effect.

How can drug binding to a receptor affect the body?

It can activate or block normal physiologic processes.