Chapter 4: Pharmacokinetics

Which of the following is the definition of pharmacokinetics?

For most medications, the greatest barrier is crossing the many membranes that separate the drug from its target.

Which of the following are challenges that drugs must face while moving toward target cells?

Select all the types of drugs that could EASILY pass through the plasma membrane.

Drugs always have to enter the cell to produce their effects.

All drugs must be absorbed to produce an effect

The rate of [blank_start]dissolution[blank_end] determines how quickly the drug disintegrates and is dispersed into simpler forms.

[blank_start]Absorption[blank_end] is a process involving the movement of a substance from its site of administration, across body membranes, and to circulating fluids. It determines the [blank_start]length of time[blank_end] it takes a drug to produce its effect. [blank_start]Distribution[blank_end] involves the transport of drugs throughout the body. The simplest factor determining this is the amount of [blank_start]blood flow[blank_end] to body tissues. [blank_start]Metabolism[blank_end], also called [blank_start]biotransformation[blank_end], is the process of chemically converting a drug to a form that is more easily removed from the body, The [blank_start]liver[blank_end] is the primary site for this process, although the kidneys and intestinal cells also help with it. [blank_start]Excretion[blank_end] is the process by which drugs are removed from the body. The rate at which this process occurs is a primary determinant of the [blank_start]concentration[blank_end] of the drugs in the bloodstream and tissues.

Which of the following does NOT affect absorption?

All of the following are things that affect absorption of medications. - Drug formulation and dose: [blank_start]Liquid[blank_end] formulations of an oral drug are absorbed faster, and [blank_start]higher[blank_end] doses will have a more rapid onset of action. -Route of administration: Drugs given [blank_start]intravenously[blank_end] will absorb faster. -Size of drug molecule: [blank_start]Larger[blank_end] drug molecules take longer to absorb. -Surface area of absorptive site: The [blank_start]larger[blank_end] the surface area, the faster the drug will be absorbed, -Digestive motility: Changes in GI motility can either speed up or slow down, depending on the drug and where it is absorbed. -Blood flow: Greater blood flow to [blank_start]site of administration[blank_end] results in faster absorption. -Solubility of drug: [blank_start]Lipid[blank_end] soluble drugs are absorbed more quickly. -Degree of ionization: [blank_start]Basic[blank_end] drugs are absorbed and distributed better in alkaline environments, while [blank_start]acids[blank_end] are better absorbed in acids. The pH of the local environment [blank_start]directly[blank_end] influences drug absorption through its ability to ionize the drug. -Drug-drug or drug-food interactions: [blank_start]High-fat[blank_end] meals can significantly slow stomach motility and delay absorption of oral meds. Some dietary supplements have a [blank_start]laxative[blank_end] effect, which can slow intestinal transit time and reduce drug absorption.

Which areas of the body are less likely to get a high concentration of a drug?

Which of the following tissues have an especially high affinity for certain medication?

Not all drug molecules in the plasma will reach their target because they bind reversibly to plasma proteins to form drug-protein complexes. These drug-protein complexes are too large to cross capillary membranes, so the drug is not available for distribution to body tissues. In essence, ONLY unbound drugs can reach their target cells or be excreted by the kidneys.

Which of the following describes drug-drug and drug-food interactions as it relates to distribution of the drug?

Each of the following are types of drug-drug interactions and what they mean: -Addition: The action of drugs taken together as a [blank_start]total[blank_end]. -Synergism: The action of drugs resulting in a [blank_start]potential[blank_end] (more than total) effect. -Antagonism: Drugs taken together with [blank_start]blocked[blank_end] or [blank_start]opposite[blank_end] effects. -Displacement: 1 drug may shift another drug at a nonspecific protein-binding site, thereby altering the [blank_start]desired[blank_end] effect.

Which of the following is the primary site of drug metabolism?

During metabolism, the addition of side chains, known as conjugates, makes drugs more lipid soluble and more easily excreted by the kidneys.

Most metabolism in the liver is accomplished by the hepatic microsomal enzyme system. A key enzyme in this system is what?

The primary actions of the hepatic microsomal enzymes are to inactivate drugs and accelerate their excretion.

A prodrug is a drug that does not need to be metabolized to work.

The first pass effect renders a large number of drugs given intravenously inactive before they can be distributed into the general circulation.

Select pathologic states that could increase the duration of drug action by interfering with natural excretion of substances.

Select the drug that is more likely to be excreted by the kidneys.

Select the drug that is LESS likely to be excreted by the kidneys.

The pH of the filtrate can affect secretion of certain drugs

Select the factors that affect respiratory secretion of drugs.

The lungs excrete less drugs in their original nonmetabolized form

Select the drug that is more likely to be secreted via a glandular route.

Drugs that are secreted in the bile are ultimately metabolized by the liver and excreted by the kidneys.

The therapeutic response of most drugs is directly related to their level in the plasma.

What is the minimum effective concentration of a drug?

What is the toxic concentration of the drug?

The [blank_start]onset of drug action[blank_end] represents the amount of time it takes to produce a therapeutic effect after drug administration. As the drug is absorbed and begins to circulate, the [blank_start]peak plasma level[blank_end] will occur when the medication has reached its highest concentration in the bloodstream. This does not, however, mean that the drug has reached its optimal therapeutic effect. [blank_start]Duration of drug action[blank_end] is the amount of time a drug maintains its therapeutic effect. It can be affected by many things, including drug concentration; dosage; route; and drug interactions with foods, supplements, herbs, and other drugs. The length of time required for the plasma concentration of a medication to decrease by 1/2 after administration is the drug's [blank_start]plasma half life[blank_end]. This is the most common description of a drug's duration of action.

The plasma half-life of a drug is an essential pharmacokinetic variable with important clinical application. It relates to [blank_start]excretion[blank_end]; the longer it takes a drug to be [blank_start]excreted[blank_end], the greater the half life. With that being stated, people with extensive [blank_start]renal[blank_end] or [blank_start]hepatic[blank_end] disease will have an increased drug plasma half life. They will need medications less frequently, or will require a reduced drug.