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The 3 phases of drug action, or the phases a drug undergoes when taken by mouth. (Enumerate)
- Pharmaceutic Phase
- Pharmacokinetic Phase
- Pharmacodynamic Phase
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Phase of drug action where drugs are in its solid or liquid form when taken by mouth.
Pharmaceutic Phase
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Phase of drug action that involves the drug's absorption, distribution, metabolism/biotransformation, and excretion when drug is taken by mouth.
Pharmacokinetic Phase
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Phase of drug action that involves the drug's onset, peak, duration, as well as the drug's interaction with receptors, enzymes, and hormones, when taken by mouth.
Pharmacodynamic Phase
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The first phase of drug action.
Pharmaceutic Phase
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A process in which a drug in its solid form (tablet or capsule) disintegrates into small particles to dissolve into a liquid.
Dissolution
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__________ and _________ that are used in drug preparation, allow the drug to take on a particular size and shape and enhance drug dissolution.
Excipient Fillers and Inert Substances
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It is the breakdown of a tablet into smaller particles.
Disintegration
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It is the dissolving of the smaller particles in the GI fluid before absorption.
Dissolution
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The two pharmaceutic phases. (Enumerate)
Disintegration and Dissolution
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Drugs in this form are more rapidly available for GI absorption than solids.
Liquid form
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Drug absorption is generally ______ for those drugs absorbed primarily in the stomach.
Slower / Faster
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____________ resist disintegration in the gastric acid of the stomach, so disintegration does not occur until the drug reaches the alkaline environment of the small intestine.
Enteric-coated drugs.
Because of this, enteric-coated tablets can remain in the stomach for a long time; therefore, their effect may be delayed in onset.
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Enteric-coated tablets or capsules and sustained-release (beaded) capsules should be crushed.
True / False
False ✓
Enteric-coated drugs should not be crushed. Crushing would alter the place and time of absorption of the drug. -
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____ in the GI tract may interfere with the dissolution of certain drugs.
Food
Food may interact with drugs in the GI tract (Food-Drug interaction, Gastric Emptying time, Gastric pH, etc.)
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The four processes of pharmacokinetics. (Enumerate)
- Absorption
- Distribution
- Metabolism (or Biotransformation)
- Excretion (or Elimination)
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Nursing responsibilities (pharmacokinetics).
1. The nurse applies knowledge of pharmacokinetics when assessing the patient for possible adverse drug effects.
2. The nurse communicates assessment findings to members of the healthcare team in a timely manner, to promote safe and effective drug therapy for the patient.
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It refers to the movement of drug particles from the GI tract to body fluids by passive absorption, active absorption, or pinocytosis.
Absorption
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Most oral drugs are absorbed into the surface area of the ________.
Small Intestine
Most oral drugs are absorbed into the surface area of the small intestine through the action of the extensive mucosal villi.
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The 3 mechanism of absorption. (Enumerate)
- Passive Absorption
- Active Absorption
- Pinocytosis
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A mechanism of absorption that occurs mostly by diffusion.
Passive Absorption
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Movement of molecules from higher concentration to lower concentration.
Diffusion
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A mechanism of absorption that requires a carrier such as an enzyme or protein to move the drug against a concentration gradient. Energy is required for this mechanism.
Active Absorption
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A mechanism of absorption where cells carry a drug across their membrane by engulfing the drug particles.
Pinocytosis
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Factors Affecting Drug Absorption.
(Enumerate)
- pH partitioning absorption
- Blood Flow
- Surface Area
- Lipid Solubility
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Weak acid drugs (such as aspirin) are less ionized in the stomach, and pass through the stomach lining easily and rapidly.
True / False
True ✓
Remember: Drugs that are lipid soluble and non-ionized are absorbed faster than water-soluble and ionized drugs.
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Poor circulation to the stomach does not hamper absorption.
True / False
- False ✓
- Poor circulation to the stomach hampers absorption. Pain, stress, and foods that are solid, hot, or high in fat can also influence to slow gastric emptying time, so the drug remains in the stomach longer.
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Drugs given IM are absorbed faster in muscles that have more blood vessels (e.g., deltoids) than in those that have fewer blood vessels.
True / False
True ✓
Additional Information: Subcutaenous tissue has fewer blood vessels, so absorption is slower in such tissue.
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The GI membrane is composed mostly of lipid (fat) and protein, so drugs that are lipid soluble pass rapidly through the GI membrane.
True / False
True ✓
Additional Information: The reason why water-soluble drugs are not able to pass rapidly through the GI membrane is due to the need of a carrier, either an enzyme or protein, to pass the membrane.
! Large particles pass through the cell membrane if they are non-ionized.
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A charged molecule, either positive or negative.
Ionized
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A molecule that has no charge.
Nonionized
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It is the process in which the drug passes to the liver first.
First-pass Effect or Hepatic First Pass
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Some drugs in the liver may be metabolized to a/an _______ that may then be excreted, thus reducing the amount of active drug.
Inactive Form
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Some drugs do not go directly into the systemic circulation following oral absorption but pass from the _______ to the liver via the portal vein.
Intestinal Lumen
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Some drugs do not undergo metabolism at all in the liver, and others may be metabolized to ______, which may be equally or more active than the original drug.
Drug Metabolite
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It is a subcategory of absorption; it is the percentage of administered drug dose that reaches the systemic circulation.
Bioavailability
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The percentage of bioavailability for the oral route is 100%, and for the IV route it is always less than 100%.
True / False
False ✓
The percentage of bioavailability for oral route is always less than 100%, but for the IV route it is 100%.
! Oral drugs that have a high first-pass hepatic metabolism may have a bioavailability of only 20% to 40% on entering systemic circulation.
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To obtain the desired drug effect, the oral dose could be ____ than the drug dose for IV use.
Higher / Lower
Higher ✓
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Factors that alter bioavailability. (Enumerate)
- The drug form (e.g., tablet, capsule, sustained-release, liquid, transdermal patch, rectal suppository, inhalation)
- Route of Administration
(e.g., oral, rectal, topical, parenteral)- GI Mucosa and Motility
- Food and other drugs, and
- Changes in Liver Metabolism
(caused by liver dysfunction or inadequate hepatic blood flow)
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_______ increases the bioavailability of the drug and can cause an increase in drug concentration. Drug toxicity may result.
Rapid Absorption
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_______ can limit the bioavailability of the drug, thus causing a decrease in drug serum concentration.
Slow Absorption
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It is the process by which the drug becomes available to fluids and body tissues.
Distribution
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Factors Influencing Drug Distribution. (Enumerate)
- Blood Flow
- The drug's affinity to the tissue
- The protein-binding effect
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________ is dependent on drug dose and its concentration in the body.
Volume of drug distribution (Vd)
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Drugs with a larger volume of drug distribution have a longer half-life and stay in the body longer.
True / False
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As drugs are distributed in the plasma, many are bound to varying degrees (percentages) with protein (primarily albumin).
Protein-binding effect
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The portion of the drug that remains unbound.
Free, active drug
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The portion of the drug that is not available to receptors.
Bound, inactive drug
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These drugs are not bound to protein and are active, and can cause a pharmacologic response.
Free drugs
Additional Information: Drugs bound to proteins cannot leave the site of action. This is why only free drug is active.
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As the free drug in the circulation decreases, ____ bound drug is released from the protein to maintain the balance of free drug.
More / Less
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A ___________ decreases the number of protein-binding sites and can cause an increase in the amount of free drug in the plasma.
Low Serum Protein Level
Additional Information: More Free drug in the plasma = Drug toxicity may result.
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To avoid possible drug toxicity, checking the protein binding percentage of all drugs administered to a patient is important.
True / False
- True ✓
- Additional Information: The nurse should also check the patient's plasma protein and albumin levels, because a decrease in plasma protein (albumin) decreases protein-binding sites, permitting more free drug in circulation.
Remember: More free drug in the plasma = Drug toxicity may result.
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Abscesses, exudates, body glands, and tumors do not hinder drug distribution.
True / False
False ✓
Abscesses, exudates, body glands, and tumors hinder drug distribution. Antibiotics do not distribute well at abscess and exudate sites.
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The __________ is a semi-permeable membrane in the central nervous system (CNS) that protects the brain from foreign substances.
Blood-Brain Barrier (BBB)
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Highly _________ drugs are able to cross the Blood-Brain Barrier (BBB).
Lipid-Soluble
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Drugs that are not bound to proteins and are not lipid soluble are able to cross the BBB.
True / False
False ✓
Drugs that are not bound to proteins and are not lipid soluble are not able to cross the BBB, which makes it difficult to distribute the drug.
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During pregnancy, both lipid-soluble and lipid-insoluble drugs are able to cross the _________, which can affect the fetus and the mother. The risk-benefit ratio should be considered before drugs are given during pregnancy.
Placental Barrier
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During lactation, drugs can be secreted into _______, which could affect the nursing infant.
Breast Milk
The nurse needs to check which drugs may cross into breast milk before administering to a lactating patient.
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