Drug Absorption and Administration Routes
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Questions and Answers

Intramuscular injection is a preferable method for administering aqueous drugs that require rapid and predictable effects.

True (A)

Which of the following is NOT a reason why subcutaneous administration of drugs can have unpredictable effects?

  • Presence of certain disease pathologies.
  • Variability in subcutaneous blood flow.
  • Limited surface area for absorption.
  • Rapid absorption into the bloodstream. (correct)

    • What is the major disadvantage of intrathecal, epidural, and perineural injection of drugs?

    The relative expertise required to perform these injections.

    The ______ is the primary site of action for many anesthetic agents, making direct injection into this space highly effective.

    <p>spinal cord</p> Signup and view all the answers

    Match the route of administration with its primary advantage:

    <p>Intramuscular = Rapid and predictable effects for aqueous drugs. Subcutaneous = Variable absorption rate due to blood flow variability. Intrathecal = Direct access to the spinal cord, bypassing absorption limitations. Inhalational = Large surface area for absorption and high blood flow in the pulmonary capillaries.</p> Signup and view all the answers

    What is primarily required for water-soluble drugs to diffuse across the cell membrane?

    <p>A hydrophilic channel (D)</p> Signup and view all the answers

    Only small lipophilic drugs can passively diffuse across biological membranes.

    <p>True (A)</p> Signup and view all the answers

    What is the process called when transmembrane carrier proteins require energy to transport drugs?

    <p>Active transport</p> Signup and view all the answers

    In the CNS, the ___________ barrier limits the transport of hydrophilic drugs.

    <p>blood-brain</p> Signup and view all the answers

    What limits the passive transport of drugs from the intravascular space into various organs?

    <p>Blood flow (A)</p> Signup and view all the answers

    Match the transport processes with their definitions:

    <p>Passive diffusion = Diffusion down a concentration gradient without energy Facilitated diffusion = Requires specific transmembrane proteins but no energy Active transport = Requires energy to move against a concentration gradient</p> Signup and view all the answers

    What type of drugs can enter the CNS by binding to specific transmembrane proteins?

    <p>Hydrophilic drugs</p> Signup and view all the answers

    Nonspecific hydrophilic channels are abundant in the CNS.

    <p>False (B)</p> Signup and view all the answers

    What is a significant reason for the decreased bioavailability of orally administered drugs?

    <p>Extensive first-pass metabolism in the liver (B)</p> Signup and view all the answers

    Sublingual administration of drugs avoids first-pass metabolism.

    <p>True (A)</p> Signup and view all the answers

    Name one drug that is commonly administered through the sublingual route.

    <p>Nitroglycerin</p> Signup and view all the answers

    What does a low therapeutic index indicate?

    <p>The drug has a narrow margin between therapeutic and toxic effects (A)</p> Signup and view all the answers

    Intravenous (IV) administration is the only method through which drugs can have a sustained and significant effect.

    <p>False (B)</p> Signup and view all the answers

    The administration route that provides rapid drug absorption due to high blood flow is __________.

    <p>intramuscular</p> Signup and view all the answers

    Which of the following methods allows penetration of intact skin for drug delivery?

    <p>Transcutaneous administration (C)</p> Signup and view all the answers

    What is bioavailability?

    <p>The relative amount of a drug dose that reaches the systemic circulation unchanged and the rate at which this occurs.</p> Signup and view all the answers

    For most intravenously administered drugs, the absolute bioavailability is close to __________.

    <p>unity</p> Signup and view all the answers

    There are many drugs suitable for transcutaneous administration.

    <p>False (B)</p> Signup and view all the answers

    Drugs that can maintain a high contact time with __________ or __________ mucosa can be absorbed sublingually.

    <p>nasal, oral</p> Signup and view all the answers

    Which factor primarily affects the absorption rate for oral administration of drugs?

    <p>Gastric emptying rate (A)</p> Signup and view all the answers

    Match the administration method to its characteristic:

    <p>Intravenous (IV) = Immediate effect with high bioavailability Oral = Variable absorption and lower bioavailability Pulmonary = Can involve first-pass metabolism Subcutaneous = Slower absorption than IV</p> Signup and view all the answers

    Match the following routes of drug administration with their characteristics:

    <p>Sublingual = Bypasses first-pass metabolism Intramuscular = Rapid and complete absorption Transcutaneous = Limited number of drugs available Oral = Significantly influenced by first-pass metabolism</p> Signup and view all the answers

    The pulmonary endothelium can slow drug absorption when drugs are administered intravenously.

    <p>True (A)</p> Signup and view all the answers

    What is a major obstacle to oral administration in anesthesia practice?

    <p>Limited and inconstant rate of bioavailability.</p> Signup and view all the answers

    What is the primary function of active transport in drug elimination organs?

    <p>To transport drugs against the concentration gradient (D)</p> Signup and view all the answers

    Active transport and facilitated diffusion are both limited by the number of carrier proteins available.

    <p>True (A)</p> Signup and view all the answers

    What type of transporters are responsible for the limited bioavailability of the drug loperamide?

    <p>P-glycoprotein (P-gp)</p> Signup and view all the answers

    The class of transporters that transports endogenous opioids into the brain is called __________.

    <p>organic anion polypeptide transporters (OATPs)</p> Signup and view all the answers

    What is the bioavailability percentage of a drug administered intravenously?

    <p>100% (C)</p> Signup and view all the answers

    Lipophilic compounds require transporters to diffuse across the capillary wall into tissues.

    <p>False (B)</p> Signup and view all the answers

    Match the following drugs or transporters with their characteristics:

    <p>Loperamide = Lipophilic potent µ-opioid agonist P-glycoprotein = Limits the bioavailability of certain drugs OATPs = Transport endogenous opioids into the brain IV administration = Ensures 100% drug bioavailability</p> Signup and view all the answers

    Which part of the body contains the organic anion polypeptide transporters (OATPs)?

    <p>Microvascular endothelium of the brain</p> Signup and view all the answers

    Flashcards

    Drug Absorption

    The process by which drugs move across cell membranes to exert effects.

    Lipid Bilayer

    A double layer of phospholipids that forms the cell membrane and influences drug passage.

    Passive Diffusion

    Movement of drugs across membranes down their concentration gradient without energy use.

    Hydrophilic Channel

    Transmembrane protein passage required for water-soluble drugs to cross membranes.

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    Blood-Brain Barrier

    A selective barrier that restricts drug passage into the central nervous system.

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    Active Transport

    Energy-requiring process that moves substances against their concentration gradient.

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    Facilitated Diffusion

    Passive movement of drugs via carrier proteins without energy use, down the gradient.

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    Transmembrane Proteins

    Proteins that span the membrane and help transport molecules across it.

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    Concentration Gradient

    Difference in concentration of a substance between two areas.

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    Saturable Process

    A process limited by available carrier proteins.

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    Lipophilic Compounds

    Substances that dissolve easily in fats and oils.

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    P-glycoprotein (P-gp)

    A transporter that extrudes lipophilic drugs from cells.

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    Bioavailability

    The extent and rate a drug enters systemic circulation.

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    OATP Transporters

    Transporters that facilitate the uptake of drugs and opioids into tissues, especially the brain.

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    Intravenous Administration

    Direct delivery of drugs into the circulatory system with immediate effect.

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    Therapeutic Index

    The ratio of toxic concentration to therapeutic concentration of a drug.

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    Plasma Concentration

    The amount of drug present in the plasma at any given time.

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    Non-IV Administration

    Routes of drug delivery other than intravenous, like oral or inhalation.

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    Gastric Emptying

    The process of food leaving the stomach to enter the small intestine.

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    Absorption Rate Variability

    The inconsistent rate at which drugs are absorbed from the GI tract.

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    Pulmonary Endothelium

    The inner lining of lung blood vessels that can affect drug absorption.

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    Maximum Drug Effect

    The highest therapeutic response achievable from a drug in the body.

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    Intramuscular Injection

    A method of delivering drugs into muscle tissue for fast effects.

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    Subcutaneous Absorption Variability

    Drug absorption can be unpredictable due to changes in blood flow in subcutaneous tissue.

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    Intrathecal Injection

    Direct injection into the spinal canal to deliver drugs, bypassing absorption barriers.

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    Epidural Administration

    Injection around the spinal cord that requires drug absorption to act effectively.

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    Inhalational Drug Delivery

    Administering drugs via inhalation using the lungs for rapid absorption into blood.

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    First-pass metabolism

    The metabolism of a drug before it reaches systemic circulation via the liver.

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    Sublingual administration

    Drug administration under the tongue for rapid absorption into the bloodstream.

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    Lipophilic drugs

    Drugs that are fat-soluble and can easily cross cell membranes.

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    Transcutaneous administration

    Delivery of drugs through the skin, often via patches.

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    Intramuscular absorption

    How drugs are absorbed from muscle tissue; often rapid and complete due to blood flow.

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    Nasal absorption

    Drug absorption through the nasal mucosa for rapid systemic effects.

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    Blood flow to depot

    The rate at which blood circulates to a drug's absorption site influences its uptake.

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    Study Notes

    Drug Absorption and Routes of Administration

    • Drugs must cross cell membranes to reach their target.
    • Lipid-soluble drugs passively diffuse across lipid bilayers.
    • Water-soluble drugs require hydrophilic channels or active transport.
    • The blood-brain barrier has limited hydrophilic channels, so active transport is crucial for CNS entry.
    • Active transport moves substances against their concentration gradient, requiring energy.
    • Facilitated diffusion does not require energy and is limited by carrier protein availability.
    • Lipophilic drugs can be transported into tissues, increasing local concentration beyond passive diffusion.
    • P-glycoprotein (P-gp) transports lipophilic drugs out of tissues.
    • Organic anion polypeptide transporters (OATPs) transport drugs into tissues, including the brain.
    • Intravenous (IV) administration provides immediate 100% bioavailability, potentially leading to rapid, severe side effects in drugs with low therapeutic indices.
    • For non-IV routes, absorption into systemic circulation determines drug action time and effectiveness.
    • Bioavailability is the amount and rate of drug reaching systemic circulation unchanged.
    • IV bioavailability is nearly instantaneous and close to 100%.
    • Pulmonary endothelium can slow IV drug absorption and metabolism.

    Oral Administration

    • Oral administration is the most convenient and safest method for most drugs, but not common in anesthesia.
    • Gastric emptying into the small intestine determines absorption.
    • Small intestine has a much larger surface area for absorption than the stomach or large intestine.
    • Intestine mucosa actively metabolizes drugs, decreasing bioavailability.
    • Liver metabolism of most orally administered lipophilic drugs is extensive.
    • Oral doses must be higher than IV doses to produce therapeutic plasma concentrations.
    • Timing of peak concentration is prolonged and variable.
    • Lipophilic drugs can be absorbed through nasal or oral mucosa (sublingual).
    • Sublingual administration bypasses hepatic first-pass metabolism.

    Transcutaneous Administration

    • Lipophilic drugs in patches can penetrate intact skin, producing systemic concentrations for maintenance therapy.
    • Electric current can increase passive drug diffusion speed, but is not often practical.

    Intramuscular and Subcutaneous Administration

    • Intramuscular absorption is rapid and complete due to high muscle blood flow.
    • Subcutaneous absorption varies depending on blood flow, which can be influenced by diseases.

    Intrathecal, Epidural, and Perineural Injection

    • Intrathecal injection directly targets the spinal cord, bypassing absorption issues.
    • Epidural and perineural administration require drug absorption through membranes.
    • Relative expertise is needed.

    Inhalational Administration

    • Inhalational administration is desirable due to high pulmonary surface area and blood flow.
    • New technologies can aerosolize drugs for IV-comparable pharmacokinetics.

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    Drug Absorption and Routes of Administration PDF

    Description

    This quiz explores the mechanisms of drug absorption and the various routes of administration. It covers the importance of solubility, the role of transport proteins, and bioavailability in drug efficacy. Test your knowledge on how different drugs interact with cell membranes and their implications for treatment.

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