Pharmacology: Drug Absorption & Administration

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Questions and Answers

Which of the following factors is NOT a primary determinant of passive drug diffusion across cell membranes?

Lipid solubility of the drug

Presence of hydrophilic channels

Concentration gradient of the drug

Blood flow to the target organ (correct)

What is the primary reason why water-soluble drugs need hydrophilic channels to cross cell membranes?

To bypass the lipophilic core of the cell membrane (correct)

To bind to specific transmembrane proteins

To create a pathway for active transport

To increase the concentration gradient of the drug

Which of the following statements accurately describes the difference between active transport and facilitated diffusion?

Active transport requires energy, while facilitated diffusion does not

Active transport utilizes specific carrier proteins, while facilitated diffusion does not

Both A and B are correct (correct)

Active transport can move drugs against their concentration gradient, while facilitated diffusion cannot

Why is the passive transport of drugs from the bloodstream to the interstitium of most organs primarily limited by blood flow?

Because the capillary endothelium of most organs is highly permeable (B) Signup and view all the answers

What is the primary reason oral administration of drugs often requires higher doses compared to intravenous administration?

Oral drugs experience significant first-pass metabolism in the liver. (C) Signup and view all the answers

Which of the following statements best describes the blood-brain barrier?

A barrier that limits the passage of hydrophilic drugs into the CNS (A) Signup and view all the answers

Which route of administration is considered impractical for rapid therapeutic effects in the perioperative setting?

Oral (D) Signup and view all the answers

What is the primary mechanism by which hydrophilic drugs enter the CNS?

Active transport via specific carrier proteins (A) Signup and view all the answers

What characteristic primarily affects the ability of a drug to passively cross cell membranes?

Solubility of the drug in lipids (A) Signup and view all the answers

What advantages does sublingual administration offer over oral administration?

Sublingual administration avoids first-pass metabolism, allowing for smaller doses to achieve desired effects. (B) Signup and view all the answers

Which of the following is NOT a characteristic of active transport?

Utilizes specific carrier proteins (B) Signup and view all the answers

What is a key factor limiting the practical application of transcutaneous administration of drugs?

Low absorption rate through intact skin. (D) Signup and view all the answers

What is the primary factor determining the rate of absorption of intramuscularly administered drugs?

The blood flow to the injection site. (C) Signup and view all the answers

Which of the following drugs is specifically mentioned in the text as suitable for sublingual administration?

Fentanyl (B), Nitroglycerin (D) Signup and view all the answers

Which of the following administration routes is most likely to result in the fastest onset of action for a lipophilic drug?

Sublingual (B) Signup and view all the answers

What is a major limitation for the use of electric current to enhance drug absorption through the skin?

It is expensive and requires specialized equipment. (C) Signup and view all the answers

Which of the following is a reason why subcutaneous injection of certain drugs can be unpredictable?

Variability in subcutaneous blood flow (C) Signup and view all the answers

Which route of administration bypasses the limitations of drug absorption and distribution?

Intrathecal injection (B) Signup and view all the answers

Why is inhalation an extremely desirable route of drug administration?

It offers rapid and predictable effects (B) Signup and view all the answers

Which of the following is NOT a limitation of epidural and perineural administration of local anesthetics?

Limited ability to reach the spinal cord directly (D) Signup and view all the answers

What is a major challenge with the administration of certain drugs, like heparin and insulin, subcutaneously?

The time of onset and peak effect can be unpredictable. (A) Signup and view all the answers

What is the primary factor that determines the rate of absorption of an orally administered drug?

The rate of gastric emptying (C) Signup and view all the answers

What is the likely consequence of a rapid increase in plasma concentration of a drug with a low therapeutic index?

Potential for immediate and severe side effects (D) Signup and view all the answers

Which of the following routes of administration typically has the fastest absorption rate?

Intravenous (B) Signup and view all the answers

What is the main reason why oral administration is not commonly used in anesthesia practice?

Unpredictable and variable bioavailability (C) Signup and view all the answers

What is the therapeutic index of a drug?

The ratio of the toxic dose to the therapeutic dose (A) Signup and view all the answers

Which of the following is NOT a factor that can influence the rate of absorption of a drug?

The chemical structure of the drug (C) Signup and view all the answers

What is the significance of maintaining a plasma concentration above the minimum effective plasma concentration?

Maintaining a sustained drug effect (D) Signup and view all the answers

Which of the following statements about bioavailability is TRUE?

Bioavailability is the amount of drug that reaches the systemic circulation unchanged (D) Signup and view all the answers

What does the provided text state about lipophilic drugs and their movement across capillary walls?

For lipophilic drugs, transport across capillary walls does not require carrier proteins but can be influenced by transporter presence. (D) Signup and view all the answers

What is the primary factor limiting the rate of active transport or facilitated diffusion of drugs?

The number of carrier proteins available. (D) Signup and view all the answers

What is a notable characteristic of the P-glycoprotein (P-gp) transporter system?

It can limit the bioavailability and CNS penetration of some lipophilic drugs by transporting them out of tissues. (C) Signup and view all the answers

Which type of transporter is responsible for the transport of endogenous opioids into the brain?

Organic anion polypeptide transporters (OATPs) (C) Signup and view all the answers

What does the text suggest about intravenous (IV) administration of drugs?

IV administration allows for immediate delivery of the drug, resulting in 100% bioavailability. (C) Signup and view all the answers

Why does loperamide, a lipophilic µ-opioid agonist used for diarrhea, have limited bioavailability?

The presence of P-gp transporters at the intestinal portal capillary interface limits its absorption. (A) Signup and view all the answers

What is a common characteristic of both facilitated diffusion and active transport of drugs?

They both are saturable processes. (C) Signup and view all the answers

Why are there limited research findings on the impact of transporter proteins on individual drug responses?

All of the above. (D) Signup and view all the answers

Study Notes

Drug Absorption and Routes of Administration

Drugs must cross cell membranes to reach their site of action. Lipid-soluble drugs passively diffuse across lipid bilayers.
Water-soluble drugs require hydrophilic channels in membranes for passive diffusion.
CNS drug entry is often limited by the blood-brain barrier. Active transport mechanisms move drugs across the blood-brain barrier against concentration gradients.
Active transport and facilitated diffusion are saturable processes, limited by the number of carrier proteins.
Lipophilic drugs, while not needing transporters to enter tissues, may be removed by ATP-dependent transporters like P-gp.
Organic anion polypeptide transporters (OATPs) transport endogenous opioids and some drugs into the brain.
Intravenous (IV) administration provides immediate, 100% bioavailability, but rapid overshoot may occur with drugs having low therapeutic indices.
Bioavailability is the rate and extent to which a drug reaches the systemic circulation unchanged.

Oral Administration

Oral administration is safe and convenient, but bioavailability is variable and often less than 100%.
Gastric emptying and intestinal surface area influence absorption rates.
First-pass metabolism in the liver significantly reduces bioavailability for many orally administered drugs.
Oral administration is typically less desirable for rapid effects in a clinical setting because of inconsistent rates of bioavailability and variable times to reach peak concentration.
Sublingual administration bypasses first-pass metabolism and can rapidly achieve high plasma concentrations.

Transcutaneous Administration

Some lipophilic drugs can penetrate intact skin.
Transcutaneous patches provide sustained drug delivery for conditions like maintenance therapy, but they take a longer time to reach therapeutic levels compared to other routes.
Using electricity to enhance transdermal drug absorption has been explored but remains limited in practical applications.

Intramuscular and Subcutaneous Administration

Intramuscular (IM) absorption is usually rapid and complete due to high muscle blood flow.
Subcutaneous (SC) absorption is more variable due to varying subcutaneous blood flow. This leads to variable absorption rates and times to onset of action when compared to IM.

Intrathecal, Epidural, and Perineural Injection

Intrathecal injection directly delivers drugs to the spinal cord, avoiding absorption and distribution limitations.
Epidural and perineural injections require drug absorption through the dura or nerve sheath, respectively.

Inhalational Administration

Inhalational administration of drugs is highly effective due to the lung's large surface area and high blood flow.
Newer technologies enable rapid and predictable aerosolization of drugs, achieving comparable pharmacokinetic effects to intravenous administration.

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Description

This quiz focuses on the processes involved in drug absorption and the various routes of administration. It covers essential topics such as lipid and water-soluble drugs, the blood-brain barrier, and the mechanisms of drug transport. Testing your understanding of these concepts will enhance your knowledge in pharmacology.