Pharmacology of GABA and Benzodiazepines

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Questions and Answers

What is the result of exogenous agonists such as benzodiazepines on the receptor-effector system?

Excitation and neural stimulation

Sedation and GABA-like inhibition (correct)

Anxiety and inhibition

Muscle relaxation and blockade

What is the mechanism by which drugs can move into or out of cells?

Passive diffusion through aqueous channels

Active transport by carriers

Endocytosis and binding to cell surface receptors

All of the above (correct)

What is the purpose of administering a drug into a specific body compartment, such as the gut?

To ensure rapid distribution to the site of action

To facilitate absorption into the blood (correct)

To minimize the risk of toxicity

To maximize the therapeutic effect

What is the effect of inverse agonists on the receptor-effector system?

Anxiety and inhibition Signup and view all the answers

What is the mechanism by which flumazenil blocks the effect of benzodiazepines?

Competitive inhibition Signup and view all the answers

What is the role of the bloodstream in the distribution of a drug?

To distribute the drug to the site of action Signup and view all the answers

What is the primary characteristic of an inverse agonist?

It binds to a receptor to reduce constitutive activity Signup and view all the answers

What is the purpose of a prodrug?

To convert an inactive precursor into an active drug Signup and view all the answers

What is the primary goal of pharmacokinetics in therapeutics?

To ensure a drug reaches its intended site of action Signup and view all the answers

What is the result of a drug having a much stronger affinity for the Ri state than for the Ra state?

Reduced constitutive activity at the receptor Signup and view all the answers

What is the term for the process of converting an inactive precursor into an active drug?

Metabolic conversion Signup and view all the answers

What is an example of a direct route of administration?

Topical application Signup and view all the answers

What is the term for the receptor-effector system that is activated by the endogenous transmitter GABA?

GABAA receptor-effector Signup and view all the answers

What is the result of a drug stabilizing a large fraction of receptors in the Ri state?

Reduced constitutive activity at the receptor Signup and view all the answers

Which of the following drugs is a Schedule I controlled substance?

Flunitrazepam (Rohypnol) Signup and view all the answers

What is the main difference between Schedule II and Schedule III controlled substances?

Penalties for illegal possession Signup and view all the answers

Which of the following opioids is a Schedule III controlled substance?

Buprenorphine (Buprenex, Subutex) Signup and view all the answers

What is the primary purpose of the scheduling system for controlled substances?

To classify drugs based on potential for abuse Signup and view all the answers

Which of the following is NOT a Schedule IV controlled substance?

Methamphetamine (Desoxyn) Signup and view all the answers

Which of the following drugs is a Schedule V controlled substance?

Codeine Signup and view all the answers

What is the main difference between Schedule II and Schedule III opioids?

Combination with nonopioid ingredients Signup and view all the answers

Which of the following drugs is a cannabinoid?

Nabilone (Cesamet) Signup and view all the answers

What is the purpose of the prescription requirements for Schedule II controlled substances?

To limit prescription refills Signup and view all the answers

Which of the following is a characteristic of Schedule I controlled substances?

High potential for abuse Signup and view all the answers

Study Notes

Drug Administration and Pharmacokinetics

Administering a drug into one body compartment (e.g., the gut) requires it to move to its site of action in another compartment (e.g., the brain) via absorption into the blood and distribution to the target site.
The drug must permeate through various barriers, such as aqueous channels, lipid cell membranes, and cell surface receptors.

Mechanisms of Drug Permeation

Passive diffusion through aqueous channels in intercellular junctions (e.g., tight junctions)
Diffusion through lipid cell membranes
Carrier-mediated transport into or out of cells
Endocytosis and binding to cell surface receptors

Pharmacokinetic Principles

A drug's ability to reach its intended site of action after administration is critical in practical therapeutics.
The active drug molecule may be administered as such, or an inactive precursor chemical (prodrug) may be given, which is converted to the active drug by biologic processes inside the body.
In some cases, a drug can be applied directly to the target tissue, such as topical application of an anti-inflammatory agent to inflamed skin or mucous membrane.

Drug Receptor Interactions

Exogenous agonists, like benzodiazepines, facilitate the receptor-effector system and cause GABA-like inhibition, resulting in sedation as the therapeutic effect.
Conventional antagonists, like flumazenil, can block this inhibition.
Inverse agonists, which have a higher affinity for the Ri form, can reduce constitutive activity and produce a contrasting physiologic result.
The γ-aminobutyric acid (GABAA) receptor-effector system, a chloride channel in the nervous system, is activated by the endogenous transmitter GABA and causes inhibition of postsynaptic cells.

Schedules of Controlled Drugs

Schedule I: drugs with high abuse potential, no accepted medical use, and lack of safety for use under medical supervision (e.g., heroin, LSD, marijuana)
Schedule II: drugs with high abuse potential, accepted medical use, but severe restrictions on use (e.g., opioids, stimulants, depressants)
Schedule III: drugs with moderate to low abuse potential, accepted medical use, and moderate restrictions on use (e.g., anabolic steroids, opioids, stimulants)
Schedule IV: drugs with low abuse potential, accepted medical use, and limited restrictions on use (e.g., benzodiazepines, opioids, stimulants)
Schedule V: drugs with low abuse potential, accepted medical use, and minimal restrictions on use (e.g., codeine, difenoxin, pregabalin)

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Description

Understand how benzodiazepines facilitate the GABA receptor-effector system, causing sedation, and how it can be blocked by antagonists. Learn about drug administration and movement to its site of action.