AM Lecture 27 Jan Pharmacology and Anesthesia Flashcards
What are the two main concepts discussed in the context of anesthesia?
Pharmacodynamics and pharmacokinetics
What is the primary goal regarding drug onset and offset in anesthesia?
To produce a quick onset and offset of drugs
What are the severe consequences of underdosing anesthesia drugs?
Bronchospasm and ineffective anesthesia
What can happen if anesthesia drugs are overdosed?
Potentially lethal effects
What does the term ‘therapeutic index’ refer to?
The range between effective and lethal doses of a drug
What is the significance of receptor binding in drug effects?
The effect depends on the number of receptors a drug binds to
What are the three types of bonds through which drugs bind to receptors?
- Ionic
- Hydrogen
- Van der Waals
What is the difference between agonists and antagonists?
Agonists activate receptors; antagonists block receptors
What is the concept of ‘tolerance’ in pharmacology?
Decreased response to a drug after repeated use
What are the four main processes of pharmacokinetics?
- Absorption
- Distribution
- Metabolism
- Excretion
What is the elimination half-life (EHL) of a drug?
The time it takes for the plasma concentration to reduce by half
What does context-sensitive half-life (CSHL) refer to?
The half-life of a drug when administered as an infusion
How does ionization affect drug effectiveness?
It influences drug distribution and efficacy in different tissues
What is the relationship between pH and drug ionization?
pH affects the ionization state of weak acids and bases
What is the difference between potency and efficacy?
Potency refers to the amount needed for effect; efficacy is the maximum effect achievable
What are enantiomers in the context of pharmacology?
Chiral compounds that can have different effects in the body
Fill in the blank: The process of measuring plasma concentration levels helps determine _______.
[drug effects]
True or False: Antagonists can activate receptors.
False
What factors can affect drug response?
- Age
- Enzyme activity
- Genetic disorders
What is tachyphylaxis?
A rapid decrease in response to a drug after repeated doses
What role do liver enzymes like CYP450 play in pharmacokinetics?
They are crucial for drug metabolism
What impact does renal function have on drug elimination?
It affects the clearance of drugs from the body
What is the importance of understanding receptor types in anesthesia?
It helps achieve desired effects based on how drugs bind
What is the potential benefit of genetic testing in anesthesia?
To personalize anesthesia plans based on individual responses
What is the significance of a low therapeutic index?
There is a small margin between effective and harmful doses
What are the implications of drug accumulation due to repeated dosing?
Increased potential for side effects
What should be considered when adjusting multiple drugs during anesthesia?
The potential for instability and unclear effects
What happens to albuterol effectiveness with frequent use?
It gets less and less effective due to tolerance.
What is ephedrine primarily used for in anesthesia?
It is used for low blood pressure.
How does ephedrine function as a beta agonist?
It increases norepinephrine to act as a beta agonist.
What is a common dosage of ephedrine for low blood pressure?
Five milligrams.
What condition is associated with constant catecholamine release and receptor tolerance?
Pheochromocytoma.
What does the acronym A, D, M, E stand for?
Absorption, Distribution, Metabolism, Excretion.
What does ‘volume of distribution’ refer to?
The extent to which a drug disperses throughout body compartments.
What is the first group a drug goes to after injection?
Vessel-rich group (heart, lungs, liver, kidneys).
What type of drugs typically have a larger volume of distribution?
Fat-soluble drugs.
What factors can affect the volume of distribution?
- Blood volume
- Protein binding
- Lipophilicity or hydrophilicity
What happens to the free drug concentration when plasma protein levels decrease?
The free drug concentration increases.
What is the significance of free drug in pharmacology?
It is the active form that can cross lipid bilayers and exert effects.
What happens to the volume of distribution if a patient receives additional blood?
It increases due to greater blood volume.
What is the effect of dehydration on volume of distribution?
It decreases due to reduced intravascular volume.
What does metabolism generally convert lipid-soluble drugs into?
Water-soluble metabolites.
What is the benefit of having inactive metabolites?
They ensure predictability in drug effects.
Name one active metabolite of Valium.
Diazepam.
What type of drugs become active only after ingestion?
Prodrugs.
True or False: Most anesthesia drugs have inactive metabolites.
True.
What is the primary purpose of drug metabolism?
To prepare drugs for excretion.
What is a pro drug?
A substance that is inactive until ingested, then becomes active
Pro drugs often have metabolites that are active after metabolism.
How are most anesthesia drugs metabolized?
Predominantly by the cytochrome P450 system in the liver
A few drugs are metabolized by the kidneys or tissue esterases.
What are the two phases of drug metabolism?
Phase I: oxidation, reduction, or hydrolysis; Phase II: conjugation
Phase I prepares drugs for elimination, while Phase II adds a polar molecule for water solubility.
What is the role of CYP450 enzymes?
They are a family of microsomal enzymes that metabolize various drugs
CYP3A4 is the most common enzyme for anesthetic drug metabolism.
What happens when CYP450 enzymes are induced?
Metabolism of the drug is enhanced, leading to faster breakdown
This can affect the effectiveness of drugs like anticoagulants.
What effect does grapefruit juice have on drug metabolism?
It inhibits CYP450 enzymes, leading to increased drug levels in the body
This can result in higher circulating levels of drugs like Coumadin.
What is hepatic clearance?
The liver’s ability to clear drugs from the bloodstream
It can become limited in cases of liver disease or age.
What is elimination half-time?
The time necessary to eliminate 50% of a drug from the plasma after a bolus dose
This differs from elimination half-life, which refers to the amount of time to eliminate 50% from the body.
What is the difference between elimination half-time and elimination half-life?
Elimination half-time refers to plasma clearance; half-life refers to body clearance
Half-time is easier to measure through blood samples.
What is context-sensitive half-time?
The time to 50% decrease in drug effect after discontinuation of an infusion
This applies to continuous drug administration like drips.
What is the significance of distribution in pharmacology?
It involves how drugs reach effector sites and their ability to cross membranes
Lipophilicity and ionization are important factors in drug distribution.
Fill in the blank: CYP3A4 is the most common enzyme for the metabolism of _______.
anesthetic drugs
True or False: All anesthetic drugs are metabolized by the kidneys.
False
Most are metabolized by the liver; only a few are metabolized by the kidneys.
What can happen if a patient has liver disease?
Drug metabolism may be impaired, leading to accumulation of drugs in the body
This can increase the risk of side effects and toxicity.
What is the significance of lipophilicity in drug distribution?
Lipophilicity allows drugs to cross lipid membranes to reach effector sites.
What happens when the pK and pH of a drug are identical?
About 50% of the drug is ionized and about 50% is non-ionized.
What are most drugs categorized as in terms of acid-base properties?
Weak acids or weak bases.
Fill in the blank: If an acid is placed in a base, it _______.
ionizes
What determines whether a drug is active in terms of ionization?
Non-ionized drugs are more likely to be active and lipid soluble.
What occurs when a drug is ionized?
It remains in a water-soluble form and does not effectively cross lipid barriers.
What is the formula for determining ionization of weak acids?
PK after the pH.
What is the formula for determining ionization of weak bases?
PK before the pH.
How does a weak acid behave in a basic pH?
It becomes ionized.
How does a weak base behave in an acidic pH?
It becomes ionized.
True or False: Local anesthetics are more effective in normal pH tissue than in acidic tissue.
True
What happens to local anesthetics and opioids when they reach an acidotic environment?
They become ionized and are trapped in the baby.
What is the effect of drug concentration gradients in the placental circulation?
Drugs continue to move from mother to baby until equilibrium is reached.
What is the primary reason a local anesthetic may not work in ischemic tissue?
The drug cannot cross the lipid bilayer due to acidotic conditions.
What does pharmacodynamics refer to?
What the drug does to the body.
What is measured to understand drug effects in pharmacodynamics?
Plasma concentration levels.
What can affect the response to drugs in older patients?
Different amounts of protein, fat, and cardiac output.
Define potency in pharmacology.
The concentration of drug required for a desired effect.
What is efficacy in relation to drugs?
The full clinical effect achieved by the drug.
What is the therapeutic index?
The ratio between effective dose (ED50) and lethal dose (LD50).
What is the ideal therapeutic index for a drug?
A higher ratio indicates a safer drug with a wider margin of safety.
What are enantiomers?
Chemically identical molecules that are mirror images of each other.
Fill in the blank: The effective dose required to produce an effect in 50% of patients is known as _______.
ED50
What is LD50?
The dose required to kill 50% of the population.
Why is it important to know the ED95 rather than just the ED50?
ED95 provides a better indication of the drug’s effectiveness for a larger population.
What is a common characteristic of drugs that have a rapid rise in plasma levels?
They may have a delay before their effects are felt.
What are enantiomers?
Molecules that are chemically identical but are mirror images of each other
Enantiomers have asymmetric centers or chiral compounds.
What is the significance of enantiomers in drug development?
Some enantiomers can have active effects while others have inactive effects or undesirable side effects
The goal is to create ideal molecules that minimize side effects.
What does it mean if an enantiomer rotates light to the right?
It is called dextroretari
The left rotation is referred to as Levo.
What is a racemic mixture?
A 50/50 mixture of enantiomers that rotate light in opposite directions
An example is racemic epinephrine.
Which isomer of ketamine is more potent and has less delirium?
The S isomer
The R isomer is known for causing delirium.
What is the advantage of Lbuvicaine over its CO isomer?
It has much less cardiac toxicity
This is particularly beneficial for patients with cardiac issues.
What is the difference between cisatracurium and atracurium?
Cisatracurium does not release histamine, unlike atracurium
Atracurium can cause tachycardia and vasodilation due to histamine release.
What is the isomer of albuterol mentioned in the text?
Open X
Open X does not cause tachycardia like albuterol.
What is the future goal of drug administration mentioned?
Personalized anesthetic plans based on genetic testing
This would tailor dosages to individual patient needs.
True or False: All inhalation agents have the same effects on the cardiovascular system.
False
Some inhalation agents may increase or decrease systemic vascular resistance (SVR).
What is a potential study aid mentioned for learning inhalation agents?
Charts that list inhalation agents and their effects on various systems
These charts help identify similarities and differences among agents.
Fill in the blank: The _____ isomer of atracurium is known for its cleaner profile without histamine release.
cis
The cis isomer is also referred to as Nimbex.
What is the benefit of grouping similar anesthetic drugs when studying?
It allows for understanding of patterns and exceptions rather than memorizing every detail
This approach can simplify the learning process.
What common issue does ketamine cause when administered without benzodiazepines?
Delirium
Patients may exhibit confusion and repetitive questioning.
What is the main focus of future drug development as stated in the text?
Creating drugs that are purely active with the desired effects and minimal side effects
The aim is to eliminate inactive components in drug formulations.
