Recommended Pharmacology Review Flashcards
Define tachyphylaxis.
Rapid loss of drug effectiveness after repeated use.
Examples of drugs with a narrow therapeutic margin?
Warfarin, phenytoin, lithium.
Drugs not to be combined with herbs at all?
Warfarin, phenytoin, lithium.
Role of CYP 450 enzyme system?
Many drugs are metabolized in phase 1 by the CYP 450 system (oxidation reaction catalyzed by CYP 450).
The cytochrome P450 (CYP450) system plays a critical role in drug metabolism. It is a family of enzymes primarily located in the liver (but also in other tissues) that catalyze the oxidation of drugs, preparing them for elimination from the body.
Define therapeutic index.
Measurement of how safe a drug is.
Ratio between the toxic dose and the therapeutic dose.
Larger the number the safer the drug is.
Drug response in pediatric patients?
Drug absorption differs:
Infants have a small skeletal muscle mass and limited movement.
Distribution of drugs differs:
Infants have a higher percentage of body water and a lower percentage of body fat.
Drug metabolism and excretion is slower in infants.
Drug response in geriatric patients?
Delayed drug absorption and slower drug action onset.
Increased plasma drug concentration and pharmacological effects.
Decreased drug metabolism rate. Increased drug action duration and intensity.
Slower excretion.
Factors affecting bioavailability?
First-pass hepatic metabolism:
Refers to drugs entering the hepatic portal system from the intestines.
Drug solubility:
Very hydrophilic or hydrophobic drugs have difficulty crossing cell membranes and entering the circulation.
Chemical instability:
Some drugs may be affected by the pH in the stomach or various degradative enzymes in the GI tract.
Chemico-physical properties of the drug formulation:
Many factors can play a role in bioavailability such as particle size, salt form, and excipients, among others.
Factors determining drug-herb interaction?
Pharmacokinetic Factors
Absorption: acidity, GI (herbs that alter gastric pH or motility), binding (herbs that bind to drugs and decrease their absorption).
Distribution: protein binding. Herbs can compete for protein-binding sites, increasing free drug concentrations, leading to toxicity.
Metabolism: CYP 450 enzyme modulation. Some herbs induce or inhibit liver enzymes, altering drug metabolism.
Elimination: clearance interference.
Pharmacodynamic Factors
Additive or Synergistic Effects: Herbs with similar effects to drugs can amplify therapeutic or toxic effects.
Antagonistic Effects: Herbs with opposing effects to drugs can reduce/counteract drug efficacy.
Routes of elimination?
Several methods by which a drug can be eliminated from the body including excretion:
in the bile
into the intestines
through the lung
or even in the milk of lactating mothers
Excretion by the kidneys, however, is by far the most common route of elimination of drugs in the body.
Phase 1 and phase 2 metabolism means?
Phase I reactions convert lipophilic drugs into more polar (water soluble) molecules.
Phase II metabolism involves the conjugation of the drug. Conjugation involves adding a molecule to a drug. Makes the drug much more polar and hydrophilic allowing for elimination by the kidneys.
Importance of drug protein binding?
Most common protein for drug binding is the most common protein in the plasma: albumin.
Protein-bound drugs cannot cross cell membranes or bind to receptors. Only free drugs are active. Protein-bound drugs remain in the plasma. They cannot cross the blood-brain barrier or enter tissues easily. Protein binding slows the rate of elimination. Only free drugs are filtered by the kidneys or metabolized by the liver. The bound drug is released gradually, extending the drug’s duration of action.
Describe volume of distribution as it relates to drugs.
Large drugs cannot escape plasma. Small drugs can leave plasma.
The volume of distribution (Vd) is a pharmacokinetic parameter that quantifies how extensively a drug is distributed throughout the body relative to the concentration of the drug in the plasma. It is a theoretical value that helps understand where a drug resides in the body (e.g., in the plasma, extracellular fluid, or tissues).
Factors affecting distribution of drugs?
Four main factors affect distribution:
Blood flow.
Capillary permeability.
Drug structure.
Degree of binding to proteins.
If blood flow is decreased, there is less opportunity for a drug to move from the plasma into the area of reduced flow. Brain, liver, and kidneys have excellent blood flow. Skeletal muscles and skin less. Adipose tissues even less.
Determined by how “leaky” specific, local capillaries are. E.g., due to plasma filtration function of the spleen and liver, their capillaries are very permeable, and most drugs will be able to more easily move from the plasma. Central nervous system (CNS) protected by blood-brain barrier. Very few drugs can enter the brain, only those that are lipid soluble and without charge or polarity can enter the CNS.
Hydrophobic drugs can easily cross cell membranes. This affects how easily a drug can leave the circulation. Distribution of a very hydrophobic drug is primarily determined by the amount of blood flow to a given area.
Most drugs reversibly bind to plasma proteins. Slows overall distribution of the drug from the plasma and creates a reservoir of the drug.
Pros and cons of oral drug administration?
Commonest route of administration.
Safest, most convenient, and most economical route of administration.
Disadvantages:
Reduced drug absorption.
Vomiting.
Destruction of some of the drug through enzymatic degradation and gastric acid.
Inconsistent absorption.
Patient compliance issues.
Pros and cons of sublingual administration?
Allows the drug to bypass the intestines and liver preventing first pass metabolism.
Absorption can be very rapid as well.
Few drugs chemically appropriate for this route of administration.
Pros and cons of rectal administration?
Advantage
Drug bypasses the stomach and its gastric acid which could destroy some of the drug.
About 50% of the drug enters the liver and metabolized.
Disadvantage
Irregular and incomplete absorption.
Irritation of the rectal mucosa.
Pros and cons of parenteral administration?
Advantages over oral administration:
More rapid.
Extensive.
Predictable administration.
Can be given to unconscious patients.
Some drugs cannot be delivered in their active form in any other way.
Disadvantages:
Necessity for aseptic protocols.
Pain.
Difficult self-medication.
Expense.
Local trauma.
Oral inhalation drug administration pros and cons?
Allow for rapid drug delivery through large surface area of the lung mucosa. Can minimize systemic side effects.
Only gases, very small particulates, and fine droplets of liquid can be administered.
Define clearance.
Clearance (CL) in pharmacology refers to the rate at which a drug is removed from the body, specifically measuring the volume of plasma (or blood) that is completely cleared of the drug per unit of time. It is a key pharmacokinetic parameter that helps determine drug dosing and elimination.
Define efficacy.
Drug efficacy refers to the maximum effect a drug can produce, regardless of the dose. It measures the ability of a drug to elicit a desired biological response when it binds to its target receptor or acts on its site of action.
Define tolerance.
Drug tolerance refers to a reduced response to a drug over time, requiring higher doses to achieve the same therapeutic effect. It occurs when the body adapts to the drug’s presence, diminishing its effectiveness.
Define potency.
Drug potency refers to the amount of a drug required to produce a specific effect. It measures the strength of a drug in achieving its desired action at a given dose.
Define polypharmacy.
Polypharmacy refers to the use of multiple medications by a single individual, often defined as taking five or more drugs simultaneously. While it can be appropriate in certain medical conditions, excessive or inappropriate polypharmacy increases the risk of adverse drug interactions, side effects, and medication nonadherence.
Define dependence.
Dependence in pharmacology and medicine refers to a condition where an individual relies on a substance to function normally. It can be categorized into two main types: physical dependence and psychological dependence.
Define pharmacokinetics.
Pharmacokinetics is the branch of pharmacology that studies how a drug moves through the body over time. It focuses on the processes that determine the drug’s absorption, distribution, metabolism, and excretion (often abbreviated as ADME).
Define pharmacodynamics.
Pharmacodynamics is the branch of pharmacology that studies the effects of a drug on the body and the mechanism of its action. It focuses on the interaction between the drug and its target, such as receptors, enzymes, or other cellular components, and how this interaction leads to a therapeutic or toxic effect.
Define side effects.
Drug side effects are unintended or secondary effects that occur in addition to a drug’s desired therapeutic effect. They can range from mild and temporary to severe and life-threatening, and their occurrence depends on factors like the drug’s properties, dosage, and the individual’s physiology.
Define therapeutic effects.
Therapeutic effects refer to the desired and intended outcomes of a medication or treatment. These effects are the primary reason the drug or therapy is prescribed, aiming to alleviate symptoms, cure a condition, or improve the quality of life for the patient.
Define adverse effects.
Adverse effects refer to unintended, harmful, or undesired outcomes that occur as a result of taking a medication, undergoing treatment, or being exposed to a therapeutic intervention. These effects may range from mild to severe and can sometimes outweigh the benefits of the treatment.
Define toxic effects.
Toxic effects refer to the harmful and potentially dangerous effects of a drug or substance that occur when it is present in excessive amounts or when the body cannot adequately metabolize or eliminate it. These effects are often dose-dependent and can result in significant damage to organs, tissues, or physiological systems.
