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What is the primary focus of pharmacokinetics?
What is the primary focus of pharmacokinetics?
Which of the following is NOT a phase of pharmacokinetics?
Which of the following is NOT a phase of pharmacokinetics?
What occurs during the metabolism phase of pharmacokinetics?
What occurs during the metabolism phase of pharmacokinetics?
Which factors most directly influence the route of administration chosen for a drug?
Which factors most directly influence the route of administration chosen for a drug?
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What are enteral routes of drug administration characterized by?
What are enteral routes of drug administration characterized by?
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What is a disadvantage of oral drug administration?
What is a disadvantage of oral drug administration?
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What does the distribution phase of pharmacokinetics involve?
What does the distribution phase of pharmacokinetics involve?
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How does the choice of drug route affect pharmacokinetics?
How does the choice of drug route affect pharmacokinetics?
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What is a primary disadvantage of oral drug administration?
What is a primary disadvantage of oral drug administration?
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Which factor affects the efficiency of absorption from the GI tract?
Which factor affects the efficiency of absorption from the GI tract?
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In which route of administration is the first-pass effect avoided?
In which route of administration is the first-pass effect avoided?
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What is one of the main advantages of parenteral routes of drug administration?
What is one of the main advantages of parenteral routes of drug administration?
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What is a consequence of using intramuscular drug administration?
What is a consequence of using intramuscular drug administration?
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Which route offers a rapid onset of action due to large surface area and high blood flow?
Which route offers a rapid onset of action due to large surface area and high blood flow?
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What can significantly interfere with oral drug absorption?
What can significantly interfere with oral drug absorption?
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Why might a rectal route be preferred for certain patients?
Why might a rectal route be preferred for certain patients?
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What is the potential drawback of subcutaneous drug administration?
What is the potential drawback of subcutaneous drug administration?
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What happens during the first-pass effect?
What happens during the first-pass effect?
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What is the primary advantage of transdermal drug administration?
What is the primary advantage of transdermal drug administration?
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In the context of drug administration, what does intraosseous access provide?
In the context of drug administration, what does intraosseous access provide?
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Which route of administration typically has the fastest onset of effect?
Which route of administration typically has the fastest onset of effect?
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What is the main purpose of time-release drug formulations?
What is the main purpose of time-release drug formulations?
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Which factors affect a drug's ability to cross biological membranes?
Which factors affect a drug's ability to cross biological membranes?
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What distinguishes active transport from facilitated diffusion?
What distinguishes active transport from facilitated diffusion?
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What is a characteristic of passive diffusion?
What is a characteristic of passive diffusion?
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In relation to drug properties, what is the significance of a drug being lipid-soluble?
In relation to drug properties, what is the significance of a drug being lipid-soluble?
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Which statement about weak acids and bases is correct?
Which statement about weak acids and bases is correct?
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What is the primary function of the kidneys regarding drugs in the body?
What is the primary function of the kidneys regarding drugs in the body?
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Which of the following routes of administration may involve variable absorption times?
Which of the following routes of administration may involve variable absorption times?
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How do large molecules typically traverse biological membranes?
How do large molecules typically traverse biological membranes?
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What type of transport requires a carrier but no energy?
What type of transport requires a carrier but no energy?
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Which factor does NOT determine the route of administration for a drug?
Which factor does NOT determine the route of administration for a drug?
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What characterizes the ionized form of a drug in terms of solubility?
What characterizes the ionized form of a drug in terms of solubility?
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Which of the following statements is true regarding weak acids and pH?
Which of the following statements is true regarding weak acids and pH?
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What is the Henderson-Hasselbalch equation used for?
What is the Henderson-Hasselbalch equation used for?
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When the pH is less than the pKa for a weak base, which form predominates?
When the pH is less than the pKa for a weak base, which form predominates?
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Which body fluid has a pH close to neutral and is vital for drug distribution?
Which body fluid has a pH close to neutral and is vital for drug distribution?
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What impacts bioavailability for a drug administration route?
What impacts bioavailability for a drug administration route?
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What defines bioequivalence between two drugs?
What defines bioequivalence between two drugs?
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Which factor does NOT influence drug distribution?
Which factor does NOT influence drug distribution?
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What characterizes a drug with high lipid solubility in relation to tissue distribution?
What characterizes a drug with high lipid solubility in relation to tissue distribution?
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After administration, which organs receive the highest distribution of drugs due to their blood flow?
After administration, which organs receive the highest distribution of drugs due to their blood flow?
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How does decreasing the pH affect the ionization of a weak acid?
How does decreasing the pH affect the ionization of a weak acid?
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What is the primary protein that drugs bind to in plasma?
What is the primary protein that drugs bind to in plasma?
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In biologically relevant environments, weak bases tend to be ionized when:
In biologically relevant environments, weak bases tend to be ionized when:
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What happens to a weak acid when the pH is greater than its pKa?
What happens to a weak acid when the pH is greater than its pKa?
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Study Notes
Module 1: Pharmacokinetic Principles
- Pharmacokinetics is the study of how the body absorbs, distributes, metabolizes, and excretes drugs.
- It focuses on what the body does to the drug.
Pharmacology
- Pharmacology is the study of drugs and their interactions with living organisms.
- It includes pharmacokinetics (what the body does to the drug) and pharmacodynamics (how the drug works on the body).
Drug Administration
- The route of administration (ROA) significantly impacts how quickly and efficiently a drug acts.
- Routes of drug entry are broadly categorized as enteral and parenteral.
Enteral Routes
- Enteral routes place drugs directly in the gastrointestinal (GI) tract.
- Common enteral routes include oral and rectal administration.
Oral Administration
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Advantages: Convenient, self-administration, drug absorption along the entire length of the GI tract, and cost-effective compared to most parenteral routes.
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Disadvantages: Gastric acid/juices may destroy drugs, potential GI damage, inconsistent absorption rates, too slow for emergencies, unpleasant taste/unsuitable for unconscious patients.
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Factors influencing oral absorption: blood flow, surface area, and contact time. High intestinal blood flow and large surface area leads to better absorption than from the stomach. Food and diarrhea can decrease absorption.
Rectal Administration
- Advantages: Useful for unconscious patients, nausea, and vomiting. Easy to terminate exposure, and convenient in some cases.
- Disadvantages: Variable absorption rates.
Parenteral Routes
- Parenteral routes involve injecting drugs into the body.
- Examples of parenteral routes:
- Intravascular (IV, IA): Direct injection into blood vessels. Provides 100% bioavailability, rapid onset, and allows for large dosages. But carries a higher risk of adverse effects like infection or vessel damage.
- Intramuscular (IM): Injection into muscles, often ideal for depot (sustained release) preparations. Provides rapid absorption of aqueous solutions, or slower effects for depot preparations. However, pain at injection sites are common.
- Subcutaneous: Injection beneath the skin. Enables slow, consistent absorption suitable for depot preparations, but may need to be adjusted if circulatory problems are present.
- Inhalation: Absorption of drugs through the lungs. High blood flow, large surface area, and thin membranes allow for rapid onset, but the drug delivery systems needs to be optimized.
- Topical: Application to skin or mucous membranes for local or systemic effects. Can treat specific areas for topical medication or to increase absorption for systemic medication.
- Sublingual: Administered under the tongue allowing for rapid absorption by capillaries. This avoids a possible first pass effect. But requires careful selection for the needs of the patient.
- Intraosseous (IO): Injection into bone marrow providing direct, non-collapsible access into the systemic venous system. Useful when IV access is not available or is needed quickly.
First-Pass Effect
- Hepatic metabolism of drugs occurs as they pass through the liver.
- The liver often inactivates drugs, making less drug available to the body.
- The greater the first-pass effect, the less drug will reach systemic circulation.
Drug Distribution
- Drugs are distributed throughout the body. factors affecting distribution include:
- Lipid solubility (capillary permeability): Lipophilic (fat soluble) drugs pass through membranes easily.
- Organ blood flow: High blood flow organs like liver, heart, and kidneys receive higher concentrations of drug.
- Plasma protein binding: Bound drugs are not biologically active; free drugs are available to interact with tissues.
- Depot storage: some drugs accumulate in tissues (e.g., fat) and are slowly released.
- Molecular size: Larger molecules are more likely to remain in blood vessels (e.g., heparin).
- Body fluid compartments
Volume of Distribution (Vd)
- A calculation indicating the apparent volume in which a drug is dissolved in the body.
- Assumes even distribution of drug.
- Doesn't correspond to a real volume. -Formula: Vd = Dose (mg) / Plasma Concentration (mg/mL)
Bioavailability
- The fraction of administered drug reaching systemic circulation unchanged.
- Affected by factors like first-pass effect, solubility, chemical instability, formulation.
Bioequivalence
- Drugs considered bioequivalent exhibit similar bioavailability and peak blood concentration times.
Therapeutic Equivalence
- Drugs deemed therapeutically equivalent have similar efficacy and safety profiles.
Drug Metabolism/Elimination
- The liver and kidney are the major sites of drug metabolism and elimination.
- Lipid-soluble drugs converted to more polar, excretable metabolites.
- Phase I reactions (oxidation, reduction, hydrolysis): Converts lipophilic molecules to more polar forms.
- Phase II reactions (conjugation): Add polar functional groups to make drugs more polar (and quickly excreted by the kidneys).
- Elimination routes: Urine, feces, sweat, exhaled air, mother's milk.
- Renal elimination (urine): involves filtration, secretion, and reabsorption, and impacted by urine pH and other conditions.
- Enterohepatic circulation: recirculation of drugs in bile to the intestines.
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