Questions and Answers
What is a key advantage of intravenous drug administration?
What factor affects drug absorption the most in the oral route?
Inhalation administration provides rapid access to systemic circulation primarily due to:
Which route of drug administration is notably affected by liver metabolism and the first-pass effect?
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What is a disadvantage of using rectal administration for drug delivery?
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What aspect of pharmacogenomics is critical to understanding drug metabolism?
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Which of the following is a characteristic of intravenous administration?
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Which of the following is not a benefit of sublingual administration?
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What is the primary role of metabolism in pharmacokinetics?
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Which factor does NOT influence drug passage through cell membranes?
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How does polarity affect a drug's kinetic properties?
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What mechanism primarily drives the distribution of a drug throughout body tissues?
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Which statement is true regarding the absorption of drugs from the GI tract?
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In the context of drug action, which property most directly affects membrane permeability?
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Which route of administration is likely to result in the most rapid onset of drug action?
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How does the pH of the surrounding environment impact weak acid drugs?
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Which mechanism allows drugs to be absorbed against their concentration gradient?
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What characterizes facilitated diffusion in drug absorption?
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What primarily determines the rate of drug absorption following oral administration?
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Which route of administration is least influenced by the first-pass metabolism?
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In which of the following mechanisms are large drug molecules absorbed?
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What is a primary characteristic of aqueous (passive) diffusion?
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What factor primarily influences drug absorption through the parenteral route?
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Which attribute does NOT apply to facilitated diffusion?
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Study Notes
Parenteral Administration - Intravenous
- Bioavailability achieved is 100%, bypassing first-pass metabolism.
- Allows precise control of drug levels in the bloodstream.
- Provides extremely rapid onset of effects.
- Suitable for large volume administration, especially irritant drugs.
- Immediate visible toxic reactions can occur, making it the most dangerous route.
- Must ensure drug solubility in aqueous solution.
- Dosing errors can lead to serious complications.
- Once administered, drugs cannot be extracted from the system.
Inhalation
- Rapid onset of drug action due to extensive lung surface area.
- Commonly used for volatile anesthetics.
- Enables management of local conditions such as bronchoconstriction or COPD.
- Solutions can be converted to fine droplets via aerosols and nebulizers.
Sublingual Administration
- Allows for rapid absorption through the oral mucosa.
- Venous drainage from the mouth goes directly to the superior vena cava.
- A common example is nitroglycerin.
Rectal Administration
- Absorption can be erratic, influenced by rectal vasculature.
- Useful when oral administration is impractical, as ~50% of the drug bypasses the liver's first-pass metabolism.
- May irritate rectal mucosa, making it suitable for pediatric use.
Oral Administration
- Most convenient route, allowing self-administration by patients.
- Generally considered safe, with predictable absorption variable.
- Can cause gastric irritation (e.g., Aspirin) and is ineffective during vomiting.
- Risk of drug degradation by gastric acidity can affect efficacy.
Pharmacogenomics
- Focuses on genetic variations affecting drug metabolism and individual responses to medications.
Mechanisms of Drug Absorption/Permeation
- Aqueous (Passive) Diffusion: Driven by concentration gradient, occurs spontaneously and bidirectionally.
- Facilitated Diffusion: Requires carrier proteins, can be saturated and still driven by concentration gradients.
- Active Transport: Involves energy expenditure (ATP) to move drugs against concentration gradients via specific carrier proteins.
- Endocytosis/Exocytosis: Engulfing of substances by cell membranes to transport larger molecules.
Therapeutic Window
- Refers to the range of drug dosage which can treat disease effectively without having toxic effects.
Routes of Administration of Drugs
- Drugs typically enter the body far from their target tissue and require blood transport to reach sites of action.
- Absorption rate and efficiency are influenced by the chosen route based on drug properties, patient condition, and the desired therapeutic response.
Parenteral Injections
- Intravenous (I.V.): Provides immediate drug action and precise dosage control.
- Subcutaneous (S.C.): Useful for poorly absorbed drugs, slower onset.
- Intramuscular (I.M.): Allows for rapid absorption and dosing flexibility.
- The absorption rate is determined by the solubility of the drug in interstitial fluid.
Pharmacodynamics
- Examines how drugs interact with the body, focusing on receptor binding and the resulting effects, including therapeutic and toxic responses.
- Agonist drugs activate receptors, while antagonists block action by competing for receptor sites.
Basic Pharmacokinetic Principles
- Absorption: Movement from the administration site to systemic circulation.
- Distribution: Drug movement from blood to target tissues.
- Metabolism: Conversion of drugs into active or inactive forms, often in hepatic tissues.
- Excretion: Removal of drugs from the body, primarily through kidneys.
ADME: Drug Passage Principles
- Factors influencing drug passage through membranes include molecular size, ionization degree, lipid solubility, and binding to serum or tissue components.
Physicochemical Properties of Drugs
- Polarity and lipid solubility inform drug movement and absorption.
- Gas exchange across membranes is influenced by partition coefficients, which compare solubility in aqueous vs. oil-like environments.
- Large molecular weight often hinders membrane crossing.
- Ionization impacts water solubility; uncharged drugs cross membranes more easily than charged forms.
Influence of pH
- The pH of the environment can affect the ionization state of weak acids and bases, influencing drug distribution between compartments (e.g., plasma vs. gastric juice).
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Description
This quiz explores the size of molecules and the advantages and disadvantages of parenteral administration, specifically intravenous techniques. It covers key aspects such as bioavailability, dosage control, and potential risks associated with this route of administration.
