Podcast
Questions and Answers
What factor does not typically affect the initial loading dose of a medication?
What factor does not typically affect the initial loading dose of a medication?
- Properties of the medication
- Patient's age
- Volume of distribution (correct)
- Initial severity of the condition
Which of the following routes is considered a parenteral route of administration?
Which of the following routes is considered a parenteral route of administration?
- Oral
- Subcutaneous (correct)
- Rectal
- Sublingual
When should a patient with decreased clearance likely receive a lower maintenance dose?
When should a patient with decreased clearance likely receive a lower maintenance dose?
- When transitioning to oral medication
- When they have liver or renal disease (correct)
- When they demonstrate increased appetite
- When they are experiencing acute pain
Which parameter is crucial for calculating maintenance and loading doses?
Which parameter is crucial for calculating maintenance and loading doses?
What does the choice of dosing regimen primarily depend on?
What does the choice of dosing regimen primarily depend on?
Which category of administration includes routes that bypass the gastrointestinal tract?
Which category of administration includes routes that bypass the gastrointestinal tract?
What is a major consideration when choosing enteral administration for medication?
What is a major consideration when choosing enteral administration for medication?
Which of the following routes is considered topical administration?
Which of the following routes is considered topical administration?
Why should some medications not be administered perorally?
Why should some medications not be administered perorally?
What routes fall under the enteral administration category?
What routes fall under the enteral administration category?
Which statement accurately describes first-pass metabolism?
Which statement accurately describes first-pass metabolism?
What is the primary goal of topical administration?
What is the primary goal of topical administration?
Which route of administration is the least likely to be affected by first-pass metabolism?
Which route of administration is the least likely to be affected by first-pass metabolism?
What is the primary advantage of intravenous (IV) administration over oral administration?
What is the primary advantage of intravenous (IV) administration over oral administration?
What does the term bioavailability refer to?
What does the term bioavailability refer to?
How is a maintenance dose of a medication determined?
How is a maintenance dose of a medication determined?
What defines a continuous infusion regimen?
What defines a continuous infusion regimen?
For what purpose is a loading dose administered?
For what purpose is a loading dose administered?
Which of the following statements about dosing regimens is true?
Which of the following statements about dosing regimens is true?
The rate of elimination of a medication is generally equal to which of the following during steady state?
The rate of elimination of a medication is generally equal to which of the following during steady state?
How does oral administration compare to intravenous administration in terms of absorption speed?
How does oral administration compare to intravenous administration in terms of absorption speed?
Which variable directly influences the time required to reach steady state during continuous infusion?
Which variable directly influences the time required to reach steady state during continuous infusion?
What is generally true about the dosing interval in intermittent dosing regimens?
What is generally true about the dosing interval in intermittent dosing regimens?
Which of the following factors does NOT influence the maintenance dose calculation for non-IV medications?
Which of the following factors does NOT influence the maintenance dose calculation for non-IV medications?
What major factor differentiates between medications with small and large volumes of distribution when calculating loading doses?
What major factor differentiates between medications with small and large volumes of distribution when calculating loading doses?
What outcome does a single dose regimen produce in terms of plasma concentration?
What outcome does a single dose regimen produce in terms of plasma concentration?
Why might a rapid administration of a loading dose be critical in certain medical scenarios?
Why might a rapid administration of a loading dose be critical in certain medical scenarios?
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Study Notes
Routes of Administration
- Medication administration can occur through various routes: enteral, parenteral, and topical.
Enteral Administration
- The most common route, involving the gastrointestinal (GI) tract.
- Methods of enteral administration include:
- Oral (peroral): Swallowed through the mouth.
- Sublingual: Placed under the tongue for rapid absorption.
- Buccal: Administered between the gums and cheek.
- Rectal: Introduced into the rectum.
Parenteral Administration
- Bypasses the GI tract for direct entry into circulation.
- Common parenteral methods include:
- Intravenous (IV): Direct injection into a vein.
- Subcutaneous (SC): Injection under the skin.
- Intramuscular (IM): Injection into muscle tissue.
Topical Administration
- Medications applied directly to skin or mucous membranes for localized or systemic effects.
- Examples include antifungal creams for localized treatment and patches for systemic effects.
Factors Influencing Route Choice
- Chemical properties of medications, including stability and absorption barriers, impact route selection.
- First-pass metabolism occurs when medications are metabolized by the liver before entering systemic circulation, affecting efficacy.
- Medications extensively metabolized via the first-pass effect are less effective if taken orally.
- IV administration bypasses the first-pass effect, useful for unstable or poorly absorbed medications.
Bioavailability
- Defined as the fraction of a medication that reaches systemic circulation through non-IV routes.
- Oral medications may have reduced bioavailability due to absorption issues; for example, aspirin taken orally may only reach 60% bioavailability (60 mg of 100 mg absorbed).
- IV medications have a bioavailability of 100%.
Dosing Regimens
- Dosing regimens involve the frequency (dosing interval) and quantity (dose) of medication given.
Types of Dosing Regimens
- Single Dosing: One dose administered, leading to a peak and decline in plasma concentration.
- Continuous Infusion: Medication infused at a constant rate, achieving a steady state where dosing equals elimination.
- Intermittent Dosing: Doses given at intervals, causing plasma concentration to fluctuate, but reaching steady state after 4-5 half-lives.
Half-life and Steady State
- Half-life: The time it takes for plasma concentration to decrease by half.
- Steady state: Achieved when the rate of administration equals the rate of elimination, typically reached after 4-5 half-lives.
- Maintenance dose is determined based on target plasma concentration and clearance rate, with consideration for bioavailability in non-IV routes.
Loading Dose
- A large initial dose designed to quickly achieve peak plasma concentration.
- Calculated based on volume of distribution (Vd); larger Vd requires larger loading doses.
- For non-IV medications, the loading dose must be adjusted for bioavailability.
- Patients with renal or liver impairment may need lower maintenance doses but typically the loading dose remains unchanged.
Summary of Key Points
- Medication administration includes enteral (oral, sublingual, buccal, rectal), parenteral (IV, SC, IM), and topical routes.
- Route selection is based on medication properties and clinical context.
- Dosing regimens encompass single dosing, continuous infusion, and intermittent dosing based on specific pharmacokinetic principles.
- Maintenance and loading doses are influenced by bioavailability, clearance rates, and volume of distribution, especially in populations with altered metabolism.
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