Phamacological Principles - Pharmacokinetics Flashcards
Pharmacokinetics
How the body interacts with administered drugs until it leaves the body
Absorption
Movement of drug from site of administration into the bloodstream. Once it is in the bloodstream, it can circulate throughout the body
What is the enteral route of administration?
Route of administration through the oral cavity and will go through the GI tract
First-Pass-Effect
The metabolism of a drug leading to lower concentration of active drug in the circulatory system and thus target tissues. It inactivates >90% of orally administered drugs and very minimally will it activate a drug
What are the 2 types of enteral route?
- Mouth - its absorption site is the mucosa of stomach, small intestine, or large intestine. Its metabolism site is the liver via portal vein. It undergoes the First-Pass-Effect
- Sublingual/Buccal - its absorption site is the vascularized tissue of oral mucosa. It does not have a metabolism site, therefore, FPE doesn’t occur
What 5 factors affect absorption in the enteral route?
- Stomach acidity
- Stomach motility
- Changes in intestinal mucosa
- Blood flow to the stomach or intestine
- Food and liquid
Bioavailability
The amount of active drug absorbed into the circulatory system and thus target tissue
What is the clinical implication of FPE and bioavailability?
A high FPE indicates a higher dose of the medication to allow for better availability
What is the purpose of enteric coating? What happens if the stomach is too acidic?
It protects the stomach wall and allows for dissolution and absorption of drugs to take place in the intestine
If the stomach is too acidic, decreased absorption in the intestine occurs
Advantages and disadvantages of the oral route (enteral) and their clinical implications
Advs:
- Easier and more convenient to administer
- Safer than injection and easier to reverse accidental ingestion
Disadvs:
- Variable absorption
- Inactivation of some drugs by stomach acid
Nursing Considerations:
- Involves a variety of dosage forms (ex. liquids, solutions, tablets, enteric-coated)
- Some need to be taken with food, others not
- What other medications is the patient taking?
Advantages and disadvantages of the sublingual/buccal route (enteral) and their clinical implications
Advs:
- Absorbed more rapidly from oral mucosa than oral route
- More rapid onset of action
- No breakdown of drug by stomach acid
- No FPE
Disadvs:
- Patient may accidentally swallow pill as it needs to be dissolved under tongue/cheek
- Need salivary secretions
Nursing Considerations:
- Sublingual: needs to be placed under the tongue
- Buccal: needs to be placed between the cheek and gum
What is the parenteral route of administration?
Any route of administration other than the GI tract
What are the 4 types of parenteral route?
- Intravenous (IV) injection - injected directly into the circulatory system
- Intramuscular (IM) injection - absorption through the vasculature of the muscles
- Subcutaneous (SC) injection - absorption through the vasculatur of the SC tissue
- Intradermal injection - absorption through the vasculature of the dermal tissue
No method undergoes the FPE
What 4 factors affect absorption in the parenteral route?
- Temperature
- Messaging
- Blood pressure
- Peripheral circulation
What are the clinical implications of the parenteral route?
- Great for when the patient cannot take a drug orally (ex. nausea and vomiting, or lack of swallowing reflex)
- Fastest route of absorption; great for immediate effects
- Requires immediate and close monitoring of both positive and negative drug impacts
Advantages and disadvantages of the IV route (parenteral) and their clinical implications
Advs:
- Rapid onset
- Able to directly control drug level in blood
- Allows for larger fluid volume
- Avoid FPE
Disadvs:
- Higher cost
- Inconvenience
- Fluid overload (too much volume in body, affecting perfusion)
- Risk of infection
-Possibility of air embolism
- Difficulty to reverse drug effect
Nursing Considerations:
- If continuous infusion, need frequent monitering
- Need to always check for compatibility
- Need to always monitor for site of administration
Advantages and disadvantages of the SC route (parenteral) and their clinical implications
Advs:
- Allows for slow, sustained absorption. Allows for prolonged effect
Disadvs:
- Discomfort of injection
- Inconvenience
- Bruising
Nursing Considerations:
- Need to landmark site of administration
Advantages and disadvantages of the IM route (parenteral) and their clinical implications
Advs:
- Absorption can be longitudinal
- Onset of action will differ
Disadvs:
- Discomfort of injection
- Inconvenience
- Bruising
Nursing Considerations:
- Need to landmark site of administration
What is the topical route of administration?
Administration through body surfaces
What are the 7 types of topical route?
- The skin, eyes, ears, nose, lungs, and vagina all have their absorption site in the capillaries that feed into the tissue. No FPE
- The rectum has its absorption site in the capillaries that feed into the tissue and/or the capillaries that feed the portal vein. Has mixed FPE and non-FPE absorption and metabolism
What factor affect absorption in the topical route?
Perfusion to the site
Distribution and what 4 factors is it impacted by?
The journey of the drug through the bloodstream until it reaches the target tissues and cells
Impacted by:
1. Plasma proteins (ie. albumin). Drugs bound by albumin are inactive as it cannot enter cells. This impacts the conc. of active drugs
2. Competing drugs
3. BBB
4. Blood-placental barrier
Clinical implications of plasma proteins (ie. albumin)
- Drugs bound to albumin are pharmacologically inactive
- Low levels of albumin means increased concentration of pharmacologically active drugs, thereby increasing possibility of drug toxicity
- Low levels of albumin may be due to liver dysfunction, malnourishment, and severe burns
- Albumin is made by the liver
Metabolism
The process by which the drugs are modified (bio-transformed) from its original form to either:
- A more soluble compound
- An inactive metabolite
- A potent metabolite
- Less active metabolite by enzymes
