Week 2 - Pharmacokinetics - Review Questions Flashcards
Compare different routes of administration and their reason for use.
- PO is easiest and most common
- IV is quickest and can deliver large amounts over time (infusion)
- IM or Subcut is used for slower rate
What routes are required for specific sites?
- Inhalation for respiratory
- Epithetlial for skin, cornea, nasal mucosa
- Subling for rapid absorption into systemic circulation, bypass liver
- Rectal for GI or when PO/IV not possible
How will drug lipid-solubility affect absorption and distribution?
- Higher lipid-solubility = faster absorption across membranes
- High lipid-soluble distribute throughout body
- Low lipid-soluble/insoluble distribute in plasma and interstitial fluid
Contrast effects of pH on absorption of drug from different area of GI tract.
- Acidic drug (Aspirin pH3.5) absorbed in the stomach
- Basic drug (Atropine pH9.8) absorbed in the small intestine
A drug has a Vd of 10, what is its distribution and what are the consequences?
- Accumulate in the fat
- Stay in te system for longer
Define “first pass metabolism”
Drug may be substantially metabolised during first passage through the liver before entering systemic circulation.
Define the Single Compartment Model
The body is a single well-stirred compartment
Define First Order Kinetics
Rate of excretion is dependent on drug [plasma]
What are two types of reactions that occur between drugs as a result of their pharmacokinetic properties?
- Elimination rate and half-life can determine rate of repeated dose
- If drug [plasma] not decreased or not cleared, the amount absorbed will add on to the current amount. Until rate of elimination = rate of absorption; and plateau achieved.
Why is Aspirin absorbed in the stomach?
Aspirin takes uncharged form to get through charge selective membrane, and changes to charged form to stay in blood.
What is ADME of Pharmacokinetics?
Administration/Absorption
Dsitribution
Metabolism
Excretion
Define the Two Compartment Model
Central compartment = Plasma
Peripheral compartment = Bodily tissues
Ethanol Absorption
Rapidly absorbed from the stomach and intestines
Ethanol Distribution
- Lipid-soluble; quick distribution
- Rapid absorption and high portal vein [ ]
= large amount of systemic circulation - Slow absorption
= high 1st pass metabolism in liver
Ethanol Metabolism
- Dehyrdogenase cycle
- Larger % cleared by1st pass metabolism
- 90% metabolised
- Metabolism reduced due to limited cofactor (NAD+) {10drinks need 1.5kg NAD+}
- 0.5kg ethanol removed at 8g/hr (long)
