6 - Nicotine Flashcards
What receptors does nicotine bind to and where? What effects does it have?
- Binds stereo-selectively to nicotinic-cholinergic receptors in the brain
- Has stimulating (low doses) and rewarding (high doses) effects
How much nicotine do cigarettes contain and how much is absorbed?
- Contain 8-20 mg
- 1 mg is absorbed
How is nicotine absorbed from the patches and gum? Describe it
- Drug diffusion
- Passive process to achieve controlled delivery
- Transfer of molecules of a substance along a concentration gradient
Passage through a barrier occurs by ____ (example ____)
- Occurs by permeation or through pores
- Ex: polymeric matrix in the patch
Describe Fick’s law
- Correlates amount of material going through a barrier with time and speed
- Diffusion occurs in the direction of decreasing concentration
- Diffusion coefficient changes at higher concentrations and is affected by temp, pressure, and solvent properties
What happens at the beginning of diffusion? What does this correlate with?
- Molecules move from high to low concentration until they reach steady state (flux becomes constant)
- Ability to reach this release rate decides how fast the drug is absorbed across the skin and how long Css is maintained
What is chromatography used for?
- Quality control
- Research
Examples of chromatography
- Paper
- Thin-layer
- Gas
- High-performance liquid
Describe chromatography
- Procedure by which a solute is separated by a migration process in a system of 2 or more phases
- One phase moves continuously in 1 direction (mobile) and substances show differences in mobility based on adsorption, partition, solubility, vapor pressure, MW, and charge in stationary phase
- Mobile phase transfers solute through medium until constituents are eluted
Is chromatography useful for qualitative or quantitative analysis?
Both
___ chromatography is best for separation of individual components
Column
Which chromatography types allow for precise quantitative measurement?
HPLC and gas
Describe TLC
- Finely powdered material applied to glass/ plastic/ metal plate and acts as open column
- Micropipette used to spot the plate
- Plate is placed in a developing chamber w/ solvent (mobile phase)
- Can view the spots w/ reagent sprayer or UV light source
- Observe spots of identical retention factor (Rf) values to compare to standards based on migration distances
Describe HPLC
- Pumping system mixes mobile phase in the column and an injector introduces the samples
- Analytes are separated and eluted on a column and recorded by a device
Describe the purpose of ferric ammonium sulfate
- Ferric ammonium sulfate changes from gold to dark purple when it contacts sodium salicylate
- Ferric ammonium sulfate added into gelatin base so we can observe colour change when sodium salicylate in various dosage forms contacts it
- Used powder, 0.5 g dissolved in 1 mL water, 1.0 g dissolved in 1 mL water, and 1 g in lotion
What was the nicotine gum mixed with? Where was the aliquot taken from?
- 50 mL hexane and 50 mL solvent
- Aliquot taken from lower layer (hexane portion?)
How do you calculate Rf value?
Distance test or standard travelled from its origin (cm) / distance solvent travelled (cm)
What was used in the developing solvent for the TLC?
Chloroform, acetone, and diethylamine
Describe the methods for TLC
- Weigh one piece of gum and cut
- Transfer 2 mg to centrifuge tube and add chloroform
- Vortex for 15 min to dissolve and centrifuge for 10 min
- Cool in ice bath and add HCl; shake and centrifuge again
- Transfer upper layer to separatory funnel and adjust w/ NaOH to pH > 10
- Add chloroform, shake, and use chloroform layer as test solution
Drug absorption through a biological membrane relies on ____
Passive drug diffusion along a concentration gradient
What is diffusion?
- Process of mass transfer of individual molecules brought about by random molecular motion and associated w/ a concentration gradient
- Passage of matter through a barrier may occur by simple molecular permeation or movement through pores and channels
Which types of chromatography are best for substance identification and why?
- Paper and thin-layer
- Assay convenience and simplicity
What are the components of a TLC assay?
- Plate (stationary phase) that is coated w/ adsorbent material
- Developing chamber and developing solvent (mobile phase) that separates components to be analyzed
- Micropipette to deliver samples to the plate
- Reagent sprayer that emits a fine spray of chemical reagents to reveal the spots
- UV light source to visualize the spots
Components of an HPLC system
- Pumping system that mixes and delivers mobile phase to the column
- Injector that introduces samples to the system
- Column on which analytes are separated and eluted
- Detector that quantitatively determines analytical interests
- Data collection device that records and compares the chromatographic results
