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
Why do we put nicotine in an ice bath?
Nicotine is volatile, so adding acids can increase heat and cause nicotine to explode
