Download Bimm 118 Worksheet #2

Bimm 118 Worksheet #2
TA: John Diep
For #1 and #2; answer in terms of hydrophilicity/lipophilicity of drug and base.
1. For percutaneous drugs, which formulation provides the best absorption? Explain.
Lipophilic Drug in Hydrophilic Base – best absorption
-drug readily separates from base and can penetrate lipophilic membranes of the
body
2. What is the most suitable formulation for a sun block lotion? Explain.
Hydrophilic Drug in Lipophillic Base – Hydrophilic drugs cannot be absorbed thru the skin
-the drug and base will separate; but drug remains on skin surface
-base acts as an occlusive covering
Examples: waterproof sun block/tan lotion, neomycin
3. What determines the site of drug delivery for nebulizers (pulmonary meds)?
Size of aerosol determines the site of drug delivery in the respiratory tract
>100um: nasopharynx
10-100um: trachea and bronchii
<10um: bronchioli and alveoli
-small particles penetrate deeper in the respiratory tract
4. List the 4 requirements for parenteral drugs.
1. Sterility – clean; free of microbes
2. Iso-Osmolar – same osmolarity as blood; to avoid lysing blood cells
3. Pyrogen-Free – see #5
4. pH 7.4 – must be at blood pH
5. What is meant by “Pyrogen-free”?
Pyrogen-Free – cannot contain particles that may induce fever
Ex. LPS or Lipopolysaccarrides are components of the outermembrane of gram negative bacteria
that elicits a strong immune response triggering a release of pro-inflammatory cytokines….Fever
6. List the three types of membrane permeation in terms of drug distribution. Which one is the
most common?
Passive Diffusion (most common)
Active Transport – drug uses cellular transporters
Receptor-mediated Endocytosis
7. Explain the concept/mechanism for “ion trapping”.
Ion Trapping
The drug will be in equilibrium between its ionized and unionzed form (if it’s a weak acid/base).
-The compartment pH determines whether it will mostly be ionized or unionized
In its unionized form, the drug can pass thru to the adjacent compartment
-it will reach an equilibrium between its ionized/unionized form in this new compartment
-if the ionized form is dominant in this compartment, then it will become “trapped”
(Refer to Henderson-Hasselblach Equation and Passive Diffusion/Equilibrium)
Lecture#2 Slide Title: “Drug Distribution” under “Membrane Permeation”
8. What urine pH (alkaline or acidic) would favor the excretion of Aspirin (a weak acid)? Why?
Alkaline urine. Based on the Henderson-Hasselblach Eqn., under basic conditions, there will be
more ionized Aspirin. As such, it will remain in the urine compartment after diffusion from the
plasma due to the ion trapping effect.