Npsc521P Lecture 3 Drug Molecules

Front 1

1. Describe the characteristics of small molecule drugs

Back 1

Small molecule drugs:
- Relatively low MW
- Organic, heterocyclic
- Source usually chemical synthesis
- Weak acids and weak bases
- Ionized at physiological ph

Front 2

2. Describe the ionization of weak acid drugs and weak base drugs relative to: differences between weak acids and weak bases in terms of GI tract absorption

Back 2

In general drugs have a faster onset of action and better absorption rate if they are an acid, because acids are absorbed better at low pH in the stomach.

b. Weak acids are absorbed in the stomach: in the stomach most of the weak acid is in a nonionized, acid form, it is well absorbed, it is lipid soluble, whereas weak bases are absorbed in the upper intestine: base form is nonionized, lipid soluble and is readily absorbed in the intestine.) Rule: For weakly acidic drugs, a great proportion is nonionized at pH lower than drug pKa. Weak acids such as asprin pKa=3, will be mostly nonionized in stomach (pH=1) and will be absorbed. As pH approaches neutral and above, more acidic drug becomes ionized.

c. Weak bases: weak bases such as quinine will be mostly ionized in stomach, as pH approaches neutral and above, more drug becomes nonionized and a greater amount of basic drug will be absorbed from small intestine (pH=6.8)

(See gal's notes for more in depth explanation)

Front 3

3. For large molecule drugs, describe the characteristics which differ from small molecule drugs

Back 3

- Peptides and proteins
- Very difficult to synthesize
- Produced by DNA recombinant techniques
- Degraded in GI tract
- Must be given by alternate routes
- Very expensive
- Includes monoclonal antibodies

Front 4

4. List and describe the drugs/drug dosage forms described in this series of slides:
-Tablet, caplet, capsule (gelcaps), chewable tablets, oral disintegrating tablets
-Controlled release "pills"
- solution, syrup, suspension, emulsion, tincture, elixir
- parenteral liquids
- ointments, creams, gels
- transdermal patch
- gases, aerosol inhalants, local drops, others

Back 4

-Tablet, caplet, capsule (gelcaps), chewable tablets, oral disintegrating tablets:
1. Molded or compressed powder containing drug, fillers, binders, lubricants, dissolution agents, coloring agents. Coated or Uncoated. Scored or underscored. Chewable Tablets: More rapid absorption from GI tract, faster onset of drug effect. Orally Disintegrating Tablets: More rapid absorption, faster onset
2. gelatin shell containing drug and filler, disintegrates in stomach fluids to release contents; usually opaque and colored; can also contain liquids; gelatin dissolves more rapidly

-Controlled release "pills":

- solution, syrup, suspension, emulsion, tincture, elixir

- parenteral liquids

- ointments, creams, gels

- transdermal patch

- gases, aerosol inhalants, local drops, others

See notes for answer

Front 5

5. Define drug potency

Back 5

Potency relates to amount of drug necessary to produce the effect

Front 6

6. Define drug efficacy

Back 6

Efficacy is the degree of maximum intensity of effect

Front 7

7. Differentiate between drug potency and drug efficacy with regard to the relationship between drug dose and effect

Back 7

Drug potency – a smaller dose of one drug can be given if it is more potent
Efficacy- can add more of drug A and it may never reach the levels of drug b

i.e. for d. Meperidine (Demerol) and Morphine, they are similar in efficacy because maximum effect of each is to relieve severe pain. Differ in potency because 100 mg required of meperidine while 10 mg required of morphine.