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Pharmacology: Receptors Lecture

Terms in this set (81)

The uncharged weak acid (HA) and the uncharged weak base (B) penetrate the cell membrane; the charged forms A- and BH+ do not.
4. The concentration of the forms on either side of a membrane is determined by the relative concentration of charged vs. uncharged forms, which is, in turn, determined by the pH at the site of absorption and the pKa
5. pKa is a measure of the strength of the acid or base; the lower the pKa the stronger the acid; the higher the pKa the stronger the base
6. The relationship between pKa and pH is expressed by the Henderson-Hasselbalch equation:

[Non-protonated form]
Log ---------------------------- = pH - pKa
[Protonated form]

[A-]
Log ------- = pH - pKa For acids
[HA]

[B]
Log ------- = pH - pKa For bases
[BH+]
The uncharged weak acid (HA) and the uncharged weak base (B) penetrate the cell membrane; the charged forms A- and BH+ do not.
Drug Scheduling:
What is C-I's abuse potential and what are examples of it?
Abuse potential: High
Examples: Illegal drugs like heroin, LSD, marijuana, mescaline, and phencyclidine (PCP)
Drug Scheduling:
What is C-II's abuse potential and what are examples of it?
Abuse potential: High
Examples: Morphine and Methylphenidate
Drug Scheduling:
What is C-III's abuse potential and what are examples of it?
Abuse potential: Moderate
Examples: Codeine mixtures like Tylenol #3
Drug Scheduling:
What is C-IV's abuse potential and what are examples of it?
Abuse potential: Less
Examples: Benzodiazepines
Drug Scheduling:
What is C-V's abuse potential and what are examples of it?
Abuse potential: Less
Examples: Some codeine-containing cough syrups
***__________ elicit a biological response when bound by an agonist.
True receptors elicit a biological response when bound by an agonist.
Most drugs interact with a receptor. Give examples of receptors.
Receptors may be membrane proteins, cytoplasmic or extracellular enzymes or a nucleic acid.
A drug may show tissue __________ for the receptor; ex: drug may show selective actions on cardiac compared to pulmonary tissue.

Many receptors are distributed unequally among various organs. Some drugs may not bind to receptors
selectivity
What is the Receptor Ligand Binding Theory?
1. Drug molecule and biological target must come together (don't act at a distance)
2. The interaction between drug and receptor must result in selective binding of drug to biological target before a response can take place
3. Most receptors are proteins:
a) proteins undergo three dimensional structure changes
b) proteins have spatially and energetically favorable molecular domains for binding
Most receptors are _________.
proteins
Drug molecule and biological target must ____________.
come together (don't act at a distance)


This activity has to be selective. It has to bind to the specific receptor you want the response from.
What are Inert Binding Sites?
Inert Binding Sites are where a drug can bind but won't have a biological response.

Many drugs can bind to nonregulatory molecules such as plasma proteins which results in no detectable changes in function of the biological system. These molecules are called inert binding sites and affect the distribution of the drug and the amount of free drug available to bind to the receptor.


Ex. Plasma protein like albumin: A drug can bind to albumin but it doesn't cause a response from that drug.
Drug receptor interactions are a result of concerted effect of various bonds.

The initial bond is often _________.
ionic

so the fraction of drug ionized is important.

Drug ionization is determined by Henderson-Hasselbalch equation (also important for absorption and distribution of drug; discussed in a later section)
Nature of Drugs:
What are two characteristics of drugs?
1. Physical characteristics
2. Drug Size
3. Drug reactivity and bonding
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