Chapter 5 Actions and Metabolism

Question 1

Chemical name

Answer 1

assigned by IUPAC; describes the chemical structure of the drug

Question 2

Generic name

Answer 2

the name for that drug, no matter who is making it

Question 3

Trade name

Answer 3

chosen by the drug company; is trademarked and only the holder of the trademark can use it. the appearance of a drug can also be trademarked

Question 4

Issue of placebo effects

Answer 4

• some response to therapeutic drugs is a placebo effect
  -placebo effects are particularly common with drugs for depression, anxiety and pain
• some research suggests that subjects using an antidepressant will see continued effects, compared to placebo users
• there can also be a “nocebo” effect

Question 5

LD50

Answer 5

the estimated lethal dose in 50% of the population

Question 6

therapeutic index (TI)

Answer 6

• the LD50/TD50
• you want the TI to be larger
• a bare minimum of safety; drugs can have adverse effects at doses well below the LD50 so there is more focus on the safety margin

Question 7

Potency

Answer 7

refers to the dose that produces an effect, not the degree of effect
- LSD and fentanyl are very potent, alcohol is not

Question 8

Efficacy

Answer 8

the degree to which a drug or neurotransmitter activates the receptor when bound

Question 9

Affinity

Answer 9

how tightly the drug or neurotransmitter binds to the receptor

Question 10

Four basic processes of drug pharmacokinetics

Answer 10

Absorption, distribution, metabolism, and elimination

Question 11

Absorption

Answer 11

• refers to the entry of the drug into the body
• anything in the bloodstream can only enter the brain by crossing the blood-brain barrier
• drugs are bound to proteins in the bloodstream to some degree; a bound molecule cannot cross the BBB, so a drug that binds readily to proteins may not be distributed well into the brain

Question 12

Distribution

Answer 12

• a drug that binds strongly to proteins can displace another drug with weaker binding
• distribution to a tissue is largely a function of blood supply and tissue proteins
• tissue that has a good blood supply will tend to get more drug than poorly vascularized tissue
• a very lipophilic drug such as THC will be absorbed into fat and preferentially stored there

Question 13

Metabolism

Answer 13

• typically a function of the liver
• most drugs are broken down by CYP-450 enzymes
• anything that increases or decreases activity of these enzymes will affect drug metabolism
• there are very few drugs that aren’t metabolized and are excreted unchanged
• the drug taken is the parent drugs
• Primary metabolite(s): the result of the first round of metabolism
• Secondary metabolite: happens if the primary metabolite isn’t the final metabolite

Question 14

Elimination

Answer 14

• a drug must be at least somewhat lipophilic to pass the blood-brain barrier to enter the brain
• most drugs are ultimately cleared in urine, which is definitely not a lipid
• when a drug is metabolized it is usually broken down into successively hydrophilic metabolites and eventually passes into the urine
• many drugs are also excreted via the sweat, breath and feces, but usually in small quantities.

Question 15

Half-life

Answer 15

used to indicate how fast the drug is metabolized
- the time it takes for half of the original dose of the drug to be removed
- if you take the drug at every half-life, you will reach a fairly steady state of drug levels by about 4 half-lives

Question 16

Routes of administration

Answer 16

• oral
• injection (intravenous, intramuscular, subcutaneous, intrathecal/epidural)
• inhalation
• mucous membranes (oral/nasal mucosa, anal, vaginal)
• dermal
• not every drug can be given by all routes