Intro to pharmacology

Question 1

Pharmacology:

Answer 1

The study of drugs and their effects on life.

Think of drug as an exogenous chemical

The goal of pharmacology is to understand the mechanisms by which drugs interact with biologic systems.

Question 2

Absorption:

Answer 2

-drugs need to get from the site of administration to a target tissue

-Most drugs are absorbed by passive diffusion

-Some drugs use physiological transport processes

-Absorption is also dependent on the route of administration

Question 3

Effect of pH:

Answer 3

-Many drugs are weak acids or bases

-Only non-ionized forms of drugs can easily pass through a lipoid bilayer

-For orally administered drugs there are two significant pH compartments in the digestive tract

-Stomach with low pH (normally around 1)

-Small intestines with neutral pH (normally around 7)

Question 4

Biavailability:

Answer 4

The fraction of the administered dose of a drug that reaches the systemic circulation in an active (unchanged) form

Influenced by several factors

Intravenously administered drugs are 100% bioavailable by definition

Question 5

Distribution:

Answer 5

In terms of tissue targets, this is influenced by:
-Size of the organ
-Blood flow
-Drug solubility
-Protein binding

Question 6

Metabolism:

Answer 6

Aka biotransformation

The enzyme-catalyzed conversion of drugs to their metabolites

Most of this takes place in the liver, but the gut, kidneys, brain, and lungs and skin also contain drug-metabolizing enzymes.

The primary goal is to inactive or detoxify foreign substances and to prepare them for excretion

Generally, the idea is to make a xenobiotic more water-soluble so that it can be readily excreted in by the kidney’s

Not every drug needs to be metabolized to be eliminated

Not every drug is inactivated by metabolism

Prodrugs are common and are activated by metabolism

Metabolites may retain some degree of pharmacological activity (active metabolites)

Not evert xenobiotic is immediately detoxified.

Question 7

First pass effect:

Answer 7

Drugs absorbed via the gut reach the liver via the portal vein before entering the systematic circulation.

The degree to which the drug is inactivated by the liver enzymes prior to entering the systematic circulation substantially alters the drugs bioavailability.

Question 8

Phase 1 metabolism:

Answer 8

-Primary goal is to introduce or open up a binding site for hydrophilic compounds to be added later by phase II mechanisms

Oxidative reactions by far the most common

Microsomal cytochrome P450 (CYP450) system

Question 9

Phase 2 metabolism:

Answer 9

Not all drugs require phase I metabolism prior to phase II but most do

These reactions essentially conjugate a water-soluble molecule to the spot opened up by phase 1 reactions

In many instances, this means conjugating something to an available hydroxyl group

Each phase 2 mechanism has its own enzyme that catalyzes the reaction.

Question 10

Enterohepatic circulation:

Answer 10

Glucuronide conjugates are excreted in bile

Some commensal gut bacteria have glucuronidase enzymes which can cleave the glucuronide off the metabolite resulting in the parent drug being able to be reabsorbed

Question 11

Elimination:

Answer 11

Most water-soluble drug metabolites are excreted by the kidneys

Various mechanisms exit throughout the sections of the nephron

Lipid soluble drugs are excretes int he distal tubule if they’re small enough

Lipid soluble drug metabolites and glucuronide-conjugates are excreted by the liver into bile and are excreted in feces

Question 12

Pharmacodynamics:

Answer 12

Essentially the study of a drug’s mechanism of action

Drug-receptor characterization and mechanics

Signal transduction mechanisms

Question 13

Agonist:

Answer 13

a substance that initiates a physiological response when combined with a receptor.

Question 14

Antagonist:

Answer 14

a substance that interferes with or inhibits the physiological action of another substance.

Question 15

Competitive:

Answer 15

used to describe when two substances use the same binding site on a receptor

Question 16

Allosteric:

Answer 16

used to describe when a substance binds to a receptor away from an active binding site but still alters the physiological effects of

Question 17

Measures of safety:

Answer 17

Therapeutic index (TI)

LD50-dose at which causes death in 50% of individuals (animal)

ED50-dose at which causes a therapeutic response in 50% of individuals (human)

Question 18

Prescribing standards:

Answer 18

Generic name: most suitable drug name to use as it is standard across all jurisdictions

Brand name: registered trademarked name of a drug used in marketing

Example: atorvastatin vs Lipitor

Question 19

Prescribing requirements:

Answer 19

-date
-name and address of patient
-name, strength, quantity and form of drug or ingredient(s)
-Directions for use (include frequency or interval or maximum daily use)
-Refill authorization (number and interval between refills)
-Name and college ID of practitioner
-Signature of practitioner

Question 20

Prescribing standards:

Answer 20

It is generally advised to write full words as much as possible and to avoid abbreviations

-Never abbreviate the drug name

-Use generic names unless you specifically want a brand name drug dispensed

Question 21

Drug charting:

Answer 21

-Date
-Related subjective and objective symptoms
-Assessment
-Purpose and/or goal(s) of medication(s)
-Name, dose, dosage form and quantity of medication prescribed
-Monitoring plan
-Informed consent
-Signature