1 - Administration / Absorption / Distribution

Question 1

These cannot act at target sites, nor can they be metabolized. This affects 3 aspects of drug action:

Answer 1

Drug molecules that are bound to inactive depots, including plasma proteins.

• onset
• duration
• magnitude

Question 2

Movement of the drug from the site of administration to the blood circulation. Some is taken in by stomach, but most drugs not fully taken in until they reach small intestine.

Answer 2

Absorption

Question 3

A drug rarely acts where it contacts the body. Process by which drug must pass through variety of cell membranes to enter blood plasma, which transports it to virtually all of the cells in body.

Answer 3

Absorption and Distribution

Question 4

Absorption is dependent on (4)

MISI

Answer 4

• MOA (movement to circulation influenced by factors like type of/food in stomach, physical activity, etc.
• ionizatoin of the drug
• solubility
• individual differences in age, sex, and body size

Question 5

Acid / Base and Drug Absorption

Answer 5

Substances most fat-soluble (least ionized) absorb in solutions with pH most like their own

* Feces is a bit basic

Question 6

Once in blood plasma, some drug molecules move to tissues for ___ to active target sites/receptors. While in the blood, a drug may also attach to plasma proteins (called ___ ___ ) or may be stored temporarily in bone or fat, where it remain inactive.

Answer 6

Binding | Depot Binding

Question 7

The amount of drug in the blood that is free to bind at specific target sites to elicit drug action.

Answer 7

Bioavailability

Question 8

This limits drug concentration in the CNS. It is formed by specialized capilaries that have few pores to allow drugs to leave the circulation.

Answer 8

Blood Brain Barrier

Question 9

Drug Absorption Factors (5)

Answer 9

• Lipid bilayers (phospholipid membranes) keep charged (ionized) molecules out of the cell and allow fat-soluble (non-ionized) substances into cells (passive diffusion)
• Concentration gradient determines the rate of diffusion into cells
• Simple diffusion is how cells “breathe” (oxygen in, carbon dioxide out)
• Rate of passage through cell walls — More/faster movement to where there is less of the substance
• Drug redistribution: As plasma levels fall, drug concentration in highly vascularized organs will be greater than in the blood, so the drug will move from those organs back into the plasma to maintain equilibrium.

Question 10

Drug Action

Answer 10

Molecular changes produced by a drug when it binds to a target site or receptor.

​*The site of drug action may be different from the site of the drug’s effects.

Question 11

Methods of Administration (8)
SORT IIII

Answer 11

• Subcutaneous (popping)
• Oral (subject to First Pass Metabolism)
• Rectal (Low in rectum / hemorrhoidal vein skips first pass metabolism)
• Transdermal
• Intramuscular
• Intravenous
• Inhalation
• ​Intranasal (bypasses blood-brain barrier; e.g., powder cocaine)

Question 12

Drug Effects

Answer 12

The alterations of physiological or psychological functions caused by those molecular changes.

*The site of drug action may be different from the site of the drug’s effects.

Question 13

Oral and rectal routes of administration are ________ because they involve the gastrointestical tract; all other methods are called ________

Answer 13

Enteral | Parenteral

Question 14

Used when spinal anesthetics are administered directly into the cerebrospinal fluid surrounding the spinal cord of a mother during childbirth, bypassing the blood–brain barrier.

Answer 14

Epidural Injection

Question 15

Interacting pharmacokinetic factors that determine free drug quantity in blood (5)

Answer 15

• Method of administration,
• Rate of absorption and distrubution,
• Binding at inactive sties,
• Biotransformation/Metabolism
• Excretion

Question 16

Implanted under skin of scalp and programmed to deliver constant dose of antibiotic into cerebral ventricle. Permits treatment of brain infection and useful because antibiotics are normally prevented from passing blood–brain barrier.

Answer 16

Infusion Pump

Question 17

Injected directly into the cerebrospinal fluid–filled ventricles. Experimenters can study electrophysiological, biochemical, or behavioural effects of drugs on particular nerve cell groups.

Answer 17

Intracerebro-Ventricular Injection

Question 18

A microsyringe or a cannula enables precise drug injection into discrete areas of brain tissue.

Answer 18

Intracranial Injection

Question 19

Alternative to IV injection; provides slower more even absorption over time. Can be slowed by combining drug with 2nd drug that constricts blood vessels. Slower sustained action by injecting drug in suspension of vegetable oil.

Answer 19

Intramuscular Injection (IM)

Question 20

Drug injected through abdominal wall into peritoneal cavity around organs. Rapid effects but not as rapid as IV injection. Variability in absorption, depending on whereexactly drug is placed.

Answer 20

Intraperitoneal Injection (IP)

Question 21

Most rapid, accurate method of drug administration. A precise quantity of agent is placed directly into blood and passage through cell membranes such as stomach wall is eliminated. Quick onset of drug effect is a potential hazard since drug cannot be removed from body (as with stomach pumping).

Answer 21

Intravenous (IV)

Question 22

Only these drugs can readily enter the brain.

Answer 22

Lipid Soluble

Question 23

Drugs with high lipid solubility (not ionized) move through cell membranes by passive diffusion, leaving the water in the blood or stomach juices and entering lipid layers of membranes.

Answer 23

Lipid-Soluble Drugs

Question 24

Method of Aministration influences absorption because (3)

Answer 24

• determines the area of the absorbing surface,
• number of cell layers through which the drug must pass,
• extent to whcih first-pass metabolism affects drug

Question 25

Each method of administration provides advantages and disadvantages involving (6)

Answer 25

• rate of onset,
• level of drug acheived in blood
• duration of action
• convenience
• safety
• special uses

Question 26

Pharmacokinetic factors determing drug action & bioavailability (5)

Answer 26

1. Administration: drug moves through cell membranes into blood
2. Absorption and Distribution; circulates to all cells in body.
3. Binding: Some drug molecules may bind to active target sites (receptor). May also bind to inactive sites such as plasma proteins or storage depots (depot binding) or stored temporarily in fat or bone (inactive). Blood-borne drug molecules also enter liver for…
4. Inactivation (biotransformation), (primarily a result of metabolic process) where they may be transformed into metabolites and travel to kidneys and other discharge sites for excretion. Inactivation influences both intensity and duration of drug effects.
5. Excretion in feces, urine, water vapour, sweat, and saliva.

Question 27

the pH value of a solution that would maintain ionization of half of the molecules of a drug

Aspirin = ______

Answer 27

pKa Value

pKa of Aspirin = 3.5 (50% ionized and 50% non-ionized)

Question 28

Separatees maternal circulation from fetal circulation but does not impeded passage of most drug molecules.

Answer 28

Placental Barrier

Question 29

Drug-filled suppository placed in rectum to dissolve. Depending on placement, drug absorbed from lower rectum into hemorrhoidal vein may bypass First Pass Metabolism. Deeper placement absorbed by veins drains to portal vein, then to liver. Bioavailability difficult to predict and absorption is irregular. Effective route for infants and those vomiting, unconscious, or unable to take orally.

Answer 29

Rectal Administration

Question 30

Route of administration determines (2)

Answer 30

• Onset
• Duration of Drug Action

Question 31

How and where a drug is administered. Determines how quickly and how completely it is absorbed into blood.

Answer 31

Route of Administration

Question 32

Drug injected below skin and absorption dependent on blood flow to site. Absorption usually slow/steady but variability occurs. Rubbing skin dilates blood vessels and increases rate of absorption. Injection of a drug in a nonaqueous solution (peanut oil) or implantation of a drug pellet further slows rate of absorption.

Answer 32

Subcutaneous (SC)

Question 33

Application involves placing drug under tongue, where it contacts mucous membrane and is absorbed rapidly into a rich capillary network. It is not broken down by gastric acid / enzymes. Absorption is directly into blood and not dependent on how quick stomach empties into small intestine. Not absorbed from the GI tract and avoids First-Pass Metabolism.

Answer 33

Sublingual (topical)

Question 34

Involves application to nasal mucosa (mucous membrane) by sniffing powder or nasal spray. Drug moves rapidly across a single epithelial cell layer into bloodstream, avoiding First-Pass Metabolism and producing higher bioavailability than if taken orally.

Answer 34

Intranasal (topical)

Question 35

Drug rapidly absorbed into blood by passing through lungs. Pulmonary absorbing surface is large and rich with capillaries. Effect on brain very rapid because blood from capillaries of lungs travels a short distance back to heart before being pumped quickly to brain via carotid artery. Preferred method for self-administration when oral absorption is slow. Avoids destruction of drug in GI tract.

Answer 35

Inhalation (topical)

Question 36

Patches provide controlled and sustained delivery of drug by absorption through skin at a preprogrammed rate. Reduces danger of needle sticks / unsafe used needle disposal. Used for motion sickness (scopolamine), cigarette craving (nicotine), angina pectoris (nitroglycerin), and hormones after menopause or for contraception. Limited drugs work via this method because skin is designed to keep things out.

Answer 36

Transdermal

Question 37

A _____ is a delivery system used to carry a gene into the nuclei of target cell in order to alter protein synthesis. They are usually injected directly into the brain region targeted for modification.

A _____ _____ is often considered because of their special ability to bind to and enter cells / nuclei but this process may carry risks.

Answer 37

Vector | Viral Vector

Question 38

Volume of blood flow to the tissue…

Answer 38

affects Drug distribution

Question 39

Drugs that are weak acids tend to remain ___ ___ or ___ ___ in acidic body fluids such as stomach juices. They are more readily absorbed there than in the more ___ intestinal fluid.

Answer 39

Non-Ionized or Lipid Soluble | Alkaline

Question 40

Drugs that are weak bases are more ___ in acidic body fluids such as stomach juices. They are less readily absorved there than in the intestine, which is more ____ and where ___ is reduced.

Answer 40

Ionized | Basic | Ionization