Lecture 2: Pharmacokinetics & Dynamics

Question 1

4 Processes of Pharmacokinetics

Answer 1

1. Absorption
2. Distribution
3. Metabolism
4. Excretion

Question 2

Diffusion or Passive Transport

Answer 2

• Usually small, nonionized, or lipid-soluble molecules

- People in a crowded room, “passively” spilling into the hallways

Question 3

Active Transport

Answer 3

• Usually large, ionized, or water-soluble molecules

- People “pushing” their way into our crowded pharmacology classroom

Question 4

Absorption

Answer 4

• Movement from site of administration to circulating fluids

- Primary factor determining length of time for effect of drug to occur

Question 5

Factors Affecting Drug Absorption

Answer 5

• Route of administration
• Drug formulation
• Drug dosage
• Digestive motility (if givenPO)
• Digestive tract enzymes (if given PO)
• Blood flow at admin site (IM or Subcut)
• Degree of ionization of drug
• pH of surrounding environment (PO)

Question 7

Distribution

Answer 7

Medications are distributed by Blood

• Greater blood flow to area, higher concentration of drug is delivered
• IV vs. IM vs. Subcut

Question 8

Enterohepatic Recirculation

Answer 8

• Drugs excreted in bile
• Bile recirculates to liver
• Prolongs activity of drug

Question 9

Excretion

Answer 9

Primary site of excretion of drugs is kidneys.

-Secretion mechanism is less active in infants and older adults

Question 10

Excretion

-Renal failure

Answer 10

• Drugs retained for extended times
• Dosages must be reduced

-Must avoid any nephrotoxic drug, but all drugs should be monitored and doses lowered.

Question 11

Serum Peaks and Troughs

Answer 11

• A serum trough level is drawn about 30 minutes prior to your next dose of the medication. This will show the amount of the drug at its lowest level in your system
• The peak level is usually drawn 30 minutes after med admin if in IV form or about an hour or two if orally. The peak shows the medication at its highest level in your system .

This allows the doctor to maintain a safe level of medication in the system

Question 12

Median Effective Dose (ED50)

Answer 12

Dose that produces therapeutic response in 50% of a group

Many clients require more or less

Question 12

Absorption

-Food

Answer 12

food increases the pH of the stomach
food can SLOW absorption

Drug-drug interactions can compete for absorption
Herbs can make a difference in absorption

Question 13

Barriers affecting drug distribution

& Capillary beds

Answer 13

Blood-brain barrier
fetal-placental barrier

Drug-protein complexes make the drug to large to pass through capillary beds or cells

Question 14

Drug-Protein Complexes

Answer 14

These complexes are too large to cross capillary membranes; thus the drug is not available for distribution to body tissues.

Only unbound (free) drugs can reach their target cells or be excreted by the kidneys.

Question 15

Considerations for Pt’s w/ Low Albumin

• Albumin 2.1
• Total protein 3

Answer 15

If a pt has low albumin levels and overall protein levels drugs will not bind with protein complexes.

The drugs should be given in lower doses
Pts should be monitored for adverse signs

Question 16

Metabolism

Answer 16

The liver is the primary site of drug metabolism

Question 17

Hepatic microsomal enzyme system

-P-450 system

Answer 17

Most metabolism in the liver is accomplished by the hepatic microsomal enzyme system. This enzyme complex is sometimes called the P-450 system.

Question 18

First-pass effect

Answer 18

Drugs taken orally can cross directly into the hepatic portal circulation, which carries blood to the liver before it is distributed to other body tissues.

Some drugs can be completely metabolized to inactive forms before they reach circulation.

Question 19

Enterohepatic recirculation

Answer 19

Some drugs are secreted in the bile, a process known as biliary excretion. Most bile is circulated back to the liver by enterohepatic recirculation

This can increase the half-life of the drug significantly.

Question 20

Blood Flow and Excretion TEST ?

Answer 20

If there is low blood flow to the kidneys, excretion will be adversely effected and drugs can create toxicity in ALL DRUGS.

BUN
Creatinin

Question 21

People that might develop toxicity more easily w/ excretion??
TEST QUESTION

Answer 21

Kidney disease
Liver disease
Low protein in blood stream

Question 22

pH and Urine TEST

Answer 22

Kidneys will excrete medication faster if it is the OPPOSITE pH of the urine.

A drug that is basic in acidic urine will lead to faster excretion

Question 23

Oral medication and Constipation?

Answer 23

Increase absorption

Question 24

Diarrhea and oral medication

Answer 24

decreased absorption because it won’t spend enough time in the GI

Question 25

High Protein Levels and Meds

Answer 25

Increase dose of medication due to drug protein complex.

If there is low protein…
decrease dose of medication

Question 26

Empty Stomach and Med

Answer 26

Makes the stomach more Acidic

Acidic drugs will be absorbed more readily

Question 27

Plasma Half-life

Answer 27

Length of time required for the plasma concentration of a med to decease by half after admin.

Question 28

Therapeutic range

Answer 28

The plasma drug concentration between the minimum effective concentration and the toxic concentration