Lecture 2: Pharmacokinetics & Dynamics Flashcards Preview

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Flashcards in Lecture 2: Pharmacokinetics & Dynamics Deck (28):
1

4 Processes of Pharmacokinetics

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

2

Diffusion or Passive Transport

-Usually small, nonionized, or lipid-soluble molecules

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

3

Active Transport

-Usually large, ionized, or water-soluble molecules

-People "pushing" their way into our crowded pharmacology classroom

4

Absorption

-Movement from site of administration to circulating fluids
-Primary factor determining length of time for effect of drug to occur

5

Factors Affecting Drug Absorption

-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)

7

Distribution

Medications are distributed by Blood

-Greater blood flow to area, higher concentration of drug is delivered

-IV vs. IM vs. Subcut

8

Enterohepatic Recirculation

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

9

Excretion

Primary site of excretion of drugs is kidneys.

-Secretion mechanism is less active in infants and older adults

10

Excretion
-Renal failure

-Drugs retained for extended times
-Dosages must be reduced

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

11

Serum Peaks and Troughs

-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

12

Median Effective Dose (ED50)

Dose that produces therapeutic response in 50% of a group

Many clients require more or less

12

Absorption
-Food

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

13

Barriers affecting drug distribution
& Capillary beds

Blood-brain barrier
fetal-placental barrier

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

14

Drug-Protein Complexes

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.

15

Considerations for Pt's w/ Low Albumin
-Albumin 2.1
-Total protein 3

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

16

Metabolism

The liver is the primary site of drug metabolism

17

Hepatic microsomal enzyme system
-P-450 system

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

18

First-pass effect

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.

19

Enterohepatic recirculation

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.

20

Blood Flow and Excretion **TEST ?**

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

BUN
Creatinin

21

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

Kidney disease
Liver disease
Low protein in blood stream

22

pH and Urine ***TEST***

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

23

Oral medication and Constipation?

Increase absorption

24

Diarrhea and oral medication

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

25

High Protein Levels and Meds

Increase dose of medication due to drug protein complex.

If there is low protein...
decrease dose of medication

26

Empty Stomach and Med

Makes the stomach more Acidic

Acidic drugs will be absorbed more readily

27

Plasma Half-life

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

28

Therapeutic range

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