1General Concepts Flashcards
Pharmacokinetics
What body does to a drug
Pharmacokinetics -4processes
1.Absorption
2.Distribution
3. Metabolism (Biotransformation)
4. Excretion
Li
Nk between pk and pd
Concentration
Absorption
Drug uptake from site of ADMINISTRATION to BLOOD stream
Factors related to drug absorption
- DRUG characteristics
2.Route of administration
3.Blood flow
4.CELL MEMBRANE characteristics
 Drug characteristicsg
Drug formulation
Concentration of the drug
Lipophilic, lipophobic
non-ionized drugs , ionized
Acidic drugs,alkali drug
Blood flow
Increase blood flow causes increased absorption
Decrease blood flow causes decreased absorption
Cell membrane characteristics
Drugs cross the membrane via passive diffusion or active transport
Routes of drug administration
5
Enteral
Parenteral
Inhalation
Topical
Transdermal
Enteral route
- buccal or sublingual.
- Oral -most common
Most unpredictable
Least effective
30 minutes
Absorption in the DUODENUM - Rectal -anima or suppository 
Parenteral route
Intramuscular
Intravenous
Subcutaneous 
- Inhalation.
5 minutes
Can be titrated
IV. Can also be treated.
- Topical
Placed on skin for local effects
- Transdermal.
 Patch placed on the skin(fentanyl patch)
15 minutes
Intravenous
100% bioavailability
Immediate action, very rapid
Titration can be done
Disadvantage -can cause overdose due to rapid onset
Intramuscular
Acts in 5 minutes
Site buttocks, gluteal, muscle,upper lateral quadrant
Deltoid
Anterior thigh
Injected at 90°
Depth -adults 1 inch
Kids 1/4 inch
Never beyond 2/3 of the needle
length
Absorption : QUICKLY from AQUEOUS solutions and SLOW from OILYsolutions
- subcutaneous.
Action is in 15 minutes
The angle is 45°
Important points for onset of drug effects
Oral route 30 minutes
Subcutaneous injection and patch—- 15 minutes
INtramuscular and INhalation—- 5 minutes
IV-immediate
Bioavailability
How much a Drug reaches the circulator system is AVAILABLE AT THE SITE OF ACTION .
It is an INDEX
Factors affecting bioavailability
8
1 drug chemical formulation
2 Route of administration
3. Degradation of the drug prior to absorption
4. G.I. perfusion and the pH
5. Presence of other substances, like binders, or dispersing agents in G.I. tract
6. GI absorption mechanism that is active transport versus passive diffusion
7. Solubility to be well absorbed, the drug must be likely hydrophobic
8. Hepatic first pass mechanism
Normal drug metabolism
Normally, swallow drugs—— G.I. system—-blood—-site of action—-go to the liver—-gets metabolized——-excreted by the kidneys
Hepatic first pass metabolism
Swallowed drug——-a portion of the drug goes to the digestive system, and it gets metabolized——-another potion goes to the hepatic portal system—— then to the liver—— then to the rest of the body
So efficacy decreases, and by availability decreases, it’s only for some medications
The biological membran
It’s a bilayer of phospholipid, 100 Angstrom thick and adsorbed protein molecules
Transfer mechanisms across the biological membranes
1 passive transfer
2. Active transport