Absorption Flashcards
What does a wider therapeutic range mean as far as drug safety goes?
Safer drug
What does a narrow therapeutic range mean as far as drug safety goes?
Less safe drug
Absorption is how
Drug enters blood or lymphatic system
If the drug conc. and action increase, then the absorption and distribution…
Increases
If the drug conc. and action decreases, then the metabolism and excretion will…
Decrease
Factors that influence absorption rate
- transportation type
- route of admin.
- physiochemical properties of drug
- drug conc.
- protein binding
- dosage forms
- circulation at site of absorption
Passive diffusion depends on
Concentration gradient, molecule size, lipophilic nature, temp., membrane thickness
Smaller molecule size, higher lipid solubility, and thinner membranes cause the diffusion rate to
Increase
Time for absorption PO
Mins to hours
(Is primary ROA)
Sublingual/buccal absorption time
3-5 mins
Rectal absorption time
5-30 mins
Enteral routes of administration
- PO
- Sublingual/buccal
- Rectal
Parenteral routes of administration
- IV
- SQ
- IM
Time of absorption for IV
- 30-60 sec
- 100% bioavailability
Time of absorption IM
10-20 mins
Time of absorption SQ
15-30 mins
Major factors that determine ROA in different species
- small intestine
- epithelial surface
- motility
- surface area
- efflux proteins (p-glycoprotein)
Rank solutions, capsules, suspensions, emulsions, slow release products, and tablets ROA in order from fastest to slowest
- solutions
- emulsions
- suspensions
- capsules
- tablets
- sustained release products
Lipid soluble and unionized drugs are absorbed faster or slower?
Faster
How do higher water partition coefficients affect absorption
Increases absorption
How do drugs that are ionized and larger than 50 daltons move across cell membrane?
Active transport
Drugs between 50-600 daltons move thru the cell membrane via
Passive diffusion
When the pKa and pH are equal, that means
50% of the drug is ionized
Unionized drugs pass through the membrane more difficult or easily?
Easily
When pH is 1 unit below pKa, that means
- acid 9% ionized
- base 91% ionized
When pH is 2 units below pKa, that means
- acid is 1% ionized
- base is 99% ionized
pH partition hyposthesis
- basic drugs in blood easily pass into acidic tissue/fluid and conc. there
- acidic drugs conc. in basic tissue/fluid
Will acidic drugs be absorbed more in the intestine or stomach?
Stomach b/c acid+acid= unionized
In the intestine (more alkaline), will a weak acid or base be absorbed better?
Weak base
To get rid of a drug, you should put it in a pH that is similar or different to it?
Similar
F means what in pharmacology? Give the definition
- Bioavailability
- how much unchanged drug is in systemic circulation
3 things used to describe bioavailability
- Cmax: peak plasma conc.
- time to reach peak conc.
- AUC
Bioavailability formula
100* ( (AUC po x Dose iv)/ (AUC iv x Dose po) )
First pass effect
Drug metabolized at a specific site that reduces its concentration upon reaching its site of action
(Usually liver)
Factors affecting bioavailability
- first pass effect
- gastric emptying
- drug solubility
- drug stability in GI fluids
Drugs w/ extensive first pass effect
- Morphine
- propranolol
- buprenorphine
- diazepam
- midazolam
- pethidine
Purpose of efflux proteins
- move drugs and xenobiotics out cell
- important in drug resistancer
Mutation in MDR1 or ABCB1 genes in BBB dangerous bc
Causes toxic neurological effects with drugs like loperamide and ivermectin
