bioavailability

Bioavailability: 

Definition: "Bioavailability of a drug administered intravenously is by definition 100%. Bioavailability is less or equal to 100% for any other route of administration."(1)

Formula: Bioavailability = (AUC oral / AUC iv) x 100%

Clinical implication :
- Use oral bioavailability to calculate needed oral dose. Ex: a drug of 10% oral bioavailability, you'll need an oral dose 10 times of the IV dose (2)

Cite:
(1) http://sepia.unil.ch/pharmacology/index.php?id=51
(2) https://books.google.com/books?id=wYRRAAAAQBAJ&pg=PA5&dq=bioavailability+examples+clinical&hl=en&sa=X&ved=0ahUKEwiRgeSysPHLAhXGs4MKHW1iAKAQ6AEIMTAC#v=onepage&q=bioavailability%20examples%20clinical&f=false

MCQ resources:
 Question #9: 
http://global.oup.com/uk/orc/pharmacy/ifp_therapeutics/student/mcqs/ch01/



MCQ by npprep.blogspot.com - Wonder Me!:
1. What is the bioavailability of Valium IV?:
a. 80%
b. 100%
c. unknown
d. Needs more info.

Correct answer: b. 100%



2. What is the availability of  Oral Lithium?:
a. less than 100%
b. 100%
c. over 100%
d. 60%

Correct answer: a. less than 100%



3. You CANNOT determine bioavailability based on:
a.  urinary excretion of the drug
b.  enteral contents of the drug
c.  plasma contents of the drug
d.  parenteral contents of the drug


Correct answer: b. enteral contents of the drug. Remember: generally, parenteral = IV, plasma ; enteral = PO; urinary excretion = amounts of drug excreted/eliminated

4. An IV drug dose is _____ compared with oral drug dose?
a. smaller
b. larger
c. same
d. non-comparable

Correct answer: a. smaller


5. An oral drug dose is ____ compared with IV drug dose?
a. smaller
b. larger
c. same
d. non-comparable

Correct answer: b. larger


6. What would be the order of greater or lesser bioavailability of the dosage forms?
a. PO > IV > rectal > topical
b. IV > topical > rectal >PO
c.  IV > rectal > PO > topical
d. IV > PO > rectal > topical

Correct answer: c.  IV > rectal > PO > topical


7. Oral bioavailability is NOT dependent on:
a. dosage
b. first pass effect
c. water solubility
d. lipid solubility
e. protein binding

Correct answer: a. dosage  (remember: bioavailability is a percentage %, so it's not dose-dependent or grams-dependent)

8. Bioavailability is dependent on:
a. pharmaceutical formulation
b. dosage
c. absorption
d. first pass effect

Correct answer: a. pharmaceutical formulation (i.e., PO, rectal, IV, topical, ointment, etc.). Remember: absorption is due to first pass effect. A low bioavailability does NOT always mean low absorption rate. It could be absorbed very well but due to first pass effect, it's all eliminated from the body. Thus, it makes the drug bioavailability smaller.

9.  If a drug has oral availability of 20%. The IV dose is 500mg. What's your oral dose?
a. 1000mg
b. 125mg
c. 500mg
d. 2500mg

Correct answer:  d. 2500mg


10. Food can increase the drug bioavailability:
a. True
b. False

Correct answer: a. True. Remember: grape fruit & meds?