intro

Question 1

what is biopharmaceutics?

Answer 1

It is the study of the factors influencing the
bioavailability of a drug in man and animals and
the use of this information to optimize
pharmacological and therapeutic activity of drug
products

Question 2

give examples on the factors that influence bioavailability

Answer 2

1-Chemical nature of a drug (weak acid or weak
base)

2- Inert excipients used in the formulation of a
dosage form (e.g. diluents, binding agents,
disintegrating agents, coloring agents, etc.)

3- Method of manufacture (dry granulation
and/or wet granulation).

4-Physicochemical properties of drugs (pKa,
particle size and size distribution, partition
coefficient, polymorphism, etc.).

Question 3

what is the goal of biopharmaceutics?

Answer 3

to develop a dosage form that will provide consistent
bioavailability at a desirable rate, which is important for drugs with a narrow therapeutic window

Question 4

what is the LADME process?

Answer 4

• Liberation
• The release of the drug from its dosage form
(Dissolution)

• Absorption:
• It is defined as the process by which a drug proceeds
from the site of administration to the site of
measurement (usually blood, plasma or serum).

Distribution:
• It is the process of reversible transfer of drug to and
from the site of measurement (usually blood or
plasma).
• Any drug that leaves the site of measurement and
does not return has undergone elimination

Metabolism:
• It is the process of a conversion of one chemical
species to another chemical species.
• Usually, metabolites will possess little or none of the
activity of the parent drug.

Elimination:
• It is the irreversible loss of drug from the site of
measurement (blood, serum, plasma).
• Elimination of drugs occur by one or both of:
• Metabolism
• Excretion.

Excretion
• It is defined as the irreversible loss of a drug in a
chemically unchanged or unaltered form.
• The two principal organs responsible for drug
elimination are the kidney and the liver.

Question 5

The rate and extent of drug distribution is determined
by?

Answer 5

• How well the tissues and/or organs are perfused
with blood.

• The binding of drug to plasma proteins and tissue
components. bound drugs do not cross membranes

• The permeability of tissue membranes to the drug
molecule.

all of them depend on the physicochemical properties of the drug

Question 6

give an example on drugs that are specifically concentrated in one or more tissues

Answer 6

• Example: iodine is concentrated by the -thyroid
gland.
• Example: highly lipid soluble compounds are
extensively distributed into fat tissues

Question 7

give an example on active metabolites

Answer 7

• Procainamide: active metabolite is Nacetyl
procainamide
• Propranolol HCl: active metabolite is 4-
hydroxypropranolol
• Diazepam: active metabolite is
desmethyldiazepam.

Question 8

what are the sites for metabolism

Answer 8

Liver is the primary route of drug metabolism, other
tissues such as kidney, lung, small intestine, and skin
also contain biotransformation enzymes

Question 9

what are the organs for excretion?

Answer 9

The kidney is the primary site for removal of a drug in a
chemically unaltered or unchanged form (i.e. excretion) as well as for metabolites.

The lungs, occasionally, may be an important route of
elimination and excretion for substances of high vapor pressure

Another potential route of drug removal is a mother’s milk.
• Although not a significant route for elimination of a drug
for the mother, the drug may be consumed in sufficient
quantity to affect the infant.

Question 10

what is disposition?

Answer 10

all the processes that occur subsequent to the absorption of the drug.(distribution,metabolism,and excretion)

Question 11

what are the following

Cmax
Tmax
AUC
MTC
MEC
onset time
Duration of action

Answer 11

• Cmax: the highest plasma drug concentration observed.

• Tmax: the time at which Cmax occurs following administration of an extravascular dose.

• AUC: Area under the curve: It is related to the amount of drug absorbed systemically.

• MTC: Minimum toxic concentration: The drug concentration needed to just produce a toxic effect.

• MEC: Minimum effective concentration: The minimum
concentration of drug needed to produce the desired
pharmacologic effect.

• Onset time: The time required for the drug to reach the MEC.

• Duration of action: The difference between the onset time and the time for the drug to decline back to the MEC.

Question 12

what is the bioavailability

Answer 12

the rate, and extent to which,the drug reaches the systemic circulation.

property not only of the drug but also of the
dosage form.

should be constant among, batches and brands

measured by AUC (extent) and Cmax(rate and extent)and Tmax (rate)

Question 13

what is the bioavailability factor

Answer 13

It is the fraction of the dose that is able to gain access to the systemic circulation. It is assessed by means of the AUC and is directlyproportional to Cmax.

Question 14

what are chemically equivalent drugs

Answer 14

These are two or more drug products that contain equal amounts
of the same therapeutically active ingredient(s) in identical
dosage forms, and have the same chemical form

Question 15

what is bio equivalence

Answer 15

two or more chemically or
pharmaceutically equivalent products produce comparable
bioavailability characteristics in any individual when
administered in equivalent dosage regimen

Question 16

what are pharmaceutical alternatives

Answer 16

contain the same therapeutic moiety but differ in salt or ester form, in the dosage form,or in the strength, release.(not interchangable)

For example, Atarax (hydroxyzine HCl) and Vistaril (hydroxyzine
pamoate) are examples of different salts; as are Tofranil (imipramine
HCl) and Tofranil PM (imipramine pamoate). Keflex capsules
(cephalexin) and Keftab tablets (cephalexin HCl) are different salts
and different dosage forms. Calan SR is a controlled-release dosage
form of verapamil HCl; while Calan is a conventional tablet dosage
form of the same salt. Wellbutrin XL and Wellbutrin SR both are
controlled-release dosage forms of bupropion HCl; however, the
mechanisms of drug release are different.

Question 17

what are the types of bioavailability

Answer 17

a) Absolute
b) Comparative (or relative).

Question 18

what is absolute bioavailability

Answer 18

(AUC of dose\AUC iv) * (doseIV\Dose oral)

Absolute bioavailability is assessed by:
a) comparing the values of (AUC)0
∞ and/or:
b) comparing the cumulative mass of drug excreted in the urine

Question 19

what is comparative bioavailability

Answer 19

two dosage forms or routes

comparative (relative)
bioavailability of a drug can be >1, <1 or 1.

So, we again have two methods:
a) comparing the values of (AUC)0
∞ and/or:
b) comparing (Xu)

(AUCdosage1\AUC dosage2)*(dose2\dose1)

Question 20

examples

Answer 20

Valium (diazepam): tablet and intramuscular (innovator products
administered via two different extravascular routes).
- Tagamet (cimetidine): tablet and syrup (innovator products
administered orally via two different dosage forms).
- Cephalexin: capsule dosage form (generic product) marketed by
two different manufacturers (different formulations).

Question 21

what is Comparative bioavailability

Answer 21

to find out if the drug is bioequivalent

AUC generic\AUC standard *doseStandered\dosegeneric

Question 22

examples

Answer 22

propranolol: Inderal tablet (innovator product by Wyeth
Laboratories) and propranolol HCl tablet (generic brand).
- cephalexin: Keflex capsule (innovator product) and cephalexin
capsule (generic product).
- sertraline: Zoloft tablet (innovator product by Pfizer) and
sertraline HCl tablet (generic product).

Question 23

Note that the difference between a bioequivalence study and a
comparative bioavailability study is that a bioequivalence study
compares a drug formulation with a reference standard that is
the innovator product. Moreover, both formulations must be
identical dosage forms. The parameters evaluated in a
bioequivalence study are AUC, Cmax, and tmax .