Pharmacokinetics 1 Flashcards
Solving for pH, what is the Henderson-Hasselbach equation for weak bases?
pH = pKa + log10[BH+ /B]
Can you use IM or subcutaneous injections for large volumes?
You cannot.
When performing IM or subcutaneous injections, some drugs cause _______ and _______ at the injection site.
Pain and necrosis at the injection site.
The pH surrounding a drug can affect what pharmacokinetic processes?
Hint: Pharmacokinetic processes are ADME.
Absorption
Distribution
Excretion
Oral bioavailability is determined by what ratio?
Coral / Cintravenous
All IM and subcutanoues injections are quickly absorbed, true or false?
False, some subcutaneous/IM injections can be repository preparations that are slow and sustained releasing.
If you acidify the urine, this will increase the excretion of which of the following?
(a) Weak acids
(b) Weak bases
Weak bases.
The increase in H+ groups causes them to bind to weak bases, meaning they become more ionised. Molecules that are more ionised are more readily excreted in the urine.
Rectal drugs are only good for systemic effect, true or false?
False. They can be used for local or systemic effect.
What are some benefits to IV administration:
- No _______ phase
- Useful for ______ _______
- _______ concentration in the blood, _______
- Allows for _________
- No absorption phase
- Useful for large volumes
- High concentration in the blood, rapidly
- Allows for titration
Terminating exposure to drugs that are administered rectally is considered _________.
Easy.
Name the eight methods of drug delivery:
- Oral
- Sublingual
- Intravenous
- Intramuscular
- Subcutaneous (arguably related to IM)
- Rectal
- Spinal/Epidural
- Topical
What are the six issues with oral administration of drugs?
- _______ pass ________
- Irregular ________
- _______ irritation
- _______ pH may cause ________ __________
- _______ size
- _______ ________
- First pass metabolism
- Irregular absorption
- Gatric irritation
- Low pH may cause drug inactivation
- Particle/molecule size
- Patient compliance
Spinal/Epidural anaesthetics are preferred over GA in what kinds of surgeries?
Lower abdominal, lower limb, child birth.
Sublingual administration has what benefits?
- ______ absorption
- Avoids exposure to ______ _______
- Avoids _______ _______ _______
- Rapid absorption
- Avoids exposure to gastric pH
- Avoids first pass metabolism
Which diffusion mechanism is the most common way in which drugs cross lipid membranes?
Passive diffusion.
Topical drugs are applied to ______ _______
Mucosal membranes.
Weak acids tend to accumulate in body compartments with what sort of pH? Why?
Body compartments with high pH. The high pH causes them to become ionised and means it is harder for them to cross lipid membrane barriers into other compartments.
What is the most important factor for the absorption of drugs via the oral route?
Surface area. The surface that is in contact with the drug. This is why you are asked to take drugs with a glass of water, it increases the surface area of the drug in contact with the GIT.
A topical drug can be used only for local effect, true or false?
False. A topical drug can be used for local or systemic effect.
Weak bases tend to accumulate in body compartments with what kind of pH? Why?
Low pH. This means they can become ionised and hence become harder for them to cross lipid membrane barriers, leading to them accumulating in that compartment.
IV injection is not suitable for what kind of solutions?
Oily or poorly soluble drugs.
A topical drug used for systemic effect is termed _______.
Transdermal.
If you increase plasma pH, in which direction will drug movement occur?
(a) CNS to plasma
(b) Plasma to CNS
(a) CNS to plasma
True or false, there is first pass metabolism for transdermal drugs.
False.
IM or subcutaneous injections can or cannot be used for poorly soluble solutions?
Can be used for poorly soluble solutions.
f you decrease the plasma pH, in which direction will drug movement occur?
(a) CNS to plasma
(b) Plasma to CNS
Plasma to CNS
What are the two qualities that a drug must satisfy to be topical?
Potent and lipophillic.
Solving for pH, what is the Henderson-Hasselbach equation for weak acids?
pH = pKa + log10[AH/A-]
If you alkanise the urine, the excretion of which will increase?
(a) Weak acids
(b) Weak bases
Weak acids.
This is because they will then donate their protons to the free hydroxyl groups and become more ionised. The more ionised a drug, the more readily it is excreted
