Pharmacokinetics

Question 0

What determins bioavailability of a drug?

Answer 0

First pass metabolism

Absorption

Question 1

What is the bioavailability of a drug?

Answer 1

The fraction of a dose reaching the systemic circulation after oral dosing

Question 2

How are drugs distributed around the body?

Answer 2

Protein binding
Blood flow
Lipid solubility
Important compartments
Blood brain barrier
Placental barrier

Question 3

What factors determine drug distribution?

Answer 3

Blood flow
Protein binding
Lipid solubility
Capacity of organ

Question 4

What do acidic drugs mainly bind to in the blood?

What about basic drugs?

Answer 4

Acidic - albumin

Basic - acid glycoproteins

Question 5

Why do drugs suck as morphine become ‘trapped’ in the brain?

Answer 5

The acidic brain traps ionised weak bases. Does this lead to increased toxicity?

Question 6

How does the body get rid of drugs?

Answer 6

Drug excretion

Drug metabolism

Question 7

What type of drugs can be directly excreted through the kidney?

Answer 7

Water soluble drugs

Question 8

How are fat soluble drugs removed from the body?

Answer 8

Hepatic metabolism and then hydrophilic metabolites can be excreted

Question 9

What two things can happen do drugs when they are metabolised by the liver?

Answer 9

De activation (decreased pharmacological effect, decreased toxicity)
Activation (increased pharmacological effect, increased toxicity)

Question 10

What happens to ACE inhibitors in the liver?

Answer 10

The metabolic action activates them

Question 11

What are the clinical manifestations of hypersensitivity

Answer 11

Cardiovascular collapse hypertension
Severe respiratory distress- difficulty breathing oedema of respiratory tract and anorexia
Skin reactions and urticarial rash photosensitivity And

Question 12

How do you treat anaphylaxis?

Answer 12

Adrenaline IM
Antihistamine chlorphenamine
Steroid hydrocortisone
Bronchodilator beta agonist/aminophylline

Question 13

What tricks give increased risk of bleeding when also taking warfarin?

Answer 13

Steroids: the inhibit clotting factors
Tetracyclines: inhibit vitamin K
Aspirin: inhibits platelets, is ulcerogenic(any bleeding may be increased by warfarin)

Question 14

What effect does grapefruit juice have a metabolism?

Answer 14

Grapefruit juice is an enzyme inhibitor and can increase the plasma concentration raise blood levels for things like antibiotics, oversedation for example with increasing midozalam can lead to an increase of airway obstruction

Question 15

What are some substrates for cytochrome CYP3AM?

Answer 15

Midozalam plus other benzodiazepines
Cyclosporine 
methadone 
statins 
HIV protease inhibitors

Question 16

What are some inducers of cytochrome CYP IIIa?

Answer 16

Carbamazepine 
phenytoin
Rifampicin
Glucocorticoids
Ritonavir
St John's wort

Question 17

What are some inhibitors of cytochrome CYP3A?

Answer 17

Mithramycin
Ketoconazole
itraconazole
grapefruit juice
Omeprazole

Question 18

What drugs has a erythromycin been reported to increase the effect of by inhibiting a cytochrome? And which one?

Answer 18

Warfarin
Carbamazepine
Theophylline
Cyclosporin

P450

Question 19

What can the plasma concentrations of midozalam be increased by?

Answer 19

Clarithromycin
Ketoconazole plus other fungals
Omeprazole
Grapefruit juice

Question 20

What happens if you have metronidazole and alcohol? And what causes this?

Answer 20

Nausea, vomiting, flashing of the face
Tachycardia, shortness of breath, headache

Increased levels of acetaldehyde to inhibition of acetaldehyde dehydrogenase? (non- CYP interaction)
Avoid alcohol!