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Flashcards in Pharmacokinetics 3 Deck (29)
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1
Q

Active secretion of drugs (even protein bound ones) occurs in which part of the nephron?

(a) Glomerulus
(b) Proximal convoluted tubule
(c) Distal convoluted tubule

A

b) Proximal convoluted tubule.

2
Q

List the groups that Phase II reactions can conjugate a drug with:

  1. G________ _______
  2. A_______ a______
  3. G________
  4. S________
  5. M______
  6. A______
A
  1. Glucoronic Acid
  2. Amino acids
  3. Glutathione
  4. Sulphate
  5. Methyl
  6. Acetyl
3
Q

A molecule can be excreted after Phase I, true or false?

A

True.

4
Q

Passive reabsorption of lipid soluble drugs occurs where in the nephron?

(a) Glomerulus
(b) Proximal convoluted tubule
(c) Distal convoluted tubule

A

(c) Distal convoluted tubule.

5
Q

What is the catalytic centre of the CYP450 group of enzymes? Why is it the catalytic centre?

A

The heme-iron complex. It donates and accepts electrons.

6
Q

Which phase of metabolism involved anabolic reactions?

A

Phase II.

7
Q

The OAT carrier system in the nephron secretes which kinds of drugs:

(a) Weak acids
(b) Weak bases
(c) Lipid soluble

A

(a) Weak acids

8
Q

Phase II reactions can occur by themselves (i.e. without Phase I), true or false?

A

True.

9
Q

Hydrolysis occurs in which phase of metabolism?

A

Phase I

10
Q

The OCT carrier system in the nephron secretes which kinds of drugs:

(a) Weak acids
(b) Weak bases
(c) Lipid soluble

A

(b) Weak bases

11
Q

Microsomal enzymatic reactions mostly occur in which part of the hepatic cell?

A

Smooth endoplasmic reticulum.

12
Q

Which of the following is true:

(a) Lipophillic drugs are made more ionic, in order to be excreted.
(b) Ionic drugs are made lipophillic, in order to be excreted.

A

(a)

This is because it is much easier to secrete ionic/metabolites across the distal convoluted tubule. Lipophillic drugs however can simply diffuse through the lipid membrane, returning to the bloodstream, after being secreted.

13
Q

Give an example of co-adminsitration of drugs to reduce excretion.

A

Penicillin and probenicid. They compete for the same secretion transporter in the nephron and hence it slows the loss of penicillin from the blood.

Probenicid = Increases in Rx of Gout. Increase uric acid excretion.

14
Q

Conjugation of a drug with hydrophilic groups usually occurs in which phase of metabolism?

A

Phase II.

15
Q

Oxidation occurs in which phase of the metabolism?

A

Phase I

16
Q

Protein bound drugs are only eliminaed by?

A

Tubular secretion.

17
Q

Re: drugs in the blood stream, what factors will stop them being filtered?

A

Being protein bound or too big to be filtered, e.g. heparin.

18
Q

Catabolic reactions occur in which phase of metabolism?

A

Phase I

19
Q

Is it low or high molecular-weight drugs that are poorly excreted in bile?

A

Low. Anything <500-700 daltons is not easily secreted in bile.

20
Q

True or false, all drugs get changed before excretion.
If true, explain why.
If false, give examples.

A

False.

Digoxin
Gentamicin
Methotrexate

21
Q

Non-microsomal enzymatic reactions mostly occur in which part of the hepatic cell?

A

Mitochondria.

22
Q

The transfer from plasma to bile occurs via:

(a) Passive diffusion
(b) Active transport

A

(b) Active transport

23
Q

Reduction occurs in which phase of metabolism?

A

Phase I

24
Q

Phase I reactions cannot create active metabolites, true or false?

A

False.

Prodrugs are metabolised in Phase I reactions and turned into an active metabolite. E.g. codeine > morphine.

25
Q

Briefly explain enterohepatic recirculation.

A

Bile (containing a bile-excreted drug) goes into the stomach.
This then moves through into the duodenum.
The bile and drug then get absorbed into the portal vein, which goes to hepatocytes.
Hepatocytes conjugate the drug with glucuronic acid.
Drug is then hydrophillic and moved back to the small intestine.
Drug then moves to the ileum.
Ileum contains Beta-glucuronidase, which breaks off the bond between drug and glucuronic acid.
Drug is now lipophillic and moves back through the membrane of gut wall and off to the portal vein. (See line 3).

26
Q

Which phase of metabolism involves the CYP450 mixed function oxidase system?

A

Phase I

27
Q

Which phase of metabolism is more likely to produce reactive or toxic metabolites/compounds?

A

Phase I.

28
Q

A molecule can only be excreted after going through Phase I reactions, true or false?

A

False. Phase I reactions can allow for Phase II reactions to occur.

29
Q

Phase I usually introduces reactive groups (four) to the molecule, what are they?

A
  1. -OH (Hydroxyl)
  2. -SH (Sulfide)
  3. -NH2 (Amide)
  4. -COOH (Carboxyl)