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DYS: Pharmacology + ADME > Clinical pharmacology + ADME > Flashcards

Clinical pharmacology + ADME Flashcards

(58 cards)

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1
Q

Pharmacokinetics

A

Time course of a drug from absorption to elimination
Determines drug regimen
- Dose
- How often

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2
Q

Therapeutic drug monitoring

A

Measuring plasma concentration after patient takes drug

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3
Q

Absorption mechanism

A

Active Transport
Bulk flow of water
Passive diffusion

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4
Q

Active transport

A

Drugs structurally-related to endogenous chemical

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5
Q

Bulk flow of water

A

Small water-soluble drugs

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6
Q

Passive diffusion

A

Movement of drugs

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7
Q

Small Intestines

A

Large surface area = 200m^3
Good blood flow
Long residence time
- High levels of unionised drugs

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8
Q

First-pass metabolism

A

Drug absorbed from small intestines to liver via hepatic portal vein

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9
Q

Calculate Bioavailability (F)

A

F = AUC oral / AUC iv

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10
Q

Clearance (Cl)

A

Volume of plasma cleared of drug per unit of time

  • ml/min
  • l/hr
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11
Q

Calculate Clearance

A

Clearance = Renal clearance + Hepatic clearance

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12
Q

Volume of distribution (Vd)

A

Apparent volume in which a drug is dissolved in the body

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13
Q

Regimens

A

Convenient dosing to obtain stable plasma concentration within window

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14
Q

How does the presence of food affect stomach?

A

Prescence of food increases time in stomach

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15
Q

Acid stable drugs

A

Slowed absorption

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16
Q

Acid labile drugs

A

Stay longer + more readily broken down

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17
Q

Example of Acid labile drugs

A

PPIs - they are given in gastro-resistant capsules

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18
Q

Half life

A

Time for plasma concentration to decrease by 50%

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19
Q

Calculate half life

A

t1/2 = 0.693 / K = 0.693Vd / Cl

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20
Q

K

A

Rate constant = fraction eliminated per unit time

K = Clearance / Vd

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21
Q

Calculate dose given

A

Dose given = Amount needed / F

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22
Q

Where does absorption take place

A

After taken an oral dosage form: it crosses gastrointestinal tract to blood stream

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23
Q

What alters absorption

A

Food / gastric emptying

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24
Q

First order kinetics

Study These Flashcards
A

Rate of elimination is proportional to concentration of drug

Ct = Coe^-kt

25
Ct (in first order of kinetics)
Conc at t=t
26
Co (in first order of kinetics)
Conc at t=0
27
K (in first order of kinetics)
Rate constant
28
T (in first order of kinetics)
Time
29
Resources to find out drug interactions
BNF Stockley's drug interactions Computer alerts
30
What inhibits CyP450
``` Cimetidine Antifungal agents (Ketoconazole) Erythromycin / clarithromycin (macrolide) Ciclosporin Psolaralen ```
31
What is the speed of the onset of CYP450 inhibition
1-2 days = Rapid onset | Reverses quickly on stopping
32
What makes clopidogrel less effective
Omeprazole | - therefore avoid omeprazole and esomeprazole
33
Types of drug interactions
Drug - drug | Drug - food
34
Enzyme induction
Increase activity of metabolising enzyme
35
What drugs have an effect on metabolism
Metoprolol - enhance action of poor metabolisers Fluoxetine Codeine - reduced response in poor metabolisers ( needs to be metabolically converted) Tamoxifen -
36
GI tract interactions
- pH (drugs are passively absorbed best unionised; rise in pH can influence absorption of other drugs) - Absorption (2 drugs may alter absorotion) - GI motility/emptying (affect - absorption = metoclopramide acclerates absoription of other drugs) - Binding (colestyramine binds bile in GI Tract to prevent its reabsorption)
37
What can increase pH
Antacids, PPIs, H2RAs
38
MDR 1 (+other known names)
multiple drug resistance is an efflux transporter or pump which pumps drugs out into lumen (P-glycoprotein / ATP binding cassette = ABC) - Digoxin is a substrate - Rifampicin = inducer - Verapamil = inhibits (also psoralen
39
Why does omeprazole make clopidogrel less effective
Due to being biotransformed by same Cyt P450 - includes esomeprazole - clopidogrel no longer converted to active metabolite
40
What is the current advice to take clopidogrel
Use another H2RA / PPI - not cimetidine - pantoprazole does not affect Cyt P450 + evidence suggest that it does not interact
41
Most common polymorphism
SNP - single nucleotide polymorphism - mutations - lead to amino acid substitution (sickle cell)
42
Therapeutic monitoring window for induction + inhibition
Inhibitor Therapeutic window Inducer
43
What drugs are enzyme inducers + what do they do
``` Barbiturates Rifampicin Griseofulvin Phenytoin Ethanol Carbamazepine - autoinduction St John's wort ``` They reduce conc of a range of drugs as the increase metabolism of OCs
44
How long is the onset of enzyme inducers
1-2 weeks | - effects can still continue after stopping inducer
45
What increases drug interactions
Polypharmacy Conditions e.g. renal impariment - problem for drugs with narrow therapeutic window
46
CYP2D6
``` Genetic polymorphism - poor metaboliser of debrisoquine - homozygous for recessive genes Extensive metaboliser = wild type Ultrarapid metabolisers = multiple copies of CYP2D6 gene ```
47
How do you report an ADR?
Yellow card Scheme In BNF, submit to CSM (committee on safety of medicines) who monitor ADRs - especially new meds + ADRs resulting in hospital admission Report all black triangle drugs
48
Type A ADR
Augmented responses - Undesirable pharmacological response Dose-related Predictable
49
Type B ADR
``` Bizarre Unrelated to pharmacology Unpredictable Rare Severe Related to genetic or immunology ```
50
Ulcerogenic effects of NSAIDs
NSAIDs + corticosteroids associated with peptic ulceration/damage
51
State how ulcerogenic effects of NSAIDs can be minimised
Use paracetamol instead for pain-relief | Use PPI with Misoprostol (stable PGE1 analogue, acts on prostanoid receptors to inhibit gastric H+ secretion)
52
Example of an immunological
Penicillin allergy - Treat with H1 - antagonist - allergic to one means likely to be allergic to all
53
NSAIDs
Non-steroidal anti-inflammatory drugs - aspirin, ibuprofen, diclofenac - inhibit cyclooxygenase - pain-relief - anti-platelet - aniti-pyretic - anti-inflammatory
54
How can you manage Type A
Managed by dose adjustment
55
Most important ADR
NSAIDs
56
% of hospital admissions ADR-related
5%
57
% of hospital patients that suffer an ADR
10-20%
58
% of patients who die from ADR
0.1%

DYS: Pharmacology + ADME (6 decks)

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