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FRACP written exam preparation > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

Name two drugs which exhibits saturable protein binding:

A

Aspirin, disopyramide

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2
Q

Describe 2 phases of liver metabolism.

A
  1. Oxidation, reduction, hydrolysis

2. Conjugation (eg: glucuronidation, acetylation)

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3
Q

What is the clinical significance of CYP2D6?

A

Metabolises prodrug codeine to morphine.
Timolol may lead to systemic beta blockade.
Perhexiline can cause neuropathy and liver toxicity.
5-10% of caucasians and 1-3% in other races are poor metabolizers.

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4
Q

Name 5 inhibitors of CYP 2D6

A

Antidepressants - Paroxetine, Fluoxetine, Bupropion, and Duloxetine
Antipsychotics - Thioridazine, Perphenazine, Pimozide
Cardiac drugs - Quinidine and Ticlopidine
Antifungal - Terbinafine
Miscellaneous medication - Cinacalcet

Importantly, tamoxifen is a substrate for CYP2D6.

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5
Q

What is the clinical significance of CYP2C9?

A

1-3% are poor metabolizers of warfarin and requires only a very small dose.

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6
Q

What is the role of P glycoproteins?

Name its substrates, inducers and inhibitors.

A

Efflux mechanism in the GI tract - causes reduced levels of drugs in the plasma.

Substrates:
Ciclosporin, HIV protease inhibitors (ritonavir, indinavir), digoxin, various chemotherapy agents such as doxorubicin, taxanes, vincristine/blastine

Inhibitors: 
Amiodarone
ciclosporin
diltiazem/verapamil/CCBs
erythromycin
ketoconazole/itraconazole

Inducers: RCP
Rifampicin, phenytoin, clotrimazole

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7
Q

How do you calculate the dosing interval?

A

Dosing interval = bioavailability x dose / Cpss

In other words:

Cpss = Bioavailability x dose/dosing interval

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8
Q

Describe zero order kinetics.

Name 5 drugs which exhibit zero order kinetics.

A

Same AMOUNT of drug is eliminated per unit time.
Drugs exhibit saturable metabolism which results in disproportionately large change in drug level with change in dosing regimen.

  1. Phenytoin
  2. Alcohol
  3. Theophylline
  4. Aspirin
  5. Perhexilline
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9
Q

Define the following terms:

  1. Medication incidents
  2. Adverse drug events
  3. Adverse drug reactions
A
  1. Problems associated with medications - most do not cause harm to patients
  2. Harm occurs to patients but this may include factors outside intrinsic properties of the medications eg: prescribing error, non-compliance etc
  3. Specifically related to the action of the drug.
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10
Q

How does cardiac failure affect pharmacokinetics? (3 factors)

A
  1. Decreased hepatic and renal blood flow affects clearance in general
  2. Decreased tissue perfusion leads to decreased Vd affecting lipophilic drugs
  3. Decreased mesenteric blood flow leads to decreased absorption.
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11
Q

How does pharmacokinetic changes in elderly? 3 factors.

A
  1. Decreased clearance with reduced renal/hepatic function
  2. Decreased Vd due to decreased lean body mass, water and increased fat
  3. Decreased protein binding due to decreased serum albumin
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12
Q

Pharmacokinetic changes in pregnancy - 3 factors

A
  1. Increased Vd by 20%
  2. Decreased protein binding
  3. Increased cardiac output with increased hepatic and renal blood flow and hormonal enzyme induction
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13
Q

What are the three most important factors in renal tubular reabsorption of the drug?

A
  1. Lipid soluble (in order to cross the tubular membrane)
  2. Non-ionized state (which depends on urine pH)
    3 Magnitude of the concentration gradient for passive tubular reabsorption
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14
Q

What pharmacological feature is most important in efficacy of lincosamides such as clindamycin and lincomycin and also beta lactams?

A

Time dependent killing.
Time of drug concentration above the minimum inhibitory concentration. Should exceed the MIC for at least 40-50% of the dosing interval.

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15
Q

What pharmacological feature is most important in efficacy of aminoglycosides and quinolones?

A

Concentration dependent killing.

Maximum plasma drug concentration at the binding site that eradicates the bacteria.

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16
Q

What pharmacological feature is most important in efficacy of vancomycin?

A

Exposure dependent killing.
Dependent on the total exposure of the body to the antibiotic (as indicated by the ratio of AUC over 24 hour period to MIC)

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17
Q

What factor is associated with isoniazid induced liver toxicity?

A

Increasing age, especially female >60

18
Q

What is the mechanism of caspofungins?

A

Echinocandin. Non competitive inhibition of synthesis of fungal cell wall B(1-3)-D-Glucan. Glucan is a microfibril composed of three helically entwined polymers of glucose and the major component of the fungal cell wall.

19
Q

What is the mechanism of azoles?

A

Prevents synthesis of ergosterol from lanosterol by inhibiting CYP450 dependent 14alpha demethylation.

20
Q

What is the mechanism of Griseofulvin?

A

Deposits in newly formed keratin and disrupting microtubule structure.

21
Q

What is the mechanism of terbinafine?

A

Prevents ergosterol synthesis by inhibiting squalene epoxidase.

22
Q

Through what receptors does opiates exert their effect?

A

Mu and Kappa - analgesia, miosis, respiratory depression

Sigma receptors - dysphoria, hallucinations, psychosis

23
Q

How is ATG produced?

A

By immunizing horses or rabbits with human lymphoid cells and harvesting the IgG and absorbing out toxic antibodies against platelets and erythrocytes.
Rabbit formulation is more potent than horse.

24
Q

What are the important side effects of sirolimus?

A

Interstitial pneumonitis especially in impaired renal function
Hyperlipidaemia, anaemia, thrombocytopenia, impaired wound healing

25
Q

What is the action of Basiliximab?

A

Chimeric mab against CD25 (IL2 receptor alpha chain) used in kidney transplantation for induction in patients who have low-moderate risk of rejection.

Because CD25 expression requires T cell activation, anti-CD25 antibody causes little depletion of T cells.

26
Q

Mechanism of cocaine

A

Blocks uptake of dopamine, noradrenaline and serotonin.

Avoid using beta blockers - due to risk of unopposed alpha mediated coronary vasospasm.

27
Q

Management of TEN?

A

IVIG
Supportive cares
Other immunosuppressants such as ciclosporin, cyclophosphamide, plasmapheresis

28
Q

2 mechanism of interaction for grapefruit juice

A
  1. Irreversible inhibition of CYP3A4 at the intestine, leading to decreased presystemic metabolism and increased drug bioavailability leading to toxicity eg simvastatin toxicity
  2. Reversible inhibition of organic anion transporter polypeptides leading to decreased absorption and decreased drug bioavailability and lack of drug efficacy (relevant in celiprolol, aliskiren, otherwise of no significance)
29
Q

Compare zero order and first order kinetics

A

Zero order - constant AMOUNT eliminated per unit time. Non-linear, saturable kinetics.

eg: ethanol, phenytoin, salicylates

First order - constant PROPORTION eliminated per unit time. Linear, non saturable kinetics.

30
Q

Why is oxazepam preferred over diazepam in liver disease/elderly for ETOH withdrawal?

A

Diazepam are first metabolized by hepatic oxidation then glucuronidation. Lorazepam and oxazepam undergo only hepatic glucuronidation.

Benzodiazepine oxidation is decreased in liver failure and in the elderly whereas glucuronidation is preserved. Oxazepam/lorazepam are therefore minimally affected.

31
Q

SSRIs and NSAIDs

A
  1. gastrointestinal symptoms are the most common side-effect
  2. there is an increased risk of gastrointestinal bleeding in patients taking SSRIs. A proton pump inhibitor should be prescribed if a patient is also taking a NSAID
32
Q

CYP P450 enzyme inducers

A

CRAPGPS

Carbamazepine
Rifampicin*
Alcohol (chronic)
Phenytoin*
Griseofulvin
Phenobarbitone
St Johns wort

*Also P glycoprotein inducers

33
Q

CYP P450 enzyme inhibitors

A

SICKFACES.COM group

Sodium valproate 
Isoniazid 
Cimetidine
Ketoconazole*
Fluconazole 
Alcohol..binge drinking 
Chloramphenicol 
Erythromycin*
Sulfonamides 
Ciprofloxacin 
Omeprazole 
Metronidazole
Grapefruit juice
34
Q

Define pharmacokinetics

A

The action of the body on the drug.

Features - absorption, distribution, metabolism and clearance of the drug etc

35
Q

How do you calculate the loading dose?

A

Depends on the volume of distribution.

Loading dose = Vd x Cpss

Loading dose allows Cp to quickly reach therapeutic levels.

36
Q

Name 5 substrates for CYP3A4.

Name 3 CYP3A4 inhibitors.

A

Substrates:

  1. Cyclosporin
  2. Warfarin
  3. Quinidine
  4. Carbamazepine
  5. Lovastatin

Inhibitors

  1. Erythromycin
  2. Azoles
  3. Non-dihydropyridine CCBs such as verapamil/diltiazem
37
Q

What is the significance of slow/fast acetylation as it pertains to procainamide, hydralazine and isoniazid?

A

In Caucasians, 50% are slow acetylators and 50% are fast acetylators.

Procainamide and hydralazine - causes SLE in slow acetylators

Isoniazid - slow acetylators develop peripheral neuropathy, fast acetylators develop hepatitis

38
Q

Adverse drug reaction - A and B

A

Type A - related to pharmacodynamics properties of the drug. Dose dependent and predictable (eg: drowsiness with morphine, bleeding with warfarin)

Type B - unrelated to pharmacodynamics properties (ie, Bizarre). Mostly immunological. eg drug rash.

39
Q

Pregnancy drug risk categories from A to X

A

A - no known risk
B - non known risk in animal studies but no human studies
C - risk in animal studies but not human studies
D- some risk
X - contraindicated. High risk.

40
Q

Hydrocortisone to prednisone conversion

A

4:1

ie, 100mg hydrocortisone equates to 25mg prednisone.

FRACP written exam preparation (18 decks)

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