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Y3 TRANSITION > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

What is pharmacokinetics?

A

How the body affects the drug

absorption, distribution, metabolism, excretion

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2
Q

State the calculation for rate of elimination

A

CL x Cp

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3
Q

Most drugs exhibit first-order kinetics. What is meant by this?

A

The rate of elimination is directly proportional to drug concentration

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4
Q

Define clearance (CL)

A

Volume of plasma cleared of a drug in unit time

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5
Q

What determines the maintenance dose rate of a drug?

A

Clearance

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6
Q

What is meant by ‘steady state’ of a drug?

A

Rate of drug administration = rate of drug elimination

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7
Q

Define volume of distribution (Vd)

A

The volume into which a drug appears to be distributed in fat with a concentration equal to that of plasma

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8
Q

What is the purpose of using a loading dose of a drug initially?

A

Decreases time to steady state for drugs with long half lives

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9
Q

Define half life of a drug

A

The time for the concentration of drug in plasma to halve

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10
Q

How is half life of a drug calculated?

A

0.693 x Vd / CL

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11
Q

A few drugs are administered by zero order kinetics. What is meant by this?

A

The drug is eliminated at a constant rate

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12
Q

List the four possible mechanisms of action of drug metabolism

A

Convert drugs to less active metabolites
Convert inactive to active compounds
Have unchanged activity
Possess a different type of action

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13
Q

What is the main organ of drug metabolism?

A

Liver

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14
Q

Describe phase 1 of drug metabolism

A

Makes drugs more polar by adding a chemically reactive group, permitting functionalization

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15
Q

Describe phase 2 of drug metabolism

A

Adds an endogenous compound to increase polarity (conjugation)

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16
Q

What is the function of CYP450 monoygenases?

A

Mediate oxidation reactions (phase 1) of many lipid soluble drugs
Convert substrate into hydroxyl product

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17
Q

What are the three basic processes of renal excretion?

A
  1. Glomerular filtration
  2. Active tubular secretion
  3. Passive reabsorption by diffusion
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18
Q

All drugs can enter the filtrate via glomerular filtration. True/False?

A

False
Only unbound drugs, thus if a drug binds to a plasma protein there will be less of it than the total plasma concentration

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19
Q

___% of renal plasma flow is filtered through the glomerulus, the remaining ___% is delivered to proximal tubule

A

20%

80%

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20
Q

State the two transporter systems that actively secrete drugs into the lumen of the nephron

A

Organic anion transporter (acidic drugs)

Organic cation transporter (basic drugs) e.g. metformin

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21
Q

At the basolateral membrane, organic anions enter cell by…

A

Diffusion

Or in exchange for alphaKG via OATs

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22
Q

At the apical membrane, organic anions enter cell by…

A

Multi-drug resistance protein 2 (MRP2)

OAT4 in exchange for alpha KG

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23
Q

At the basolateral membrane, organic cations enter cell by…

A

Diffusion

OCT

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24
Q

At the apical membrane, organic cations enter cell by…

A

Multi-drug resistance protein 1 (MRP1)

OC+/H+ antiporters (OCTN)

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25
Q

How are drugs that are highly protein bound excreted by the kidney?

A

Via tubular secretion

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26
Q

How do you calculate the therapeutic ratio of a drug?

A

Maximum tolerated concentration/

Minimum effective concentration

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27
Q

What is meant by ED50?

A

Median effective dose in 50% of the population

28
Q

What is meant by TD50?

A

Median toxic dose in 50% of the population

29
Q

What is meant by LD50?

A

Median lethal dose in 50% of the population

30
Q

What is meant by a pharmacodynamic drug interaction?

A

Drug A modifies the effect of drug B without altering its concentration in tissue fluid

31
Q

What is meant by a pharmacokinetic drug interaction?

A

Drug A modifies the concentration of drug B that reaches its site of action

32
Q

What is the main difference between a pharmacodynamic and pharmacokinetic drug interaction?

A

Pharmacodynamic interactions are usually predictable

33
Q

Drugs that increase or decrease the rate of emptying of the stomach may affect what aspect of pharmacokinetics?

A

Absorption

34
Q

Drugs bound to a plasma protein may affect what aspect of pharmacokinetics?

A

Distribution

35
Q

Drugs that induce hepatic enzymes may affect what aspect of pharmacokinetics?

A

Metabolism

36
Q

Drugs that share a common transporter may affect what aspect of pharmacokinetics?

A

Excretion

37
Q

What effect does competitive enzyme inhibition have on Km and Vmax respectively?

A

Higher Km

Same Vmax

38
Q

What effect does non-competitive enzyme inhibition have on Km and Vmax respectively?

A

Same Km

Lower Vmax

39
Q

Renal impairment can affect drug elimination. What measurement can be taken to help adjust drug dosage?

A

Creatinine clearance

40
Q 
Which one of the following drugs is most likely to cause hyperkalaemia?
A. Allopurinol
B. Simvastatin
C. Omeprazole
D. Ramipril
E. Metformin
A

Ramipril
Decreased secretion of aldosterone, therefore less absorption of sodium and less potassium secreted

Furosemide causes hypokalaemia

41
Q 
Which one of the following drugs does not interact pharmacodynamically with the others listed to cause hypotension?
A. Allopurinol
B. Simvastatin
C. Omeprazole
D. Ramipril
E. Metformin
A

Simvastatin

42
Q

The combination of which PPI with clopidogrel should be avoided?

A

Omeprazole

43
Q 
Which of the following drugs does not need to be used with caution in patients with renal impairment?
A. Allopurinol
B. Simvastatin
C. Omeprazole
D. Ramipril
E. Metformin
A

Omeprazole

Almost completely metabolised by the liver

44
Q

Describe how you calculate the loading dose of a drug (per kg)

A

Vd x target Cp (for IV adminstration)

Vd x target Cp)/ bioavailability (oral administration

45
Q

State the calculation for Vd of a drug

A

Dose of a drug given by IV bolus /

Drug concentration at t=0

46
Q

For drugs eliminated by first-order kinetics, half life is constant regardless of concentration. True/False?

A

True

47
Q

What is meant by bioavailability of a drug

A

Fraction of an administered dose of unchanged drug that reaches the systemic circulation
e.g. 0.5 = half of drug will reach circulation (need twice as much to create the same effect)

48
Q

Offer all patients who have had an MI the following drugs…

A

ACE inhibitor
Dual antiplatelet therapy (aspirin + second antiplatelet)
Beta-blocker
Statin

49
Q

State how you calculate the steady state plasma concentration of a drug

A

Maintenance dose rate /

Clearance

50
Q

State the calculation for the concentration of a drug at time t

A

Ct = Co x (0.5)n

where n is the number of half lives

51
Q

Mr SH obtains sildenafil from an internet pharmacy. Whilst waiting for the beneficial effect he collapses. What is the likely pharmacodynamic interaction that is most likely to have occured?

A

Isosorbide mononitrate
NO causes an increase in cGMP in smooth muscle and erectile tissue increasing blood flow.
Organic nitrates cause venodilation by producing NO (also increases cGMP)

52
Q

Mrs SH is taking warfarin for AF and has had no problems for several months. Her GP diagnoses a fungal infection and prescribes treatment for this. Later, the women notices blood in her urine. What is the likely pharmacodynamic interaction that is most likely to have occured?

A

Fluconazole

Inhibits CYP450 enzyme that metabolises warfarin

53
Q

Mr SH suffers from gout for which he takes allopurinol. From the list below select which medication might plausibly exacerbate this?

A

Furosemide (or another diuretic)

Entry to the renal tubules is mediated by secreting OAT transporters, these also secrete urate

54
Q

Mr SH starts to consume large quantities of grapefruit juice. After a few days he begins to experience muscle pains. What pharmacokinetic reaction is most likely to explain this event?

A

Simvastatin with a component of the juice

55
Q 
The effectiveness of which one of the following drugs taken by Mr SH may be decreased by his impaired renal function?
A. Metformin
B. Simvastatin
C. Furosemide
D. Aspirin
E. Bisoprolol
A

Furosemide

Reduced secretion of furosemide at the proximal tubule, and binds to protein in urine

56
Q 
Mr SH sees his GP with a flare up on gout despite being on allopurinol. He has a PMHx of LVF and renal impairment. Which agent would you not consider to treat his acute flare?
A. Colchicine
B. Naproxen
C. Oral prednisolone
D. IM steroid
E. IA steroid
A

Naproxen
He has LVF and renal impairment, glomuleral filtration relies more on prostaglandins to maintain pressure in the glomerulus

57
Q

What is included in the triple whammy combo to precipitate acute renal failure?

A

ACEi
Diuretic
NSAID

58
Q 
Mr TP takes warfarin as an anticoagulatn for the prophylaxis of chronic AF. He suffers from moderate OA pain. Which of the following analgesics would be most suitable?
A. Aspirin
B. Diclofenac
C. Paracetamol
D. Ibuprofen
E. Naproxen
A

Paracetamol

NSAIDs could precipitate GI bleeding

59
Q

Mr TP is scheduled for a THR of his OA hip. For ho many days before surgery should his warfarin medication for chronic AF be withdrawn?

A

5 days

Half life of warfarin is around 40 hours

60
Q

A man presents to A&E following a suicide attempt, 6 hours after the incident. He reports taking a paracetamol overdose. What is the most appropriate treatment?

A

IV N-acetylcysteine

It is effective up to 8 hours after the reported incident of overdose

61
Q

A man presents to A&E following a suicide attempt, less than one hour after the incident. He reports taking a paracetamol overdose. What is the most appropriate treatment?

A

Oral administration of activated charcoal

It should be used if the incident occurred within the previous hour

62
Q

If a patient becomes hypotensive after a spinal anaesthetic, the normal course of action would be to give the patient oxygen, IV fluids and a drug to bring up the blood pressure. Which drug is typically used?

A

Ephedrine
It has an indirect sympathomimetic causing release of noradrenaline
It has some B-agonist and A1-agonist activity

63
Q

Rate of elimination is independant of Vd. True/False?

A

False

Rate of elimination is related to the Vd, larger Vd results in a slow elimination

64
Q

Vd may exceed the total volume of the body. True/False?

A

True

Vd is typically a very large value

65
Q

A patient is given a spinal anaesthetic before surgery to replace is OA hip. Spinal anaesthesia most commonly causes hypotension by what mechanism?

A

Blockade of sympathetic transmission (loss of Ap generation in cell bodies of preganglionic neurones) to blood vessels, causing vasodlatation

Y3 TRANSITION (10 decks)

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