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Pharmacology > Prescribing in Special Circumstances > Flashcards

Prescribing in Special Circumstances Flashcards

1
Q

What is treatment burden?

A

The workload of healthcare for individuals managing long term health conditionss

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2
Q

What is patient capacity in the context of treatment burden?

A

The degree to which patients can cope with management of their illness

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3
Q

What is pharmacokinetics?

A

The science of the rate of movement of drugs within biological systems, as affected by the absorption, distribution, metabolism and elimination of medications

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4
Q

What is pharmacodynamics?

A

The study of the biochemical and physiological processes underlying drug action including mechanism of action, drug/receptor interactions, efficacy and safety profile

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5
Q

What is bioavailability?

A

The fraction of the administered dose of drug which reaches the systemic circulation

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6
Q

What factors affect bioavailability?

A

Molecular weight
Absorption
Gastric pH
First pass metabolism

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7
Q

What is the clearance of a drug?

A

The volume. of plasma which is cleared of the drug per unit time

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8
Q

What is half life?

A

The time required for serum plasma concentration of a drug to decrease by half

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9
Q

What is the volume of distribution?

A

The volume in which the amount of drug would need to be uniformly distributed to produce the observed blood concentration

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10
Q

How many half lives does it take for a drug to reach steady state?

A

4-5 half lives

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11
Q

Loading doses are often used for what kind of drugs?

A

Drugs with long half lives

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12
Q

Describe the relationship between dose and serum concentration in linear pharmacokinetics?

A

Doubling the dose. of the drug will result in double the serum concentration of the drug

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13
Q

Why is the serum concentration of a drug not proportional to the dose in non-linear pharmacokinetics?

A

The dosage increase can saturate binding sites, resulting in non-proportional increases in drug levels
The rate of elimination is constant regardless of the amount of drug present

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14
Q

With age, there is a decreased volume of distribution due to a decrease in muscle mass (and total body water). How might this affect drugs such as lithium and aminoglycosides?

A

These are water soluble drugs and so their serum concentration will increased with decreased volume of distribution

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15
Q

With age, there is increased body fat. How might this affect fat-soluble drugs such as diazepam and thiopental?

A

Increased half lives of these drugs

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16
Q

Why can there be an increased propensity to toxicity in elderly patients for drugs which undergo significant first pass metabolism e.g. benzodiazepines?

A

With age there can be decreased haptic blood flow which decreases first pass metabolism

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17
Q

Why is there a decreased hepatic clearance of drugs with increasing age?

A

Decrease in oxidative metabolism of drugs through cytochrome p450 with age

18
Q

What formula is used by pharmacists to calculate creatinine kinase to inform prescribing?

A

Cockcroft Gault

19
Q

Give examples of drugs which have increased effects with age?

A

Alcohol
Opiates
Sedatives
Theophylline

20
Q

Give examples of drugs which have decreased effects with age?

A

Isoproterenol

Beta blockers

21
Q

Give examples of common drug-disease interactions

A

Increased risk of drug induced confusion in PD
NSAIDs exacerbate heart failure
Urinary retention in BPH with decongestants and anticholinergics
Constipation is worsened by calcium, anticholinergics and calcium channel blockers
Neuroleptics and quinolones lower seizure thresholds

22
Q

Give examples of common adverse drug interactions

A

Statins and chlarithromycin
Verpamil and beta blockers
Warfarin and multiple drugs (aspirin)
ACE inhibitors increase hypoglycaemic effect of sulphonylureas

23
Q

How does renal disease affect pharmacodynamics and pharmacokinetics?

A

Decreased drug elimination, protein binding and hepatic metabolism
Altered sensitivity to drugs
Increased adverse effects

24
Q

Give examples of drugs which have decreased elimination in renal disease?

A 
Aminoglycosides
Lithium
Digoxin
Methotrexate
Penicillins
25
Q

Describe how renal failure leads to decreased protein binding to drugs?

A

Renal failure leads to acid retention which causes a conformational change in albumin which results in acidic drugs being less bound to albumin

26
Q

Give an example of a drug for which the. decreased. protein binding in renal impairment is significant?

A

Phenytoin

27
Q

Give an example of a drug for which there is increases sensitivity in renal failure?

A

Sedatives

28
Q

How can NSAIDs harm the kidneys?

A

Fluid retention

29
Q

How can tetracylcines harm the kidneys?

A

Increase uraemia

30
Q

How can amiloride and digoxin harm the kidneys?

A

Electrolyte disturbances

31
Q

How can amphotericin and gentamicin harm the kidneys?

A

Nephrotoxins

32
Q

Give examples of drugs which should be avoided in renal disease?

A

Metformin

NSAIDs

33
Q

Give examples of drugs whose dose should be reduced in renal disease?

A

Antibiotics
Low molecular weight heparin
Digoxin
Pheytoin

34
Q

How does hepatic disease affect pharmacodynamics and pharmacokinetics?

A

Effects first pass metabolism and activation of prodrugs
Decreases protein binding and elimination of drugs
Alters sensitivity to drugs

35
Q

Gove examples. of drugs for which there are significant changes in bioavailability due to changes in first pass metabolism in hepatic impairment?

A

Chlormethiazole
Verapamil
Paracetamol

36
Q

Give examples of drugs for which there. is high extraction in hepatic impairment?

A

Morphine
Verapamil
Lignocaine

37
Q

Give examples of drugs for which there. is low extraction in hepatic impairment?

A

Chloramphenicol

Theophyline

38
Q

What factor effects the extraction of drugs which are metabolised at a high rate by the liver?

A

Changes in blood flow

39
Q

What factor effects the extraction of drugs which are metabolised at a low rate by the liver?

A

Changes in liver enzyme activity

40
Q

How should dosing be changed for patients with hepatic impairment?

A

Start drugs at a low dose and titrate upwards using therapeutic drug monitoring

41
Q

What drugs can there be increased sensitivity to in hepatic impairment?

A

Anticoagulants

Sedatives

42
Q

What adverse drug reactions can be precipitated by hepatic impairment?

A

Encephalopathy
Fluid retention
Hepatorenal syndrome

Pharmacology (3 decks)

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