Prescribing in special groups

Question 1

Why is it always important to consider pregnancy in women of childbearing age?

Answer 1

Drugs can still affect a foetus before women know they are pregnant

Question 2

When is the most teratogenic part of pregnancy?

Answer 2

3-8 weeks as this is when the organ systems are forming. After this point drugs can still cause fetotoxicity

Question 3

What is usually done about medication for chronic conditions during pregnancy?

Answer 3

They are continued because usually the chronic condition would cause more of a problem than the drug

Question 4

Why may drugs with a narrow therapeutic index need altering in pregnancy?

Answer 4

Because pregnancy can alter the pharmacokinetics of drugs - blood volume increases, renal excretion and liver matbolism change

Question 5

Which drugs cross the placenta?

Answer 5

Presume all drugs cross the placenta unless they have a very high molecular weight, this is why prescribing should be avoided in the first trimester of pregnancy

Question 6

What are reccommendations with breastfeeding?

Answer 6

To avoid prescribing unless nescessary however drugs will only be found in very small quantities in the breast milk

Question 7

What drugs can affect lactation?

Answer 7

Dopamine altering drugs due to its effects on prolactin

Question 8

What are the main pharmacokinetic factors that differ in children to in adults?

Answer 8

Absorption from the GI tract changes with age
Distribution differs as children have a higher body water content relative to weight
Metabolism varies
Excretion is reduced as the kidneys are developing

Question 9

How is dosing usually calculated for children?

Answer 9

Related to childs body surface area

Question 10

Which route of administration is preferred in children?

Answer 10

Oral drug administration via flavoured liquids

Question 11

What are the main changes that occur to the pharmacokinetics in the elderly?

Answer 11

Absorption altered due to changes in gastric motility
Distribution
Reduced hepatic blood flow causes decreased first pass metabolism
Decreased renal elimination with age

Question 12

What are the changes that occur in the elderly in terms of specific drugs?

Answer 12

Decreased dopamine receptors increase the chances of extrapyramidal effects
Decreased baroreceptor response increases likelihood of postural hypotension
Increased response to anticoagulants such as warfrin

Question 13

What are the four ‘geriatric giants’ in old age?

Answer 13

immobility, instability, incontinence and impaired intellect

Question 14

What are the main effects liver failure can have on the body?

Answer 14

Hypoproteinaemia
Slower clotting due to decreased clotting factors
Fluid overload

Question 15

Which drusg should be avoided in liver failure and why?

Answer 15

NSAIDs in fluid overload as they worsen this

Some drugs can cause encephalopathy such as sedatives and diuretics

Question 16

What are the main drugs that should be avoided in renal failure?

Answer 16

Nephrotoxic and renally cleared drugs
This includes:
Gentamycin - toxic and cleared
Vancomycin - - cleared
Nitrofurantoin