PK and PD in pregnancy

Question 1

What are some cardiovascular changes in pregnancy

Answer 1

1. increased CO
2. increased HR
3. increased SV which is caused by an increase in end diastolic volume
4. increase in fluid volume
5. decrease in TPVR - vessels become floppy and less resistant causing a decrease in pressure
6. increase in Hb produced however the concentration is lower due to an increased Vd

Question 2

What are some respiratory changes in pregnancy

Answer 2

1. breathe deeper and faster
2. lungs work harder to get oxygen
3. affects drugs that are absorbed through the lungs causing a dose adjustment

Question 3

What are some gastrointestinal changes in pregnancy

Answer 3

1. decreased gastric emptying and intestinal motility
2. nausea and vomiting

Question 4

What are some liver changes in pregnancy

Answer 4

1. increased cardiac output, increased blood flow through liver
2. reduced protein concentration

Question 5

What are some changes in the kidneys during pregnancy

Answer 5

1. increased cardiac output which leads to increased GFR
2. increased delivery of solutes to the collecting system can overwhelm reabsorption mechanisms
3. increased urine
4. decreased absorption

Question 6

What are some changes in absorption in pregnancy

Answer 6

most of the drug is absorbed in the small intestine

reduced GI motility may delay absorption this can increase tmax and decrease cmax (this is because as soon as it is absorbed it is metabolised and excreted

Question 7

How does increased fluid affect Vd

Answer 7

it increases Vd and is a dilutional effect which may affect drugs with concentration dependent PD

Question 8

How does metabolism change in pregnancy

Answer 8

there is an increased flow which affects metabolism of drugs and hepatic extraction

Question 9

What is meant by the hepatic extraction ratio

Answer 9

the fraction of drug in the blood entering the liver. that is irreversibly removed during one pass of blood through the liver

Question 10

Name 3 significant factors of hepatic clearance

Answer 10

• fraction of unbound drug (Fu)
• intrinsic ability of the liver to clear drug (CLint)
• blood flow (Qh)

Question 11

Give 3 examples of drugs with high extraction ratio

Answer 11

1. morphine
2. lidocaine
3. propanolol

Question 12

Give 2 examples of drugs with low extraction ratio

Answer 12

1. warfarin
2. phenytoin

Question 13

what is meant by teratogenicity

Answer 13

persistent, structural, or functional adverse effects due to the influence of the drug on foetal development

Question 14

What are 4 teratogenic effects

Answer 14

1. alter chromosomes
2. prevent implantation
3. foetal death
4. functional impairment

Question 15

Give 2 examples of drug with teratogenic effects

Answer 15

1. oestrogen
2. lithium