Drug interactions pregnant and lactating women

Question 1

What are some factors affecting maternal drug absorption?

Answer 1

1. Vomiting
2. INCREASED gastric pH, reduced acid secretion -
3. Decreased intestinal motility
4. Increased CO (as much as 50%)
   NO effect on bioavailability, NOT clinically significant

Question 2

What are some factors affecting maternal drug Distribution?

Answer 2

1. INCREASE in plasma volume (up to 40% )
2. Changes in blood flow to (kidney, skin, breasts, skeletal muscle)
3. Increase in total body water (as much as 8L)
4. DECREASE in plasma protein binding, increased clearance, reduced free drug in third trimester
   IS CLINICALLY SIGNIFICANT

Question 3

What are 3 drugs that may need to be given at higher concentrations because they induce CYPs…

Answer 3

1. Phenytoin (anti seizure med)
2. Nicotine (maybe higher concentration patch)
3. Lamotrigine (increased clearance by phase 2 enzymes)

Question 4

What are 2 CYPs that are inhibited during pregnancy and what downstream effects do they have

Answer 4

1. CYP1A2 (effects on caffeine)

2. CYP2C19 (Omeprazole)

Question 5

What are two factors affecting drug excretion

Answer 5

1. Increased renal plasma flow

2. Increased glomerular filtration rate

Question 6

What type of drugs are more likely to accummulate in the fetal compartment?

Answer 6

Basic drugs - ion trapped - lower Ph of fetal compartment

can also have iontrapping in breast milk, lower Ph

Question 7

important considerations for neonate

Answer 7

1. milkk-to-plasma ratio
2. infant drug clearance
3. Caution if the neonate is expected to receive more than 10% of the dose of the drug that would be given for therapeutic reasons