Pregnancy and Lactation

Question 1

Pharmacokinetic changes of pregnancy

Answer 1

INCREASED

• plasma volume
• cardiac output
• GFR
• Body fat
• Hepatic Perfusion
• gastric pH (more alkalotic)
• Estrogen and Progesterone (increased liver enzyme activity)

DECREASED

• Albumin concentration
• Gastric emptying (slows)

Question 2

Overview of pharmacokinetic changes

Answer 2

• Volume of distribution increases
• Clearance increases** (this one wins out most of the time)
• Decreased protein binding

Question 3

Lipophilic drugs and the placenta

Answer 3

cross placenta more easily

Question 4

Protein binding and fetal circulation

Answer 4

Less protein bound, more likely to end up in fetal circulation (ex. digoxin, ampicillin)

Question 5

Molecular weight and crossing the placenta

Answer 5

Will cross if <500 daltons (ex. Warfarin)

Cross slowly if 600-1,000 daltons

Don’t cross if >1,000 daltons (ex. insulin, heparin)

Question 6

Difference and significant of fetal versus Maternal blood

Answer 6

Fetus blood is more acidic/lower than Maternal blood

Question 7

What corticosteroid can be used in pregnancy and why?

Answer 7

Prednisolone because the placenta (CYP450) will convert this to an inactive form of prednisone

Question 8

When performing a C-section why is it important to get baby out as soon as possible after induction of anesthesia?

Answer 8

anesthesia and analgesics cross the placenta well

Question 9

When does the fetal drug metabolism system develop?

Answer 9

CYP450 appears at about 14 weeks and increases throughout the pregnancy

Question 10

Examples of antihypertensive drugs safe in pregnancy

Answer 10

1. Beta blockers (labetolol and propranolol)
2. Methyldopa
3. Hydralazine
4. CCB (Nifedipine)
5. Magnesium sulfate

Question 11

Which antihypertensive meds are BAD in pregnancy

Answer 11

ACE and ARB :(

Question 12

Which antibiotics are safe for UTI in pregnancy

Answer 12

1. Nitrofurantoin
2. Penicillin (ex. ampicillin)
3. Cephalosporins

Question 13

Why are sulfonamides avoided in pregnancy

Answer 13

displace bilirubin from albumin and enhance kernicterus

Question 14

Antiemetics safe in pregnancy

Answer 14

1. Promethazine (Phenergan)

2. Ondasetron (if refractory)

Question 15

Why should bromocriptine be avoided for suppression of lactation?

Answer 15

• increased stroke risk
• MI
• seizures
• HTN (in post partum women)

Question 16

What does a milk-to-plasma ratio of >1 mean?

Answer 16

drug is concentrated in breast milk

Question 17

Most drugs have a ratio of _______ or less in regards to milk to plasma

Answer 17

<1

Question 18

What is considered a “safe” exposure index value that is commonly and arbitrarily used as a conservative cutoff for concern?

Answer 18

if less than 10% of a therapeutic dose for infants

(exceptions 1. drugs that cause hemolysis in infants with G6PD deficiency
2. Chemotherapy agents

Question 19

Lithium and the placenta

Answer 19

can concentrate in the fetus, easily crosses placenta

Question 20

Pain medications safe vs. unsafe

Answer 20

safe: Methadone, low dose morphine, intermittent low dose oxycodone
unsafe: oxycodone and meperidine in large doses

Question 21

Drugs to avoid in pregnant ladies

Answer 21

1. Methotrexate
2. Lithium
3. Phenobarbital, primidone, and ethosuximide
4. Chemotherapy drugs
5. Amiodarone (affects the thyroid)
6. Atenolol
7. Nadolol
8. Tinidazole
9. Phenytoin
10. Lamotrigine
11. Carbamazepine
12. Phenobarbital

Question 22

Which thyroid medication is used in 1st trimester versus 2nd and 3rd?

Answer 22

1st - PTU (risk of hepatotoxicity)

then, switch to methimazole for 2nd and 3rd