Therapeutic Considerations in Pregnant and Lactating Animals

Question 1

Considerations in Pregnant Animals

Answer 1

• What is the effect on the pregnancy?
  ○ Will it cause abortion?
  ○ Will it induce parturition?
• What is the effect on the fetus?
  ○ Teratogenesis - abnormalities of fetus
  ○ At birth
• Is there a label indication?
• Need to find balance between treating dam and potential harm to fetus
• Are dose adjustments required for safety/efficacy?

Question 2

Considerations in Lactation

Answer 2

• What is the effect on the neonate?
  ○ Will it cause harm?
• Is there any effect on lactation/milk production
  ○ Some drugs adversely effect lactation
• Is the drug licensed?
  ○ Many are not
• Metabolic status of dam
  ○ May be under metabolic stress due to energy consumption in lactation
• New route of elimination
  ○ Increased elimination = lower plasma concentrations
• Milk withdrawal times and human consumption

Question 3

Absorption in pregnancy therapeutics

Answer 3

○ Reduced abdominal space to accommodate fetus
○ Increased gastric pH
Changes Cmax and Tmax

Question 4

Distribution in pregnancy therapeutics

Answer 4

○ Additional compartment/plasma volume
Changes concentration - drug and distribute more widely
○ Drugs with high Vd more likely to cross placenta

Question 5

Metabolism in pregnancy therapeutics

Answer 5

○ Altered metabolism due to additional need for detoxification of foetal metabolites

Question 6

Excretion in pregnancy therapeutics

Answer 6

Alkalosis/acidosis can alter excretion
Can alter ionisation state of drug

Question 7

Ion trapping of drug in fetus

Answer 7

pH of mothers blood will be different to fetus
* Therefore ionisation state of drug may be different in mother to fetus
* Drug may be able to cross placenta into fetus but not cross back

Question 8

Metacam

Answer 8

Do not use in pregnant/lactating animals

Question 9

Pharmacokinetics in Lactation

Answer 9

A new route of drug elimination is introduced
Particularly for:
* Lipid soluble
* Basic, non-ionised
* Lower plasma protein binding
Some drugs are inactivated by milk
Mastitis may influence milk pH and/or influence blood flow to mammary gland