Drugs Flashcards
Most influential factors in drug transfer to milk
- Maternal plasma levels
- Molecular weight of drug
- Oral bioavailability of drug in mother and infant
- Protein binding of the medication
______phase has highest level of passive diffusion of drug into milk
Because____
Drug levels are low/high during this time because ____
Secretory or colostral
Junctions are still loose between alveolar cells
Low, because the amount of colostrum is small
Ion trapping
Example -
Milk is more acidic than plasma, weak bases will become polarized and cannot diffuse back into plasma through lactocyte lipid bilayer as easily
Ex/ barbituates and ranitidine
Molecular weight influence
The smaller the drug the easier to diffuse across lactocyte
Drugs larger than 1000 dont pass through in significant amounts
Ex/ high weight -heparin
Low weight - lithium
Lipophilicity
- More fat-binding, the greater the transfer
2. CNS active drugs tend to bind to fat easily
Maternal plasma levels
- most important factor
- peak level in maternal plasma will be peak level in milk
- if drug isnt absorbed well or if it is distributed quickly, will not enter milk
Bioavailability
Amount of drug that reaches systemic circulation after admin
- can be decreased by liver metabolism, unstable in gastric contents, etc
Ex/LMW heparin, PPI, vanco
Calculating infant exposure
Actual dose = drug concentration at Cmax X volume of milk ingested
Relative infant dose = actual dose received by infant(mg/kg/day)/ maternal dose(mg/kg/day)
Relative infant dose
- greater than 10% is concerning
= drug received by infant/maternal dose
To reduce infant exposure, choose drugs that have
- RID <10%
- Poor oral bioavailability or low systemic absorption
- Short half life
- High protein binding
- Poor penetration to CNS
- High molecular weight
Drugs that inhibit milk production
Ergot alkaloids
Estrogens and progestogens
Pseudophedrine
Ergotamine
