Drug handling in pregnancy Flashcards
When does teratogenicity of vitamin A derivatives occur?
First 3 weeks - before pregnancy declares itself
Describe the teratogenic effects of vitamin A derivatives
Severe CNS, cardiac and craniofacial abnormalities
Name a vitamin A derivative and state its use
Isotretinoin - acne
Which women can take vitamin A derivatives
Effective contraception and counselling recipients
List some teratogenic drugs
Isotretinoin Valproate Alcohol Tetracyclines Warfarin Antibiotics Antithyroid drugs Anticonvulsants Antihypertensives Lithium Herbal remedies
List some drugs which pose pharmacological risks
NSAIDs
Opiates
Antidepressants
Describe drug absorption in pregnancy
Reduced gastric emptying
Reduced small intestine motility
Enhanced effect via inhalation
Enhanced effect via intramuscular injection
Describe the volume of distribution
Apparent volume into which a drug appears to be distributed with a concentration equal to that of plasma.
What does the volume of distribution depend on?
Lipid solubility
Protein binding
Give the equation for the volume of distribution
Vd = Dose/Plasma conc
What happens to the volume of distribution during pregnancy
Increases
May affect loading doses
What happens to protein binding in pregnancy?
Reduced maternal albumin concentrations - may affect levels of highly protein bound drugs
Describe the metabolism of drugs in pregnancy
Induction of cytochrome P450 enzymes
Competitive inhibition of some cytochrome P450 enzymes
Cholestasis
What happens to drug clearance in pregnancy?
Renal blood flow increases
Describe safe use of drugs in pregnancy
Avoid drugs if possible
Risk/benefit
Use drugs of proven safety
Short courses and lower doses
Always check if not sure!
