Pregnant/Breast feeding

Pregnant/Breast feeding

All drugs cab diffuse across the placenta  some foetal exposure will occur.
Drugs can affect the pregnancy (eg teratogenicity; increased risk for complications) and the pregnancy can affect the drugs (eg Vd is decreased by about 20%; albumin concentrations decrease).

FDA classification of drugs:
• Category A – controlled studies in animals and women have not shown risk
• Category B – animal studies have not shown risk but there is no controlled studies in pregnant women OR animal studies have shown risk but controlled studies in women have not (eg paracetamol; NSAID’s)
• Category C – animal studies have shown risk but studies in women have not done so (eg antihistamines)
• Category D – positive evidence of some human risk but benefits may in some circumstances outweigh risk (eg diuretics; warfarin)
• Category X – too dangerous/contraindicated (eg thalidomide)

General advice:
• avoid all drugs, if possible, especially during first trimester
• use drugs with greatest track record of safety and least toxicity
• use shorter courses and lowest doses

Drugs in human milk:
• all drugs diffuse in varying amounts into breast milk by passive diffusion
• risk is related to the dose, the plasma concentration in the infant and the toxicity of that plasma concentration

General advice:
• avoid drugs if possible
• feed baby prior to next dose
• alternative breast and bottle feeding to reduce possible dose

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