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Drugs in Pregnancy and Lactation. Max Brinsmead MB BS PhD February 2014. Thalidomide – a lesson in medicine. Thalidomide. Developed in Germany in 1954 Promoted as a tranquiliser and anti emetic Taken by thousands of pregnant women Resulted in >10,000 children with birth deformities

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drugs in pregnancy and lactation

Drugs in Pregnancy and Lactation

Max Brinsmead MB BS PhD

February 2014

thalidomide
Thalidomide
  • Developed in Germany in 1954
  • Promoted as a tranquiliser and anti emetic
  • Taken by thousands of pregnant women
  • Resulted in >10,000 children with birth deformities
  • McBride in Australia and Lenz in Germany raised the alarm
  • Withdrawn in 1961
  • Has found new uses as an immune modulator & for multiple myeloma
teratogenic action of thalidomide
Teratogenic action of Thalidomide
  • Inserts itself into DNA of embryonic promotor zones for ears, limbs and eyes
  • 15+ possible mechanisms of action
  • Inhibits the angiogenic network
  • Will have different teratogenic effects when taken at different stages of pregnancy
lessons from thalidomide
Lessons from Thalidomide
  • The placental barrier is not effective against most orally administered drugs
  • Animal teratogenic testing can be misleading
  • Drug companies have a powerful commercial agenda
  • But are not the sole culprits in a tragedy such as this
when considering drugs in pregnancy there are 4 different scenarios
When considering drugs in pregnancy there are 4 different scenarios
  • A pregnant woman who has ingested a drug and is seeking information about its possible consequences
  • A pregnant woman with a medical condition for which a drug is usually prescribed - what is the safest and most effective drug to use?
  • A woman planning pregnancy who requires long term medication seeks your advice about the teratogenicity of that medication
  • Safe drugs to use in a woman of childbearing age
we need to remember that
We need to remember that:
  • We are in the post-thalidomide era
  • Drug metabolism is altered by pregnancy
  • Most drugs cross the placenta freely

But

  • Only a handful have been shown to be teratogenic

And

  • Some of the defects are relatively minor
effects on the fetus
Effects on the fetus:
  • Can be irreversible teratogenesis

e.g. Thalidomide

  • Can be reversible side effects of the drugs

e.g. anti depressant medication

principles of safe prescribing
Principles of safe prescribing:
  • Is there a non pharmacological alternative?
  • Do the benefits outweigh the risks?
  • Extra caution in the first trimester
  • Use drugs tested by TIME in WOMEN
  • Choose the least harmful drug for the minimum time possible
drug categorisation for pregnancy
Drug categorisation for Pregnancy
  • Different in different countries
  • Australian Drugs in Pregnancy – see MIMS
    • A Okay to use
      • B1 – no known effects in women or animals but more data required
      • B2 – no known effects in women or animals but more testing required
      • B3 – no known effects in women but teratogenic in some animals
    • C Harmful effects - not teratogenic
    • D Suspected of causing irreversibe damage
    • X High risk of permanent damage.
known teratogenic drugs
Known Teratogenic Drugs
  • Systemic retinoids e.g Isotretinoin. Category X Drug
    • CNS abnormalities
    • Congenital heart defects
    • Facial dysmorphism
    • Risk approx. 40%
  • Stilboestrol
    • Vaginal adenocarcinoma
    • Male & female genital tract abnormalities
    • Risk varies 22 – 58%
  • Folic acid antagonists e.g. Methotrexate
    • Neural tube defects
    • Craniofacial abnormalities & Limb defects
    • Risk approx. 30%
known teratogenic drugs 2
Known Teratogenic Drugs (2)
  • Thalidomide
    • Phocomelia
    • Congenital heart defects, GIT & renal malformations
    • Risk approx. 20%
  • Cytotoxic drugs e.g. Cyclophosamide
    • Various effects including fetal death & IUGR
    • Risk approx. 20%
  • Anticonvulsants e.g. Phenytoin, Valproic acid, Carbamazepine
    • Risk 3 – 9%
  • Warfarin
    • Dysmorphic face, congenital heart disease, genital defects, Brain effects
    • Risk 4 – 8%
known teratogenic drugs 3
Known Teratogenic Drugs (3)
  • Tetracyclines e.g. Doxycycline
    • Dental staining
    • Non dysforming skeletal effects
    • Risk rate unknown
  • Misoprostol
    • Moebius sequence i.e. Paralysis 6th & 7th cranial nerves
    • Risk may be as high as 50%
  • Paroxetine
    • Congenital heart defects
    • Risk rate unknown
known teratogenic drugs 4
Known Teratogenic Drugs (4)
  • Alcohol (Ethanol)
    • Fetal alcohol syndrome – characteristic face
    • Mental retardation, neurobehavioural abnormalities
    • Risk is dose dependent (no safe level?)
  • Cocaine
    • Renal tract malformations
    • Risk rate unknown
  • Heroin, Marijuana and Amphetamines
    • Are not teratogenic
antibiotics in pregnancy
Antibiotics in Pregnancy
  • Penicillins
  • Erythromycin
  • Cephalosporins
  • Nitrofurantoin
  • Metronidazole
  • Trimethoprim
  • Sulpha drugs
  • Chloramphenicol
  • Tetracycline
  • Gentamicin
  • A
  • A
  • A
  • A
  • B2
  • B3
  • C
  • A
  • D
  • D
anti malarial drugs for pregnancy
Anti-malarial drugs for Pregnancy
  • Chloroquine
  • Quinine
  • Paludrine
  • Maloprim, Daroprim
  • Larium
  • Fansidar
  • Doxycycline
  • A
  • D
  • B2
  • B3
  • B3
  • D
  • D
haart drugs for pregnancy
HAART drugs for Pregnancy
  • AZT
  • Lamivudine
  • Nevirapine
  • 3TC
  • Abacavir
  • B3
  • B3
  • B3
  • B3
  • B3
anti emetics for pregnancy
Anti-emetics for Pregnancy
  • Pyridoxine
  • Diphenhydramine
  • Metoclopromide
  • Hyoscine
  • Ondansetron
  • Promethazine
  • Prochlorperazine
  • A
  • A
  • A
  • B2
  • B1
  • C
  • C
antihypertensive drugs in pregnancy
Antihypertensive drugs in Pregnancy
  • Aldomet
  • Hydralazine
  • Beta blockers
  • Ca channel blockers
  • Thiazides
  • ACE Inhibitors
  • A
  • C
  • C
  • C
  • C
  • D
  • ↑risk of CNS & CHD defects 3-fold in 1st trimester, ?cause fetal death in 3rd trimester
analgesic drugs for pregnancy
Analgesic Drugs for Pregnancy
  • Paracetamol
  • Codeine
  • Aspirin
  • Narcotics
  • NSAIDs
  • A
  • A
  • C
  • C
  • C
  • Have the potential to cause in utero closure of the ductus arteriosus >34w
anticonvulsant drugs for pregnancy
Anticonvulsant Drugs for Pregnancy
  • All anticonvulsants are teratogenic
      • But there is a genetic component because epileptics on no drugs have ↑rate defects
      • Offspring of epileptic men have ↑rate defects
  • Maternal and fetal risk of fits is greater than the teratogenic risk
  • Some defects can be detected by prenatal testing
      • Spina bifida with sodium valproate
  • Others are deemed acceptable risks
      • 1% risk of isolated oral clefts with Lamatrogine
  • Dilantin is best avoided
      • Carbamazepine & Na valproate reasonable alternatives
psychiatric drugs for pregnancy
Psychiatric Drugs for Pregnancy
  • Most anti-depressants are Category C
      • Except for Moclobemide & MAO Inhibitors (B3)
      • Tricyclics slightly safer than SSRI’s
      • Fluoexetine is the SSRI with the lowest known risk
      • Paroxetine is teratogenic (D)
  • Benzodiazepines and Barbiturates are (C)
      • Benzo’s particularly bad because they accumulate in the fetus
      • And the neonate metabolises them slowly
      • But barbiturates actually hasten the resolution of neonatal jaundice
drugs and lactation
Drugs and Lactation:
  • Most drugs which circulate in the blood will appear in breast milk

But

  • The dose which reaches the infant is small

And

  • In general it is inappropriate to deny the BABY and the MOTHER the benefits of breastfeeding
x rays and pregnancy
X Rays and Pregnancy:
  • The first 4 weeks of amenorrhoea is not a critical period of radiosensitivity in humans
  • Risk of microcephaly is linear from 8 - 15w

And ? no threshold

  • Thereafter threshold is 50-150 rads
    • Chest Xray is <1 rad
    • IVP is about 15 rads
    • CT may involve 15 rads
if a pregnant woman is exposed to radiation
If a pregnant woman is exposed to radiation:
  • Carefully calculate the dose involved
  • Consult the best available authority
  • Counsel along the same lines as for a woman inadvertently exposed to a drug
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