Drugs in pregnancy

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Drugs in pregnancy

  1. 1. 7 LECTURE # 05
  2. 2. DRUGS IN PREGNANCY DR. NAHEED BANO Assistant Professor, Obs/Gynae Rawalpindi Medical College, Rawalpindi.
  3. 3. IMPORTANT ASPECTS 1. Physiological changes of pregnancy affect DRUG METABOLISM 2. Drug may cross the placenta and affect the fetus (TERATOCENICITY)
  4. 4. PHYSIOLOGICAL CHANGES OF PREGNANCY THAT AFFECT DRUG METABOLISM GIT:  Nausea and vomiting of early pregnancy  Acid content of the stomach is ↓  Delayed gastric emptying Continued:
  5. 5. SKIN AND MUCOUS MEMBRANE:  ↑ Blood flow to the skin leads to more rapid absorption e.g. glyceryl trinitrate patches used to suppress preterm labour  → Blood flow to nasal and oral mucous membrane absorption. → leads to more rapid
  6. 6. CNS: ↑ Vascularity of epidural space e.g. opiates used for analgesia are rapidly absorbed PLASMA AND BLOOD VOLUME: ↑ Plasma and blood volume causes haemodilution affecting drug concentration PLASMA PROTEINS: ↓ In plasma proteins affect drugs that are bound to proteins e.g. diazepam, phenytoin leading to ↑ free drug in circulation URINARY SYSTEM: ↑ Renal blood flow and GFR affecting concentration and elimination of many drugs.
  7. 7. TERATOGENICITY  Drugs that affect organogenesis are described as TERATOGENIC DRUGS  Drug exposure accounts for 2-3 % of all birth defects  Most critical period is embrogenic period which is from 2nd to 8th week post conception or day 31 to day 71 from LMP in a 28 day cycle  Exposure prior to day 31 produces all or none effect i.e. either the fetus dies in utero or has no effect.  Exposure from day 31 to day 71 may lead to fetal abnormality or fetal death.
  8. 8. FACTORS THAT INFLUENCE TERATOGENICITY  Nature of the agent  Dose  Route  Frequency of exposure  Duration of exposure
  9. 9. FACTORS THAT INFLUENCE TERATOGENICITY  Gestational timing  Concurrent exposures  Concurrent illness  Genetic susceptibility * Mother * Fetus
  10. 10. DIAGRAMATIC REPRESENTATION DRUG TOXICITY Conception Heart & CNS Ear & Palate Organogenesis 14 31 71 209
  11. 11. PRINCIPAL MECHANISMS OF TERATOGENESIS Cell growth or proliferation Cell death Cell migration Cell and tissue interactions Disruptions
  12. 12. BIRTH DEFECTS IN CHILDHOOD Baird et al. AJHG 42:677, 1988
  13. 13. FDA CLASSIFICATION OF DRUG SAFETY IN PREGNANCY United States food and drug administration categories for drug use in pregnancy A. Controlled studies show no risk B. No evidence of risk in humans C. Risk cannot be ruled out D. Positive evidence of risk E. Contra – indicated in pregnancy
  14. 14. Awareness of potential advise effects of drugs increased after THALIDOMIDE TRAGEDY
  15. 15. FETAL HYDANTION SYDROME Cranio- facial abnormalities , cardiac defects, IUGR WARFARIN EMBRYOPATHY Nasal hypoplasia, hydrocephaly, microcephaly, IUGR NON –TERATOGENIC FETAL CONSEQUENCES IUGR, mental retardation, intracranial hemorrhage.
  16. 16. DRUGS & BREAST FEESING Drug may affect the infant in various ways Drug may inhibit lactation
  17. 17. TAKE HOME MESSAGE DRUGS SHOULD BE PRESCRIBED TO PREGNANT AND LACTATING WOMEN WITH EXTREME CAUTION

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