Drugs in pregnancy
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Transcript of Drugs in pregnancy
Catch-22
Damned if you do, damned if you don’t
Drugs in pregnancy
Affect both mother & fetus, so drug treatment is all about
balancing risks
Catastrophe Thalidomide causing phocomelia
Physiology of pregnancy Cardiovascular Cardiac output increases by 30-50% from 6 th-30th week,
with increase in HR & stroke volume Blood Total blood volume increases, with plasma volume increasing
more than hematocrit, causing dilutional decrease in hemoglobin
Urinary GFR increases, causing decrease in BUN & creatinine &
increased frequency of urination Renin-angiotensin-aldosterone system activation causes
salt & water retention
continued Respiratory Respiratory rate increases to decrease CO2 & increase O2 GIT GI motility decreases causing dyspepsia & constipation Alkaline phosphatase increases due to release from placenta Endocrine Enlarged pituitary releases more prolactin to ensure lactation Placenta produces
TSH like hormone that increases free T4, CRH increases adrenal hormones promoting edema, HPL & insulinase increase insulin resistance, MSH increases pigmentation- melasma
Periods of fetal development Pre-implantation 1st week Damage causes abortion Organogenesis 2nd-8th week Organs are formed Damage can cause structural malformation Growth or maturation 3rd-9th month Damage may modify function of organs
Placental barrier
Most drugs cross placenta,exception being heparin & insulin
Scientific data
Insufficient, largely due to concern about teratogenecity
Definitely teratogenic drugs Warfarin- 25% Phenytoin- ~6% Carbamazepine- 6% Na valproate- 2% Lithium- 2% Retinoids- high
Fetal ultrasound
At ~10 & ~18 weeks detects most of clinically
significant structural abnormalities
FDA categorization of drugs A- safest, based on human studies B- no risk in animal studies, not enough
human data C- inadequate studies in animals or
humans D- evidence shows harm to fetus, but
benefits may outweigh risks X- risks outweigh benefits, do not use
Safest drugs in pregnancy
Mineral & vitamin supplementsOthers, use if necessary
Important drugs Antibiotics- B- penici l l in, cephalo., metro., NFT, clinda., azithro. C- chloroquine, quinolones, fluconazole, albendazole D- doxycycline, aminoglycosides Cardiovascular- B- LMW heparin C- β-blockers, dihydropyridine CCB, methyldopa,
furosemide, digoxin, heparin D- ACEI, ARB, warfarin, thiazides, diltiazem Other- B- acetaminophen, insulin C- aspirin, clonidine, rofecoxib, glyburide, metformin D- NSAID, diazepam, carbamazepine, valproic acid Vaccines- C- OPV, MMR, BCG, HBV/HAV & rabies vaccine
Smoking in pregnancy Increases risk of- Spontaneous abortion Abruptio placentae, placenta previa, PROM Preterm birth Low birth weight Sudden infant death syndrome Best to quit, may require nicotine
replacement
Alcohol in pregnancy Ethanol freely crosses the placenta Complications are dose related,
worse in first trimester Fetal alcohol syndrome- Growth retardation Facial abnormalities- shortened palpebral fissure,
low-set ears, midfacial hypoplasia, thin upper lip CNS dysfunction- microcephaly, MR, behavioural disturbances Best is no alcohol