11. Prescribing in Pregnancy Flashcards
Pharmacokinetics in pregnancy
- Slow gastric emptying (reduced drug absorption)
- Increased maternal plasma volume (low serum levels of drugs, reduced effect)
- Increased maternal hepatic metabolism (reduced plasma drug levels)
- Increased renal perfusion and drug elimination (drugs cleared by the kidneys quicker so its’ plasma levels drop)
Pre-implantation period development:
2 weeks post conception – ‘All or none effect’
Embryonic period development:
3rd -7th week (Day 18-55) post conception – problems in organogenesis causing permanent anatomical defects
Foetal period development
8th week post conception to birth – growth and functional maldevelopment
Shortly before term development:
Adverse effects on labour or neonate
Drugs causing anatomical defects:
Alcohol, lithium, phenytoin, tetracycline, thalidomide, warfarin, isotretinoin, danazol
Phenytoin effect on foetus:
- Cleft palate
Tetracycline
- Teeth staining
Thalidomide
- Embryopathy
Folate antagonist drugs
Anticonvulsants, methotrexate, sulfasalazine,
Neural crest cell disruption drugs
Retinoids
Oxidative stress-causing drugs
Thalidomide, anticonvulsants, anti-arrhythmic
Vascular disruption-causing drugs
Misoprostol, aspirin, ergotamine
Receptor or Enzyme-mediated teratogenesis
NSAID, statins, ACE inhibitors, Angiotensin II receptor blockers
Drug abuse: tobacco
- IUGR
- Placenta praevia, placental abruption, ectopic pregnancy, PPROM
Drug abuse alcohol
- FAS (mental and growth retardation)
- Spontaneous miscarriage in 1st trimester
Drug abuse: cocaine
- Vasoconstrictor
- Placental abruption, growth and mental retardation, spontaneous miscarriage
Drug abuse: heroin or opiates
- Vasoconstrictor
- Spontaneous miscarriage, growth retardation, placental abruption
- Neonatal withdrawal symptoms
- Respiratory depression
Ecstasy and LSD:
- No withdrawal but delayed neonatal development
Anti-emetics in pregnancy:
Safe: Prochlorperazine, Ondansetron, Metoclopramide, Domperidone, Cyclizine
SE: drowsiness, muscle spasm
Hyperemesis gravidarum treatment:
Anti-emetics + Thiamine 1.5mg OD + Prednisolone 16mg OD + Parental fluids
Antacids in pregnancy :
Simple (Ca, Mg, Aluminium)
H2 blockers: Cimetidine, Ranitidine
PPI: Omeprazole
Analgesics in pregnancy:
Aspirin: safe, but not in late pregnancy – delays labour and increases haemorrhage risk
NSAIDs: avoid post 30/40 as causes PDA closure, necrotising enterocolitis and pulmonary hypertension in bebo. Postpartum Ibuprofen preferred than Diclofenac
Opioids: safe for short term/ or neonatal withdrawal – Codeine, Dihydrocodeine, Morphine, Pethidine, Fentanyl, Methadone
Laxatives in pregnancy:
- Lactulose, Glycerine suppositories: not absorbed, safe
Laxatives to avoid in pregnancy:
Senna, bisacodyl (cause contractions), purgatives with Mg, Na – cause electrolyte imbalance
Antifungals in pregnancy:
Topical (safe as pessaries or creams): Clotrimazole, Econazole
Antifungals to avoid in pregnancy:
Systemic (hepatotoxic, teratogenic): Fluconazole, Griseofulvin, Terbinafine
Antibiotics in pregnancy:
Safe: Penicillins, Cephalosporins, Erythromycin, Metronidazole, Ethambutol, Isoniazid
Antibiotics to avoid in pregnancy:
Ototoxic: Streptomycin
NTD, facial cleft: Rifampicin, Trimethoprim
Arthropathy: Ciprofloxacin, Quinolones
Cataract, dysplasia of bones, teeth staining: Tetracycline
Anticoagulants in pregnancy:
Heparin (unfractioned does not cross placenta) and LMWH safe
Anticoagulants to avoid in pregnancy:
DOAC – contraindicated, risk of bleeding
Warfarin in pregnancy:
- Teratogenic; not given in 1st trimester (blindness, mental retardation, midface hypoplasia)
- 2nd and 3rd trimester: risk of placental/foetal haemorrhage
Anti-epileptic drugs in pregnancy:
Teratogenic/NTD, but Lamotrigine, Carbamazepine – safest.
Hypertension in pregnancy:
- B blockers (safe in 3rd trimester)
- Methyldopa
- Nifedipine
- IV labetalol (avoid in asthma) or hydralazine
- Magnesium sulphate
Hypertension in pregnancy – contraindicated treatments:
- ACE inhibitors and Angiotensin II receptor blockers (cross placenta: foetal hypotension, IUGR, renal dysgenesis, lung underdevelopment)
- Diuretics
Diabetes in pregnancy:
Metformin and insulin – safe
Diabetes in pregnancy treatment to avoid:
- Sulphonylureas – foetal hyperinsulinemia and hypoglycaemia
- Steroids avoided
Anaemia in pregnancy:
- Iron deficiency (6-180mg elemental iron)
- Megaloblastic anaemia (400-500mcg folate)
- Sickle cell (folate supplements and transfusion at 6 week intervals)
Thyroid disease in pregnancy:
Hypothyroid: levothyroxine safe
Hyperthyroid: radioactive therapy is contraindicated; Carbimazole and propylthiouracil -> cross placenta so use lowest dose
Asthma in pregnancy:
Oral/IV corticosteroid + nebulised b2-agonist for exacerbations (Prednisolone preferred to corticosteroids for oral treatment)
Which vaccinations to avoid in pregnancy?
Live vaccines, rubella vaccine, MMR, Polio
Vaccines contraindicated in pregnancy:
o BCG vaccine o Measles vaccine o Rubella vaccine o Varicella vaccine o Vaccinia (pox) vaccine o HPV vaccine
Recommended vaccinations in pregnancy:
o Inactivated influenza vaccine o Pertussis vaccine o Inactivated polio vaccine o Diphtheria toxoid o Tetanus toxoid
Drugs to reduce vertical transmission in HIV:
- Zidovudine
- Combination ART (Tenofovir DF/ Abacavir + Emtricitabine / Lamivudine)
Pregnancy and HIV treatment:
Mother: combined ART (Tenofovir DF/ Abacavir + Emtricitabine / Lamivudine)
Baby: Low risk: Zidovudine PO until 6 weeks old OR High risk: Combination PEP
Antipsychotics in pregnancy side effects:
GDM
Least toxic antipsychotics in pregnancy:
Haloperidol, Olanzapine, Quetiapine, Risperidone
TCAs in pregnancy side effects:
Imipramine: tachycardia, muscle spasms, respiratory distress
SSRI/SNRI in pregnancy side effects:
Anencephaly, cardiovascular malformations, neonatal hypoglycaemia, persistent pulmonary hypertension
Fluoxetine
Lithium in pregnancy:
Teratogenic, cardiac abnormalities, goitre, hypotonia, DI
Benzodiazepines in pregnancy:
Risk of cleft palate, neonatal withdrawal and hypotonia, and cardiac malformations
Mifepristone
Anti-progestogenic steroid, sensitises myometrium to PGs, induces contractions and dilates the cervix – used in TOP
Induction of labour drugs:
- Vaginal prostaglandin (PGE2 or Dinoprostone): to induce labour in women with ‘favourable cervix’
- Oxytocin (syntocinon) – slow IV infusion by syringe pump
Anaesthetic agents
- GA (Depress neonatal respiration if used in 3rd trimester)
- Local anaesthetic (with large dose, respiratory depression, hypotonia, bradycardia)
- Prilocaine and Procaine – neonatal methemoglobinemia
Tocolytics:
Uterine relaxants/Labour suppressants: Delay of uncomplicated premature labour between 24 and 33+6 gestational weeks with intact membranes
Contraindications for tocolytics:
- Cardiac disease,
- Foetal death
- Antepartum haemorrhage
- Cord compression
- Placenta praevia
Types of tocolytics:
- Oxitocin receptor antagonist
- Nifedipine
Ureterotonics:
Induce contraction or greater tonicity of the uterus. Used both to induce labour and to reduce postpartum haemorrhage
Indications for ureterotonics:
- Induction of labour
- Management of 3rd stage of labour (prevention of PPH, uterine contractions post C-section)
- Bleeding in spontaneous miscarriage
Mechanism of action of uterotonics:
Contractions of fundus by acting on local oxytocin receptors
Adverse effects of uterotonics:
Uterine spasm, nausea, vomiting, hypotension, tachycardia
Contraindications:
- Mechanical obstruction in pregnancy
- Predisposition for uterine rupture
- Foetal distress
Drugs to supress lactation:
- Cabergoline (same action, first line)
- Bromocriptine: dopamine receptor agonist (inhibits prolactin release)
Contraindications for lactation suppression drugs:
Hypersensitivity, hypertension, coronary artery disease, or mental disorders
Side effects of lactation suppression drugs:
Nausea, vomiting, constipation, headache, dizziness, postural hypotension, drowsiness, vasospasm