Obstetric Pharmacology Flashcards
Historically speaking, have pregnant women been involved in pharmocological studies?
No
Have realised that the physiological changes during preganancy alters the physiology of the women -> standard drug treatments aren’t suitable to them in this state
This was the case of H1N1 outbreak several years ago
What four principles of pharmacokinetics are important in pregnant and lactating women?
Drug absorption – pregnant woman and fetus
Drug distribution – pregnant woman and fetus
- Primary factors
- Crossing capillary membranes
- Crossing lipid membrane
- Secondary factors
- Blood flow
- pH differences between the two compartments
- Protein binding
- Binding of other tissue components
Drug metabolism/biotransformation – pregnant woman and fetus
Drug excretion – pregnant woman and fetus, via breast milk/lactation to neonate
and infant
What factors influence the transfer of drugs from the mother to the foetus across the placenta?
What factors affect uterine blood flow?
Maternal factors that determine transfer of drugs to the fetus:
- Drug dose
- Route of administration
- Maternal metabolism and excretion
- Maternal protein binding
- Maternal pH and ionisation of the drug
- Uterine blood flow
Uterine Blood Flow
Uterine blood flow (UBF) = uterine artery pressure – (uterine venous pressure/ uterine vascular resistance)
UBF is decreased by:
- Decreased blood pressure
- Hypovolaemia
- Aortocaval compression
- Vasoconstrictors – endogenous/exogenous
What placental factors influence the the transfer of drugs across the placenta?
Molecular weight of the drug
Lipid solubility
Degree of ionisation
Described by Fink’s equation
What fetal factors affect the pharmokinetics of drugs having crossed the placenta?
Foetal uptake of the drug
Feotal distribution of drug
Feotal metabolism of the drug
When administering drugs to lactating women; what principles need to be adhered to?
- Minimise the amount of drug in the milk
- Minimise disruption to breastfeeding
- Effectively treat the woman’s condition
What pharmacodynamic considerations must be adhered to in prescribing medications to pregnant/lactating women?
- Mechanism of drug action
- Desired effects on organ systems
- Side effects - Teratogenicity
- Toxicity
- Allergic potential
Teratogenicity = any significant postnatal change in function or form after prenatal treatment. Results in morphological changes, biochemical changes and behavioural changes
Discuss the epidemiology and aetiology of maternal mortality in Australia.
Compare this with Africa
The maternal mortality rate in Melbourne is 7/100,000 live births
The most common causes of this is cardiovascular disease (women pregnant older now -> greater CVD disease), pre-eclampsia and haemorrhaging
The mortality rate in Africa 1/50 live births resulting from haemorrhage, pre-eclampsia, infection, unsafe abortion or obstructed labour
What is the risk of maternal morbidity in Melbourne?
1 / 200 women suffer severe morbidity
Most common morbidities include haemorrhage, renal or liver dysfunction, eclampsia or pulmonary oedema
Discuss the mortality and morbidity rates of neonates!
Approximately 10 million neonates die as a result of birth complications globally each year
Inappropriate drug administration to pregnant women accounts for 2% of all cuases of developmental defects and is frequently preventable
Define major obstetric haemorrhage
How should you manage it?
Major obstetric haemorrhage is most commonly post-partum haemorrhaging with the loss of blood > 1500mL (either vaginally or caesarean birth)
1.8% of all women giving birth will require a blood transfusion following obstetric haemorrhaging
Management goals:
- Control the bleeding
- Restore adequate O2 carrying capacity
- Maintain adequate tissue perfusion
Discuss important drugs for obstetric haemorrhages
Oxytocin
- Most important drug
- Synthetic peptide identical to endogenous hormone
- Stimulates smooth muscle contraction
- IV or IM administration
- Side effects: hypotension, tachycardia,
water intoxication
Ergometrine
- Amine ergot alkaloid compound
- Stimulates smooth muscle contraction as
well as vascular smooth muscle
contraction - IV and IM administration
- Side effects: hypertension, nausea and vomiting
Intravenous fluid therapy
- 0.9% isotonic sodium chloride
Blood transfusion
What role can **Rapid Obstetric Screening Echocardiography Scan (ROSE) **play in obstetric haemorrhaging?
Cardiac monitoring with echocardiography can obtain cardiovascular information in real time concerning the effects of pregnancy:
- Structural information
- Functional information
- Real time
- Non-invasive/safe
- At the bedside
- Liked by pregnant women
Characterise pre-eclampsia
Preeclampsia is hypertension occuring in women during their pregnancy
It occurs in 5-8% of pregnant women
Diagnosis is made on the assumption that high blood pressure develops in pregnancy (as opposed to unrelated disease)
Typically occurs >20 weeks gestation - normally at this time dilation remodelling of maternal blood vessels occurs ; those with preeclampsia fail to do this which elevates TPR.
Death from preeclampsia occurs due to:
Cerbral complications: high pressure in brain vasculature leads to intracerebral haemorrhages
Cardiorespiratory failure: hypertension mediated acute pulmonary oedema and diastolic heart failure (reduced filling)
The long term complications of preeclampsia are the same as normal hypertension: ischemic heart disease, cerebrovascular disease, heart failure, chronic kidney disease
What is the different between mild and severe preeclampsia
Severe preeclampsia is symptomatic
Abnormal biochemistry or haematology is usually present in severe disease
