Therapeutics- Prescribing in Special Groups- Pregnant Women Flashcards
In general should medications for chronic disorders be stopped during pregnancy?
No it is usually better not to stop
Risk from untreated disease is usually greater as it can adversely effect the pregnancy
Are OTC drugs safe to use in pregnancy?
Yes, generally any adverse effects would cause the drug to not be available OTS
How does ECF change during pregnancy?
ECF increases and therefore the renal clearance of renally cleared drugs increases
How does drug absorption change?
Nausea and vomiting can occur during pregnancy which can reduce absorption of oral drugs. GI transit time also increases which delays absorption
How does absorption from IM injections change?
Blood flow increases and so absorption increases
How does absorption from inhaled medications change?
Blood flow increases (ECF increases) and so absorption increases
When are foetuses most sensitive to teratogens?
During the first trimester as this is when the development of major organs is occuring
What is a teratogen?
A substance, organism, physical agent or deficiency state capable of inducing abnormal structure or function
What percentage of prescribed drugs are known teratogens?
1%
How many congenital malformations are due to drugs?
2-3%
What is the all or nothing effect during the pre-embryonic phase?
This is in the first 14 days
Insult at this stage either leads to spontaneous recovery or loss
What effect could teratogenic drugs have during the first or second trimester?
Affect growth
Affect functional development
Toxic effect on tissues- Fetotoxicity
What are some drugs to be avoided in pregnancy?
ACEi ARBs Quinolone antibiotics Tetracyclines Warfarin Sodium Valproate Androgens Opiates
What changes occur to maternal drug concentration in pregnancy?
As ECF increases and renal clearance decreases the concentration will be reduced compared to a non-pregnant woman with the same dose
Foetal and placental metabolism also affect drug concentrations
Till what age is it advised to exclusively breast feed?
6 months
Why are neonates most at risks with drugs that can be excreted in the breast milk?
They have immature excretory functions and so there is a risk of drug accumulation
What characteristics would make a drug less likely to enter the breast milk?
High molecular weight
Low lipid solubility
High protein binding in the plasma
Lower pH- breast milk has a lower pH than plasma and so acidic drugs (e.g. amoxicillin) will be less likely to enter the breast milk
Which drugs should be avoided in breastfeeding?
Amiodarone
Antithyroid drugs- can cause neonatal goitre and hypo-thyroidism
Benzodiazepines- enter the breast milk
Lithium salts- Present in breast milk and risk of toxicity
Radioactive iodine
Statins- high concentration in breast milk
Sulphonamides
How might certain drugs affect lactation?
Dopamine prevents prolactin release and so dopamine agonists can reduce prolactin release
This decreases milk production
Give an example of a dopamine agonist/antagonst
Agonist- cabergoline
Antagonist- Domperidone
What are the age categorisations?
Premature baby- less than 36 weeks Newborm/Neonate- Up to 27 days old Infant- 28 days to 23 months old Child- 2 years to 11 years Adolescent- 12 years to 16 years
How is oral absorption different in children?
Absorption is affected by slower gastric emptying which takes 6-8 months to reach adult levels
How is the uptake of IM drugs altered in children?
Neonates have a low muscle mass and there is variability in blood flow to muscles making IM absorption unpredictable
How is percutaneous drug absorption different in children?
Percutaneous absorption is increased as the stratum corneum is thinner in children and there is increased skin hydration
How is the distribution of water soluble drugs different in children?
Children have a much higher % of body water and so there is a greater volume of distribution for water soluble drugs. This decreases as children age. This causes lower concentration of the drug so higher doses may be required (e.g. Gentamicin)
How is the binding of drugs to plasma proteins altered in children?
Neonates have less plasma proteins and so binding is reduced. This can cause increases in the free and active form of the drug
Why might sulphonamides cause jaundice?
They can displace bilirubin from albumin and this increase in bilirubin causes jaundice
How is excretion different in neonates compared to adults?
Neonates have reduced ability to excrete drugs. Renal function is not fully developed and so the elimination of renally cleared drugs is reduced, drugs cleared by the kidney’s can therefore accumulate (e.g. gentamicin)
What measurements may be used when deciding doses for children?
Age banding- low therapeutic index drugs (parcetemol, amoxicillin)
Weight- many drugs
Surface Area- for small therapeutic index drugs
Over what age are children classed as adults for dosing purposes?
12 years
What colour should syringes be for orally given drugs?
Purple
These syringes are not compatible with IV lines, this prevents incorrect administration of the drug
What is the intraosseous route? When might it be used?
This is delivery of drugs into the bone marrow
It is used in paediatric emergency situations
The bone marrow is highly vascular
Which drugs should be avoided in children?
Tetracyclines- Cause yellow discolouration of teeth (Not given to children under 12)
Aspirin- Risk of Reye’s Sndrome (Should not be given to children under 16)
Cloramphenicol- Grey Baby Syndrome in neonates
