W04: Pharmacology in Pregnancy; Pharmacology in Breast Feeding

Question 1

Explain pharmacokinetics in pregnancy

Answer 1

pharmacokinetics = passage of drugs throughout the body

• oral route compromised dt N/V
• ⇩gastric emptying and gut motility
• ⇧abs of inhaled drugs dt ⇧CO and ⇩tidal vol.
• altered distribution dt ⇧plasma volume and ⇧ fat change
• ⇧plasma dilutation = ⇧plasma proteins = ⇧free drug circulating
• oestrogen and progesrone levels = altered drug metabolism
  = differing [drg] will affect pharmacodynamics
• ⇧ GFR = ⇧ Excretion
• may require higher drug conc for renally cleared drugs e.g gentamicin, digoxin

Question 2

Outline the main concerns regarding the use of medication in pregnancy

Answer 2

risks must outweight benefits
* drugs should be avoided
* e.g consider risks such as epilepsy and effect of uncontrolled epilepsy on baby

• placenta is not a barroer (apart from high molecular weight such as aspirin and heparin) THUS drugs can travel across and affect unborn baby
• TERATOGENS = malformation, prevent implantation, abortion etc.

Question 3

Outline the main concern regarding the use of medication in breast feeding

Answer 3

Some medicines can pass from women through breastmilk to their baby. Only small amounts of the medicine usually reach the baby and most medicines can be used while breastfeeding. For some medicines, this may mean the baby should be monitored more often to make sure they are not harmed by the medicine whilst they are breastfed.

Question 4

Describe where to find information about risks with specific drugs in pregnancy/ breast feeding

Answer 4

BNF
gov.uk pregnancy prevention programme: valporate

Question 5

Explain the principles of prescribing for these patients

Answer 5

CONSIDERATIONS FOR WOMEN OF CHILD-BEARING AGE

• always consider possibility of pregnancy
• warn of risks
• advice tratment options prior to stopping meds
• contraception discussion
• certain drugs have pregnancy prevention programmes
• AVOID ALL DRUGS IN FIRST TRIMESTER
• • drugs given after first 2 mos of preg more likely to cause abruption to growth or interefere with essential development
• consider dose changes and therapeutic monitoring

Question 6

Phenytoin levels in pregnancy

Answer 6

Are increased dt metabolism being induced

• anti-seizure medication. It is useful for the prevention of tonic-clonic seizures and focal seizures, but not absence seizures.

Question 7

Theophylline levels in pregnancy

Answer 7

Increased dt metabolism inhibited = more free drug in circ.

• theophylline used in asthma

Question 8

Explain pharmacodynamics in pregnancy

Answer 8

Body’s response to drug.
* altered site of action/receptor response, efficacy, adverse effects

Question 9

Fetal pharmacokinetics

Answer 9

Altered ADME

DISTRIBUTION
* diff. circulation, less protein binding = more free drug
* little fat thus less destirbution
* more blood flow to brain

EXCRETION
* excr. into amniotic fluid and swallowed and re-circulated = thus risk of accumulation in amniotic fluid

METABOLISM
* less enzyme activity which increases with gestation

Question 10

Considerations of prescribing valporate in women and girls of childbearing age

Answer 10

Must meet pregnancy prevention programme dt teratogenic medicines

• epilepsy

Question 11

Significance of prescribing Trimethoprim in pregnancy

Answer 11

• safe in 2nd or 3rd trimesters but
  AVOID IN ALL TRIMESTERS FOR THOSE WITH FOLATE DEF., LOW DIETARY FOLATE, OR TAKING FOLATE ANTAGONISTS

Question 12

Mgmt of UTI in pregnancy

Answer 12

First trimester
> NITROFURANTOIN
> CEFALEXIN

2nd and 3rd Trimester
> NITROFURANTOIN
!avoid during labour and 36w+

> TRIMETHROPRIM

3rd Trimester after 36w
> TRIMETHOPRIM
> CEFALEXIN: req uterine culture seven days to check therapeutic effect

Question 12

Mgmt of UTI in pregnancy

Answer 12

First trimester
> NITROFURANTOIN
> CEFALEXIN

2nd and 3rd Trimester
> NITROFURANTOIN
!avoid during labour and 36w+

> TRIMETHROPRIM

3rd Trimester after 36w
> TRIMETHOPRIM
> CEFALEXIN: req uterine culture seven days to check therapeutic effect

Question 13

Understand the pharmacological properties during lactation

Answer 13

Almost all drugs cross into breastmilk but multiple factors affect this:

*maternal factors: dose, ADME
* drug characteristics: pH ionisation, lipid solubility, protein binding, molecular weight
* breast physiology: vol of milk and yield

Question 14

Outline the risks of taking certain medication while breastfeeding; consider neonatal monitoring

Answer 14

monitoring if possibility of harm to baby?

Question 15

Demonstrate the ability to use relevant information resources to determine the risk of using specific drugs while breastfeeding

Answer 15

BNF
UK Tetrology service
Summary of Product Characteristics
Patient information leaflet

Question 16

Explain the principles of prescribing for women while breastfeeding

Answer 16

• preference for durgs that are highly protein bound
• avoid long half lives
• delay treatment?
• pump out affected milk and dump?
• question OTC and herbal medicines
• in general if safe in paediatrics and neonates, likely to be safe in breastfeeding

avoid:
- cytotoxics
- imm suppr.
- anti convulsants
- drugs of abuse
- amioda9rone (Vent tachy. etc.)
- lithium (mood)
- radio-iodine

Question 17

Diazepam in breastfeeding

Answer 17

risk of accumulation and sedation

Question 18

Barbituates in breastfeeding

Answer 18

risk of lethargy, sedation, and poor suck reflexes

Question 19

Drugs affecting lactation

Answer 19

> CABERGOLINE inhibition of lactation

> METOCLOPRAMIDE enhances lactation

Question 20

Importance of non-pharma approaches

Answer 20

> hot/cold treatment for pain
exercise for pain
physio for pain

Question 20

Importance of non-pharma approaches

Answer 20

> hot/cold treatment for pain
exercise for pain
physio for pain