Pharmacology drug treatment during pregnancy, breastfeeding and the neonate

Question 1

How are absorption and distribution of drugs affected in pregnancy?

Answer 1

Absorption- gastric emptying delayed for oral drugs
Distb.- total body water/fat ^, lower concs water/lipid sol drugs
- ^ active free drug as protein binding reduced

Question 2

How are metabolism and elimination affected in pregnancy?

Answer 2

Metabolism- ^ clearance of drugs which depend on liver enyzme activity- phenytoin/theophyline
Elimination- ^ renal plasma flow doubles elimiation of renally cleared drugs e.g penicillin

Question 3

Drug effects on fetus

Answer 3

Most cross placenta to varying degrees- lipid/water sol, molec.size, protein binding and metabolism affect transfer

Question 4

Seven A’s and DMARDS

Answer 4

ACEi/ ARBS, anticonvulsants (e.g phenytoin), antibiotics (tetracyclines), antipsychotics (lithium), antithyroid (iodine), anticoagulant(warfarin), abuse (drugs, alcohol nicotine etc), DMARDS (methotrexate)

Question 5

What are the rules for prescribing in pregnancy?

Answer 5

Avoid prescribing in 1st trimester (only exceptional circumstances)
If possible choose drug w/ proven safety record (labetalol vs an ACE inhibitor in HT)

Question 6

Nausea and vomiting as side effect in pregnancy?

Answer 6

Mild- nothing, vitamin/electrolyte support
1st line- promethazine, antihistamines- asses 24hrs later, switch classs if poor
2nd- metoclopamide - methylprednisone in severe cases

Question 7

Asthma and hypertension as drug effects in pregnancy?

Answer 7

Asthma- maintain good inhaler technique, prednisolone ok if needed
HT- older drugs (labetalol/ methyldopa/nifedipine)

Question 8

Protocol for suspected UTI in pregnant women?

Answer 8

Prescribe an antibiotic to all women with suspected UTI during pregnancy

Question 9

Common drug issues in pregnancy

Answer 9

Anticoagulation- Heparin/LMW heparins relatively safe but avoid wafarin- DOAC’s avoid (manufacturers advice)
Anticonvulsants- seizure most risk than drug, refer to specialist

Question 10

What drugs to be cautious with in nursing mothers?

Answer 10

Diazepam, alcohol, lithium, iodine/propylthiouracil, opioids, tetracyclines, CCS
Most drugs detectable in v. low conc in milk

Question 11

How is absorption of a drug altered in the neonate?

Answer 11

Skin- SA/B weight greater > greater absorption of topical agents increased e.g steroids
Intramuscular absorption impaired (red mass)
Rectal relatively efficient e.g diazepam, theophyllines

Question 12

How is drug distribution affected in the neonate?

Answer 12

Body water % greater than older children- ^ loading dose for aminogylcosides, digoxin+ aminophylline based on BW
Albumin binding decreased ^ free concn highly bound drugs, ^ risk of drug/bilirubin interactions

Question 13

How is drug metabolism affected in the neonate?

Answer 13

1/2 that of an adult- impaired oxidation, ^ drug concs warfarin, diazepam, theophylline
Impaired glucuronidation- ^ risk toxicity to drugs metabolised this way e.g chloramphenicol
Grey baby syndrome

Question 14

How is the elimination of drugs affected in neonates?

Answer 14

Glom filtration/tubular secretion/reabsorption all impaired- dose reduction for renally cleared drugs based on BW- AG, digoxin and penicillins
by 6 months renal function normal, standard dose PW

Question 15

Inherited conditions affecting drug response

Answer 15

Oxidation/acetylation- slow (exaggerated/toxic responses)
fast- failure to respond to standard doses
Glucose- 6- phosphate dehydrogenase deficiency- acute haemolysis
Pseudocholinesterase deficiency- prolonged apnoea after neuromuscular blockade

Question 16

Rules of prescribing to neonates

Answer 16

• when poss. base on est. body SA
  use paeds formulary, adjust esp. in neonates
  avoid new drugs, remember most drugs NOT LICENSED in children