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ACEM Primary Written > Fundamentals: Pharmacology - Drugs in pregnancy and the elderly > Flashcards

Fundamentals: Pharmacology - Drugs in pregnancy and the elderly Flashcards

1
Q

Seven factors affecting placental drug transfer

A
  1. Lipid solubility: increased lipid solubility increases placental transfer (e.g. thiopental)
  2. Drug ionisation: increased ionisation decreases placental transfer (relative: increased transfer with increasing concentration and lipid solubility)
  3. Molecular size: cross placenta easily if 250-500MW
  4. pKa: maternal blood pH is 7.4 and foetal blood pH is 7.3 (basic drugs with pKa >7.4 will undergo ion trapping in foetus)
  5. Placental transporters: may pump drugs back into maternal circulation (or vice versa)
  6. Protein binding: drug transfer impeded by maternal protein binding (more important for lipid soluble drugs), foetal proteins also have lower binding affinity than maternal (e.g. sulfonamides, barbiturates, phenytoin, local anaesthetics)
  7. Placental and foetal metabolism: placenta itself can metabolise drugs to produce either active or inactive metabolites (e.g. prednisolone metabolised to inactive prednisone - can be used in pregnancy without steroid exposure to foetus), 40-60% of umbilical venous blood enters liver (first pass metabolism), some drugs in umbilical artery may be shunted through placenta back to umbilical vein
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2
Q

What % of umbilical venous blood enters the liver?

A

40-60%

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3
Q

Three characteristics of teratogens

A
  1. Results in characteristic set of malformations
  2. Exerts effects at particular stage of foetal development
  3. Shows dose-dependent incidence
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4
Q

Describe the five teratogenic risk categories

A

Category A: possibility of harm remote
Category B: no risk in animal-reproduction studies but no studies in human pregnancy, OR adverse effect in animal-reproduction studies but not confirmed in human pregnancy
Category C: adverse effect in studies in animals, but no studies available in human pregnancy (or no studies available at all)
Category D: evidence of human foetal risk but benefits to pregnant woman may be acceptable (e.g. life-threatening or no alternatives in serious disease)
Category X: evidence of risk in human and animal studies (or in clinical experience), risk outweight benefit

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5
Q

Six examples of drugs that are category A in pregnancy

A
  1. Cephalexin
  2. Chloromycetin ear drops
  3. Nitrofurantoin
  4. Metoclopramide
  5. Sulfasalazine
  6. Methyldopa
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6
Q

Two examples of drugs that are category B in pregnancy

A
  1. Dicloxacillin
  2. Vancomycin
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7
Q

Eight examples of drugs that are category C in pregnancy

A
  1. Oxycodone
  2. Morphine
  3. Enoxaparin
  4. Heparin
  5. Promethazine
  6. Metoprolol
  7. Nifedipine
  8. Digoxin
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8
Q

Two adverse effects of ACEIs in pregnancy

A
  1. Renal damage
  2. Hypocalvaria
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9
Q

Two antibiotics contraindicated in pregnancy and their effects

A
  1. Tetracyclines (contraindicated throughout pregnancy): discolouration and defects of teeth and altered bone growth
  2. Chloramphenicol (contraindicated in 3rd trimesters): “grey baby syndrome” (cyanosis, hypothermia, CV collapse)
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10
Q

During what trimester of pregnancy are ACEIs contraindicated?

A

Throughout

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11
Q

Seven recreational drugs contraindicated in pregnancy and their adverse effects

A
  1. Amphetamines: abnormal developmental patterns, decreased school performance
  2. Barbiturates: neonatal dependence with chronic use
  3. Cocaine: increased risk of spontaneous abortion, placental abruption, premature labour, and neonatal cerebral infarction; abnormal development, decreased school peformance
  4. Ethanol: foetal alcohol spectrum disorder
  5. Diazepam: neonatal dependence with chronic use
  6. Heroin, methadone: neonatal abstinence syndrome with chronic use
  7. Tobacco smoking: IUGR, prematurity, SIDS, perinatal complications
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12
Q

Four anticonvulsants contraindicated in pregnancy and their adverse effects

A
  1. Phenytoin (contraindicated throughout pregnancy): foetal hydantoin syndrome (IUGR, microencephaly, limb defects, congenital heart defects)
  2. Valproate (contraindicated throughout pregnancy): neural tube defects, cardiac and limb malformations, developmental delay, possibly autism
  3. Carbamazepine (contraindicated in 1st trimester): neural tube defects
  4. Topiramate (contraindicated in 1st trimester): oral cleft
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13
Q

Adverse effects of warfarin in pregnancy

A

1st trimester: hypoplastic nasal bridge, chondrodysplasia punctata
2nd trimester: CNS malformations
3rd trimester: risk of bleeding (discontinue for 1 month before delivery)

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14
Q

Oral hypoglycaemics contraindicated in pregnancy and their adverse effects

A

Chlorpropamide (sulfonylurea): prolonged symptomatic neonatal hypoglycaemia

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15
Q

Three thyroid medications contraindicated in pregnancy and their adverse effects

A
  1. Iodide: congenital goiter, hypothyroidism
  2. Methylthiouracil: hypothyroidism
  3. Propylthiouracil: congenital goiter
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16
Q

Adverse effects of isotretinoin in pregnancy

A

Extremely high risk of CNS, face, ear and other malformations

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17
Q

Adverse effects of lithium in pregnancy

A

1st trimester: Ebstein’s anomaly (congenital heart defect involving tricuspid valve)
3rd trimester: neonatal toxicity

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18
Q

Adverse effects of corticosteroids in pregnancy

A

Cleft palate in 1st trimester

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19
Q

Two antidepressants contraindicated in pregnancy and their adverse effects

A

In 3rd trimester:
1. Tricyclic antidepressants: neonatal withdrawal
2. SSRIs: neonatal abstinence syndrome, persistent pulmonary HTN of newborn

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20
Q

Adverse effects of androgens in pregnancy

A

Masculinisation of female foetus in 3rd trimester

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21
Q

How does IM drug absorption differ in infants from adults?

A

IM absorption unpredictable in sick preterm infants due to low muscle mass and decreased peripheral perfusion (high-risk drugs in this setting include cardiac glycosides, aminoglycosides, anticonvulsants)

22
Q

In what three ways does oral drug absorption differ in infants from adults?

A
  1. Gastric acid secretion increases over hours after birth in full-term infants (slower in pre-terms, highest on day 4)
  2. Gastric emptying prolonged (up to 6-8hrs) first day post delivery: results in increased absorption in the stomach and decreased in the small intestine
  3. Decreased GI enzyme activity (including pancreatic enzymes, bile acids, lipase)
23
Q

Three drugs whose (oral) absorption is decreased in neonates

A
  1. Paracetamol
  2. Phenobarbital
  3. Phenytoin
24
Q

Two drugs whose (oral) absorption is increased in neonates

A
  1. Ampicillin
  2. Benzylpenicillin
25
Q

Three drugs whose (oral) absorption is unchanged in neonates

A
  1. Diazepam
  2. Digoxin
  3. Sulfonamides
26
Q

Describe the differences in drug distribution in infants compared with adults

A
  1. Increased total body water in infants: extracellular water (up to 40%) decreases concentration of drug at receptor sites (mainly relevant for water-soluble drugs)
  2. Decreased body fat in preterm infants compared with full-term
  3. Decreased protein binding in neonates: results in increased concentration of free drug -> increased effect or toxicity despite normal total serum concentration (e.g. local anaesthetics, diazepam, phenytoin, ampicillin, phenobarbital)
27
Q

How is CYP450 activity different in neonates compared with adults? What does this mean for drug metabolism?

A

Decreased (50-70% lower)
Results in slower clearance and prolonged elimination t1/2

28
Q

Give an example of a maternal drug which induces foetal hepatic enzymes

A

Phenobarbital

29
Q

How does drug metabolism differ in toddlers compared with adults?

A

Metabolic rate of drugs higher during toddlerhood (12-36 months)
Increased dose/kg needed compared with adults

30
Q

How does drug excretion differ in neonates compared with adults? What about during toddlerhood?

A

Decreased GFR in newborns (30-40%)
Reaches adult values by 6-12 months
Exceeds adults during toddlerhood

31
Q

When should breastfeeding be ideally timed relative to maternal drug administration?

A

Medication should be taken 30-60mins after nursing and 3-4hrs before next feed

32
Q

Six medications which are present in breastmilk in high concentrations, and their effects in the newborn

A
  1. Tetracycline: tooth staining
  2. Isoniazid: pyridoxine deficiency
  3. Opiates (particularly codeine if mother is a rapid metaboliser): neonatal dependence
  4. Lithium: toxicity
  5. Iodinated albumin and radioiodine: thyroid suppression (breast feeds should be withheld for days to weeks after small doses)
  6. Amiodarone: thyroid dysfunction
33
Q

Two methods for calculating paediatric drug doses using age and weight

A

Dose = adult dose x [age/(age+12)]
Dose = adult dose x (weight/70)

34
Q

How does drug absorption change with advanced age?

A

No major changes
Altered nutritional habits, increased consumption of non-prescription drugs (e.g. antacids, laxatives), slowed gastric emptying

35
Q

What factors result in altered drug distribution in the elderly?

A

Decreased lean body mass
Decreased body water
Increased fat percentage
Decreased serum albumin (binds weak acids), increased orosomucoid (binds basic drugs): decrease loading dose but no change to maintenance

36
Q

How does hepatic metabolism change with age? Is this change greatest in phase I or II reactions? What causes this change?

A

Decreased hepatic metabolism (for some drugs more than others)
Greatest change in phase I reactions
May be caused by decreased hepatic flow (e.g. in setting of heart failure), severe nutritional deficiencies, or decreased ability to recover from injury (e.g. alcohol or viral hepatitis)

37
Q

How does drug excretion change with advancing age?

A

Decreased CrCl (2/3 of population) -> prolonged t1/2

38
Q

What is the difference in serum creatinine in the elderly?

A

Creatinine may be normal despite decreased CrCl
Due to decreased muscle mass

39
Q

Describe two drugs with altered pharmacodynamics in the elderly

A
  1. Sedative-hypnotics: increased sensitivity
  2. B-agonists: decreased responsiveness
40
Q

Those with Alzheimer’s disease are more sensitive to which class of drugs?

A

Antimuscarinics

41
Q

Two classes of drugs used to treat Alzheimer’s disease

A
  1. Cholinesterase inhibitors
  2. NMDA channel blockade
42
Q

Three examples of cholinesterase inhibitors used in Alzheimer’s disease

A
  1. Donepezil
  2. Rivastigmine
  3. Galantamine
43
Q

Example of an NMDA channel blocker used in Alzheimer’s disease

A

Memantine

44
Q

Pharmacokinetics of cholinesterase inhibitors

A

Absorption: orally active
Distribution: good CNS penetration

45
Q

Two adverse effects of cholinesterase inhibitors

A
  1. Nausea, vomiting, diarrhoea
  2. Peripheral cholinomimetic effects
46
Q

Do cholinesterase inhibitors alter disease progression in Alzheimer’s?

A

No

47
Q

Which class of drugs can interact with cholinesterase inhibitors to cause toxicity?

A

CYP450 inhibitors

48
Q

Why should cimetidine be avoided in the elderly?

A

Increased risk of confusion and slurred speech in elderly
Inhibits metabolism of other drugs including phenytoin and warfarin

49
Q

11 drugs with age-related decrease in hepatic clearance

A
  1. Alprazolam
  2. Barbiturates
  3. Clobazem
  4. Diazepam
  5. Flurazepam
  6. Imipramine
  7. Nortriptyline
  8. Propranolol
  9. Quinidine
  10. Theophylline
  11. Tolbutamide (sulfonylurea)
50
Q

9 drugs with no age-related change in hepatic clearance

A
  1. Ethanol
  2. Isoniazid
  3. Lidocaine
  4. Lorazepam
  5. Nitrazepam
  6. Oxazepam
  7. Prazosin
  8. Salicylate
  9. Warfarin

ACEM Primary Written (150 decks)

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