PEBC MCQ study guide: Special Populations: Geriatrics, Pediatrics & Perinatal

Providing Care – Clinical Care

Age-appropriate prescribing, the Beers Criteria, pediatric dosing, and pregnancy/lactation safety.

Geriatrics & the Beers Criteria

The American Geriatrics Society's 2023 Beers Criteria (still the current version) identifies medications that are potentially inappropriate in older adults due to an unfavourable risk-benefit ratio in this population specifically. High-yield Beers-listed classes: first-generation antihistamines (diphenhydramine — anticholinergic, sedating, fall risk), benzodiazepines (falls, cognitive impairment, especially long-acting agents like diazepam), muscle relaxants (cyclobenzaprine — anticholinergic, sedating, poorly tolerated), sulfonylureas with long half-life (glyburide — prolonged hypoglycemia risk), and anticholinergic-burden drugs generally (oxybutynin, first-generation antihistamines, tricyclic antidepressants) which compound to increase delirium/falls/cognitive decline risk when stacked.

Pharmacokinetic changes with aging relevant to dosing: reduced renal clearance (start low, go slow for renally-cleared drugs), increased fat:lean mass ratio (prolongs half-life of lipophilic drugs like many benzodiazepines/sedatives), reduced hepatic first-pass metabolism (higher bioavailability for high-extraction drugs), and reduced total body water (higher peak levels of hydrophilic drugs). "Start low, go slow" is the guiding dosing principle, but under-treatment (e.g., inadequately managing pain or depression out of excess caution) is also a recognized geriatric prescribing pitfall.

Pediatric Dosing Principles

Most pediatric dosing is weight-based (mg/kg) rather than fixed adult dosing, with a maximum single or daily dose cap (often the adult dose) to avoid exceeding adult-equivalent exposure in larger children/adolescents. Body surface area (BSA)-based dosing is used for select high-risk-index drugs, notably many chemotherapy agents.

Key pediatric-specific contraindications/cautions: aspirin is avoided in children/teens with viral illness (Reye's syndrome risk) — acetaminophen or ibuprofen are used instead for fever/pain; codeine and tramadol are contraindicated in children under 12 (and cautioned in adolescents 12–18 with risk factors like obesity/sleep apnea) due to unpredictable CYP2D6-mediated morphine conversion causing respiratory depression, including in breastfeeding mothers (metabolized to morphine, transferred in breast milk); fluoroquinolones are generally avoided in children (cartilage/joint toxicity in animal studies) except for specific indications where benefit outweighs risk; tetracyclines are avoided under age 8 (permanent tooth discoloration, bone growth effects).

Pregnancy & Lactation

The FDA's old A/B/C/D/X letter categories are considered outdated and are no longer used for new drug labelling (replaced by the narrative Pregnancy and Lactation Labeling Rule, PLLR) — the exam expects familiarity with SPECIFIC known teratogens/risks rather than the old letter system.

High-yield teratogens/pregnancy risks: ACE inhibitors/ARBs (fetal renal toxicity, oligohydramnios — contraindicated, especially 2nd/3rd trimester), warfarin (fetal warfarin syndrome — switch to LMWH/heparin in pregnancy, which do not cross the placenta), isotretinoin (severe malformations — absolute contraindication, mandatory contraception), valproic acid (neural tube defects), methotrexate (abortifacient/teratogenic — also requires contraception in RA patients of childbearing potential), and most live vaccines (contraindicated in pregnancy due to theoretical fetal infection risk, though inactivated vaccines including influenza and pertussis-containing Tdap are recommended in pregnancy).

Lactation safety generally favours drugs with low milk transfer, short half-life, and low oral bioavailability in the infant; a maternal medication is usually compatible with breastfeeding unless specifically flagged (codeine/tramadol above being a key exception due to active metabolite transfer, not simply drug transfer).

High-yield points

Beers Criteria 2023: first-gen antihistamines, benzodiazepines, glyburide, and anticholinergic-burden drugs are the highest-yield "avoid in elderly" classes.
Aspirin avoided in children with viral illness (Reye's syndrome) — use acetaminophen/ibuprofen instead.
Codeine/tramadol contraindicated under 12 (and breastfeeding mothers) — unpredictable CYP2D6 morphine conversion.
ACE inhibitors/ARBs, warfarin, isotretinoin, valproic acid, and methotrexate are the highest-yield pregnancy contraindications — know each mechanism, not just the "avoid" list.
Old FDA A/B/C/D/X pregnancy categories are outdated — think in terms of specific known risks, not letter grades.

Guideline references

American Geriatrics Society 2023 Beers Criteria
Canadian Paediatric Society
Motherisk / Canadian guidance on medication use in pregnancy and lactation