Population-Specific Considerations in Drug Therapy: Pregnancy, Lactation, Pediatrics, and Geriatrics

Population-Specific Considerations in Drug Therapy

Introduction

Population-specific considerations in drug therapy are essential for optimizing medication safety and efficacy across diverse patient groups. Pharmacists must understand how physiological, developmental, and cultural factors influence drug response and risk.

Defining Special Populations

Who Are Special Populations?

• Racial & Ethnic Minorities

• Transgender & Gender-Diverse Persons

• Rural Americans

• People with Limited English Proficiency

• Military Veterans

• Pediatrics

• Geriatrics

These populations may have unique health care needs, medication responses, and barriers to care.

Pregnancy and Lactation

Key Definitions

• Teratogen: An agent present during critical periods of development that can produce a congenital defect. Susceptibility depends on developmental stage; teratogens may not affect the mother but can increase embryonic mortality.

• Congenital defect: Major or minor malformations in structure or function that deviate from the norm.

Stages of Pregnancy

• First Trimester (0-12 weeks)

  • Week 5: Neural tube development

  • Week 6: Heart & major blood vessels

  • Week 7: Arms & legs

  • Week 9: Bones, muscles, face, neck, brain waves, skeleton, fingers, toes

  • Week 10: Kidneys begin to function; most organs formed

  • Weeks 3-8: Most vulnerable to birth defects

• Second Trimester (13-24 weeks)

  • Week 14: Fetus can hear

  • Week 16: Fingers grasp, fat deposited, hair, eyebrows, eyelashes

  • Week 20: Placenta fully formed

  • Week 24: Chance of survival outside uterus

• Third Trimester (25 weeks to delivery)

  • Week 25: Lungs mature

  • Delivery: 37-42 weeks

Placental Structure and Function

The placenta facilitates nutrient and gas exchange between mother and fetus. It is composed of villi, placental membrane, and blood vessels, and is a key site for drug transfer and potential teratogenic effects.

FDA Categories of Risk for Drugs During Pregnancy (Former System)

Category	Description
A	Adequate, well-controlled studies show no risk to fetus in first trimester or later.
B	Animal studies show no risk; no adequate studies in pregnant women.
C	Animal studies show adverse effect; no adequate human studies, but potential benefits may warrant use.
D	Positive evidence of human fetal risk, but potential benefits may warrant use.
X	Studies show fetal abnormalities; risks outweigh benefits.

Current FDA Pregnancy & Lactation Labeling Rule

• Eliminates letter categories

• Separate sections for pregnancy and lactation

• Includes contact info for pregnancy registry if available

• Standard statement: "All pregnancies have a background risk of birth defect, loss, or other adverse outcome regardless of drug exposure."

• Sections include:

  • Risk Summary: Probability of adverse outcome (none, low, moderate, high, unknown)

  • Clinical Considerations: Prescribing info, consequences of not treating

  • Data: Clinical trial/study details

Note: These rules do not apply to OTC products.

Lactation Section

• States amount of drug in breast milk and potential effect on infant

• Ways to minimize exposure in breast-fed infant

• If drug is undetectable and does not affect milk or child, label states: "The use of (drug) is compatible with breastfeeding."

Reproductive Potential Section

• Information about need for pregnancy testing or contraception

• Potential for infertility in men and women

Goals of Therapy for Lactating/Breast-Feeding Women

• Avoid drug use in nursing women if possible

• If essential, choose drugs safe for infants and not excreted in breast milk

• Alter timing of drug regimen to minimize infant exposure

• If nursing must be discontinued, extract and store breast milk before treatment

Pregnancy & Lactation Resources

• Textbooks: Briggs, Shepard

• Databases: TERIS, LactMed

• Journals/Case Reports

• Websites/Hotlines: Motherisk

• FDA Reports/Drug Manufacturers

• LexiComp

Special Considerations in Pediatrics

General Pediatric Pharmacy Objectives

• Understand differences between children and adults

• Recognize importance of clinical presentation

• Pharmacokinetic/pharmacodynamic differences

• Dosing strategies

• Appropriate medication formulations

• Medication administration devices

• Counseling parents

Clinical Presentation in Pediatrics

• Children may not verbalize symptoms; recognize signs of common disorders:

• Sepsis/Meningitis: Temperature instability, feeding intolerance, lethargy, grunting, flaring, retractions, bulging fontanelle, seizures

• RSV Infection: Wheezing, lethargy, irritability, poor feeding, apnea

• Otitis Media: Ear pain, middle ear inflammation, bulging tympanic membrane, purulent fluid

Pediatric Pharmacokinetics and Pharmacodynamics

• Absorption, distribution, metabolism, and elimination vary with age

• Body composition changes with age

• Dosing strategies differ from adults

Children's Body Composition vs. Adults

Age/Weight	Fat (%)	Protein (%)	Water (%)
Premature (2 kg)	3.2	12.0	80.0
Full term (3.5 kg)	13.4	13.4	70.0
1 yr (10 kg)	22.4	17.3	61.2
10 yr (31 kg)	18.1	18.1	64.8
15 yr (60 kg)	13.0	18.0	64.6
Adult (70 kg)	18.0	18.0	54.0
Elder (65 kg)	30.0	12.0	54.0

Additional info: Water content decreases and fat content increases with age, affecting drug distribution.

Children's Clearance vs. Adults

Drug clearance rates differ by age, with neonates and infants often having lower clearance than older children and adults. This impacts dosing and risk of toxicity.

Pediatric Dosing Principles

• Dosing in children <12 years is a function of age, body weight, or both

• Predominantly weight-based (mg/kg)

• General rule: Use weight-based dosing up to 40 kg; if it exceeds adult dosing, use adult dose

• Do not confuse mg/kg/dose with mg/kg/day

• Convert pounds to kilograms: $1~kg = 2.2~lbs$

• Dose frequency may differ from adults

Patient Example: Amoxicillin Formulations

• Capsule: 250 mg, 500 mg

• Tablet: 500 mg, 875 mg

• Chewable tablet: 125 mg, 250 mg

• Powder for suspension, oral:

  • 125 mg/5 mL (80, 100, 150 mL)

  • 200 mg/5 mL (50, 75, 100 mL)

  • 250 mg/5 mL (80, 100, 150 mL)

  • 400 mg/5 mL (50, 75, 100 mL)

Additional info: Selection of formulation depends on age, ability to swallow, and required dose.