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

Population-Specific Considerations in Drug Therapy

Introduction

This section provides an overview of how drug therapy must be tailored for special populations, including pregnant and lactating women, pediatric patients, and other groups with unique physiological or social considerations. Understanding these differences is essential for safe and effective medication management.

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

Special populations may have unique physiological, social, or cultural factors that affect drug therapy.

Drug Use in Pregnancy and Lactation

Key Definitions

• Teratogen: An agent present during critical periods of development that can produce a congenital defect. Susceptibility depends on the developmental stage. Teratogens may not affect the mother but can cause malformations or 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: Fetus may survive outside uterus

• Third Trimester (25 weeks to delivery):

  • Week 25: Lungs mature

  • Delivery: 37-42 weeks

Placental Structure and Function

The placenta acts as an interface between maternal and fetal blood supplies, allowing for nutrient and waste exchange. Some drugs can cross the placental membrane and affect fetal development.

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

Category	Description
A	Adequate studies show no risk to fetus in first trimester or later trimesters.
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 in prescribing information

• 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."

Core Elements in Labeling

• Risk Summary: Probability of adverse outcome; animal data categorized as none, low, moderate, high, or unknown

• Clinical Considerations: Prescribing information, consequences of not treating maternal condition

• Data: Detailed discussion of clinical trials or studies

Lactation Section

• Same format as pregnancy 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 (name 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 medication is essential:

  • If safe for infant, usually safe for mother

  • Choose drugs not excreted into breast milk

  • Alter timing to minimize infant exposure

  • Extract and store breast milk if nursing must be discontinued temporarily

Resources for Pregnancy & Lactation

• 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 be able to describe symptoms

• 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, 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)	2.0	12.0	80.0
Full term (3.5 kg)	3.2	13.4	70.0
1 yr (10 kg)	3.0	22.4	61.2
10 yr (31 kg)	4.2	17.8	64.8
15 yr (60 kg)	5.5	18.1	64.6
Adult (70 kg)	18.0	13.0	54.0
Elder (65 kg)	30.0	12.0	54.0

Children's Clearance vs. Adults

Children's drug clearance rates differ from adults and change with age, affecting dosing and drug selection.

Pediatric Dosing

• 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 dosing

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

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

• 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 mL, 100 mL, 150 mL)

  • 200 mg/5 mL (50 mL, 75 mL, 100 mL)

  • 250 mg/5 mL (80 mL, 100 mL, 150 mL)

  • 400 mg/5 mL (50 mL, 75 mL, 100 mL)

Example: For a 1-year-old child weighing 26 lbs, convert to kg: $26~ ext{lbs} imes rac{1~ ext{kg}}{2.2~ ext{lbs}} = 11.8~ ext{kg}$; dosing is 25-50 mg/kg/day divided every 8 hours, max 500 mg per dose.

Additional info: Pediatric dosing must consider both age and weight, and formulations should be appropriate for the child's ability to swallow or tolerate medication.