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Medication Administration: Pregnancy, Pediatrics, and Geriatrics

Pregnancy and Medication Administration

First Trimester: High Risk Period

  • Rapid Cell Division: The first trimester is characterized by quick cell division and the formation of all major fetal structures, including eyes, skeletal system, bones, and organs.
  • Medication Caution: Due to this rapid development, almost all medications are discouraged. Typically, only acetaminophen (Tylenol) is considered safe, and even its safety has been a subject of ongoing review.

Placental Barrier and Drug Transfer

  • Not an Absolute Barrier: The membranes of the fetus do not act as an absolute barrier. Any substance ingested by the mother can be transferred to the baby, though not necessarily 100\%.
  • Mechanism of Transfer: Diffusion: Drugs move from an area of higher concentration (mother's bloodstream) to an area of lower concentration (baby's bloodstream).

Problems with Drug Use During Pregnancy

  • Birth Defects: Drugs taken during the first trimester pose a significant risk for birth defects, which can be mental, skeletal, or affect birth weight.
  • Opioid Dependence: Mothers using opioids can lead to opioid dependence in the baby after birth, causing issues during and after pregnancy.

Factors Related to Medications During Pregnancy

  1. Drug Properties:
    • Dosage: The amount of drug taken by the mother.
    • Chemistry/Composition: The chemical makeup of the drug.
    • Drug Interactions: How different medications interact with each other in the mother's system, potentially affecting the fetus.
  2. Gestational Age:
    • Greatest Risk: The first trimester (weeks 1-12) carries the highest risk for developmental issues because organs are forming.
    • Last Trimester Risk: While organs are developed (ten fingers, ten toes, kidneys, heart), there is increased drug transfer to the fetus. This doesn't affect musculoskeletal or organ development but can have implications for the baby after birth (e.g., withdrawal if the mother is dependent).
  3. Maternal Factors (Pharmacokinetics):
    • Kidney Function: If the mother's kidneys have problems with excretion (filtering drugs out), drug levels can become too high, potentially toxic to the baby.
    • Liver Metabolism: Impaired liver function or lack of specific enzymes for drug metabolism can also lead to drug accumulation and toxicity for both mother and baby.

Increased Drug Transfer in the Last Trimester

  • Enhanced Blood Flow: During the third trimester, there is enhanced blood flow from the mother to the fetus.
  • Larger Fetus: The baby is physically larger and requires more blood supply.
  • Free Drug Circulation: Increased free drug circulating in the mother leads to more drug transfer, necessitating careful monitoring, especially near the due date.

Pregnancy Categories (Old System: A, B, C, D, X)

  • Under Review: This categorization system is being re-evaluated, potentially moving towards more specific information for pregnant and breastfeeding mothers across trimesters.
  • Where to Find: Pregnancy categories are listed on drug labels and in drug reference books.

Category Definitions:

  • Category A: No risk to the fetus demonstrated in studies. Considered safe for the mother to take (e.g., Tylenol, though current information warrants caution).
  • Category B: No risk found in animal studies; human data is not available. Assumed to be low risk for humans.
  • Category C: Animal studies show adverse effects, or no human/animal studies are available. Benefits may outweigh potential risks in selected cases, requiring individual consideration.
  • Category D: Positive evidence of human fetal risk, but potential benefits may outweigh risks in life-threatening situations or for serious diseases where safer drugs are ineffective (e.g., a mother with severe cardiomyopathy requiring essential heart medications).
    • Example (Cardiomyopathy): A young mother with severe congestive heart failure (8-10\% ejection fraction, normal \approx50\%) required Category C/D heart medications. Stopping these medications would pose a greater risk to the mother's life than the potential risk to the baby. Decisions are made on a case-by-case basis through discussion between the healthcare provider and the patient.
  • Category X: Absolute contraindication in pregnancy. Studies in humans or animals have shown fetal abnormalities, or there is other evidence of fetal risk. The risks clearly outweigh any potential benefits (e.g., Accutane for acne, Lipitor/atorvastatin for cholesterol). Accutane often requires strict lock-and-key systems for dispensing to young women of childbearing age due to its almost 100\% certainty of causing birth defects.

Breastfeeding and Medications

  • Risk of Exposure: Breastfed infants are at risk of exposure to drugs consumed by the mother because mammary glands excrete medications.
  • Dosage: The amount of medication transferred to milk is usually lower than in the mother's bloodstream.
  • Risk vs. Benefit: Decisions are made on a case-by-case basis.
    • Short-Term Needs: For short-term conditions like a urinary tract infection (UTI) requiring antibiotics, the mother can pump and discard milk, using formula, and resume breastfeeding later.
    • Long-Term/High-Risk: For long-term medications or those with high risk to the baby, a thorough discussion with the healthcare provider is essential, and breastfeeding might not be recommended.
  • Factors to Consider: Amount of milk consumed by the baby, frequency of feeding (e.g., only at night vs. 24\% hours).
  • Patient Education: Mothers must inform their healthcare providers that they are breastfeeding. Providers cannot visually discern if a woman is breastfeeding, and this information is critical for prescribing safe medications.

Neonates and Pediatric Patients: Pharmacokinetics

Absorption in Babies

  • Gastric pH: Less acidic until 1-2 years of age. This means medications requiring an acidic environment for absorption will be affected because acid-producing cells are not yet fully developed.
  • Gastric Emptying: Slower, meaning medications stay in the stomach longer.
  • First-Pass Effect: Reduced in the liver, meaning a greater proportion of an orally administered drug reaches systemic circulation rather than being metabolized by the liver first. Drugs can stay in the body longer.
  • Intramuscular Absorption: Faster.

Distribution in Babies

  • Total Body Water: Younger individuals have a higher percentage of total body water and lower fat content.
  • Blood-Brain Barrier (BBB): Immature. This lack of a fully developed barrier means that medications that would typically be blocked from entering an adult's brain can easily cross into a baby's brain, potentially causing neurological effects.

Metabolism in Babies

  • Liver Immaturity: The liver is immature and does not produce as many enzymes needed to metabolize medications. This is why dosages are significantly smaller for babies.
  • Dosage Progression: As children grow, their liver function matures, allowing them to metabolize drugs more efficiently and tolerate higher doses.
  • Premature Infants: Have even less developed systems, increasing their risk for problems with drug metabolism and making them highly susceptible to adverse effects.

Excretion in Babies

  • Kidney Immaturity: Kidneys are not fully developed and do not perfuse drugs well, leading to potential problems with excretion and increased risk of toxicity.
    • Clinical Example: A nurse inadvertently administered an adult dose of heparin (a blood thinner) to twin infants. Given their immature blood-brain barrier, metabolism, and excretion systems, the babies were at severe risk. This highlights the critical importance of careful pediatric dosing.

Factors Affecting Pediatric Dosage

  • Skin: Thin and permeable, meaning topical medications are absorbed more readily into the bloodstream. Caution is needed with medicated creams and lotions.
  • Stomach: Non-acidic environment, which means it cannot kill bacteria effectively. Sterilized bottles and clean practices are crucial to prevent bacterial infections.
  • Lungs: Weaker mucus barrier, reducing their protective capabilities.
  • Temperature Regulation: Babies cannot regulate their body temperature well. They need to be kept warm and bundled.
  • Liver and Kidneys: Immature, as discussed previously.

Pediatric Dosage Calculations

  • Method: Pediatric dosages are calculated based on body weight in kilograms, not age.
  • Conversion: Remember the conversion factor: 1 \text{ kg} = 2.2 \text{ lbs}. Always convert pounds to kilograms for pediatric dosing.

Pediatric Medication Administration

  • Preparation: Always gather all necessary supplies before entering the room to maintain efficiency and confidence, and to minimize stress for the child and parent.
  • Parent/Caregiver Involvement: Ask parents/caregivers for assistance and their insights on how the child usually takes medicine.
  • Age-Specific Approaches:
    • Infants: Communicate primarily with the mother/primary caregiver.
    • Toddlers: Allow them time to warm up to you. Keep explanations short, simple, and make the process quick and painless.
    • Preschoolers/School-age: Similar to toddlers, avoid lengthy explanations. Engage them at their level.
    • Adolescents: Involve them in their care. For injections, consider asking the parent to step out momentarily to empower the adolescent and respect their desire for independence in healthcare decisions. Refer to review box on page 36 for specific strategies.
  • Mixing Medications:
    • Disguise unpleasant tastes by mixing with small amounts of desirable foods (e.g., ice cream)..
    • Do NOT mix medications with essential foods or fluids (e.g., formula, vegetables) that the child needs, or with a full bottle/cup of liquid. If the child doesn't finish the food/drink, the full dose of medication will not be received, and the exact amount consumed will be unknown. Give in a very small amount that the child will consume completely.
  • Terminology: **Never call medication