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Questions and Answers
When does gastric acid secretion begin in infants?
Soon after birth
Gastric acid secretion reaches its highest concentration on the 4th day of life.
True
What is the pH range of a full term infant's gastric acid secretion?
Why should drugs that are inactivated by low pH not be given orally to neonates?
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What is a critical factor affecting placental drug transfer?
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Gastric acid approaches adult values around ___ months in full-term infants.
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Which of the following drugs' absorption is decreased in very young children?
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Gastrointestinal function for orally taken drugs is consistent throughout the first few days of life.
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What is a primary factor influencing drug absorption in children?
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How does gastric emptying time change throughout infancy?
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What effect does reduced motility in infants have on drug absorption?
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What happens to the absorption of drugs that rely on the small intestine in infants?
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What significant change occurs in drug absorption during the first few days of life?
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How does increased peristalsis affect drug absorption in infants?
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Which physiological factor contributes to decreased lipid solubility and absorption in neonates?
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What characteristic of skin in neonates enhances transdermal drug absorption?
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Which of these statements is true regarding gastrointestinal absorption in young children?
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What change occurs in skin hydration influencing drug absorption as children grow?
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Study Notes
Gastrointestinal Function and Acid Secretion in Infants
- Gastric acid secretion commences shortly after birth.
- Full-term infants have gastric pH levels ranging from 6 to 8 during the first year, particularly in the initial months.
- Gastric acid levels gradually increase over hours, reaching the highest concentration around the 4th day of life.
- Pre-term infants exhibit a slower increase in gastric acid secretion.
Pharmacokinetics in Neonates and Children
- Understanding pharmacokinetics is crucial for administering drugs to neonates and children due to significant physiological changes in early life.
- Oral absorption of drugs is affected by the pH-dependent passive diffusion and gastrointestinal motility, influencing drug transit time.
- During the neonatal period, gastric pH values are the highest (alkaline), affecting drug metabolism and absorption characteristics.
Absorption and Its Implications
- Drugs that are inactivated by low pH should not be given orally to infants.
- Increased bioavailability of acid-labile drugs such as penicillin or ampicillin occurs, requiring careful dosage consideration.
- Conversely, weak organic acids like phenobarbital and phenytoin have decreased absorption, necessitating higher doses for effective therapeutic levels.
Critical Factors Influencing Drug Transfer and Elimination
- Drug transfer through the placenta depends on multiple factors including:
- Molecular weight and ionization degree of the drug.
- Formulation characteristics (solid dosage forms, drug release rate).
- Rate of drug crossing the placenta and duration of fetal exposure.
- Distribution variations in fetal tissues based on developmental stages.
General Principles of Drug Absorption
- Drug absorption in children follows principles similar to adults but is influenced by unique physiological factors.
- Factors include gastric acid approaching adult values around 3 months in full-term infants and blood flow variability at administration sites.
Drug Absorption in Children
- Parenteral drug routes lead to prolonged absorption times (6-8 hours) and complete stomach drug absorption.
- Gastrointestinal function affects drug absorption; gastric emptying is delayed, impacting drugs absorbed in the small intestine (SI).
- Adult-like drug absorption values in the stomach and intestine reach by 6-8 months of life.
- Drugs with limited water solubility, like phenytoin and carbamazepine, have altered absorption rates due to gastrointestinal motility changes.
Gastric Motility and Drug Absorption
- Neonates experience irregular gastric motility and unpredictable SI absorption.
- Slow peristalsis causes more drug absorption but increases toxicity risks with standard doses.
- Increased intestinal peristalsis leads to decreased drug contact time; notable during conditions like diarrhea.
- Transdermal absorption is enhanced in neonates due to hydrated stratum corneum but limited solubilization of lipophilic drugs.
Skin and Drug Absorption
- Skin thickness and hydration levels are age-dependent, impacting drug absorption efficiency.
- Newborns have a greater body surface area to body weight ratio, increasing potential toxicity from topical applications.
- Immature skin barriers in premature infants lead to heightened absorption of drugs and toxins (e.g., hexachlorophene).
Drug Binding and Clearance
- Drug binding to plasma proteins is lower at birth, influencing renal clearance; only free drugs are filtered.
- As plasma protein levels rise (achieving adult levels by year 3 for acidic drugs), prolonged elimination half-lives occur due to immature metabolic pathways.
- Different maturation timelines exist: acidic drugs reach adult binding by year 3, while basic drugs may need up to 7 years.
Dosing Guidelines for Children
- Clark's Rule provides a dosing formula:
Dose = (Adult dose x Weight in kg) / 70. - Dosing based on surface area can lead to more accurate medication administration in children.
Drug Formulations
- Elixirs are homogeneous alcoholic solutions requiring no shaking for consistent drug distribution.
- Suspensions contain undissolved drug particles that require thorough shaking before each dose; improper mixing can lead to inconsistent drug concentrations.
Issues in Pediatric Pharmacology
- Developmental factors necessitate careful weight or surface area-based dosing and additional pharmacological calculations.
- Clear communication between prescribers, pharmacists, and parents is essential for correct drug formulation and administration instructions.
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Description
Explore the critical aspects of gastrointestinal function and acid secretion in infants and children. This quiz delves into the physiological changes during the first year of life, particularly focusing on gastric acid secretion from birth. Test your knowledge on the effects of drugs on this special population.
