Pediatrics pharmacology


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Pediatrics pharmacology

  1. 1. Pharmacology and Pediatrics
  2. 2. Age Groups of Pediatrics PopulationGroup AgePreterm or premature Less than 36 weeks gestational ageNeonate Less than 30 days of ageInfant 1 month until 1 year of ageChild 1 year until 12 years of ageAdolescent 12 years of age until 18 years of age
  3. 3. Oral Drug Absorption in the Neonate vs Older Children and Adults Drug Oral Absorption Acetaminophen Decreased Ampicillin Increased Diazepam Normal Digoxin Normal Penicillin G Increased Phenobarbital Decreased Phenytoin Decreased Sulfonamides Normal
  5. 5. Premature Neonate Neonate Infant Child Adolescent AbsorptionGastric acidity Decreased Decreased Decreased Equal EqualGastric emptying time Decreased Decreased Equal Equal EqualGI motility Decreased Decreased Decreased Equal EqualPancreatic enzyme Significantly Decreased Decreased Equal Equalactivity decreasedGI surface area Increased Increased Increased Increased EqualSkin permeability Significantly Increased Equal Equal Equal increased DistributionBody composition EqualBlood-brain barrier Decreased Decreased Equal Equal EqualPlasma proteins Significantly Decreased Equal Equal Equal decreased MetabolismLiver Decreased Decreased Decreased Equal/Increased Equal EliminationRenal blood flow Decreased Decreased Decreased Equal EqualGlomerular filtration Decreased Decreased Decreased Equal EqualTubular function Decreased Decreased Decreased Equal Equal
  6. 6. Drug Distribution• Drug distribution in the neonate depends on – Amount of body water, body fat and drug binding• Body water (BW) – Neonates have more BW than adults (70% vs 50%) – Full-term: 70% body weight is water – Pre-term: 85% body weight is water• Body fat – Pre-term infants have much less fat than full-term – Lipid soluble drugs may not be accumulated• Drug binding to plasma proteins – Binding of drugs to albumin is reduced – Drug competition for binding albumin may occur
  7. 7. Drug Excretion• GFR is much lower in newborns than in older infants, children or adults• This limitation persists during the first days of life and improves thereafter• Neonatal GFR based on body surface area – Birth: Only 30-40% of the adult value – 3 weeks: 50-60% of the adult value – 6-12 months: Reaches adult values – Thus, renal elimination occurs is very slow initially• Toddlers – Have shorter drug elimination (t½) than older children and adults probably due to ↑ renal elimination and metabolism
  8. 8. Pediatric Dosage Forms• Elixir – Alcoholic solutions in which the drug molecules are dissolved and evenly distributed – No shaking is required – Generally, all doses contain equivalent amounts• Suspension – Contains undissolved drug particles that must be distributed throughout the vehicle by shaking – Caution: Risk of administering unequivalent doses may lead to toxicity or lack of efficacy• Prescriber awareness and care giver education on these differences is important
  9. 9. Compliance• Compliance may be difficult to achieve since it involves many factors – Parent’s ability to follow directions – Measuring errors – Spilling and spitting out• Recommendations to improve compliance – Pill boxes – Calibrated medicine spoon – Ask if parent gives another dose after spitting out – Stress importance of duration of treatment – Instruct whether to wake the child during q6h dosing – Give some responsibility to the child for his/her care
  10. 10. Pediatric Drug Dosage• Most drugs approved for use in children have pediatric doses, stated in mg/kg• If recommendations are not available, an approximation can be made by any of several methods• Methods include : Age, weight, or surface area – Age: Young’s rule – Weight: Clark’s rule – Doses based on age or weight are conservative – Doses based on surface area are more adequate• The calculated pediatric dose should never exceed the adult dose!
  11. 11. Clark’s Rule• Formula for Clarks Rule is: Weight of the child in pounds/150 ("normal" adult weight) X the usual adult dose• The adult dose of a medication is 30 mg. The childs weight is 30 lbs. What is the correct dose? 30/150 = 1/5 1/5 x 30 mg = 6 mg• Preferred method
  12. 12. Young’s Rule• Pediatric doses for children over the age of 2 based on the adult dose. Not as precise as Clark’s rule. Take the age of the child in years and divide that by their age plus 12.• Multiply this number times the adult dose. Pediatric dose = [age/(age + 12)] x adult dose• 2/14 X 250mg = 35 mg for a child age 2 yrs