chapter 50 children as patients

Question 1

distribution of drugs in infants/children

Answer 1

• because infants have high body water ratios-require higher doses of hydrophilic drugs and decreased distribution of lipid-soluble drugs
• infants

Question 2

phase I enzymes in infants/children

Answer 2

-drug inducing metabolic enzyme meds have great influence during 1st yr of life
-small intestines major site for absorption of drugs from these enzymes
-metabolic clearance adults at 1-2 yrs, =to adults at puberty
-cystic fibrosis can affect metabolism-requiring higher doses
-foods that impact pathway: grapefruit juice, cruciferous veggies, charbroiled foods
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Question 3

drug absorption in children

Answer 3

-factors affecting absorption: blood flow at site (IM/subQ), GI function, and thin stratum corneum
-ill newborns have poor blood flow-affecting absorption-as health improves rapid absorption can occur
-gastric acid secretion can take up to 4 days after birth to reach normal levels
-unpredictably absorbed in general
-gastric pH levels reach adult values btwn 20-30 months-prior very acidic; weak acids (i.e. phenobarbital or dilantin) less absorbed; more basic drugs (i.e. diazepam) absorbed faster
-prolonged gastric emptying time until 6-8 months-increased absorption in stomach until then; end up with increased bioavailibilty
-increased intestinal motility–limited h2o solubility
-thin stratum and larger body surface area in relation to size-children absorb topical medications more readily than adults
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Question 4

phase II enzymes in children

Answer 4

• responsible for synthesis of water soluble compounds
• premature and neonates have lower clearance than children 1-16 ya
• meds metabolized by these enzymes are: acetaminophen, morphine, propofol, caffeine

Question 5

pharmacodynamics in children

Answer 5

• antihistamines and barbiturates may cause hyperactivity in children
• systemic corticosteroids stunt linear growth with prolonged use
• isoniazid less toxic in children
• topical ointments absorbed greater rates than adults

Question 6

pediatric Research Equity Act

Answer 6

• FDA requires studies of drug applications for: new active ingredients, new indications, new dosing regimen, new routes of administration
• other history of FDA: 1906 Wiley Act, 1938: food, drug and cosmetic act-testing toxicity, 1962-mandatory clinical and pre-clinical trials

Question 7

TPMT (thiopurine Methyltransferase)

Answer 7

• there are ethnic variations i.e. Koreans do not reach adult until 7-9 years of age
• seen in common medications
• must monitor levels closely for effectiveness: tylenol, morphine, caffeine

Question 8

pediatric medication administration