Developmental Pharmacology Flashcards
Its okay to simply scale the adult dose based on the child’s body weight or surface area (T/F)
F.
Pediatric dosage regimens should take into account _____and _____.
- age or developmental stage
2. disease state of the child
Give the diseases caused by these drugs:
- THALIDOMIDE used to treat morning sickness of pregnant women
- Administration of IV CHLORAMPHENICOL in babies
- Exposure of DIETHYLSTILBESTROL in utero
- Phocomelia = loss/malformation of limbs
- Gray Baby Syndrome = immature liver enzyme cant metabolize chloramphenicol
- Adenovaginal Carcinoma
Marked the modern era of pharmaceutical regulation
Kefauver-Harris Drug Amendments of 1962
Children are not small adults.
Dosing should be based on a rule and scaling of body weight or surface area. What are those 2 rules?
Young’s Rule
Clark’s Rule
What is Clark’s Rule?
Clark’s Rule uses Weight in Lbs, NEVER in Kg.
Adult Dose X (Weight ÷ 150) = Childs Dose
What is Young’s Rule?
Young’s Rule uses age.
Adult Dose X (Age ÷ (Age+12)) = Child’s Dose
Developmental Continuum:
Weight doubles when? triples when?
Surface area doubles when?
Caloric expenditure increases how many fold by 1 year?
5 mos., 1 year;
1 year;
3-4x;
Developmental Changes that influence drug disposition
Clue: M-GRID
M-GRID:
Metabolism, GI fxn Renal fxn, Integumentary Dev’t, Distribution sites
PK - ABSORPTION:
2 main factors affecting Absorption in Pedia?
Give examples for each factor.
- Drug characteristics (solubility, size, ionization, conc, inactive components)
- Host Factors (Surface Area, Blood flow, GI Peristalsis)
Changes in GI Fxn:
Clue: P-BAGS
- Perfusion - in intestinal smooth muscles, it is decreased
- Biliary Fxn - not fully developed in neonates
- Acidity - Alakline at start (pH 6-8), becomes acidic later on (pH 1-3)
- GET - delayed (6-8hrs), during 6th-8th month of life
- Sterility
Changes in GI Fxn:
When is CYP1A1 produced?
When is glutathione conjugation possible?
@ 3mos;
1-3 y.o.;
Changes in GI Fxn:
Drugs that are absorbed in the stomach?
Drugs that are poorly absorbed?
- Weakly acidic, non ionized drugs
2. Chloramphenicol, Tetracycline, Erythro, Phenytoin, Phenobarbital, Paracetamol
Changes in GI Fxn:
2 drugs that cant be processed due to the sterile intestinal tract of neonates
Sterile GI = cannot hydrolyze prodrug into active drug:
- Chloramphenicol
- Pro-ampicilline
Integumentary Devt in Neonates:
4 routes of absorption
Percutaneous: (higher absorption in neonates than in children)
Parenteral: (erratic absopriton of IM and SQ morphine)
Rectal: (route of admin for paracetamol and diazepam)
Inhalational: (for asthma)
Integumentary Devt in Neonates:
Skin testing in Neonates to detect allergy is not informative. Why?
Due to absence of histamine in neonatal skin until 3rd week of life
PK - DISTRIBUTION:
4 factors affecting drug distribution
- Size of body compartments
- Protein binding
- Blood flow
- Development of Blood-organ barrier (blood brain, blood ocular)
Lipophilic drugs have higher Vd in neonates/infants. (T/F)
F. Neonates have more Body Water than Adults. High ECF volume leads to greater Vd of water soluble drugs (ex. Sulfa antibiotic).
Ontogeny of Body Composition:
What are the changes in body composition?
- Dec. in H2O content (85% in premature –> 75% in full term)
- Dec in ECF volume (due to shift of H2O from EC to Intracellular; 60% in premature –> 20% by puberty)
- Inc in Body fat (5% in premature –> 15% in fullterm; decreases when infant start walking)
In order to achieve comparable plasma and tissue concentration of drugs, higher doses per kg of body weight must be given to infants compared to adults. (T/F)
T
Tissue and Organ Weight:
What organs are enlarged in infants?
- Liver
- Kidney
- Brain (5x bigger than in adults by proportion)
Plasma Protein Binding:
Degree of drug binding to plasma proteins is proportional to the Vd (T/F)
F. It is inversely related to Vd.