Pediatrics: pharmacokinetics and dose calculation

Abstract

The pediatrics has various pharmacodynamic, physiological and pharmacokinetic properties as well as growth rate in comparison with adults. Gastric pH is neutral at birth but falls to pH 1-3 within twenty four to forty eight hours after birth. At birth, the blood-brain barrier is still not fully mature and medicinal products perhaps obtain access to the central nervous system with sequence toxicity. Plasma protein attaching of compounds is dependent on the amount of present attaching proteins, the number of available binding sites, the affinity constant of the medicine for the protein(s), and the availability of pathophysiological conditions or endogenous compounds that perhaps change the medicine-protein attaching interaction. Total body water, explained as percentage of body weight, reduces with age, from comparatively 80% in newborns to 60% by 1 year of age. Reversibly, body fat accelerates with age, from one percent to two percent in a preterm neonate to ten percent to fifteen percent in a term neonate and 20 to 25% in a 1-year-old. First-pass metabolism of zidovudine was decrease in the first 14 days of life. At birth, renal blood flow is only 5 to 6% of cardiac output, 15 to 25% by one year of age and reaches adult values after two years of age. Children's dosage depends on factors such as their age and weight, their health status, their respiratory system, and the stage of development of their body systems for drugs metabolism (e.g., liver enzymes) and elimination (e.g., kidneys). Young’s rule can be applied quickly approach a situation in which the patients weight is unknown; this rule cannot be used for newborns and consideration must be made for growth variability in growth at any given age. A young’s rule for calculating the dose of medicine correct for a child by adding twelve to the child’s age, dividing the sum by the child’s age, then dividing the adult dose by the figure obtained, as it expressed beneath: (age in years / age (years) + 12)) × adult dose.