**4. Pharmacodynamic changes in children**

Results obtained from clinical trials and experimentation with the animals show that receptor development leads to changes in drug response. Serotonin is a neurotransmitter paying important role in the behavioral and psychiatric disorders. Serotonin at the brain steadily decreases with the increasing age. The pharmacodynamic response of Dopamine,

Protein binding may change with age and concomitant illness. In certain circumstances, an understanding of protein binding may be needed to interpret the data from a blood level measurement and to determine appropriate dose adjustments. In vitro plasma protein binding studies can determine the extent of binding of the parent and the major active metabolite(s) and identify specific binding proteins, such as albumin and alpha-1 acid glycoprotein. Optimal estimates of the degree to which protein binding is linear may be obtained by testing

The main reason that age affects drug action is that drug elimination is less efficent in newborn babies and in old people, so that drugs commonly produce greater and more prolonged effects at the extremes of life. Other age-related factors, such as variation in

Drug excretion by the kidney is controlled by glomerular filtration, tubular secretion, and tubular re-absorption (Buxton & Benet, 2011). Because these processes mature at different rates in the pediatric population, age can affect systemic exposure for drugs where renal excretion is a dominant pathway of elimination. Consideration should also be given to the maturation of other excretory pathways, including biliary and pulmonary routes of excretion. Glomerular filtration rate (GFR) in the newborn, normalized to body surface area, is only about 20% of the adult value, and tubular function is also reduced. Accordingly, plasma elimination half-lives of renal eliminated drugs are longer in neonates than in adults. In babies born at term, renal function increases to values similar to those in young adults in less than a week, and indeed continues to increase to a maximum of approximately twice the adult value at 6 months of age. The increase in renal function occurs more slowly in premature infants. Renal immaturity in premature infants can have a very large effect on drug elimination. For example, in premature newborn babies the antibiotic Gentamicin has a plasma half-life of 18 hours or greater, compared with 1-4 hours for adults, and approximately 10 hours for babies born at term. It is, therefore, necessary to reduce and/or

Drugs and their metabolites are excreted through sweat, urine, stools, or enzymes. By the time kidney functions develop, disposing drugs via urinary system is limited. The glomerular filtration speed and the circulation in kidneys are 30-40% of adults; this ratio is even smaller for infants delivered before 34 weeks. Following the first two weeks, the glomerular filtration speed is doubled, eventually reaches to adult-levels in 2.5 – 5 months (Çetinkaya &Tengir, 2006). Glomerular filtration speed meets adult levels in 6 – 12 months

Results obtained from clinical trials and experimentation with the animals show that receptor development leads to changes in drug response. Serotonin is a neurotransmitter paying important role in the behavioral and psychiatric disorders. Serotonin at the brain steadily decreases with the increasing age. The pharmacodynamic response of Dopamine,

(Pala & Baktr, 2011). The half-lives of drugs also change (Pala & Baktr, 2011).

maximumand minimum observed concentrations (Buxton & Benet, 2011).

pharmacodynamic sensitivity, are also important with some drugs.

space out doses to avoid toxicity in premature babies.

**4. Pharmacodynamic changes in children** 

**3.4 Protein binding** 

**3.5 Excretion** 

also an important neurotransmitter, varies largely in the newborn and adult test animals. Many neurological, psychiatric and behavioral disorders are related to the dopamine at SSS. Among the pharmacodynamic responses of the drugs which are being used against this type of disorders may show significant differences during infancy and childhood.

Major factors affecting the newborn's response to a treatment: Gestation age, chronological age, weight, development phase, liquid-electrolyte balance, disorder level at the organ systems and functions, presence of co-existing diseases, accompanying other medication (Oval, 2008).
