![]() ![]() ![]() Other factors that influence the amount and rate of a drug absorbed from the gastrointestinal tract include drug formulation, drug solubility and pK, concomitant administration of other drugs, and simultaneous ingestion of food. In addition, neonates and infants have different gastrointestinal flora. When administering drugs orally in neonates and infants, one must remember that they have diminished gastrointestinal motility, resulting in a relatively slower rate for the drug to reach therapeutic systemic levels compared with older children ( 4). Being dependent on blood supply and flow to the injected muscle, intramuscular dosing of such drugs should be avoided whenever possible. In contrast, absorption of some drugs, such as phenytoin or diazepam, after intramuscular administration is slower and less complete. Administration by the intravenous route provides immediate systemic bioavailability. Thus, it is important to have a clear understanding of not only the principles of TDM but also the additional factors inherent in and specific to pediatric clinical pharmacology.ĭrug absorption is affected by numerous factors, including the route of administration, drug formulation, age of recipient, and concomitant administration of other drugs or food ( 3). Obviously, drug concentrations in many of these patients need to be monitored by the laboratory, and the possibility of drug interactions needs to be considered. Further, review of drug-dosing habits in neonatal intensive care units has shown that the average number of drugs administered to premature infants weighing less than 1,000 g varies from institution to institution but is usually in the range of 15 to 20 drugs infants weighing more than 2,500 g usually receive 4 to 10 drugs during their hospital stay. Recent indications are that approximately 12% of all drugs prescribed in the United States are for children age 9 years and younger ( 4). Neonates, infants, and children undergo major and rapid age-related physiologic and biochemical changes, especially during the first year of life, resulting in different clinical pharmacokinetic and pharmacodynamic parameters from adults ( Table 1). The criteria for monitoring drugs in children are the same as those for adults ( 6), but several additional factors must be considered. There must be a rapid and reliable method for the analysis of the drug. ![]()
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