pharm ch 10
The nurse provides teaching for the caregiver of a 2-month-old infant and a 3-year-old child. Both children will be taking oral ampicillin (an acid-labile drug) to treat a bacterial infection. The nurse determines that teaching is successful if the caregiver makes which of the following statements?
"The dose will be smaller for the baby, because the drug will be absorbed better in the stomach."
Pharmacokinetics: Children 1 year and older
*At 1 year of age, pharmacokinetic parameters are similar to those of adults. Metabolism differences: children metabolize drugs faster; may need to increase dose or decrease dosing interval *Adverse Drug Reactions
Pharmacokinetics: Neonates and Infants
*Infants have immature pharmacoknetic processes -Renal excretion -Hepatic metabolism -Blood Brain Barrier
Compliance of Medication Regimen
*Patient Education Includes: 1. Dosage size and timing 2.Route and technique of administration 3.Duration of treatment 4.Storage 5.Desired responses 6.Adverse Responses "EDUCATE THE PARENTS"
Pediatric Patients
-Pediatrics includes all patients under age 16 -Pediatric populations have 6 groups 1.Premature infants 2. Full-term infants 3.Neonates 4.Infants 5. Children 6.Adolescents
Promoting Compliance
-Use convenient drug forms -Select dosing times to fit life style of patient -Mix drugs with foods when allowed -spend extra time for demonstrations
Absorption of IM drugs in neonates is slower than in adults
. In contrast, absorption of IM drugs in infants is more rapid than in adults.
Blood Brain Barrier
. is not fully devoloped at birth. Decrease dose of CNS drugs and those durs which are potentially toxic
Children
1-12 years old
Adolescents
12-16 years old
Full-term infants (fetas)
36-40 weeks' gestation age
Infants
5-52 weeks
Pediatric Patients
All patients younger than 16 years old Pediatric patients respond differently to drugs than the rest of the population More sensitive to drugs than other patients are Show greater individual variation Sensitivity due mainly to organ system immaturity Increased risk for adverse drug reactions Ongoing growth and development Different age groups have different challenges Two-thirds of drugs used in pediatrics have never been tested in pediatric patients Two laws: Best Pharmaceuticals for Children Act (2002) Pediatric Research Equity Act of 2003 These laws were permanently reauthorized as part of the FDA Safety and Innovation Act (FDASIA) of 2012 Twenty percent of drugs were ineffective for children even though they were effective for adults Thirty percent of drugs caused unanticipated side effects, some of which were potentially lethal Twenty percent of drugs required dosages different from those that had been extrapolated from dosages used in adults
Dosage Determination
Approximate child's dose= body surface area of the child x adult dose/ 1.73 m (squared) *biggest factor is weight!!! *Use the body surface area to determine the dosage!
Increased sensitivity in infants
Caused by immature state of five pharmacokinetic processes: •Absorption •Protein binding of drugs •Blood-brain barrier •Hepatic metabolism •Renal drug excretion
Adverse Drug Reactions
Children are vulnerable to unique adverse effects related to organ immaturity and ongoing growth and development Age-related effects: •Growth suppression (caused by glucocorticoids) •Discoloration of developing teeth (tetracyclines) •Kernicterus (sulfonamides)
Pharmacokinetics: Children Age 1 Year and Older (Cont.) one important difference
Children in this age group metabolize drugs faster than adults •Markedly faster until the age of 2 years, then a gradual decline •Sharp decline at puberty •May need to increase dosage or decrease interval between doses
promoting adherence Effective education should include the following:
Dosage size and timing Route and technique of administration Duration of treatment Drug storage The nature and time course of desired responses The nature and time course of adverse responses
Dosage Determination
Dosing is most commonly based on body surface area Initial pediatric dosing is, at best, an approximation Subsequent doses need to be adjusted Approximate dosage for a child = "Body surface area of the child × Adult dose " /"1.73 m²"
Intramuscular administration.
Drug absorption following IM injection in the neonate is slow and erratic (not even or regular in pattern or movement) due to low blood flow in neonate muscle. by early infancy, absorption of IM drugs becomes more rapid than in neonate and adults.
Dosage Adjustments
For dosage adjustments to be optimal, it is essential that we monitor the patient for therapeutic and adverse responses.
gestational age
Gestational age (or menstrual age) is a measure of the age of a pregnancy where the origin is the woman's last normal menstrual period (LMP), or the corresponding age as estimated by other methods.
Renal excretion of drugs is low in neonates
Hence, drugs that are eliminated primarily by the kidney must be given in reduced dosage and/or at longer dosing intervals.
Protein-binding capacity is limited early in life.
Hence, free concentrations of some drugs may be especially high.
The blood-brain barrier is not fully developed at birth
Hence, neonates are especially sensitive to drugs that affect the CNS.
The drug-metabolizing capacity of neonates is low.
Hence, neonates are especially sensitive to drugs that are eliminated primarily by hepatic metabolism.
Initial pediatric doses are at best an approximation
Hence, subsequent doses must be adjusted on the basis of clinical outcome and plasma drug levels.
Pharmacokinetics: Children Age 1 Year and Older
Most pharmacokinetic parameters are similar to those of adults Drug sensitivity more like that of adults than for children younger than 1 year old
Pharmacokinetics: Neonates and Infants Absorption
Oral administration Intramuscular administration Percutaneous absorption
Drug Therapy in Pediatric Patients
Pharmacokinetics: Neonates and infants Determining the concentration of a drug at its sites of action Determining the intensity of the duration of response Elevated drug levels = more intense response Delayed elimination = prolonged response Immaturity of organs puts patient at risk for both of these responses
A 15-month-old patient develops chemotherapy-induced nausea and vomiting. Which medication, if ordered by the healthcare provider, should the nurse question?
Promethazine [Phenergan]
Pharmacokinetics: Neonates and Infants distribution
Protein binding Blood-brain barrier
Promoting Adherence
Provide patient education in writing Demonstration techniques should be included as appropriate
Renal Excretion
Renal blood flow low in infancy, decrease drug dosages *low blood flow, drug excretes slow
Renal excretion
Significantly reduced at birth Low renal blood flow, glomerular filtration, and active tubular secretion Drugs eliminated primarily by renal excretion must be given in reduced dosage and/or at longer dosing intervals Adult levels of renal function achieved by 1 year
A toddler has been prescribed a medication that does not have an established pediatric dose. To calculate the appropriate dose for the child, the nurse should consider what information?
The child's body surface area is 0.52 kg/m2.
A 2-year-old child is prescribed an oral drug that is eliminated by metabolism in the liver. Based on the child's age, the nurse would expect to make which adjustment?
The drug may need to be administered more frequently.
Hepatic metabolism Pharmacokinetics: Neonates and Infants
The drug-metabolizing capacity of newborns is low Neonates are especially sensitive to drugs that are eliminated primarily by hepatic metabolism The liver's capacity to metabolize many drugs increases rapidly about 1 month after birth The ability to metabolize drugs at the adult level is reached a few months later Complete liver maturation occurs by 1 year of age
Adjustment of dosage for infants in the basis of body size alone is not sufficient to achieve safe result, then What is?
The increased sensitivity of infants is due largely to the immature state of five pharmacokinetic processes: 1). Drug absorption. 2). Protein binding of drug. 3). Exclusion of drug from the central nervous system (CNS) by the blood-brain excretion. 4). hepatic drug metabolism. 5). Renal drug excretion.
Key point
The majority of drugs used in pediatrics have never been tested in children. As a result, we lack reliable information on which to base drug selection or dosage.
Pharmacokinetics: Neonates and Infants Gastric acidity
Very low 24 hours after birth Does not reach adult values for 2 years Low acidity: Absorption of acid-labile drugs is increased
blood-brain bar·ri·er
a filtering mechanism of the capillaries that carry blood to the brain and spinal cord tissue, blocking the passage of certain substances.
older patients are generally more sensitive to drugs than younger adults
and they show wider ind variation
most case 75% of nonadherence amond older adults
are intentional. reasons include expense, side effects, and the patients conviction that the drug is unnecessary of the dosage too high
tools such as the beers list or START and STOPP criteria
can be used to identify potentially inappropriate drug choices for elderly patients
because the degree of renal impairment among older adults varies
creatinine clearance (a measure of renal function) should be determined for all patients taking drugs that are eliminated primarily by the kidneys
Children 1 to 12 years
differ pharmacokinetically from adults in that children metabolize drugs faster.
Transdermal Absorption
drug absorption through the skin is more rapid and complete with infants than with older children and adult due to very thin skin stratum corneum layer.
aging-related organ decline can change
drug absorption, distribution, metabolism and (especially) excretion
In neonates and young infants,
drug responses may be unusually intense and prolonged.
individualization of therapy for older adults is essential
each patient must be monitored for desired and adverse responses, and the regimen must be adjusted accordingly.
Neonates
first 4 weeks of life
adverse reactions are much more common
in older adults than younger adults
reasons for unintentional non adherence
include complex regimens akward drug packaging forgetfulness side effects low income and failure to comprehend instructions
nonadherence
is common among older adults
Drug Absorption
it varies on physicochemical properties, it may enhanced or impeded.
Premature Infants (fetas)
less than 36 weeks' gestation age
plasma concentrations of lipid-soluble drugs
may be low in older adults, and concentrations of water-soluble drugs may be high
the rate of drug absorption
may be slowed in older adults, although the extent of absorption is usually unchanged
reduced liver function
may prolong drug effects
Hepatic Metabolism
metabolizing capacity low, decrease dose, complete maturation of liver by age of 1
In Children 1 year and older,
most pharmacokinetic parameters are similar to those in adults. Hence, drug sensitivity is more like that of adults than the very young.
Distribution. protein binding
of drug to albumin (a simple form of protein that is soluble in water ) and other plasma protein is limited in the infant
factors underlying the increase in adverse reactions included
polypharmacy severe illness comorbidities, and treatment with dangerous drugs
priority treatment
varies as goals shift from disease prevention and management to provision of comfort measures
Because of organ system immaturity,
very young patients are highly sensitive to drugs.
reduced renal function
with resultant grug accumulation, is the most important cause of adverse drug reactions in older adults
Pharmacokinetics: Neonates and Infants- Distribution Protein binding
•Binding of drugs to albumin and other plasma proteins is limited in the infant •Amount of serum albumin is relatively low
Pharmacokinetics: Neonates and Infants Absorption Oral administration
•Gastric emptying time Prolonged and irregular Adult function at 6 to 8 months
Pharmacokinetics: Neonates and Infants Endogenous compounds compete with drugs for available binding sites
•Limited drug/protein binding in infants •Reduced dosage needed •Adult protein binding capacity by 10 to 12 months of age
Absorption Transdermal absorption neonates and infants
•More rapid and complete for infants than for older children and adults •Stratum corneum of infant's skin is very thin •Blood flow to skin greater in infants than in older patients •Infants at increased risk of toxicity from topical drugs
Pharmacokinetics: Neonates and Infants-Distribution Blood-brain barrier
•Not fully developed at birth •Drugs and other chemicals have relatively easy access to the central nervous system (CNS) •Infants especially sensitive to drugs that affect CNS function •Dosage should also be reduced for drugs used for actions outside the CNS if those drugs are capable of producing CNS toxicity as a side effect
Intramuscular administration- absorption neonates and infants
•Slow •Erratic •Delayed absorption as a result of low blood flow during the first few days of life •During early infancy, absorption of intramuscular drugs more rapid than in neonates and adults
A nurse is preparing to orient new nurses to the pediatric unit. When discussing the differences in the distribution of medication for infants as compared with adults, the nurse will inform the orientees that the amount of water in a young infant's body differs from that found in the body of an adult. How does it differ? What are the clinical implications?
•The water content in the body of a young infant is about 70%. This will drop to 50% as the young infant matures. Until the age of 2 years, babies require a larger dose of water-soluble medications to achieve desired therapeutic effects as a result of the large proportion of water in their bodies. Because of the higher proportion of water as compared with adults, young infants have more extracellular fluid, thereby increasing their chances of becoming dehydrated.
Is there any information that the nurse should teach the new orientees about the administration of medications to young infants with regard to the blood-brain barrier?
•Yes. The new orientees should be made aware that the efficacy of the blood-brain barrier in infants is decreased as compared with that of adults, so the chance of a young infant developing neurologic toxicity is increased.
What should the nurse teach the orientees about young infants' medication requirements related to the administration of fat-soluble medications and medications that bind to plasma proteins?
•Young infants have less body fat than adults. As a result, doses of fat-soluble medications as well as medications that bind to plasma proteins will need to be decreased.
