Principles of Pharmacologic Management
Medication administration is one of the most challenging and critical aspects of pediatric nursing. Unlike adult medication administration, in which a “one-dose-fitsall” principle generally applies, pediatric dosing must be individualized. Pediatric medication administration must focus on age-related developmental considerations because the pharmacokinetic and pharmacodynamic drug effects are less predictable in children, especially in preterm and young infants because of their much smaller size and their organ system immaturity. Therefore, close monitoring is important. Likewise, safe administration of the right dose to the right patient at the right time through the right route is a critical issue because children are at highest risk for medication errors and are a group more vulnerable to potential side effects and overdose. Ensuring safe administration of medication is a multidisciplinary responsibility that involves the prescriber, pharmacist, and nurse who serve as a check and balance team. Education of nurses is a key element to ensure reliable administration of medications. This is particularly true for those nurses who administer medications that present a heightened risk of causing significant patient harm when used incorrectly.
DEVELOPMENTAL CONSIDERATIONS IN PHARMACOKINETICS AND PHARMACODYNAMICS
Children can vary greatly, from the 500-g (1.1-lb) premature newborn infant to the 100-kg (220.5-lb) overweight teenager. Thus, size and age are key factors that affect the child’s ability to handle the absorption, distribution, metabolism, and elimination of drugs. For instance, although neonates are born with all the enzymes necessary for drug metabolism, only 10% to 40% of these enzymes have the ability to adequately metabolize drugs compared with that of the adult. Renal elimination of drugs in the neonate is also less efficient and takes several years to reach adult capacity, although liver function reaches adult capacity and exceeds it within the first several months of age. The age of a child is one of the most influential variables in understanding the four pharmacokinetic functions of absorption, distribution, metabolism, and elimination/excretion of drugs; this calls for differing dosages for neonates (preterm and term), infants, and young children. Chart 6-1 lists key developmental issues related to pharmacokinetics and the route of administration. All four pharmacokinetic functions are important considerations in the choice of medications and selecting dosages that can be safely prescribed for a child.
A related concern is the mother who is breast-feeding and taking medications or herbs (supplements and teas) and whether there is the potential for harm to the infant. Certain drugs are contraindicated with breast-feeding because of their adverse effect on the developing infant. The American Academy of Pediatrics Web site (www. aap.org) has information about such contraindicated drugs. Other medications may be taken by the mother with instructions about how soon before or after breastfeeding she may take the drug, taking the drug before the infant’s longest sleep period, and, if necessary, the need to temporarily withhold breast-feeding. Hale’s Medications and Mother’s Milk (2012) is an excellent resource on this topic. It is also important to consider herbal supplements because they may have one or two main ingredients but may contain many other chemicals not identified on the label. Mothers often assume that herbs are natural and thus safe when breast-feeding. The Organization of Teratology Information Services (http://www.otispregnancy.org) has information on medications and herbal agents in its databases. Nurses must be aware of these issues when caring for an infant who is receiving breast milk and educate mothers about the safe use of medications and herbs.
THE SIX RIGHTS
THE RIGHT MEDICATION
Selection of a medication is based on the child’s need for pharmacologic therapy and the ability of the child’s body to handle the drug; that is, to absorb, distribute, metabolize, and eliminate/excrete the drug. Many of
the medications prescribed for pediatric patients do not have U.S. Food and Drug Administration (FDA) approval for use in pediatric patients; this practice is known as off-label use. Prescribers use pediatric pharmacologic reference sources to prescribe these off-label medications and ask pediatric nurses to administer these medications. With the enactment of the FDA’s Pediatric Studies rule in 1998, new drugs that seek FDA approval and are likely to be used in children must include labeling information for pediatric use.
the medications prescribed for pediatric patients do not have U.S. Food and Drug Administration (FDA) approval for use in pediatric patients; this practice is known as off-label use. Prescribers use pediatric pharmacologic reference sources to prescribe these off-label medications and ask pediatric nurses to administer these medications. With the enactment of the FDA’s Pediatric Studies rule in 1998, new drugs that seek FDA approval and are likely to be used in children must include labeling information for pediatric use.
CHART 6-1 Developmental PharmacokineticsFactors that Affect Absorption of Drugs
Gastrointestinal
Gastric pH is high in neonates, with adult values by 2 years of age. Acidic drugs are more bioavailable; basic drugs have decreased bioavailability. Gastric and intestinal motility (transit time) is decreased in neonates and infants but increased in older infants and children.
The bile acid pool and biliary function are diminished in the newborn and reach full capacity over the first several months of life.
Rectal
Only selected drugs are suitable for rectal administration. In addition, length of exposure to the rectal mucosa affects absorption.
Intramuscular
Variable in the pediatric age group secondary to (a) blood flow and vasomotor instabilities, (b) insufficient muscle tone and contraction, and (c) decreased muscle oxygenation.
Percutaneous
Decreased with increased thickness of the stratum corneum and directly related to skin hydration. Neonates and infants have increased skin permeability, allowing greater penetration of medication and a greater surface area-to-body weight ratio with potential for toxicity.
Intraocular
The membranes of infants and neonates are particularly thin; ophthalmic eye medications can cause systemic effects in infants and young children.
Factors that Affect Distribution
Neonates have a higher proportion of total body water that rapidly reduces during the first year of life. Adult values are gradually reached by 12 years of age. This factor is an important consideration related to the water solubility of a drug.
Children have a lower proportion of body fat than do adults.
Protein binding of drugs is age dependent. Total protein concentration at birth is only 80% of adult values, which leads to more free- or active-drug circulation and potential for toxicity.
Fetal albumin in the newborn period has limited drugbinding ability.
An immature blood-brain barrier during the newborn period can lead to higher concentrations of drugs in the brain than at other ages.
Factors that Affect Metabolism
The newborn’s enzymatic microsomal system is less effective.
Liver maturation varies among individuals; each liver enzyme becomes functional at a different rate.
Factors that Affect Elimination
Glomerular filtration and tubular secretion are reduced at birth.
There is gradual increase in renal function, with adult values reached the first 1 to 2 years of life.
View the nurse’s responsibility in administering “the right medication” as a multistep process. The nurse must know the indications for the medication prescribed and its potential side effects and must be knowledgeable about the child’s medical illness, disease, or condition. Thus, if an unusual, unlikely, or contraindicated medication is prescribed for a child, the nurse must clarify the order. For example, an order to give trimethoprim-sulfamethoxazole (Bactrim) to a child with a known sulfa allergy should alert the nurse to address this issue with the practitioner who prescribed the medication. Ensure that all allergies to medication are clearly visible on the patient record, all order forms, and on the medication administration record (MAR). On a busy pediatric unit, records of patients with the same last name can be confused, and medication orders may be written for the wrong patient. An order for furosemide (Lasix) prescribed for Mary Smith could inadvertently be written as an order in Margaret Smith’s record. An alert should be posted on the record regarding similar names.
The nurse must also properly identify the medication sent from the pharmacy or taken from the patient’s medication drawer with the patient’s MAR. This is another step in the verification process to ensure that the correct medication is administered. Check the expiration date. Do not use expired medications; return them to the pharmacy and order a replacement medication. To reduce the chance that the wrong medication is administered, amber-coated syringes are often used as an added safeguard to help differentiate oral medications from intravenous (IV) medications that are dispensed in clear syringes from the pharmacy.
To administer the right medication, the nurse should do the following:
Know the medication to be administered, its indication for use, action, contraindications, and side effects.
Understand the connection between the patient’s condition, illness, or disease and the use of a particular medication. If such a linkage is not present, clarify the medication order.
Select the correct medication from the patient’s medication drawer or from medications sent to the unit from the pharmacy.
Verify the medication label with the patient’s MAR. A triple verification of labels with the MAR can help to prevent medication identification errors. Check the label when first obtaining the drug, when preparing the dose, and when returning the container to the patient’s medication box or discarding it.
THE RIGHT DOSE
There are two “rights” in dosing. Prescribing the correct dose for the child is the first right, and dispensing the correct dose is the second.
Prescribing the Correct Dose
The nurse is responsible for knowing that the prescribed dose of medication is within safe dosage range. In pediatrics, dosages are calculated using body weight or body surface area (BSA).
To verify the right dose using body weight, look up the established standard dose from a pediatric reference and multiply the child’s weight in kilograms to see whether the dose ordered is correct. For example, if the reference dose is 10 to 20 mg/kg per 24 hours divided every 6 hours and the child’s weight is 10 kg, the child should receive 100 to 200 mg per 24 hours, or 25 to 50 mg every 6 hours. Compare the actual order to verify that it is within the recommended range.
A reverse calculation can also be done starting with the original order. For example, the order says to give 250 mg every 6 hours for a child weighing 10 kg. Multiply 250 mg times 4 (every 6 hours is four times a day) to find the total daily dose, which in this case is 1,000 mg per 24 hours. Divide the 1,000 mg per 24 hours by the patient’s weight to obtain the milligrams per kilogram per 24 hours. Thus, 1,000 mg per 10 kg comes out 100 mg/kg per 24 hours. Look up the reference range for the drug and compare the two. In this case, the reference range is 50 to 150 mg per 24 hours; hence, the dose that was ordered (100 mg per 24 hours) is within the established reference range.
To calculate a dose using BSA, the child’s height and weight are needed. Verify the correct dose from a pediatric reference source and then use a nomogram, which computes the relationship between height and weight to obtain the BSA (Figure 6-1). An alternative to using the nomogram to calculate BSA is Mosteller formula:
BSA is used primarily when calculating doses of cancer chemotherapeutic drugs because it is the most accurate measure for dosing medications for pediatric patients. For example, if the reference source recommends 100 mg/m2 per 24 hours in two divided doses and the child’s BSA is 0.5 m2, then 0.5 m2 times 100 mg equals 50 mg per 24 hours, or 25 mg every 12 hours. The actual order reads 25 mg every 12 hours (50 mg per 24 hours), so the dose ordered is within the established reference range.
Always double-check medication calculations. Misplacing a decimal point can result in the patient receiving one tenth of the required amount of medication or 10 times the ordered amount of drug. For example, if the patient is to receive 1 mg and the decimal point is misplaced while calculating, the result could be 0.1 or 10 mg.
When looking up reference ranges for dosing, verify the maximum amount of the medication that should be given either per dose or per 24 hours. Maximum dosage is important, especially in the overweight child. For example, if the body weight of a child weighing 100 kg was used to determine a drug dose, the amount of drug ordered would likely exceed the capacity of the liver of the child to metabolize the drug or the renal system’s ability to safely eliminate the drug. Often, adult range of dosing is used as the drug reference for children who weigh more than 50 kg (with some healthcare prescribers using 40 kg as the cutoff point).
Most drugs are dosed by weight; however, there are certain factors that may also influence dosing in children. Age-related metabolic changes and organ dysfunction may be factors in addition to weight that are considered in determining an appropriate dose of a medication for an individual child.
Dispensing Individual Doses
Pediatric nurses are often called on to draw up an individualized dose before administering the medication to the patient. It is important to set up equations in a consistent fashion when drawing up a medication from a multidose container or from a single-dose container that contains more medication than the ordered dose. For example, if a multidose container is labeled as cephalexin (Keflex), 250 mg per 5 mL, and the ordered amount is 200 mg of oral suspension, set up the equation as 250 mg/5 mL = 200 mg/X mL to calculate that 4 mL must be drawn up to obtain the necessary 200 mg. Similarly, an oral syringe containing ranitidine syrup, 15 mg/mL, may be sent from the pharmacy. If the order reads ranitidine, 10 mg orally, set up the equation as
15 mg/1 mL = 10 mg/X mL to calculate that the nurse would draw up 0.67 mL.
15 mg/1 mL = 10 mg/X mL to calculate that the nurse would draw up 0.67 mL.
 Figure 6-1 Nomogram for estimation of body surface area. If the child is of average size, use the shaded box on the left to find the weight (left side of box) and then the corresponding surface area (right side of box). In the nomogram on the right, the child’s surface area is indicated where a straight line that intersects the height and weight levels intersects the surface area column. |
Administration of IV medication is often challenging in pediatrics, especially if the nurse must prepare a drug that comes as a powdered medication. The nurse must first dilute the powdered medication with sterile normal saline or water, determine the final concentration of medication, and then calculate how much fluid is needed to obtain the ordered amount of medication. For example, a child is to receive 225 mg of ampicillin intravenously and a 250-mg vial is sent from pharmacy. The vial says to use 1.8 mL of sterile diluent with a resulting final volume of 2 mL. The nurse sets up a math proportion and calculates that 1.8 mL of the solution is needed to obtain 225 mg of ampicillin. Always double-check medication calculations if the drug is not sent from the pharmacy as a unit dose that contains the exact dosage of medication as ordered. Infusion times, the length of time the medication is infused over, are also important considerations for maintaining blood levels of the drug or to prevent adverse reactions. Use only recommended infusion times to deliver IV medications. Infusion times (e.g., 5, 20, 30, 60 minutes) and required fluid volume dilutions for medications are based on established concentration levels necessary to deliver IV medications; consult a reference source for dilutions and infusion times.
Key points to remember in determining the right dose include the following:
Pediatric dosages are calculated based on weight in kilograms or BSA.
Adult dose reference ranges, rather than kilogram dosing, may be used in children who weigh more than 50 kg (with some healthcare prescribers using 40 kg as the cutoff point).
Always double-check math calculations when preparing a medication that is not supplied as an exact dose. Double checking mathematical calculations helps to prevent mathematical errors and makes it more likely that the correct amount of medication (a portion of the amount supplied) is given to the patient.
THE RIGHT PATIENT
All children who are inpatients should be identified by an identification band attached to their body and not according to the bed they are in. Accurate identification serves two purposes: to reliably identify the individual as the person for whom the service or treatment is intended and to match the service or treatment to that individual. For administration of medication and other services or treatments, The Joint Commission (TJC) (www.jointcommission.org), an accrediting agency for healthcare organizations, adopted a two-identifier requirement to ensure reliable identification of patients as a safety goal. Acceptable identifiers can include two of the following on a wristband: the individual’s name, date of birth, assigned identification number, telephone number, or other person-specific identifier. Bar coding with two or more person-specific identifiers is also being used. Take the patient’s MAR to the bedside to perform your double-identifier check. Match the service about to be performed by checking the medication label with the child’s identification band.
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