Absorption & Distribution
These are the four phases of Pharmacokinetics
Absorption, Distribution, Metabolism, Elimination
This liver enzyme system is primarily responsible for the metabolism of many drugs
CYP450 Enzymes
This is the time required for the plasma concentration of the drug to decrease to 50%
Half-life
This is the half-life (t1/2) for a patient with a Vd of 0.4 L/kg, Ke of 0.159 /h
4.3 hours
T1/2 = 0.693 / 0.159 h(-1)
This value is used to estimate infant drug exposure through breast milk
RID (relative infant dose)
Drugs with high plasma protein binding generally have a low distribution into tissues due to their affinity for this plasma protein
Albumin
This phase of metabolism involves conjugation with endogenous substances to enhance their solubility and excretion
Phase 2 Metabolism
Medications such as ethanol, phenytoin demonstrate this type of kinetics process, in which the rate of drug elimination is constant, independent of serum concentration
Zero-order elimination kinetics
This fraction of the drug remains in the body after 24 hours. (For a drug with a half-life of 6 hours)
6.25%
A relative infant dose (RID) above this percentage is generally recommended to be avoided when considering medication safety during lactation
A neonate has started a new medication that is highly protein bound. You notice they are also on continuous infusion heparin (another highly protein bound drug). This pharmacokinetic principle may lead to increased risk of bleeding
Distribution (competing plasma protein binding)
A premature neonate is started on caffeine for apnea of prematurity. Compared to adults, caffeine metabolism in neonates is slower due to this developmental factor
Immature liver enzyme activity or decreased CYP enzyme activity
A 2-day old on ECMO is receiving vancomycin 20 mg/kg for treatment of infection. This pharmacokinetic principle is responsible for higher dosing requirements
Volume of Distribution
This is the corrected phenytoin concentration (mg/L) for a patient receiving phenytoin 5 mg/kg every 12 hours. Collected level 10 mg/L with an albumin level of 1.9 g dL.
20.8 mg/L
This approval process is utilized for a drug that would provide therapeutic benefit over current therapies
Accelerated Approval
A patient on thyroid replacement therapy and continuous feeds, this may decrease the absorption of the medication due to this interaction
Reduction in absorption due to altered gastric pH
A 2-month-old neonate with pseudomonas VAP receiving ciprofloxacin and on continuous infusion midazolam for sedation. Ciprofloxacin may cause increased levels of midazolam due to this type of drug interaction
Enzyme inhibitor
This factor, essential for determining the dose of orally administered medications, is influenced by first pass metabolism, drug solubility, and intestinal absorption
Bioavailability
This is the volume of distribution and clearance for a patient who received a dose of 4 mg/kg of gentamicin resulting in a peak concentration of 10 mg/L. (Utilize a ke = 0.159)
0.4 L/kg (Vd) and 0.0636 L/kg*h (CL)
Vd = amount of drug / plasma concentration
CL = ke x Vd
This type of use of a medication does not require an investigational new drug application or IRB approval
Off Label Use
2-month-old neonate with an ostomy, currently increasing feeds and on oral medications. Nurse reports increased ostomy output (> 35 ml/kg/day), this may affect drug absorption due to these type of changes?
Decreased surface area and altered gastric emptying time
A neonate is prescribed morphine for pain management. Due to genetic variation, the neonate is identified as this type of metabolizer of morphine (CYP2D6) which may lead to rapid conversion of morphine into its active metabolite?
Ultra Rapid Metabolizer
This constant describes the rate at which a drug is removed from the body, often expressed as a fraction per unit of time
Elimination rate constant
This is the estimated peak for a patient receiving gentamicin 5 mg/kg every 24 hours. (Vd for this patient is 0.52 L/kg, Ke is 0.063 /h)
9.6 mg/L
You would expect ______ diffusion of a medication across the placenta in a patient with placental insufficiency or abruption
Reduced