▪ Pharmacokinetics is the study of drug absorption, distribution, metabolism, and excretion in the body
▪ Factors Affecting Absorption: Rate of
... [Show More] dissolution, surface area, blood flow, lipid solubility and PH
▪ Factors affecting distribution: blood flow to tissue, ability to exit the vascular system, blood brain barrier and protein binding capacity
▪ Cytochrome P450 (CYP450) are xenobiotic-metabolizing enzymes necessary for the production of cholesterol and steroids and the detoxification of chemicals and drug metabolism
▪ CYP450 enzymes are thought to be the major family or system of enzymes responsible for phase 1 metabolism in which drugs are oxidized, reduced, or hydrolyzed—the three possible outcomes of phase 1 metabolism.
CYP450
Inhibitors: VISA CKGQ
Inducers : increase drug metabolism CRAP GPS
Carbamazepine, rifampin, alcohol, Phenytoin, griseofulvin, phenobarbital, sulfonylureas
▪ CYP-1A2 metabolizes Acetaminophen : 2A
▪ CYP-2E1: Ethanol (alcohol) 21 to drink
▪ CYP- 2C9: metabolizes warfarin (coumadin)
▪ CYP- 2D6: metabolizes cardiovascular drugs (Echo known as 2D Echo)
▪ CYP- 3A4: most common up to 60% off all the drugs
Dosages of medication in children are based on weight or body surface area (BSA) and require careful calculation.
Metabolism the fastest in children age less than 2 Intramuscular
o Neonate
o Slow and erratic due to low blood flow in muscles first few days of life
o Infancy
o Increased absorption than in in neonates and adults due to increased blood flow
Oral Administration
o Delayed gastric emptying (adult values reached by 6-8 months)
o Increased absorption for drugs that absorb in the stomach
o Decreased absorption for drugs that absorbs in the intestines
o Low gastric acidity for 24 hours after birth (adult values reached around 24 months)
o Increased absorption of acid-labile drugs
Transdermal
o Infants have thin skin with higher rates of blood flow
o Increased absorption
o Increased risk for toxicity from topical drugs
Predisposing ADR factors in the older adult include:
• drug accumulation secondary to reduced renal function
• polypharmacy (the use of five or more medications daily)
• greater severity of illness
• presence of comorbidities
• use of drugs that have a low therapeutic index (e.g., digoxin)
• increased individual variation secondary to altered pharmacokinetics
• inadequate supervision of long-term therapy
• poor patient adherence [Show Less]