Pharm Flashcards
Constant amount of drug is eliminated at any given time. Which elimination order?
Zero order kinetics
Half life depends on dose
Larger doses decreased slower
Constant percentage of drug is eliminated over time. Which kinetics?
First order (most drugs)
Halflife is constant
Large amount of drug is removed in first interval
Volume of distribution
Vd (L/kg)=Total amount of drug (mg/kg)/plasma [drug] mg/L
Cmax
Maximum [drug] at end infusion
Half-life
T1/2 (hr)=0.693 *Vd/CL
Drug clearance
CL (L/hr*kg)=dose/interval/average steady state of drug
How best is drug efficacy predicted for aminoglycosides (ie gentamicin) as it relates to drug concentrations?
Cmax>MIC ratio
Beta lactams and cephalosporins need which PD targets?
Time [drug]> MIC within dosing interval that predicts effectiveness
Vancomycin treatment target is based on which PD parameters?
AUC>MIC for dosing effectiveness
What 3 biochemical factors of a drug will improve absorption?
Molecular weight (smaller better absorbed) Lipid solubility (lipid soluble better) Degree of ionization (non-ionized better)
Premature neonates have a _____ volume of distribution and ______ clearance compared to full term infants
Higher Vd
Slower clearance
High protein binding leads to _______ Vd
Decreased
Neonates have _____ protein binding ability
Decreased protein binding ability because tod decreased total protein, albumin and glycoprotein
Name cytochrome P450 inducers
Dexamethasone
Phenobarbital
Phenytoin
Rifampin
Name cytochrome P450 inhibitors that are involved in Phase 1 reactions (drug modifications)?
Cimetidine Chloramphenicol Erythromycin Fluconazole Infomethacin Méthadone Omeprazole Ranitidine
Name modifications of drug in phase I reactions
Oxidation, reduction, hydrolysis or methylation
75% drugs are modified this way
Name examples of Phase 1 reactions
Oxidation
Reduction
Hydrolysis
De methylation
What is the most important enzyme system in phase I reactions?
Cytochrome p450 system
Microsomal enzymes that transfer electrons from NADPH to cytochrome p450
What is the most common phase II reaction ?
Glucuronidation
Excrete a constant amount of drug per unit time. What order kinetics?
Zero order kinetics
Ie aspirin, chloramphenicol, ethanol, diazepam
Half life is independent on drug dosage. Which drug kinetics?
First order kinetics
Excrete a certain percentage of drug per unit time
Rate of drug elimination is directly proportional to serum drug concentration
Describe the four phases of clinics trials
Phase I - intervention tested on a small cohort to: (1) evaluate safety; (2) establish a safe range
for dosing; and (3) document side effects
Phase II - intervention tested on a larger cohort to: (1) determine effectiveness and (2) evaluate
safety
Phase III- intervention in an even larger cohort to: (1) confirm effectiveness; (2) document
side effects; (3) compare effectiveness against other treatment modalities for the same
condition; and (4) continued safety profiling
Phase IV - tests the intervention after it has been released to the public (“post-marketing”) to
continue to establish and document: (1) benefits and effectiveness; (2) risks and side effects;
and (3) appropriate use and indications
What compartment model do aminoglycosides and vancomycin follow?
Gentamicin follows one compartment model (rapidly equilibrates and 1st order kinetics)
Linear slope
Vancomycin follows two compartments model (slow équilibration with tissues)
Distribution phase and élimination phase
Antenatal Corticosteroids cross placenta to fetus by which type of transport?
Facilitated
