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Toxicology & TDM

Therapeutic Drug Monitoring

QuestionAnswer
TDM: -Define analysis, assessment & evaluation of circulating concentrations of drugs in serum, plasma or whole blood
TDM: -Purpose ensure that a given drug dosage produces maximal therapeutic benefit & minimal toxic adverse effects
TDM: -Used when safe dosage regiments have not been established and a trial & error approach is not appropriate
TDM: -Involves ____evaluation of circulating drug concentrations quantitative
TDM: -4 key factors 1. route of administration 2. rate of absorption 3. distribution of drug w/in body 4. rate of elimination
The Role of MLS in TDM: -x3 things MLS is responsible for 1. assuring the sample is collected at requested time 2. processing STATs in timely manner 3. assuring accuracy of results by maintaining instruments and performing operations correctly
The Role of the Dr in TDM: -Interpret drug concentrations in the context of the clinical status of the PT
Ind. PT drug utilization & pharmacokinetic patterns are a direct consequences of the interaction of numerous factors including...[x6] 1. genetic makeup--pharmacoenomics 2. age 3. sex 4. physiological status 5. presence of concurrent disease 6. multiple drug therapy
Pharmacogenomics -Responders PTs benefiting from therapeutic & desired effects of drugs
Pharmacogenomics -Non-Responders PTs not benefiting from therapeutic & desired effects of drugs
Name a gene group family that affects drug metabolism? (FYI) Cytochrome P450
Indications for using TDM [1-4/8] 1. drug has narrow-therapeutic range 2. PT noncompliance is suspected 3. Drug exhibits marked pharmacokinetic variations from Pt to Pt 4. PT metabolic state is unpredictable
Indications for using TDM [4-8/8]5 5. possible drug-drug interactions 6. PT is exhibiting unexplained toxic effects 7. a medicolegal need to verify treatment exists 8. a loading dose regimen is being used
Criteria for TDM -Blood concentrations of the drug _______ w/ therapeutic correlate
Criteria for TDM -The drug has a ____ therapeutic index (TI) Low
Low Therapeutic Index means that the dose providing the therapeutic effect is very close to the dose that causes toxicity
Criteria for TDM -The drug is being used to treat an intermittent condition--the resulting pharmacodynamic effect of the drug is.... hard to measure
Criteria for TDM -Evaluate the PT on chronic drug treatment so the dosage regimen can be adjusted in re: to.... physical changes
PT Info needed to TDM [1-4/8] 1. Time of last dose 2. Amt of last dose 3. Dose regimen 4. Dose route
PT Info needed to TDM [5-8/8] 5. time of dosing regimen 6. time of phlebotomy 7. PT age, weight & sex 8. Other concurrent meds
Elimination Half-Life -Defined as: the time it takes for the plasma concentration or amt of drug in the body to be reduced by 50%
Elimination Half-Life - how many half lives are required for steady state using oral dosing -how can it be achieved more rapidly? 5-7 half lives are required for stead stead --may be achieved more rapidly in IM or IV dosing
Half-Life (T1/2) -The rate at which a drug removed is called the E_____, D___, or C____time Elimination, Disappearance or clearance time
Half-Life (T1/2) - the term half-life is used to express the rate or time of elimination
Half-Life (T1/2) -i.e: if no more drug is given, it takes approx. how many half lifes to completely remove the drug from the blood? 5-7
Half-Life (T1/2) -a dosing interval SIGNIFICANTLY longer than the T1/2 results in ____fluctuations dosing interval SIGNIFICANTLY longer than T1/2 results in WIDE fluctuations b/t peak & trough levels
Half-Life (T1/2): dosing interval SIGNIFICANT Y longer -Trough level may be ____ than the lower therapeutic limit -how does this affect disease states? Trough may be lower than thera.limit --disease state may not be properly controlled
Half-Life (T1/2): dosing interval SIGNIFICANTLY shorter than the T1/2 -Peak levels compared to therapeutic range Significantly shorter --> peak levels might exceed the upper limit of thera. range & become toxic
Half-Life (T1/2: dosing interval SLIGHTLY shorter than the T1/2 -what should happen to the therapeutic range? Should maintain therapeutic range once the steady-state condition is achieved
Steady State -Defined as the time required for an amt of drug in the blood to... decline to one-half its measured values
Steady State -dependent on the D____ R____ & C_____ Dosing Rate & Clearance
Steady State -what happens to blood concentration when multiple doses of the drug are taken? Blood concentration levels continue to rise until a steady-state is reached
Steady State -how is drug intake balanced by the clearance of the drug from the body
Steady State -in order to maintain, it is important to not miss, add, or change any doses
Following the first administration of a drug, the serum concentration of the drug reaches a.... Peak or maximum level
The time b/t the first dose & reaching peak level in the blood is dependent on.... the route of administration
When a drug is administered intravenously, when is the peak level attained? 30-60 min
When a drug is administered orally, when is the peak level attained? 1-2 hrs due to intestinal absorption
A S____ R_____ oral medication takes (longer or shorter) to achieve peak serum levels Sustained-Release oral med takes longer to achieve serum peak levels
the absorption of a drug administered _______ is usually erratic, causing the time to reach peak levels to be unpredictable Intramuscularly
The serum level drops from peak concentration to zero within ____ half lives unless.... w/in 5 half-lives unless a second dose is given soon after the first
The Trough or Valley level is the blood drug level.... just before the dose is administered
Pharmacokinetics -Mathematic modeling of... drug concentration in circulation
Pharmacokinetics -Assists in... establishing/modifying a dosage regimen
Pharmacokinetics-Sample Collection -Timing -Specimen type -Timing is critical; trough concentrations--right before next dose, peak concentrations--1 hr after dose -Serum or plasma specimens
Loading Dose Regimen -how do you reach therapeutic levels w/out waiting for 5 half lives? larger or more frequently administered dose
Loading Dose Regimen--troubleshooting -Serum drawn before the admin of loading dose Indicates existing blood levels--Dr wont adjust length of admin and/or concentration correctly
Loading Dose Regimen--troubleshooting -Serum drawn during the admin of loading dose indicates possible toxic levels
Loading Dose Regimen--troubleshooting -Effects of antibiotics some drugs, including antibiotics are not effective until a min. level is attained
Created by: haley.gooch