Drug monitoring Flashcards
______ is the bodily fluid most often used for therapeutic drug monitoring, while ____ is used for drugs of abuse screening
blood for TDM
urine for DOA screening
When is therapeutic drug monitoring useful?
- Defined effective and toxic concentrations
- Narrow therapeutic windows
- Variable pharmacokinetics-
- Chronic dosing regimens
- Potential for drug-drug interactions
- High protein binding of drug
- Toxicity that mimics the indication for the drug
- Decreased elimination in patient
- Pregnant, infant, elderly patients
- Poor adherence or no effect seen
When is therapeutic drug monitoring NOT useful?
- Drugs that are converted to active forms inside the cell
- Drugs whose pharmacological effects last much longer than their presence in blood
- Opioids
List some drugs whose pharmacological effects last longer than their presence in blood
anticancer drugs warfarin antiviral drugs MAOIs Sulbactam, clavulonic acid Vigabatrin Carbidopa
Why is TDM not useful for patients prescribed opioids?
Phenomenon of tolerance- the levels needed for pain relief in one person could be toxic to another person
_______ is the most common laboratory technique for therapeutic drug monitoring
Immunoassay
List three methods of detection used in immunoassay for TDM
agglutination
fluorescence
chemiluminescence
List classes of drugs most commonly measured in TDM
- antibiotics esp aminoglycosides, fluorquinolones
- anti-seizure drugs
- immunosuppressive drugs
- CV drugs esp anti-arrhythmia drugs
- psychiatric drugs esp lithium, clozapine
When are peak and trough levels of drugs measured by TDM? Which time point is more commonly measured?
Most common to measure trough levels
Trough: just before next dose
Peak: 60 min after PO, 15-30 min after IV, 30-60 min after IM
List possible causes for higher than expected drug levels
Overdose
Decreased clearance
Increased protein binding
List possible causes for lower than expected drug levels
Decreased bioavailability Insufficient dose Nonadherence Enzyme induction Decreased protein binding
Why might it be important to measure cocaine levels in the ED?
concern about MI risk
Why might it be important to measure acetaminophen levels in the ED?
There is an antidote- can give N-acetylcysteine
Most poisonings are diagnosed ______ and managed _______
clinically; symptomatically
_______ is the most commonly diverted and abused pharmaceutical in the US
hydrocodone
Urine screening tests for drugs of abuse are ____ but not ____
sensitive but not specific
Quantitation of drugs of abuse require more sophisticated methodologies like:
GC, mass spec
What are the NIDA 5?
Cannabinoids (THC) Cocaine Amphetamines Opioids Phencyclidine (PCP)
List some substances that can cause a false positive screen for THC
ibuprofen, naproxen, sulindac, pantoprazole
List some substances that can cause a false positive screen for opioids
diphenhydramine, ciprofloxacin, levofloxacin, ofloxacin, poppy seeds, quinine, rifampin, verapamil
_____ is unique compared to other drugs of abuse in that one of its metabolites can be found in the urine long after last use
cannabis
What are some methods of interference/ adulteration of drug screening immunoassays?
Change pH
Oxidize or reduce proteins
Change the ionic environment so antibodies don’t bind
