Monitoring drug concentrations

Develop a plan for monitoring therapeutic outcomes, focusing on the individual symptom profile and level of function of each patient. Include a plan for dosage adjustments or alternate therapy if the patient fails to respond adequately. Include serum drug concentration monitoring as appropriate. 

Urine is commonly screened for evidence of illicit drug use or alcohol consumption. This may be viewed as a drug concentration monitoring procedure, even if only of a qualitative type. It remains controversial whether poppy-seed bagels can lead to positive urine screens for opioids ... 

Antidepressants are used in neuropathic pain and migraine prophylaxis. Tricyclics require monitoring of plasma drug concentrations to achieve optimal effect... 

Frequently monitor the patient for signs of drug toxicity and seizures until the patient s drug concentrations have stabilized. Drug interactions are likely when patients are on more than one AED therefore, closely evaluate the patient s entire medication profile, and change medications or doses to minimize the interaction, if possible. 

Monitoring for successful therapy is critical in this serious infection to prevent complications, prevent resistance development, and decrease mortality. Routine assessment of clinical signs and symptoms, as well as laboratory tests (i.e., repeat blood cultures), microbiologic testing and serum drug concentrations, must be performed. 

Therapeutic drug monitoring (TDM) or applied pharmacokinetics is the use of serum drug concentrations to optimize therapy.28,36,37 Non-AIDS patients with drug-susceptible TB... 

Therapeutic drug monitoring The process of using drug concentrations, pharmacokinetic principles, and pharmacodynamic criteria to optimize drug therapy in individual patients. 

One approach to the study of solubility is to evaluate the time dependence of the solubilization process, such as is conducted in the dissolution testing of dosage forms [70], In this work, the amount of drug substance that becomes dissolved per unit time under standard conditions is followed. Within the accepted model for pharmaceutical dissolution, the rate-limiting step is the transport of solute away from the interfacial layer at the dissolving solid into the bulk solution. To measure the intrinsic dissolution rate of a drug, the compound is normally compressed into a special die to a condition of zero porosity. The system is immersed into the solvent reservoir, and the concentration monitored as a function of time. Use of this procedure yields a dissolution rate parameter that is intrinsic to the compound under study and that is considered an important parameter in the preformulation process. A critical evaluation of the intrinsic dissolution methodology and interpretation is available [71]. 

Drug concentrations should be monitored frequently because of changing volume status, changing renal function, and RRTs in patients with ARF. 

Ideally, unbound (versus total) drug concentrations should be monitored, especially for drugs that have a narrow therapeutic range, are highly protein bound (free fraction less than 20%), and have marked variability in the free fraction (e.g., phenytoin, disopyramide). 

A microdialysis study was carried out to examine transport of oxycodone into the brain of rats [67], Oxycodone was administered by i.v. infusion, and unbound drug concentrations were monitored in both vena jugularis and striatum. Steady-state equilibrium was reached rapidly and drug levels in the two compartments declined in parallel at the end of the infusion. An unbound brain to unbound plasma ratio of 3.0 was measured which is 3- to 10-fold higher than for other opioids, and explains the similar in vivo potency of oxycodone in spite of lower receptor affinity. The authors interpret these data as de facto evidence of the existence of an as-yet unidentified transporter that carries oxycodone across the blood-brain barrier. 

Over the past 20 years there has been widespread interest in monitoring plasma antidepressant, particularly tricyclic, levels to optimize the response to treatment. One aspect of this research that is universally agreed upon concerns the extensive interindividual variability among patients, but it is still uncertain whether a knowledge of the plasma drug concentration is of clinical value. 

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