therapeutic drug monitoring

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therapeutic drug monitoring

Clinical pharmacology The regular measurement of serum levels of drugs requiring close 'titration' of doses in order to ensure that there are sufficient levels in the blood to be therapeutically effective, while avoiding potentially toxic excess; drug concentration in vivo is a function of multiple factors Common TDM drugs Carbamazepine, digoxin, gentamycin, procainamide, phenobarbital, phenytoin, theophylline, tobramycin, valproic acid, vancomycin
Therapeutic drug levels in vivo–factors involved
Patient compliance  Ingestion of drug in the doses prescribed
Bioavailability Access to circulation, interaction with cognate receptor(s); ionized and 'free', or bound to a carrier molecule, often albumin
Pharmacokinetics Drug equilibrium requires 4-6 half-lives of drug clearance (a period of time for1/2 of the drug to 'clear', either through metabolism or excretion, multiplied by 4-6); the drug is affected by
Interaction with foods or other drugs at the site of absorption, eg tetracycline binding to cations or chelation with binding resins, eg bile acid-binding cholestyramine that also sequesters warfarin, thyroxine and digitoxin or interactions of various drugs with each other, eg digitalis with quinidine resulting in a 3-fold ↓ in digitalis clearance
Absorption may be changed by GI hypermotility or large molecule size
Lipid solubility, which affects the volume of distribution; highly lipid-soluble substances have high affinity for adipose tissue and a low tendency to remain in the vascular compartment, see Volume of distribution.
Biotransformation, with 'first pass' elimination by hepatic metabolism, in which polar groups are introduced into relatively insoluble molecules by oxidation, reduction or hydrolysis; for elimination, lipid-soluble drugs require the 'solubility' steps of glucuronidation or sulfatation in the liver; water-soluble molecules are eliminated directly via the kidneys, weak acidic drugs are eliminated by active tubular secretion that may be altered by therapy with methotrexate, penicillin, probenecid, salicylates, phenylbutazone and thiazide diuretics
First order kinetics Drug elimination is proportional to its concentration
Zero order kinetics Drug elimination is independent of the drug's concentration
Physiological factors
Age Lower doses are required in both infants and the elderly, in the former because the metabolic machinery is not fully operational, in the latter because the machinery is decaying, with ↓ cardiac and renal function, enzyme activity, density of receptors on the cell surfaces and ↓ albumin, the major drug transporting molecule
Enzyme induction, which is involved in a drug's metabolism may reduce the drug's activity; enzyme-inducing drugs include barbiturates, carbamazepine, glutethimide, phenytoin, primidone, rifampicin
Enzyme inhibition, which is involved in drug metabolism, resulting in ↑ drug activity, prolonging the action of various drugs, including chloramphenicol, cimetidine, disulfiram (Antabuse), isoniazid, methyldopa, metronidazole, phenylbutazone and sulfonamides
Genetic factors play an as yet poorly defined role in therapeutic drug monitoring, as is the case of the poor ability of some racial groups to acetylate drugs
Concomitant disease, ie whether there are underlying conditions that may affect drug distribution or metabolism, eg renal disease with ↓ clearance and ↑ drug levels, or hepatic disease, in which there is ↓ albumin production and ↓ enzyme activity resulting in a functional ↑ in drug levels, due to ↓ availability of drug-carrying proteins
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

ther·a·peu·tic drug mon·i·tor·ing

(TDM) (thār'ă-pyū'tik drŭg mon'i-tŏr-ing)
Clinical measurement of the effects of a drug in a specific patient rather than reliance on normative ranges (e.g., some old people need a lower dosage than their weight might suggest). Such procedures verify that therapy is as accurate as possible.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
References in periodicals archive ?
CONCLUSION: The present study concludes that there is a substantial gap of knowledge of Therapeutic drug monitoring (TDM) in second M.B.B.S students and M.B.B.S final year, so there is a need of incorporation of Therapeutic drug monitoring(TDM) in practical of second M.B.B.S curriculum and there is need to increase the weightage given to TDM in theory.
In future studies, we hope to define the role of therapeutic drug monitoring in this situation, and whether treatment with low doses of the SSRI or SNRI would be safe and effective in severe cases.
More than 100 tests are available on the system, including general chemistries, critical care chemistries, proteins, serologies and esoteric chemistries, as well as therapeutic drug monitoring and drugs-of-abuse tests.
Therapeutic drug monitoring may be of benefit in patients with multidrug-resistant tuberculosis, but it is often underutilized or used inappropriately, according to Jiehui Li, M.B., of the Bureau of Tuberculosis Control, New York, and associates.
The reactivity of these polyclonal and monoclonal antibodies make them particularly useful for immunoassays for therapeutic drug monitoring (TDM).
Apogent Technologies' Lab Vision acquired NeoMarkers, which sells antibodies and specialty markers, whlie Apogent's Seradyn acquired the operating assets of Opus Diagnostics, which sells therapeutic drug monitoring assays, calibrators and controls ...
Therapeutic drug monitoring (TDM) means measuring the level of a drug actually found in the blood (or inside certain blood cells), in order to adjust the drug dose up or down, either to make sure there is enough to inhibit HIV or to avoid side effects.
Since July 1, Opus' Therapeutic Drug Monitoring (TDM) products have shown very promising results.
The agreement gives Bayer the rights to manufacture and market PCR-based human diagnostic products in the areas of infectious disease, genetics, oncology, tissue typing as well as in therapeutic drug monitoring fields.

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