therapeutic drug monitoring

(redirected from Concomitant disease)

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 ?
STATIN THERAPY is often discontinued for older patients who have concomitant disease or other considerations, but it should still be considered in older patients when the benefits outweigh the risks, Bernard M.Y.
JULY INSTANT POLL RESULTS At what point do you contemplate pharmacologic intervention for blood pressure in most patients without concomitant disease? [greater than or equal to]120 mm Hg systolic 2% [greater than or equal to]130 mm Hg systolic 23% [greater than or equal to]140 mm Hg systolic 65% [greater than or equal to]150 mm Hg systolic 10% Results based on an informal poll completed by visitors to The Journal of Family Practice's Web site at mdedge.com/jfponline.
Such seasonal vaccines are especially important to protect the more vulnerable populations such as the very young, the elderly and those with concomitant disease from infection.
Cases of concomitant septic arthritis and crystal arthritis have been reported as well, with higher synovial leukocyte counts seen in patients with concomitant disease than in those with crystal arthritis only [12].
Because of the difficulty in documenting DVT and PE separately from concomitant disease states, along with the inherent limitations of administrative databases and community-based studies, VTE may be vastly underreported.
All patients received IEA therapy once a day and five times every week; we test patients for diplopia and function of eye movement every ten times, the data of max horizontal deviations generated by computerized diplopia test system and the difference value between abducent distances for both eyes were collected.[sup][2] The patients' age, sex, course of disease, treatment cycles, treatment duration, and concomitant disease were collected.
The following patients were excluded: pregnant and breast-feeding patients, patients with severe concomitant disease, and patients who were treated with antibiotics during the previous 4 weeks.
When vaccinated patients were compared to those who were not vaccinated, the rate of concomitant disease was significantly higher in those patients who received the influenza vaccination (70.1%, 56.4%, respectively, p<0.001).
Half of the study population were female, and the most common concomitant disease was epilepsy (52.6%), followed by cerebral palsy (8.3%), epilepsy plus cerebral palsy (6.9%), osteoporosis (0.2%), and osteopenia (0.3%).
Therefore, it is no surprise that chronic concomitant disease (OR: 5.26; 95% CI: 2.07-11.31) was independently associated with persistent organ failure since fatty liver was the most common chronic concomitant disease in our study (Table 1).
Cases who had received any medicine affecting PLT function and had a concomitant disease were excluded from the study.