pharmacokinetics


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pharmacokinetics

 [fahr″mah-ko-kĭ-net´iks]
the study of the movement of drugs in the body, including the processes of absorption, distribution, localization in tissues, biotransformation, and excretion. adj., adj pharmacokinet´ic.

phar·ma·co·ki·net·ics

(far'mă-kō-ki-net'iks),
Movements of drugs within biologic systems, as affected by uptake, distribution, binding, elimination, and biotransformation; particularly the rates of such movements.
[pharmaco- + G. kinēsis, movement]

pharmacokinetics

(fär′mə-kō-kə-nĕt′ĭks, -kī-)
n. (used with a sing. verb)
1. The process by which a drug is absorbed, distributed, metabolized, and eliminated by the body.
2. The study of this process.

phar′ma·co·ki·net′ic adj.

pharmacokinetics

(1) The formal study of the processes of absorption, distribution, metabolism and excretion (ADME) of medicinal products.
(2) The processes of absorption, distribution, biotransformation and metabolism, binding and elimination/excretion of a drug or vaccine, which corresponds to the movement of a therapeutic though a biological system, as related to the rates at which these events occur.

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

phar·ma·co·ki·net·ics

(fahr'mă-kō-ki-net'iks)
Study of the movement of drugs within biologic systems, as affected by absorption, distribution, metabolism, and excretion; particularly the rates of such movements.
[pharmaco- + G. kinēsis, movement]

pharmacokinetics

The study of how DRUGS are absorbed into, distributed and broken down in, and excreted from, the body.

phar·ma·co·ki·net·ics

(fahr'mă-kō-ki-net'iks)
Movements of drugs within biologic systems; particularly rates of such movements.
[pharmaco- + G. kinēsis, movement]
References in periodicals archive ?
The pharmacokinetics of cervical epiduralad-ministered triamcinolone is consistent with previously observed pharmacokinetics of lumbar epidural triamcinolone.
Goudah, "Pharmacokinetics of levofloxacin in male camels (Camelus dromedarius)," Journal of Veterinary Pharmacology and Therapeutics, vol.
The pharmacokinetics (PK) of meloxicam in donkeys was best fitted to a one compartment model.
For patients of typical body weight and at minimal risk of drug-drug interactions, interpatient and intrapatient consistency in pharmacokinetics is recognized, such that achieving a steady state is not necessary (2).
Pharmacokinetics: The computer software APO PC-Program, MWPHARM Version.
In the repeated administration groups the area under the concentration time curve (AUC, a pharmacokinetic parameter) of bile and the AUC bile/ AUC blood ratio increased, but only the AUC of bile showed significant differences that were dose dependant.
John's wort extract with the OC pharmacokinetics in this most recent study.
Overall, the CD-ROM contains a good introduction to what has become 'classical' pharmacokinetics and would be a useful addition to the departmental library for the use of anyone who wants a quick way to refresh basic concepts, but falls well short of being a guide to the state of the art pharmacokinetics for anaesthesia.
Reed told Reuters Health, "is an example of an herbal supplement that dramatically alters the pharmacokinetics of many drugs."
Pharmacokinetics of primaquine and carboxyprimaquine in Korean patients with vivax malaria.