biotransformation


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biotransformation

 [bi″o-trans″for-ma´shun]
the series of chemical alterations of a compound (e.g., a drug) occurring within the body, as by enzymatic activity.

bi·o·trans·for·ma·tion

(bī'ō-trans'fōr-mā'shŭn),
The conversion of molecules from one form to another within an organism, often associated with change (increase, decrease, or little change) in pharmacologic activity; refers especially to drugs and other xenobiotics.
Synonym(s): biodegradation

biotransformation

(bī′ō-trăns′fər-mā′shən)
n.
Chemical alteration of a substance within the body, as by the action of enzymes.

biotransformation

Biochemistry
Bioconversion, see there.
 
Metabolism
A series of chemical changes in a compound (e.g., a drug), which occur within the body (e.g., by enzymatic activity).
 
Pharmacology
Drug metabolism, see there.
 
Physiology
Metabolism, see there.

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

bi·o·trans·for·ma·tion

(bī'ō-trans'fŏr-mā'shŭn)
The conversion of molecules from one form to another within an organism, often associated with change in pharmacologic activity; refers especially to drugs and other xenobiotics.
Synonym(s): biodegradation.

biotransformation

see BIOCONVERSION.

bi·o·trans·for·ma·tion

(bī'ō-trans'fŏr-mā'shŭn)
The conversion of molecules from one form to another within an organism, often associated with change in pharmacologic activity.
References in periodicals archive ?
(1986a, b) studied of the biotransformation of linalool (143) in grape must three different strains of B.
In vitro and in vivo animal studies suggest that CYP2D6 plays a role in biotransformation of serotonin and dopamine.
In contrast, the toxin profile of the New Zealand scallop digestive tissues was dominated by carbamoyl toxins, confirming biotransformation of PSP toxin into more toxic compounds.
A number of microbes from different niche have been reported to have biotransformation ability (Schatzmayr et al., 2006).
Metabolic biotransformation half-lives in fish: QSAR model ing and consensus analysis.
Parasite infections have been reported to change biotransformation system (Armstrong et al., 1993), immune response (Mikraykov & Silkina, 2006) and antioxidant activities (Dautremepuits et al., 2003).
For this reason, it is conceivable that an anomalous biotransformation of biological endogenous or exogenous macromolecules may give a higher susceptibility for developing DIE.
In addition, the effects of MC-LR on the biotransformation and antioxidant defense system were investigated in the gills to assess the MC-LR toxicity and the defense mechanism.
M2 EQUITYBITES-June 12, 2018-Admescope Acquires Swedish Biotransformation Research Specialist MetaSafe
Biotransformation of biotherapeutics - Impact on candidate selection
To maximize the therapeutic potential of PC, the normal bacterial flora must carry out the process of biotransformation. Bioactivity of PC is highly dependent on intestinal absorption, especially considering that many are ingested as non-absorbable precursors.